1
Q
Structure of the Cell Membrane
A
- 8 to 10 nm in width
- contains phospholipids, proteins and a glycocalyx coat
- 2 leaflets of phospholipid molecules
- their polar, hydrophilic heads face both cytoplasm and extracellular space
- their non-polar, hydrophobic tails oppose each other
- proteins associated with the lipid bilayer are integral transmembrane proteins and peripheral membrane proteins
2
Q
Development of the Basic Limb Structure
A
- As the limb bud elongates, it becomes flattened in the dorsoventral plane of the embryo
- The distal part acquires a paddle shape
- Later, a constriction divides the cylindrical
proximal region into two segments - In the forelimb, these two segments represent the primordia of the arm and forearm and in the hind limb the thigh and leg
3
Q
Amnion
A
- Develops from the extraembryonic somatopleure, which gradually overgrows the embryo and finally fuses together
- The fluid accumulates in the amniotic cavity and forms the fluid filled sac around the embryo
- Hydroamnion is the excess amount of amniotic fluid
4
Q
Zonary Placenta
A
- based on the shape
- The chorionic villi form a band around the chorionic sac
Ex: carnivores
5
Q
Medulla of Lymph Nodes
A
- stroma and parenchyma are loosely arranged here
- the lymphatic tissue is arranged in medullary cords that branch and anastomose throughout the medulla
- medullary cords are composed of lymphocytes, plasma cells and macrophages
- the medullary cords are separated by a network of endothelial-lined sinuses and connective tissue
- In the pig, the cortical and medullary tissues are reversed
6
Q
Fibrocartilage
A
- present in the intervertebral disc and menisci
- the perichondrium is poorly developed, although it is surrounded by collagen fibers
- Stained blue with trichrome Stain
- abundance of collagen fibers
- few chondrocytes
7
Q
Stereocilia
A
- long and rigid microvilli
- mainly present in the sense organs
- > inner ear
8
Q
Order of Ossification
A
- Periosteal collar
- Shaft
- Extremity
- Epiphyseal Cartilage (last)
9
Q
Ribosomes
A
- electron dense basophilic particles
- 15-25 nm
- contain RNA
- it is acidic, or basophilic
- if in groups called polyribosomes, or polysomes
- function is for protein synthesis
- found in the cytoplasm, rough ER, and the outer layer of the nuclear envelope
10
Q
Cerebellum
A
- outer grey and inner white matters are arranged in a highly folded structure
- > folia
- White Matter is composed of nerve fibers of the cortex
- Cerebellar Cortex has 3 layers
1. Outer Molecular Layer - neuropil arranged horizontally
- Intermediate Purkinje cell layer
- a single layer of piriform cells, which send their ramified dendrites into the molecular layer and axons into the white matter*
3. Inner Granular Layer - densely packed small neurons with intensely stained nuclei
11
Q
Oligodendrocytes
A
- produces myelin which provides electrical insulation for neurons in the CNS
- wrap around the axons in the CNS
12
Q
Cardiac Skeleton
A
- three parts
1. Fibrous Rings - surround the AV, aorta and pulmonary trunk openings
2. Fibrous Triangle (fibrous ring - pulmonary aorta) - fills the space between the AV openings and the base of the aorta
- *predominantly
- > Dense irregular CT: Pigs and cats
- > Fibrocartilage: Dogs
- > Hyaline Cartilage: Horse
- > Bone: Large Ruminants(cow)*
3. Fibrous part of the interventriculer septum - collagen fiber bundles
13
Q
Echinocytes, or Crenated Cells
A
- irregular wavy border on RBC
14
Q
Cardiac Muscle
A
- centrally located single nucleus
- intercalated disc present at the junction of adjacent cells creating a syncytium
- *Contain modified cardiac muscle for impulse conduction called Purkinje Fibers
- > centrally located nucleus
- > myofibrils (contractile filaments) are fewer and found only peripherally*
15
Q
Allantois
A
- Develops from the extraembryonic splanchnopleure as a diverticulum of hindgut
- It is a reservoir for excretory products of fetus
- It fuses with chorion to develop the chorio-allantoic placenta
- The blood vessels that develop in the allantois are termed umbilical vessels
- allantoic calculi, or hipomane in mares and cows
- > small, circular, flat, smooth bodies found in the allantois fluid especially in mares and cows
- Hydroallantois
16
Q
Reticular Tissue
A
- Adult CT
- present in lymphatic organs, liver and endocrine glands
- composed of numerous reticular cells and a network of reticular fibers
17
Q
White Pulp of the Spleen
A
- consists of Periarterial Lymphatic Sheaths (PALS)
- T-Lymphocytes predominate near the artery
- B lymphocytes predominate peripherally
- the reticular fibers and reticular cells form a 3D network (stroma) containing lymphocytes and macrophages (parenchyma)
- > In the white pulp there is NO erythrocytes (RBC)
18
Q
Chondrodystrophy
A
- abnormal interstitial growth of cartilage
- premature cessation of growth leads to the shortening of bones, especially the limbs, base of the skull and vertebral column
19
Q
Parenchyma (Immune cells, or Immunocytes)
A
- functional cell of the immune system
1. Lymphocytes - T-lymphocytes
- B-lymphocytes
- Plasma Cells
- NK Cells
2. Neutrophils
3. Macrophages
20
Q
Loose, or Areolar Connective
A
- Adult CT
- abundant in ground substances
- present below the epidermis/epithelium around blood vessels
- loose network of fine collagenous, reticular and elastic fibers
21
Q
Limb Field
A
- An area of somatopleure committed to forming a limb
22
Q
Connective Tissue
A
- connects other tissue and provides a framework to support the entire body by cartilage and bones
- composed of cells, fibers and amorphous ground substances
23
Q
Amelia
A
- complete absence of a limb
24
Q
- Gestation Periods*
- mare
- cow
- ewe
- sow
- bitch
- queen
A
- Mare = 335-345 days (11 mos)
- Cow = 279-282 days (9 mos)
- Ewe & Goat = 148-150 days (5 mos)
- sheep and goat - Sow = 114-120 days (4 mos)
- Bitch = 60-65 days (2 mos)
- female dog - Queen = 60 days (2 mos)
- female cat
25
Osteoclasts
- bone eating (phagocytic) cells
- *a large multinucleated cell*
- located in the area of bone resportion or remodeling
- > absorbs bone tissue during growth and healing for bone remodeling
26
Macula Adherens, or Desmosomes
- transmembrane proteins link neighboring cells together with the assistance of an electron-dense plaque and intermediate filaments that form a hairpin loop
- found in the epidermis
27
Adipose Tissue
- Adult CT
- consists of adipocytes within the loose CT of blood vessels, nerves and mesenteries
- Unilocular (white) adipose tissue and Multilocular (brown) adipose tissue
28
Locations of: Compound Alveolar (Acinar Gland), and Compound Tubulo-alveolar
1. Compound Alveolar (Acinar Gland)
- parotid gland
2. Compound Tubulo-alveolar
- pancreas
29
Muscle Types
1. Skeletal Muscle
- striated and voluntary
- muscle attached to the bones of the skeleton
- strong and quick discontinuous contraction
2. Cardiac Muscle
- striated and involuntary
- walls of the heart
- strong and quick continuous contraction
3. Smooth Muscle
- non striated and involuntary
- Walls of most viscera
- > GI tract, urinary, uterus, etc
- weak and slow contraction
30
Neuroglial Cells (gliocytes)
- provide structural and functional support
1. In the CNS:
- astrocytes
- oligodendrocytes
- microglial cells
- ependymal cells
- > microglial cells derived from the mesoderm, all other cells are derived from the neural ectoderm
2. In the PNS
- Neurolemmocytes (Schwann Cells)
- > derived from the neural crest
31
*Myocardium*
- thickest layer composed of:
1. Cardiac muscle cells
2. **SA and AV nodes
- composed of nodal cells
- impulse generating modified cardiac muscle cells**
3. Purkinje Fibers
- impulse conducting
4. Cardiac Skeleton
32
Teratology
- the branch of embryology concerned with the study of malformations, or abnormalities
33
Developmental Periods
1. Prenatal Period
- the period of development before birth
- development proceeds rapidly with more drastic morphological changes
2. Postnatal Period
- the period of development after birth
- changes take place more gradually and are followed by aging
34
Pulmonary stenosis
- Pulmonary stenosis at the valvular and infundibular level
| - The characteristic poststenotic dilation of the pulmonary trunk, right ventricular dilation and hypertrophy
35
What is the cardiovascular system derived from?
- mesoderm
36
Pigment Cells
- melanocytes
| - cells containing pigments (melanin)
37
Erythrocytes Structure
- have a "pallor" in the center
- surrounded by a plasmalemma
- contain 33% of Hb (oxygen carrying protein)
- lose their mitochondria, ribosomes and many cytoplasmic enzymes during maturation
38
Transposition of Great Vessels
1. Aorta from the right ventricle
2. Pulmonary artery from the left ventricle
a. Interatrial septal defect,
b. Ductus arteriosus,
c. I-V septal defects
39
*Intramembranous Ossification*
- all of the skull bones except the bone at the base of the skull
- mesenchymal cells aggregate into small clusters then differentiate into osteoblast cells
- osteoblast cells secrete a protein matrix (osteoid), then mineralization of the osteoid occurs
40
Extraembryonic Germ Layers
- Due to rapid growth of embryonic disc, it is transformed from ovoid into elongated disc in shape
- The rapidly proliferating cells spread outwards from the embryonic disc to line the internal aspect of the trophoblast
- The part of the germ layer which underlies the embryonic disc is called intra-embryonic germ layer
- The cells lying peripherally under the trophoblast is called the extra-embryonic germ layer
41
Vitelline Vein
- left side regresses
- right side
- > hepatic segment of the caudal vena cava
- > hepatic sinusoids
- > portal venous system
- --> all related to the development of the liver, or venous system of the liver
42
Ribs Development
- arise from segmental sclerotome derived from condensation of mesenchymal cells lateral to the thoracic vertebrae
- Ribs and vertebrae are derived from mesenchymal cells
43
Aortic Arches in the dog
- both the common carotid artery and right subclavian join to form the brachiochephalic trunk
- Whereas, the left subclavian will develop directly from the aorta
44
Elastic Fibers
- present in the aorta and nuchal ligament
- as well as the muscular arteries, pinna of the ear, and lungs
- > present in structures that require elasticity
- stained light pink by orcein and resorchin-fuchsin
- composed of elastin protein for elasticity
45
Intermediate Mesoderm
- the junction between the paraxial and lateral mesoderm
| - gives rise to the urogenital system
46
*Bronchi*
- subdivided into primary, lobar and segmented bronchi
- lined by pseudostratified ciliated columnar with goblet cells
- > Proximodistally in the pseudostratified columnar epithelium, the epithelial height and number of goblet cells decrease whereas Clara cells (exocrine gland) increase in number
- the hyaline cartilage is in the form of irregular plates and smooth muscle is interspersed between the plates
- > *Proximodistally in the hyaline cartilage, cartilages decrease, whereas smooth muscles increase*
- propria-submucosa contains loose CT with submucosal glands that decrease distally
- *ONLY the Smooth Muscle Increases, all other factors decrease*
- > height of epithelium, thickness of propria-submucosa, gland density, and cartilage decrease
- Tunica adventitia comprised of loose CT with collagen and elastic fibers
47
*Limb Formation*
- Limbs grow outside from the body wall somatopleure as limb buds
- Bone, cartilage, and related connective tissue arise from the somatic mesoderm of the limb bud
- Dermis comes from the dermatome
- Skeletal muscles are derived from the myotome through migration of its cells into the limb
48
Elastic Fibers
- present in the aorta and nuchal ligament
- > present in structures that require elasticity
- stained light pink by orcein and resorchin-fuchsin
- composed of elastin protein for elasticity
49
*Cardiac Tube*
- both the left and the right tubes merge and develop into five parts
1. Truncus Arteriosus
2. Bulbus
3. Ventricle
4. Atrium
5. Sinus Horn
- > from cranial to caudal direction
- > blood flows from the sinus horn towards the truncus
- the cardiac tube differentiates into the endocardium, myocardium and epicardial layer
50
Discoidal Placenta
- based on shape
- The chorionic villi form one or two disc-shaped area
Ex: primates, rodents and bats
51
Sinuses of Lymph Nodes
- subcapsular sinus, trabecular sinus and medullar sinus
- lined by endothelium like reticular cells
- the lumen of the sinuses are transversed by a dense network of reticular cells and reticular fibers
- lymphocytes and macrophages lie free within the stromal mesh and in the sinus lumen
- most lymph circulates through the subcapsular, trabecular and medullary sinuses, but some percolate through the cortex and medullary cords to reach the medullar sinus
52
Changes after birth due to Prostaglandin
- prostaglandin from the placenta keeps the ductus arteriosus open before birth
- after birth due to the discontinued prostaglandin, the ductus arteriosus closes
53
Satellite Cells
- represent inactive myoblasts
| - > can be activated upon injury for regeneration of muscle fibers
54
*Basic Tissue Types*
- ONLY four basic types
1. Epithelium
2. Connective Tissue
3. Muscular Tissue
4. Nervous Tissue
55
**Mucous, or Gelatinous Connective Tissue**
- Embryonic CT
- found in the umbilical cord and bovine glans penis
- composed of fibroblasts, gel-like ground substance and collagen fibers
56
Parenchyma vs Stroma of Lymph Nodes
- stroma and parenchyma are LOOSELY arranged in subcapsular sinus and medulla
- whereas stroma and parenchyma are TIGHTLY packed in the cortex
* 1. Parenchyma
- lymphocytes, plasma cells and macrophages enmeshed in a network constitute the parenchyma*
2. Stroma
- reticular cells and fibers (reticular connective tissue) form a 3D network
57
**Differences Between Veins and Arteries**
1. Tunica Media
- relatively thinner
* 2. Tunica External
- relatively thicker*
3. Total wall thickness is relatively reduced
4. Greater Luminal Diameter
5. Veins are equipped with flap-like usually paired semilunar valves
58
Blood Vessel Structure
1. Tunica Intima
2. Internal Elastic Membrane
3. Tunica Media
- predominance of smooth muscle
- elastic and collagen fibers
4. External Elastic Membrane
5. Tunica Externa (tunica adventitia)
- collagen and elastic fibers
- contains vasa vasorum and nervi vasorum
59
Monozygous
- When one ovum is fertilized but subsequently divides at the blastocyst stage into two genetically identical masses
- > therefore always of the same sex and same blood group
- identical twins
- Three Ways this can happen:
1. Amniotic cavity and placenta is separate
- safest bc everything separate
2. Amniotic cavity separate, but placenta is common
3. Common amniotic cavity and common placenta
- Most dangerous
60
*Origin of Primordial Germ Cells*
- the primordial germ cells, which are destined to develop into gametes, are originated in the wall of the yolk sac, from where they migrate to get established in the developing gonad.
- initiates the rise of gametes
61
Zonula Adherens Junction
- transmembrane proteins link neighboring cells together with the assistance of actin
- found in the basal intestines
62
Compact Bone
- forms the outer shells of the diaphyses and epiphyses
- between the periosteum and endosteum
- *consists of osteons, or Haversian systems*
- > as well as outer and inner circumferential lamellae and interstitial lamellae
- each osteon consists of a central canal (Haversian Canal) surrounded by concentric lamellae
- *the central canals are connected by perforating canals (Volkmann's Canal)*
63
Simple Cuboidal Epithelium
- a single layer of cuboidal cells with a centrally placed nucleus
- rounded nucleus
- mainly present in the collecting ducts of the kidney
64
Organelles vs. Inclusions
1. Organelles
- functional part of the cell
2. Inclusions
- structural part of the cell
65
Villous Placenta
- based on branching of the chorionic villi
- When there is a simple branching of chorionic villi
Ex: sow, mare and ruminants
66
Diffuse Placenta
- based on the shape
- The chorionic villi are uniformly distributed over the entire sac Ex: mare and sow
- > In the sow, further development of the folds of different order increases the surface area for feto-maternal exchange
67
Fetal Circulation
1. Oxygenated blood
a. Umbilical Vein
b. Ductus Venosus
c. Caudal Vena cava
d. Right atrium
e. Foramen Ovale
f. Left Atrium
g. Aorta
2. Deoxygenated Blood
a. Cranial Vena Cava
b. Right atrium
c. Right ventricle
d. Pulmonary aorta
e. Ductus Arteriosus
f. Aorta
68
Small and Medium Sized Lymph Vessels
- have a continuous membrane
- with increasing diameter, first a small amount of CT and then one or two layers of smooth muscle and elastic fibers are added
- > Continuous tissue plus 1-2 layers of smooth muscle and elastic fiber in the Tunica media
- No Tunica externa
69
Primary vs Secondary Centers of ossification
- in the dog ossification starts from about 38 days of gestation
1. Primary
- one in the body
- one in each half of the neural arch
2. Secondary
- develops postnatally
Ex: transverse and spinous processes
70
Nondeciduate Placenta
- Based on Loss of Maternal Tissues at Parturition
- There is little loss of maternal tissue due to relatively simple feto-maternal contact
Ex: sow, mare and ruminants
71
Dorsal Mesocardium
- transverse pericardial sinus
- the developing heart tube bulges into the pericardial cavity and remains attached to the dorsal side of the pericardial cavity by a fold of mesodermal tissues called the dorsal mesocardium
- with further development, the dorsal mesocardium disappears creating the transverse pericardial sinus that connects both sides of the pericardial cavity
72
Limb bud
- Localized proliferation of mesoderm
| - covered by ectoderm
73
*Trachea in the Avian Respiratory System*
- Trachea is similar to mammals except:
| - > The Cartilaginous rings are complete and the Intraepithelial glands are numerous.
74
Stromal Cells
- supporting cells of the immune system
- stroma = network
1. Reticular Cells
2. Epithelial Reticular Cells
3. Dendritic Cells
75
Meroamelia
- means the absence of one or more parts of a limb
| - for example, in crural meromelia, the tibia and fibula are absent
76
*Major Types of GAGs*
1. Hyaluronic acid
- in the vitreous body of eye and in synovial fluid
2. Chondroitin sulphate
- in cartilage, bone, and large blood vessels
3. Dermatin
- sulphate in tendons and ligaments
4. Keratin
- sulphate in cartilage and bones
5. Heparin sulphate
- in arteries and lungs
77
Osteocytes
- mature resting bone cells
- derived from osteoblasts
- lies in a lacuna
78
Tight Junctions
- have anastamosing ridges of transmembrane proteins that seal neighboring cells together in a belt-like fashion (loop)
- found in the apical intestines and epithelial cells
79
*Red Pulp of the Spleen*
- Similar to the construction of the parenchyma and stroma, BUT has erythrocytes (RBC)
- composed of:
1. The Splenic Cords
- reticular fibers with reticular cells (stroma) enmeshed with erythrocytes (RBC), macrophages, lymphocytes, plasma cells and other leucocytes (parenchyma)
2. The Splenic, or Venous Sinuses
- wide vascular channels between the splenic cords
- > lined with endothelial cells that contain contractile microfilaments which on contraction create gaps allowing erythrocytes to pass between splenic cords and splenic sinuses
80
Lateral Mesoderm
- the laterally proliferating cells form the lateral plate, or lateral mesoderm
- the lateral mesoderm splits into two layers, the somatic and splanchnic mesoderm
- the space between the two layers forms a cavity called the coelom
- the somatic mesoderm is associated with the ectoderm to form somatopleure
- the splanchnic mesoderm is associated with the endoderm to form splanchnopleure
81
Partitioning of the Ventricles
- with the enlargement of the future halves of the ventricle, a median partition grows as a crescentic plate forming the, muscular interventricular septum
- initially this septum makes an incomplete partition and the communication between the two ventricles is known as the interventricular foramen
- The Inter-ventricular foramen is closed by the ventral growth of septum intermedium and spiral septum forming the membranous inter-ventricular septum
82
Fertilization
- is the fusion of the sperm and ovum to initiate the development of a new individual
- it is preceded by ovulation and then insemination
83
Cerebral Cortex
```
Grey Matter
- present in gyri and sulci
- 6 layers from superficial to deep
1. Molecular Layer
- composed of processes of the stellate or pyramidal neurons (neuropil), arranged tangentially
2. External Granular Layer
- small pyramidal neurons
3. External Pyramidal Layer
- small and med pyramidal neurons
4. Internal Granular Layer
- small stellate neurons
5. Internal Pyramidal Layer
- medium to large pyramidal neurons that send axons into the white matter
6. Fusiform Layer
- many spindle shaped neurons
White Matter
- composed of nerve fibers going to and coming from the cortex
```
84
Anisocytosis, Poikilocytosis and Anemia
1. Anisocytosis
- variation in the size of RBC
2. Poikilocytosis
- variation in the shape of RBC
3. Anemia
- an absolute decrease in the red cell mass as measured by RBC count, the hemoglobin concentration, PCV (plasma cell volume)
85
Micromelia
- the reduced size of a limb
| - all parts of the limb are present, but it is significantly smaller in size
86
Nasal Cavity in the Avian Respiratory System
- The nasal cavity is lined by the same types of epithelia characteristic of the mammals
- > Stratified squamous epithelium rostrally
- > Olfactory epithelium dorsocaudally
- > Respiratory epithelial lining for most of the remaining areas.
87
Dendritic Cells
- develop from bone marrow
- form the stroma of lymphatic tissue
- major function is to capture and present antigens to lymphocytes
- stellate shaped cells present in nearly all tissues
- four types
1. Follicular Dendritic Cells
2. Interdigitating dendritic cells
3. Intraepidermal macrophage (Langerhans cell)
4. Veiled cells
88
Vascular Ring Anomalies
- a persistent right aortic arch results in the vascular ring anomalies
- vascular ring encircles the esophagus and the trachea, therefore it can cause choking
89
Fibroblast Cells
- synthesis of fibers for wound repair
- most common cells
- Myofibroblasts are fibroblasts that contain actin filament
- > contraction during wound healing
- two stages of activity:
1. Active
- called a fibroblast
- contains rough ER and therefore ribosomes
2. Quiescent/inactive
- called a fibrocyte
90
Mesenchymal Cells
- Irregularly shaped with multiple processes
- primitive, or stem cells
- *found near blood vessels*
- can differentiate into other types of cells
91
*Continuous Capillaries*
- most common type of capillary
- present in muscles
- the endothelial cells are held together by tight junctions
- transcytotic vesicles are common
92
Unicellular Glands
- the only unicellular gland is the goblet cell
| - > it secretes mucus
93
*Intervertebral Disc Development*
1. Annulus Fibrosus (outer)
- develops from the mesenchyme of the sclerotome
- main support
2. Nucleus Pulposus (center)
- develops from the notochord
94
Paraxial Mesoderm
- parallel to the central axis
- the dorsally proliferating mesodermal cells on either side of the notochord become thickened to form this
- *later forms a series of mesodermal thickenings called somites*
- each somite subsequently differentiates into myotomes, dermatome and sclerotomes
- the somites are organized around the notochord and extend as far as the rostral extent of the notochord
- somites constitute the vertebral column (sclerotome), its associated muscles (myotomes) and connective tissue (dermatome)
95
Development of the Valves
- both the left and right atrioventricular valves develop around the margin of atrioventricular orifices as localized mesenchymal thickening (tubercle)
- > these become hollowed out and form endocardial cusps
- three cusps developing at the right atrioventricular orifice and two cusps developing at the left atrioventricular orifice
- There are semilunar valves at the pulmonary and aortic orifices
96
Mitochondria
- chief source of energy (ATP synthesis)
- double layered membrane
- > inner layer has folds called cristae that contain enzymes that function in oxidative phosphorylation
- stained with Janus Green B in living cells
- the only cell outside the nucleus that has its own DNA and ribosomes, or protein!
97
Establishment of Body Form Is Mainly Accomplished By?
1. The longitudinal folding of embryo in cephalo-caudal direction
- This folding is more pronounced in the cranial and caudal end of the embryo, thus the head and tail fold are formed
2. The transverse or lateral folding of embryonic disc obtains a cylindrical appearance and lateral and ventral body wall of the embryo is established
98
Cardiogenic Area, or Plates
- develops from the *splanchnic mesoderm* as a paired structure on the left and right side
- several vesicles develop in the cardiogenic plates which later unite to form a hollow tube called the cardiac tube
99
Thymus
- has a connective tissue septa capsule that penetrates the parenchyma and divides it into lobules
- > each lobule has an outer cortex (peripheral dark zone) and an inner medulla (central light zone)
100
*Conus Arteriosus*
- area around the origin of the pulmonary artery in the right ventricle
- the undivided distal part of the Bublis cordis that is incorporated into the right ventricle
101
Tetr0logy of Fallot
1. Dextroaorta
2. Pulmonary stenosis
3. I-V septal defect
4. Dilation and hypertrophy of the right ventricle
- all four conditions at the same time
102
Central NS vs Peripheral NS vs Autonomic NS
1. CNS
- brain and spinal cord
2. PNS
- cranial and spinal nerves
3. ANS
- innervates visceral organs
103
Dizygous
- when two separate ova are fertilized
- fraternal twins
- can be two different sexes
- Two ways this can happen:
1. Separate amniotic cavity and separate placenta
2. Separate amniotic cavity and common placenta
104
Interarterial Septal Defects
- Foramen secundum, Foramen ovale.
| - Dilation and hypertrophy of right ventricle, right atrium and left atrium
105
Lateral Mesoderm Further Development
- Split into Somatic and Splanchnic Mesoderm
- > the Coelom is the cavity between these two layers
1. Ectoderm + Somatic Mesoderm = Somatopleure
2. Endoderm + Splanchnic Mesoderm = Splanchnopleure
106
Mesenchymal Connective Tissue
- *ONLY Embryonic CT*
- > mesenchymal cells are present in embryonic and adult CT
- composed of mesenchymal cells and a fluid-like ground substance
- differentiates into various types of adult CT
107
Cartilage
- special CT
- consists of cartilage cells (chrondroblasts and chondrocytes) and a matrix
- *lacks blood vessels, therefore it is slow to heal*
108
Stratified Cuboidal Epithelium & Stratified Columnar Epithelium
1. Stratified Cuboidal Epithelium
- found lining the excretory ducts of glands
- Generally 2 layers, maximum of three but it is rare
2. Stratified Columnar Epithelium
- in parotid and mandibular gland ducts
- larger ducts
109
Elastic Tissue
- Adult CT
- *ONLY present in the nuchal ligament and vocal ligament*
- > elastic fibers are present throughout the body
- characterized by numerous regularly and irregularly arranged elastic fibers
110
Number of Chromosomes in the Different Species
- ovum/oocyte and sperm have half this number (haploid)
- > these are diploid
1. Horse = 64 (32 pairs)
2. Ox = 60 (30 pairs)
3. Goat = 60 (30 pairs)
4. Sheep = 54 (27 pairs)
5. Pig = 38 (19 pairs)
6. Dog = 78 (39 pairs)
- dogs have the most
7. Cat = 38 (19 pairs)
8. Human = 46 (23 pairs)
111
Arterioles Structure
- **open either directly into capillaries through pre-capillary sphincter of smooth muscles, or into meta-arterioles (mesenteric circulation)**
1. Tunica Intima
2. Internal Elastic Membrane
- fenestrated and eventually disappears in smaller arterioles
* 3. Tunica Media
- 1 to 3 layers of smooth muscle*
4. External Elastic Membrane
- absent
5. Tunica Externa
- composed of loose CT
112
Structure of the Spleen
- Surrounded by a capsule composed of connective tissue and smooth muscle
- Capsule sends out trabeculae that contain arteries, veins, lymph vessels and nerves
- The capsule, trabeculae and reticular fibers support the splenic parenchyma
- splenic parenchyma is composed of red and white pulp
113
Bone Marrow Types
- two types
1. Red Marrow
- actively involved in hematopoisis
2. Yellow Marrow
- inactive and contains fat
114
Freemartin
- In Cattle
- In Dizygous twinning the development of a common circulation by placental anastomosis usually occurs
- If the twins are of opposite sex, the development of the genital system is retarded in the female embryo due to the influence of the testosterone produced by the male embryo
- > Therefore, the female born is infertile and known as freemartin
- also develop male characteristics
115
*Marginal Zone of the Spleen*
- lies between the red and white pulp
- plays a key role in the filtration of the blood
- periphery of the white pulp is bounded by a circumferential reticular network with B cells and macrophages
- the reticular network of the marginal zone received capillaries from the white and red pulp
- the capillaries empty into the marginal sinus and the blood is drained toward the venous sinuses, or venules
of the red pulp
116
*Cardinal Vein*
- in embryonic circulation, the cranial and caudal cardinal veins join the common cardinal vein which enters the sinus venosus
1. Cranial Cardinal Veins
- become the brachiocephalic vein and the cranial vena cava
2. Caudal cardinal vein
- regresses
3. Subcardinal Vein
- becomes the caudal vena cava and the renal vein
4. The Supracardinal vein fuses together with the caudal cardinal vein
- develops into the azygos vein
117
Capacitation
- involves removal of the glycoprotein coat and seminal plasma protein from the plasma membranes that overlies the acrosomal region of the spermatozoa
118
Cilia
- for movement
- composed of microtubules
- found in the respiratory, or male/female genital tracts
119
Pericytes
- elongated cells that contain actin and myosin
- potential to transform into other cells
- participate in the healing process
- line small blood vessels
120
Alveoli
- Pulmonary macrophages (derived from monocytes) are phagocytic cells present in the alveolar lumen
- Interalveolar CT consists of a capillary plexus, fibrocytes, pericytes, lymphocytes and plasma cells, collagen and elastic fibers
- *Alveolar epithelial lining presents two cell types.
1. Pneumocyte type I (95%)
- is a squamous epithelial cell with a central nucleus
- anchored to a continuous basal lamina
2. Pneumocyte type II (5%), or Granular Alveolar Cell
- is a cuboidal cell with microvilli that is responsible for the production of pulmonary surfactant*
121
Locations of: Simple Alveolar(Acinar Gland), Simple Branched Acinar(Alveolar gland), and Simple Tubulo-acinar (Alveolus Gland)
1. Simple Alveolar, or Acinar Gland
- sebaceous gland
2. Simple Branched Acinar, or Alveolar gland
- large sebaceous gland
3. Simple Tubulo-acinar, or Alveolus Gland
- minor salivary gland of the oral cavity
122
Basophils
- segmented, or irregularly shaped heterochromatic nuclei
- cytoplasmic granules are metachromatic
- > stain reddish violet and are water soluble
- In dogs, basophils are larger and fewer granules than those of cows and horses
- Rod-shaped in cats
- plays a major role in mediating inflammatory reactions
- > release histamine and heparin
123
Formation of the Mesoderm
- Most of the cells between the ectoderm and endoderm give rise to mesodermal cells
- Arranged in 4 different ways:
1. Notochord
2. Paraxial mesoderm
3. Lateral mesoderm
4. Intermediate mesoderm
124
Parabronchi of the Lungs
- The parabronchi are lined by Simple cuboidal epithelium
- Numerous extensions (atria) of the parabronchial lumen give rise to the air capillaries
- Atria are lined by a simple squamous or cuboidal epithelium
- Air capillaries are lined by simple squamous epithelium
- The air capillaries are responsible for gas exchange
125
Collagen Fibers
- present in the tendon, ligament and organ capsule
- abundant in mature CT
- from fibroblast with synthesis of collagen protein
- > composed of fibrous protein, or collagen
- have a *wavy arrangement*
- stained red with Van Gieson's Methods
- strong and flexible, but inelastic
126
The ovulated egg pathway
1. The ovulated egg is received at the fimbriated end (abdominal ostium) of the oviduct through a constant stream of the peritoneal fluid which enters the uterine tube
2. It is transported towards the uterus through ciliary movement and muscular contraction of the uterine tube
127
Interstitial Implantation
- The embryonic sac penetrates and is embedded into the uterine wall
Ex: guinea pig, carnivores, bats and man
128
*Hematopoisis*
1. Hemocytoblasts (pluripotent stem cell)
- comes from mesenchymal cells
A. Lymphoid Stem Cells
- Lymphocytes come from here
- Thymus -> T-lymphocyte
- NK Lymphocyte
- B lymphocyte -> Plasma cells
B. Myeloid Stem Cells
- Erythrocyte
-> Reticulocyte (Immature RBC)
- Megakaryocyte (blood clotting) -> blood platelets
- Monocyte -> macrophage
- granulocytes -> Band cells -> neutrophils, basophils and eosinophils
129
Partitioning of the Truncus Arteriosus and Bulbus Cordis
- two prominent longitudinal thickenings develop in the endocardial lining of the bulbus and truncus
- two thickenings meet and fuse, thus creating a septum that divides the bulbus and truncus into the aorta and pulmonary trunk
- spiral, or aortico-pulmonary septum
- atrium grows towards the right
- truncus grows towards the left
130
*Conus Arteriosus*
- area of origin for the pulmonary artery
131
Post-capillary Venules
- similar in structure to capillaries, but larger in diameter
- have continuous or fenestrated endothelial cells.
- *They have functional significance in lymphoid organs
- have simple cuboidal epithelium *
132
Cartilage Matrix
- composed of fibers and ground substances containing proteoglycans and GAGs, also includes the adhesive molecules
- the matrix shows marked metachromasia
133
Formation of the Endoderm
- A group of cells from the inner cell mass, or embryonic disc becomes detached from its inner surface to form a new continuous sheet lining the interior of the blastocyst
- This new layer is the endoderm and it’s enclosed cavity is called the primitive gut or archenteron
- The process of detachment of the cells from the inner cell mass is called delamination
134
Dorsal Intersegmental Arteries
- Arise bilaterally between the somites
| - form the intercostal and lumbar arteries
135
Myofibrils
- composed of thick and thin myofilaments
- thick filaments have myosin
- thin filaments have actin, troponin and tropomyosin
- A Band = darker, thick and thin filaments overlap
- I Band = Lighter, Only thin filaments
- > **alternating light and dark bands are responsible for striation**
- each I band is bisected by a darker transverse line, the Z line
- Z line is made up of dense protein lines which connect the actin filaments from adjacent sarcomeres
- Each A band shows a lighter zone in the center, the H band, which is bisected by the M line
- The smallest unit of contractile apparatus is the sarcomere, which is between two adjacent Z lines
136
Endosteum
- only osteogenic layer
- lines the marrow cavity with a single layer of squamous cells
- osteoblast and osteoclasts
137
Septation of the Atrio-ventricular canal
- The dorsal and ventral endocardial cushions fuse together to form the septum intermedium
- > this creates the left and right atrioventricular orifices
138
Leucocytes
- monocytes, lymphocytes and granulocytes (blood cells) that migrate from blood vessels to connective tissue
139
Mucous Gland
- a thick, viscous (mucin) secretion that forms a protective covering
Ex: nasal discharge
140
Ectopic Cordis
- When heart is in an abnormal location
141
Vascular Endothelium
- the peripheral cells of the blood islands join together and form this lining
142
Umbilical Cord
- The unclosed area on the ventral surface of the embryo at the junction of embryonic and extraembryonic territories constitute the umbilical cord
- contains:
1. All fetal, or extraembryonic membranes
2. Yolk sac, or vitelline blood vessels
3. Allantois, or umbilical blood vessels
143
Leucocytes (WBC) Divisions/Differential Leukocyte Count
```
1. Polymorphonuclear Granulocytes:
A. Neutrophils
- dogs have the most out of all the species
- *dogs, cats and horses have a predominance of neutrophils out of other types*
B. Eosinophils
- chickens have the most
C. Basophils
- chickens have the most
2. Mononuclear Agranulocytes:
A. Lymphocytes
- dogs have the least
- cow and sheep have the most
- *cow, sheep, pigs, goats, and chickens have a predominance of this type*
B. Monocytes
- chicken have the most
```
144
Nervous System
- regulates the animals ability to respond appropriately to changes in its environment
- formed by nervous tissue, which consists of neurons and supportive cells called neuroglia
145
Hypomeres
- Innervated by ventral rami of spinal nerves
- Lateral and ventral flexors of thoracic and abdominal musculature
- > hypoaxial muscles
146
*Aortic Arches*
- arises from the aortic sac, the most cranial part of the truncus arteriosus
- 6 pairs of arches develop, but are not all present at the same time
1. 1st and 2nd
- None
- do not develop into anything and regress
2. 3rd
- develop into the common, or internal carotid artery
3. 4th
- Right side: develops into the right subclavian artery
- left side: continues as the descending aorta
4. 5th
- none
5. 6th
- subdivision of the right and left pulmonary artery
- the left 6th retains its connection to the aorta as the ductus arteriosus
147
Chorioallantoic Placentation
- placenta based on fetal membranes involved
- When the allantois fuses with chorion an chorioallantoic is formed
- This is most common type in domestic animals
Ex: ruminant, pig, carnivores and equine
148
What does the early embryonic circulation consist of?
1. A single tubular heart continuous with aortic arches that empty/open into paired dorsal aorta
2. A pair of vitelline arteries from dorsal aortae to the yolk sac
- > derived from the extraembryonic mesoderm
3. A pair of umbillical arteries from dorsal aortae to the allantois
- > derived from the extraembryonic mesoderm
4. Three pairs of venous channels that drain into the sinus venosus
a. the Vitelline Veins (omphalomesenteric)
b. The umbilical veins
c. The cardinal veins
149
Cardiac Longitudinal (head) folding
- Initially, the cardiogenic plate is located cranial to the neural plate
- During head folding, the heart becomes located first in the cervical region and finally in the thorax
150
*Parenchyma vs Stroma of the Thymus*
- parenchyma and stroma are tightly packed in the cortex and loosely arranged in the medulla
1. Parenchyma
- lymphoblasts, lymphocytes and macrophages
2. Stroma
- epithelial reticular cells and its processes
- epithelial reticular cells are stellate shaped with lightly stained oval nuclei
- > their long processes are connected to each other by desmosomes
151
*Eosinophils*
- bilobed nucleus
- cytoplasm contains only specific eosinophilic granules
- > to kill parasitic larvae and inactivate histamine
- *In horses, these eosinophilic granules are extremely large and tightly packed giving a mulberry-like appearance
- play a role in allergic and anaphylactic reaction and in parasitic infestation*
152
Secondary Bronchi of the Lungs
- The secondary bronchi are lined by simple columnar or cuboidal cells
- > NO goblet cells
- The lamina propria is composed of areolar CT
- > NO lymphatic tissue
- The lamina muscularis is interrupted and multidirectionally oriented
- NO cartilage present
153
General Structure of Tubular Organs
- Four Layers
1. Tunica Mucosa (inner layer)
- epithelium
- > glands are derived from this
- Lamina Propria
- > mainly used for connective tissue
- Lamina Muscularis
- > thin sheet
2. Submucosa
3. Tunica Muscularis
- muscles
4. Tunica Serosa, or Adventitia
154
What must spermatozoa undergo to fertilize the oocyte?
- Spermatozoa upon arrival in the female genital tract are not capable of fertilizing the oocyte
- They must undergo the process of capacitation and acrosomal reaction
155
Microglial Cells
- phagocytic cells
- they phagocytize microorganisms (antigen), myelin and other unwanted cellular debris of the nervous tissue of the CNS
- derived from the mesoderm
156
Eisenmenger Complex
1. Dextroaorta
2. I-V septal defect
3. Dilation and hypertrophy of the right ventricle
- same as tetrology fallot, but without pulmonary stenosis
157
*Where do B lymphocytes Mature and where are Epithelial Reticular Cells present?*
1. B-Lymphocytes
- mature in the Cloacal Bursa and Bone Marrow
2. Epithelial Reticular Cells
- only present in the Thymus and the Cloacal Bursa
- > Thymus degenerates, but cloacal bursa does not
158
Blood Vessels of the Lymph Nodes
- The main artery enters the lymph node at the hilus, whereas smaller vessels penetrate the capsule at various sites
- *The post capillary venules are located in the deep cortex (lymphoid organ)
- > are characterized by cuboidal columnar epithelium*
- > lymphocytes from the bone marrow and thymus reach the lymph nodes through post capillary venules
- > these venules join veins in the medullary trabeculae, which in turn empty into large veins that leave the hilus
- -> point of entry point for lymphocytes in the lymph node
159
Ependymal Cells
- line the ventricles of the brain and central canal of the spinal cord
- facilitate the movement of the cerebrospinal fluid
160
*Embryonic Structures -> Adult Structures
1. Truncus arteriosus
2. Bulbus Cordis
3. Primitive ventricle
4. Primitive Atrium
5. Sinus venosus
A. right horn
B. left horn*
```
Gives rise to...
1. Aorta and Pulmonary artery
2. Aorta, Pulmonary artery and Conus arteriosus
3. Left and right ventricle
4. Left and right atrium
5A. Sinus venerum of the right atrium
5B. Coronary Sinus of the right atrium
```
161
*Sternum Development*
- develops independently from the somatic mesoderm (primordia)
- > separately on the ventral side
- The two sternal bands are formed on either side of the midline
- These later fuse to form cartilaginous model of sternum
- Sternebrae later ossify to form a common unpaired body of the sternum which joins the distal end of the ribs
162
Hemocytoblast
- the central cells of the blood islands
| - differentiate into blood cells in the early embryo
163
Stage at Ovulation
- In most domestic animals, a secondary oocyte and first polar body are released, or ovulated from the follicle
- > The secondary oocyte must be penetrated by a spermatozoon before the second meiotic division is completed
- In the horse and the dog, a primary oocyte resting in prophase is ovulated and both meiotic divisions occur after the stimulation of penetration by sperm
164
Microtubules
- the transport of vesicles
- the major component of the centriole and plays a role in cell division
- forms the centriole, cilia and flagellum
- > the centriole acts as a microtubule organizing center
165
Apocrine
- membrane bounded granule, together with the apical cytoplasm and plasmalemma, is released from the apex of the cell
Ex: sweat and mammary glands
166
Meninges
- Dura mater, or pachymenix
- Arachnoid + pia mater = leptomeninges
- Epidural space
- Subarachnoid space for cerebrospinal fluid collection
167
Functions of the Spleen
1. It is a lymphatic tissue involved in immune responses against blood-borne antigens
2. It serves as a filter for blood by removing abnormal, or worn out erythrocytes
3. To store erythrocytes and platelets, as well as iron for reuse in hemoglobin synthesis.
4. Erythropoiesis in fetus.
168
*Reticular Cells*
- reticular cells + fibers = reticular connective tissue
- forms the framework/reticulum (stroma) in the lymphatic organs, except in the thymus and cloacal bursa
- function is formation of the reticular fibers
169
Superficial, or Central Implantation
- The embryonic sac lies in the uterine lumen or cavity
| Ex: ruminants, equines and porcine
170
Epitheliochorial Placenta
- Based on Histological Layers
- Chorionic epithelium is in contact with uterine epithelium
- All six layers are present
Ex: sow and mare
171
*Cutaneous Region of the Nasal Cavity*
- The cutaneous region, or nasal vestibule is lined by stratified squamous keratinized epithelium
- At the mid-vestibule it is thinner and non-keratinized
- In the transitional zone, it is lined by stratified cuboidal, or nonciliated pseudostratified epithelium
- in horses, a nasal diverticulum is lined by integument containing hairs, sebaceous and sweat glands
- > false nostril
- the propria-submucosa of the cutaneous region is rich in blood vessels, nerves, lymphocytes, plasma cells and macrophages
172
Types of Dendritic Cells
1. Follicular Dendritic Cell
- present antigen to B lymphocyte in lymphatic organs
2. Interdigitating Dendritic Cell
- present antigen to T lymphocyte in lymphatic organs
3. **Intraepidermal Macrophage, or Langerhans cell)
- present antigen to T lymphocyte in the epidermis**
4. Veiled cells
- present antigen to T lymphocyte in blood and lymph
173
Immune (Lymphatic) System Function
- protects the body from foreign particles (antigens) and cancer cells
174
Plasma Cells
- abundant in lymphatic tissue
- **spherical, or eccentric nucleus
- > the arrangement of chromatin gives the nucleus a cart wheel-like appearance**
- cytoplasm is intensely basophilic
- develop from B-lymphocytes and produce antibodies
175
Erythrocytes (RBC) Life Spans in
- cows
- horse and sheep
- dogs
- pigs
- cats
1. Cows
- 160
2. Horse and sheep
- 150
3. Dogs
- 120
4. Pigs
- 85
5. Cats
- 75
176
Ventral Aortic Branches
- Supply the splanchnic mesodermal and endodermal tissues of the thoracic and abdominal cavities
- These develop into the broncho-esophageal (one branch to the bronchus and one to the esophagus), celiac and caudal mesenteric arteries
177
Muscular Tissue
- has the property of contractibility
- produces organized movement on contraction
- specialized cells are myocytes
- > muscle fibers, or myofibers
- cytoplasm (sarcoplasm) is eosinophilic because of numerous myofilaments
178
Embryology
- developmental anatomy
- the study of growth and differentiation undergone by an organism from a single fertilized cell into a highly complex and independent living being like its parents
- the study of the changes which an organism undergoes during their development
179
Umbilical Artery
- proximal part contributes to the external and internal iliac arteries
- distal part forms the round ligament of the urinary bladder
180
Causes of Teratology
1. Genetical (#1 cause)
- By mutation, or by inheritance of dominant or recessive genes
- inbreeding may produce genital defect
2. Environmental: Teratogens, or agents that cause abnormal development
A. Physical agents
- X-rays
B. Chemical agents
- Vitamin A deficiency -> microphthalmia in pigs
C. Drugs
- Thalidomide in pups
D. Infectious agents
- Panleukopenia virus in kittens
3. Percents
- 50-60% of abnormal development, the majority of cases, are due to unknown etiology
181
Afferent vs Efferent Neurons
1. Afferent Neurons
- sensory nerve fibers
- arise from unipolar neurons of the dorsal root ganglion
- > forms the dorsal root
2. Efferent Neurons
- motor nerve fibers
- arise from the multipolar neuron of the ventral horn of the spinal cord
- > form ventral root
182
Hemal Node
- small, brown to dark red
- *ONLY present in ruminants*
- The cortex and medulla are not distinct
- No lymph vessels, they receive all their antigens from the blood
- > They respond to the bloodborne antigens.
- In young animals, diffuse lymphatic tissues and a few lymph nodules are present
- In healthy adults, the entire node is generally filled with erythrocytes
183
Ovulation
- is the release of the primary or secondary oocytes from the surface of the ovary
- it is spontaneous (under a 21 day cycle) in most mammals
- In the cat and rabbit ovulation is only induced by coitus
- > induced ovulators
- > every time they have sex ovulation occurs
184
Monocytes
- LARGEST leucocyte
- Nucleus may appear oval, kidney, bean shaped, or horse-shoe shaped
- The cytoplasm is abundant, a grayish blue color, often appears foamy or vacuolated, and has fine azurophilic granules
- *Precursors of tissue macrophages
-> phagocytic*
- The intimate contact of lymphocytes and monocytes is necessary
for maximal immunological response, or cell signaling
185
Epicardium
- a loose CT containing blood vessels, nerves and ganglia and adipose tissue
- lined externally by pericardium
186
Primary Bronchi of the Lungs
- Primary bronchi are lined by pseudostratified ciliated columnar epithelium with goblet cells and intraepithelial mucous glands
- *The lamina propria consists of connective tissue with numerous diffuse and aggregated lymphatic tissue
- > NO lymph nodes in birds
- > Instead there is diffuse, or solitary lymphatic tissue everywhere
- > diffuse/aggregated lymphatic tissue is in other systems of the bird as well*
- The lamina muscularis is disposed primarily as circularly or spirally oriented mass of muscle with some longitudinal bundles as well
- Hyaline cartilaginous rings are present in the initial portions of these bronchi but are replaced by plaques of cartilage
187
Bimelia
- partial or complete duplication of one limb
188
Superfetation
- When a pregnant female ovulates, conceives and produces a second younger fetus
Ex: Pigs
189
Respiratory Bronchioles
- Also called transition zone
- *The focus of most of lung disorders*
- Similar to the terminal bronchioles with the exception that the epithelium is interrupted by alveoli
- Smooth muscle bundles are present beneath the epithelium
- In carnivores, respiratory bronchioles are extensive
- In horses, cows and pigs they are short or absent.
190
Spermiogenesis
- during the spermatogenesis process, the spermatids undergo some metamorphosis to form highly differentiated and potentially motile cells called spermatozoa
- the following changes occur in this phase:
1. The chromatin content of the nucleus becomes concentrated and forms the bulk of the head of the sperm cell
2. The golgi apparatus forms the acrosomal cap over the head
3. The centriole moves away from the anterior end taking on the shape of the ring to encircle the flagellum
4. The mitochondria becomes concentrated around the proximal part of the flagellum which forms the middle piece of the spermatozoa
191
Spermatocytogenesis
1. Primordial germ cells in the testis of the male form spermatogonia
2. The spermatogonia undergoes mitosis (duplication of DNA) resulting in Type A (stem cell) and Type B spermatogonia
3. Type B proceeds and replicates its DNA in interphase of its cell cycle to form primary spermatocytes (duplicated DNA)
4. Type A divides again into one new stem cell(type A) and another cell (type B) which proceeds in spermatogenesis
- the continuity of the stem cell and spermatogenesis are maintained
5. Primary spermatocytes subsequently undergo two successive meiotic divisions
- in the first division, the chromosomes are equally distributed and each member of a homologous pair goes into one of the daughter cells
- The products of Meiosis 1 (reduction division) are called secondary spermatocytes
6. Secondary spermatocytes undergo a second division, or Meiosis 2 (equational division) in which the one member of the homologous pair is now split into two, one going into each of the daughter cells
- the result is called spermatids
7. Spermatids undergo spermiogenesis
192
Fertilization Membrane
- a fertilization reaction develops which prevents further entry of the sperm into the oocyte
- > prevents polyspermy
- most likely as a result of the zona reaction, or chemical changes in the zona pellucida
- > *the oocyte membrane is covered by the zona pellucida which is where the zona reaction occurs*
193
Hemochorial Placenta
- Based on Histological Layers
- The chorionic epithelium is in contact with the uterine blood
- Only three layer are present Ex: primates (man, monkey)
194
Mesenchymal Cells
- Irregularly shaped with multiple processes
- *found near blood vessels*
- can differentiate into other types of cells
195
Blastogenesis
- Secretion from the blastomeres collected within the morula causing a rupture of the zona pellucida and formation of a fluid filled cavity called the blastocoel
- The embryo at this stage is known as the Blastocyst
- There is a marked increase in the total size and change in shape of the embryo
- twin splitting occurs most commonly when the morula becomes the blastocyst
- Cells of the blastocyst are not identical:
1. Embryonic Disc, Inner Cell Mass, or Blastodisc
- cells of the blastocyst congregate in one small area and becomes larger than the rest of the cells
- the embryo develops from here
2. Trophoblast cells
- They facilitate the absorption of nutrients early in development
- cells on the periphery of the blastocyst
196
B-Lymphocytes
- derived from bone marrow in mammals and cloacal bursa in birds
- participate in Humoral Immunity
- > immune complex and antigen inactivation
- produce antibodies (plasma cells)
- > plasma cells are derived from B-Lymphocytes
- some develop into memory cells
- forms 10% of the circulating lymphocytes
197
Epimere
- Innervated by dorsal rami of spinal nerves
- give rise to muscles dorsal of the transverse
processes of vertebrae
-> extensors of the vertebral column, or epaxial muscles
198
Transitional Epithelium
- present in the urinary bladder and urethra
- changes its form based on the state of the bladder
- > increases by 40-50x when it is empty vs when it is full
- > has 5 or 6 layers
199
Notochord Mesoderm
- on the dorsal midline of the body
- notochord induces the ectoderm to form the neural ectoderm, or neural plate
- later the notochord regresses and persists in the adult as the nucleus pulposus of the intervertebral disc
200
Chondroblasts vs. Chondrocytes
1. Chondroblasts
- cartilage producing cells
- form the matrix of the cartilage
- found in growing cartilage
2. Chondrocytes
- located in the lacuna
- cartilage cells in the resting state, or inactive
201
Lymphocytes
- small round cells with a compact spherical nucleus and thin rim of cytoplasm
- Three Types:
1. B-Lymphocytes
2. T-Lymphocytes
3. Natural Killer (NK) cell
202
*Repair/Regeneration of Muscles: Cardiac, Skeletal and Smooth Muscles*
1. Cardiac Muscles
- have no regenerative capacity after birth
- the damage of fibers is replaced by proliferation of connective tissue forming myocardial scar
2. Skeletal Muscle
- limited regeneration, mainly due to satellite cells which are inactive myoblasts and become activated after injury
3. **Smooth Muscles
- are capable of active regeneration by mitosis of smooth muscle cells**
203
Simple Squamous Epithelium
- a single layer of thin, flat and scale-like cells
- spherical or oval bulging nucleus
- *found lining the blood vessels*, glomerular capsule and mesothelium (pleura and peritoneum)
204
Synapse
- where contact occurs between two neurons, or a neuron and other effector cell
- formed by a presynaptic terminal (telodendron), synaptic cleft (intercellular space) and post synaptic terminal on dendrites (gemmules)
205
Ectopic Implantation
- a fertilized ovum may be lost in the peritoneal cavity and becomes implanted into the peritoneal surface
- early embryonic death usually follows
206
Changes after birth involving the atrium
- Oxygenated blood returning to the left atrium causes increased blood pressure on the left atrium which will bring both the septum primum and secundum in close contact and ultimately fuse
207
Rouleaux Formation
- erythrocytes that adhere to each other and form long chains resembling stacks of coins
- prominent in Horses and cats
- intermediate in dogs and pigs
- rare in ruminants
208
Cardiac Transverse, or Lateral Folding
- during the head and lateral folding, the left and right cardiac tubes fuse together and become ventral to the foregut
209
Blood Vessels of the Spleen
1. Splenic Artery
- enters the capsule and extends into the trabeculae as trabecular arteries
- as it leaves the trabeculae, it is called the artery of the white pulp and becomes heavily infiltrated with lymphocytes (PALS)
2. Branches of the white pulp artery
- continues to feed capillary beds in the nodule and terminates in the marginal
zone, or enters the red pulp as pulp arterioles
3. *Pulp Arteriole
- continues into distinctive structures called sheathed capillaries, or ellipsoids
- sheathed capillaries, or ellipsoids are surrounded by macrophages
-> sheathed capillary is ONLY present in the spleen*
210
Nucleus Components
- is bounded by a nuclear envelope
- contains chromatin, nucleolus/nucleoli, and a nuclear matrix
- mammalian erythrocytes lack nuclei
211
Endotheliochorial Placenta
- Based on Histological Layers
- Chorionic epithelium is in contact with the endothelium of the uterine blood vessels
- Four layers are present
Ex: Carnivores (dog, cat)
212
Vascularization of the Thymus
- arteries penetrate the parenchyma at the corticomedullary junction by way of the CT septa, and form a capillary network in the cortex
- the capillary network drains into the post capillary venules in the medulla which join the vein in the CT septa
- *The blood thymic barrier is formed by the capillary endothelium, the perivascular space and a sheath of epithelial reticular cell process
- > the barrier prevents circulating antigen from reaching the thymic cortex where T-lymphocytes are being formed
- Thymus has no afferent lymphatic vessels
- It is particularly active in young animals and involutes after puberty*
213
Heinz Bodies
- are pathological
- *oxidized, or denatured Hb (hemoglobin)
- felines are most susceptible
- > 2-3% normal in felines
- more in case of toxicity are onions and Acetaminophen
214
Spongy Bone
- mainly occurs in the interior of the epiphyses
- consists of delicate bony plates and spicules which run in various directions
- below the extremities
215
Polydactyly
- is the presence of one or more extra digits
| - It is a genetic defect of cattle, sheep, pigs, and occasionally horses.
216
Microfilaments
- mainly composed of actin and myosin filaments for cellular contraction in muscle cells
- membrane bound activity such as endocytosis and exocytosis
217
Flagellum
- a single long cilium
- only one in each cell
- mainly present in spermatozoa
- composed of microtubules
218
Lymph Nodes
- Filter lymph before returning it to the blood stream
- situated along lymph vessels
- > afferent (carry lymph to) and efferent vessels (carry lymph out/exit)
- *surrounded by a capsule composed of Dense irregular CT with a few elastic fibers*
- trabeculae extend from the capsule into the parenchyma as irregular septa
219
Hemidesmosomes
- they connect the cells from the extracellular matrix protein
- > similar to the half desmosome
220
Teratology
- study of abnormal development
| - The branch of embryology concerned with the study of malformations, or abnormalities
221
Aortic stenosis
- Aortic stenosis with poststenotic dilation of the aorta, left ventricular dilation, hypertrophy and left atrial dilation
222
*Basement Membrane*
1. Basal Lamina
- > secreted by the cell membrane
- Lamina Lucida
- Lamina Densa
2. Reticular Lamina
- composed of reticular fibers
223
Sperm and ovum Viability
- in most species, the sperms remain viable within the female genital tract (sperm viability) for 1-2 days
- they may survive up to 6-7 days in the horse and the dog
- up to 32 days in the fowl and 70 days in the turkey
- > avian vaginas have sperm host glands that allows the sperm to live from a month to almost 3 months
- ovum viability is generally 24 hours
224
Yolk Sac
- Develops from the extraembryonic splanchnopleure
- In most mammals, it develops and forms temporary contact with the chorion and is called the Choriovitelline placenta
- it regresses immediately, but remains functional for sometime in dogs and horses
- > the first quarter of pregnancy
- It is well developed in birds
- > develops in the blood vessels and is termed vitelline vessels
- -> they absorb nutrition from yolk sac
225
Embryo
- the developing offspring during the embryonic period
226
Blood Islands
- the blood cells initially develop as blood islands
- blood islands are aggregates of the splanchnic mesodermal cells
- they grow and join to form blood vessels
- differentiate into vascular endothelium, or hemocytoblasts
227
Labyrinthine Placenta
- based on branching of the chorionic villi
- When there is complicated and anastomotic branching of the chorionic villi
Ex: Carnivores and primates
228
Cortex of Lymph Nodes
- parenchyma and stroma are tightly packed here
- the outer cortex consists of primary and secondary lymphatic nodules separated by diffuse lymphatic tissue
- the deep cortex is composed of diffuse lymphatic tissue
1. Primary Lymphatic Nodules
- consists of reticular CT with small, tightly packed lymphocytes
2. Secondary Lymphatic Nodules
- contain germinal centers which have a dark and light zone
-> dark zones are large lymphocytes with intense mitotic
activity
-> light zones are small lymphocytes with few mitotic cells
229
Air Sacs
- most birds have eight air sacs
- > unpaired cervical and clavicular
- > Paired cranial thoracic, paired caudal thoracic, paired abdominal air sacs
- The air sacs are lined by simple squamous, or cuboidal epithelium
- *They are poorly vascularized and do not participate in gaseous exchange
- > NO blood vessels in the air sac*
230
Thrombocytes, or Platelets
- Major role in blood coagulation
- Discoid, spherical, or elongated cells and may appear individually or in clusters
- responsible for platelet adhesive property
- Microfilament and microtubules are present beneath the plasmalemma
- > responsible for platelet shape change and clot reaction
231
Erythrocytes (RBCs) Shape and Size In Different Species
- Mature erythrocytes are non-nucleated biconcave discs
1. Shape
A. Goats and Pigs
- flattened discs
- non-nucleated
B. Camel and Llama
- elliptical shape, but non-nucleated
*C. Reptiles, Amphibians and Birds
- elliptical shaped and nucleated*
2. Size
A. Dogs
- largest erythrocytes
B. Goats
- smallest erythrocytes
232
*Choriovitelline, or Yolk sac Placentation*
- placenta based on fetal membranes involved
- The yolk sac may combine with the chorion to form choriovitelline placenta
Ex: In the horse and the dog both the chorioallantoic and
Choriovitelline placenta is present in the first quarter of gestation
-> Later the Choriovitelline regress and only chorioallantoic remains
-> in all other animals the choriovitelline regresses immediately
233
Further Development of the Embryo
- The cranial region grows rapidly forming a relatively large head which is flexed ventrally due to the development of the cervical flexure in the future neck region
- The external structures of the eye, ear and nose appear
- The limb buds appear as single paddle-shaped outgrowth of the somatopleure of the body wall at the sites of the future pectoral and pelvic girdles
- The early age of the embryo is expressed by the number of somites, later crown-rump (CR) length is used to determine the approximate age of the embryo
234
Dendrites
- highly branched processes (tree like)
- have numerous synaptic contacts from other neurons
- devoid of golgi complex
- the synaptic sites are distinguished by a thick band of electron-dense material associated with plasmalemma
- some neurons have dendritic spines (gemmules) which consist of a membrane sac containing dense material
235
Natural Killer (NK) Cells
- derived from bone marrow
- do NOT require cloacal bursa/thymus for further
development
- Innate Immune System
-> lysis of infected cell
- *have a non-specific role in immunity
-> mainly
protection against tumor cells*
- lacks an antigen receptor which is typical in comparison to B, or T-Lymphocytes
- forms 10-15% of blood lymphocytes
236
*Azygos Vein Species Difference*
- the supracardinal vein develops on both sides into the left and right azygous vein
1. Horse and the dog
- only the right azygous vein persists
2. In the pig
- only the left azygous vein persists
3. In ruminants
- both the left and right azygous veins persist
237
Intermediate Filaments
- provides mechanical stability
- keratin filaments (skin)
- desmin filaments (muscle cells)
- neurofilaments (nerve cells)
- glial filaments (schwann celels)
238
*Neurolemmocytes, or Schwann Cells*
- around axons in the peripheral nervous system
- > ONLY supporting cell in the PNS
- myelin production in PNS
- the myelin sheath is interrupted by Nodes of Ranvier
- the myelin sheath between two adjacent nodes is called an internode which represent a segment wrapped by one Schwann Cell
239
Reticular Fibers
- form the framework of the lymphatic and endocrine organs
- form delicate, flexible networks around capillaries, muscle fibers and nerves
- argyrophilic, or argentaffin fibers are stained with silver impregnation or PAS
240
Septum Transversus
- the mesoderm caudal to the cardiac tube forms this
| - future diaphragm
241
*Organization of Skeletal Muscles*
1. Each muscle fiber is surrounded by the endomysium
- > basal lamina and reticular fibers
2. Bundle of Muscle Fibers is surrounded by perimysium
3. The muscle at the gross anatomical level is surrounded by epimysium
242
Pericytic, or Collecting Venules
- in which pericytes form the continuous layer plus collagen fibers form a thin tunica externa
243
Development of the Musculoskeletal System
- Bone and muscle tissue develops from the mesoderm
- Mesenchymal cells may differentiate
in many different cell types:
-> Fibroblasts
-> Chondroblasts
-> Osteoblasts
-> Myoblasts
-> Adipocytes
-> Endothelial cells
-> Mast cells
244
Respiratory Region of the Nasal Cavity
- caudal two-thirds of the nasal cavity
- Propria-submucosa is highly vascular (cavernous stratum) containing serous, or mixed nasal glands, numerous nerves, and lymphatic nodules
- *epithelium is lined by ciliated pseudostratified columnar epithelium which has four types of cells*
1. Ciliated Cells
- motile cilia, or numerous microvilli
2. Secretory Cells
- serous, or mucous (goblet cells)
3. Brush Cells
- thick microvilli associated with sensory receptors
4. Basal Cells
245
Cerebrospinal Fluid
1. Produced by the choroid plexuses in ventricles
3. *By exiting through the Lateral Aperture it enters the Subarachnoid Space*
4. From here it goes to Venous Sinus through Arachnoid Villi.
- It provides physical protection to the brain and spinal cord.
- Ventricle -> lateral apertures -> subarachnoid space -> venous sinuses
246
Nerve Cell Body
- called a perikaryon
1. Nucleus
- is located centrally, except in the autonomic ganglia where there is an eccentrically placed nucleus
- prominent nucleolus
- sex chromatin, or barr body in cats and rodents
2. Cytoplasm
- *presents chromatophilic substances, or Nissl Substances (aggregation of rER and ribosomes)*
- neurofilaments (intermediate filaments)
- microtubules
- prominent golgi and mitochondria
- lipofuscin (ageing pigment)
247
Types of Synapses
1. Axo-somatic Synapse
- axon with a nerve cell body
2. Axo-dendritic Synapse
- axon with a dendrite
3. Axo-axonic
- axon with axon
248
Smooth Muscle
- spindle shaped and non-striated
- weak and slow involuntary contractions
- thin myofilaments are numerous
- > contain actin and tropomyosin ONLY! (lack troponin)
- thick myofilaments are sparse
- > Contain only myosin
- **Dense Bodies in the cytoplasm and cell membrane serve as anchor sites for myofilaments**
- > intermediate filaments further link the dense bodies into a meshwork array
- numerous vesicles are present along the cell membrane and play a role in Calcium
249
Superfecundation
- Impregnation by successive acts of coitus, of two or more ovum that were liberated at approximately the same time, by two or more different males
- fertilized by the sperm of two or more different males
- period of heat is prolonged
Ex: Cats and dogs
250
Tight Junctions
- have anastamosing ridges of transmembrane proteins that seal neighboring cells together in a belt-like fashion (loop)
- found in the apical intestines
251
Amorphouse Ground Substance
- composed of proteoglycans, glycosaminoglycans (GAG), and interstitial fluid
- Proteoglycans are formed by covalently linking GAGs to a protein core.
252
Terminal Capillaries of the Spleen: 3 Theories
- three theories exist regarding the junction of the terminal capillaries with the venous system
1. Closed Theory
- the terminal capillaries open directly into the splenic sinuses, or venules
2. Open Theory
- the terminal capillaries open into the spaces between the reticular cells of the red pulp and then enter the venous sinuses through the slit in
their walls
3. Third Theory
- proposes the existence of both forms, depending on the
physiological state
- when the spleen is distended, the open form predominates
- when the spleen is contracted, the closed form predominates
253
Simple Columnar Epithelium
- consists of tall and narrow cells
- oval nucleus located near the base of the cell
- mainly present in the intestine
254
Holocrine
- entire cell is released as the secretory product
| Ex: sebaceous gland
255
Spinal Cord
1. Grey Matter:
- nerve cell bodies (H shaped)
A. Ventral Horn Grey Matter
- Efferent Neurons
*B. Dorsal Horn Grey Matter
- Interneurons*
C. Lateral Horn Grey Matter
- Autonomic Neurons
2. White Matter
- processes (peripheral)
- dorsal, ventral and lateral funiculi
- ascending and descending tracts
3. Central Canal lined by ependymal cells
4. Dorsal median septum and ventral median fissure
256
Osteoblast
- bone forming cells
| - secretes osteoid, or organic matter of bony matrix, which is subsequently calcified by the deposition of calcium salts
257
Myoepithelial Cells
- are interposed between secretory cells and basement membranes
- responsible for contraction
- when contracted, these cells force the secretory product into the duct system
258
What does mammalian erythrocyte lack?
- nuclei
| - ribosomes
259
Functions of the Respiratory System
1. Gas Exchange
- the major function
- secondarily involved with acid-base balance
2. Cooling
- evaporative water loss
- > especially important in birds
- > control of water loss is equally important
3. Chemoreception
- specially developed areas
- taste buds
4. Vocalization
- the larynx is organ of voice production
260
Establishment of Body Form
- During the process of gastrulation, the ovoid embryonic disc is converted into elongated flat disc
- In the establishment of the body form, the most important aspect is the transformation of flat disc into roughly curved cylindrical embryo
261
Gastrulation
- The embryonic disc, or inner cell mass becomes rearranged to form three separate layers called germ layers
1. Ectoderm
- outermost layer
2. Mesoderm
- middle layer
3. Endoderm
- innermost layer
262
Hematopoisis
- bone marrow is the primary site of hematopoisis, or blood cell formation in adult animals
- During early embryonic life, it occurs in the wall of the yolk sac.
- Later in embryonic life, hematopoitic cells migrate from yolk sac to fetal liver.
- Subsequently cells from liver migrate to the bone marrow, spleen, lymph nodes and thymus of the embryo.
263
Periosteum
- contains BOTH fibrous and osteogenic layers
- it is absent on articular surfaces
- tendons and ligaments are embedding in the bone matrix as perforating (Sharpey's) fibers
264
*Epithelial Reticular Cells*
- form the stroma/framework of the thymus and the cloacal bursa
- > in the thymus because it regresses
- *their long cell processes are connected to each other by desmosomes and make a network*
- Do NOT produce reticular fibers
- > these cells are a process, NO FIBERS
- stellate shaped
265
Paraxial Mesoderm Further Development of Somites
1. Sclerotome
- vertebral column
- ribs
2. Myotome
- muscles
- epimere and hypomere
- > epaxial and hypoaxial muscles
3. Dermatome
- dermis
- corium and subcutis of the skin
266
Results of Body Folding
1. The embryonic disc is converted from a flat-disc into a curved cylindrical structure
2. The extraembryonic germ layers develop into extraembryonic or fetal membranes which surround the cylindrical embryo
3. The lateral and ventral body walls develop by the folding of the intraembryonic somatopleure, whereas the extraembryonic somatopleure constitute the amnion and chorion
4. The gut is formed by the intraembryonic splanchnopleure, whereas the extraembryonic splanchnopleure forms the yolk sac and allantois
5. The yolk sac communicates with gut through vitello-intestinal duct or yolk stalk
267
Alveolar Ducts and Alveolar Sacs
- Alveolar ducts arise from the respiratory bronchiole and terminates in clusters of the alveoli called alveolar sac
- *Lined by simple cuboidal or squamous epithelium*
- The subepithelial CT contains smooth muscle cells and very few elastic fibers
268
Chondrodystrophy
- abnormal interstitial growth of cartilage
- premature cessation of growth that leads to the shortening of bones, especially limbs
Ex: weiner dogs, daschunds
269
Changes after birth For
- foramen ovale
- ductus venosus
- ductus arteriosus
- umbilical vein
- umbilical artery
1. Foramen Ovale
- Fossa ovalis
- increased pressure on the left atrium
2. Ductus Venosus
- Ligamentum Venosus
- liver function
3. Ductus Arteriosus
- Ligamentum Arteriosus
4. Umbilical Vein
- round ligament of the liver
4. Umbilical Artery
- round ligament of the bladder
270
Formation of the Ectoderm
- The cells in the upper layer of the inner cell mass soon undergo considerable expansion and constitute the ectoderm
- The covering of the trophoblast cells over the embryonic ectoderm now disappears
271
*Primitive Atrium vs Sinus Horns*
- primitive atrium grows faster than the sinus horns and the right and left horns are incorporated into the right atrium
- Right horn forms the sinus venerum
- left horn forms the coronary sinus
- the left atrium develops mainly by the primitive atrium
- > initially, a single venous vessel develops into the pulmonary veins
272
Cleavage
- Cleavage is the beginning of the development of a multicellular organism.
- It is a series of mitotic cell divisions without an overall increase in the size of the zygote, which is still enveloped by zona pellucida
- It is a process of segmentation or fractionation divisions, resulting in the production of many smaller cells called Blastomeres
273
Multipolar, Bipolar and Unipolar Neurons
1. Multipolar Neurons
- one axon and several dendrites
- brain, spinal cord and autonomic ganglia
2. Bipolar Neurons
- one axon and one dendrite
- retina
3. Unipolar Neurons
- one process (axon) that bifurcates into central and peripheral branches
- > pseudopolar neuron
- sensory, or dorsal root ganglia
274
Red and White Muscle Fibers
1. Red
- slow twitch
- smaller, rich in myoglobin and mitochondria
2. White
- fast twitch fibers
- larger and have few mitochondria
275
Placenta of the Sow and Mare
- Diffuse
- Epitheliochorial
- Villus
- Nondeciduate
276
Blood Vessel Types
1. Arteries
2. Veins
3. Capillaries and Sinusoids
4. Microvasculature
- comprised of arteriole, capillaries and venules
277
Functions of the Cell Membrane
1. Selectively permeable
2. Receptor sites for antigen (foreign body) recognition and immunological mechanisms (phagocytosis)
3. Receptor sites for hormone activated cellular events
278
Cotyledonary Placenta
- based on the shape
- Tufts of the chorionic villi (cotyledons) attach to endometrial prominences (caruncle)
- The combined fetal (cotyledon) and maternal (caruncle) structures form Placentomes
Ex: ruminants
279
Septation of the Atrium
1. Septum Primum
- forms the foramen primum and foramen secundum
2. Septum Secundum
- thicker and more rigid than the septum primum
- forms the foramen ovale
- > a window that remains due to incomplete formation, a space
3. Original atrium
- development of the pectinate muscles, or the right auricle
280
T-Lymphocytes
- derived from thymus
- Adaptive Immune System
- > lysis of infected cell
- participate in cell-mediated immunity
- some cells form memory cells
- forms 75% of the circulating lymphocytes
281
- Respiratory System Components
- Nasal cavity
- Nasopharynx
- Larynx
- Trachea
- Lungs
- > air condition and gas exchange regions
282
Cloacal Bursa
- Sac like diverticulum of proctodeum present only in birds
- This is an organ of immune system and B-lymphocytes differentiate here
- It has tall mucosal folds called as plicae which have many lymphoid follicles in them.
- *Epithelial reticular cells and its processes form stroma where B-lymphocytes matures*
- Lined by pseudostratified columnar epithelium.
- Cloacal bursa was earlier known as bursa of Fabricius.
283
Skeletal Muscle Development
- skeletal muscle is derived from the
paraxial mesoderm
- *The myotome part of somites develop into muscles of the axial skeleton, body wall and limbs*
- Mesodermal cells of the myotomes differentiate into single nucleated myoblasts that fuse to form multinucleated muscle cells
284
Blood
- functions for transportation and thermoregulation
- cellular component has erythrocytes (RBCs), thrombocytes (platelets), leucocytes (WBCs)
- 8-11% of the total body weight in large animals
- 6-7% in lab animals
- consists of:
1. blood cells
- stained by Wright's Stain
2. plasma
- protein rich fluid component
285
Results of Sperm Penetration
- the 2nd meiotic division of the oocyte is complete and produces an ovum and a second polar body
- after the fertilization membrane develops...
- the nuclei of the female and male germ cells now swell and are termed as male and female pronuclei
- > these now fuse together reconstructing the diploid chromosomal number and creating a new individual, or zygote
286
Larynx
- voice box
- *The laryngeal mucosa is lined by stratified squamous non-keratinized epithelium*
- Caudal to the vocal fold it gradually changes to typical respiratory epithelium (TRE)
- The epithelium over the epiglottis may contain taste buds
- *Thryoid and Cricoid cartilages contain hyaline Cartilage
- Epiglotiss and Corniculate processes of the Arytenoid Cartilage contain elastic cartilage*
- initially, the propria-submucosa is a dense irregular CT which gradually changes to loose CT
- Diffuse lymphatic tissues, or solitary lymphatic nodules are frequently observed
- mixed glands are present in the propria-submucosa of the caudal part of the larynx
287
Nerve Repair Steps
- nerves have a limited regeneration capacity
1. Nerve Fiber Injured
- Nissl bodies move to the site of injury
- nerve fiber distal to the injury degenerates
- muscle fibers show atrophy
2. Nerve fiber regeneration in process
- Schwann cells proliferates
- Axon grows
- Muscle fiber atrophied
- Debris is phagocytosed by macrophages
3. Nerve fiber regeneration successful
- Muscle fiber is regenerated
- Nissl bodies returned to the neuronal cell body
288
Histological Relations in Placenta
- Histological classification is based on the number of layers separating the maternal blood from fetal blood
- 6 layers separate the fetal blood from the maternal blood
1. On the Fetal Side
- Chorionic (villous) epithelium
- Fetal (villous) connective tissue
- Endothelium of the allantois blood vessels
2. On the Maternal Side
- Uterine epithelium
- Uterine connective tissue
- Endothelium of the blood vessel of uterus
289
Changes after birth involving the lungs
- after birth the lungs become functional and blood flows through the pulmonary arteries and closes the ductus arteriousus
290
Merocrine
- secretory granules enclosed in a membrane
- discharged by exocytosis
- most common
291
Serous Gland
- a thin and watery secretion
| Ex: parotid salivary glands, or sweat glands
292
Elastic Arteries Structure
1. Tunica Intima
2. Internal Elastic Membrane
*3. Tunica Media
- thickest layer
- predominance of elastic laminae (fibers)
- consists of concentrically arranged fenestrated elastic laminae
with smooth muscles between the laminae*
4. External Elastic Membrane
5. Tunica Externa (tunica adventitia)
- *contains vasa vasorum and nervi vasorum
- collagen and elastic fibers*
293
Susceptibility Periods to Teratology
```
- The period of maximum sensitivity to abnormal development is the embryonic period
Most sensitive
1. Embryonic Period
2. Fetal Period
3. Pre-Embryonic Period
Least Sensitive
```
294
Neurons
- structural and functional units of the nervous system
- composed of the nerve cell body (perikaryon) and neuronal processes (axon and dendrites)
- PNS has afferent and efferent neurons
- > afferent = from PNS to CNS
- > efferent = from CNS to PNS
295
Vertebral Column Development
- migration of the sclerotome
- vertebrae develop from the sclerotome, or the most medial portion of a somite
- sclerotome cells proliferate and migrate medially to surround the neural tube and the notochord
- as a result they form a condensed mesenchyme model of the vertebra
296
Placenta of the Dog and Cat
- Zonary
- Endotheliochorial
- Labyrinthine
- Deciduate
297
**Lungs of the Avian Respiratory System Order of Components**
1. Trachea
2. Primary Bronchus
3. Secondary Bronchus
4. Parabronchus
5. Air Capillaries
298
Nasopharynx
- *Lined by pseudostratified ciliated columnar epithelium with goblet cells*
- The propria-submucosa is composed of loose C.T. containing glands.
- Lymphatic nodules are prominent in the dorsal portion of the nasopharynx, where they aggregate as the pharyngeal tonsil.
299
Corpus Luteum
- important endocrine structure
- the ruptured follicles are converted into the CL under hormonal influence
- Secretes progesterone which facilitates the implantation and maintenance of the conceptus
- > causes uterine changes
300
Syrinx
- The syrinx (avian larynx) is located at the junction of trachea and bronchi
- It is an inverted ‘Y’ shaped structure (bifurcation)
- The tympanic membranes, which vibrate during production of the sound, are lined by stratified squamous epithelium
301
* Adult Structure -> Embryonic Structure
1. Aorta
2. Pulmonary Artery
3. Conus Arteriosus
4. Left ventricle
5. Right ventricle
6. left atrium
7. Right atrium
8. Sinus venerum of Right atrium
9. Coronary Sinus
- derived from....
1. Truncus arteriosus and bulbus cordis
2. Truncus arteriosus and bulbus cordis
3. Bulbus Cordis
4. Primitive ventricle
5. Primitive ventricle and bulbus cordis
6. primitive atrium
7. primitive atrium and sinus venosus
8. right horn of the sinus venosus
9. left horn of the sinus venosus
302
Deciduate
- Based on Loss of Maternal Tissues at Parturition
- There is extensive loss of maternal tissue at the time of parturition due to complicated interlocking of fetal and maternal tissue
Ex: carnivores and primates
303
Oogenesis
1. In the ovary of the female fetus, each primordial germ cell forms oogonium which are mitotically active up to parturition
2. The oogonium replicates its DNA in interphase and enters the prophase of its first meiotic division
- the female germ cells are now called primary oocytes
3. The first meiotic division is arrested in the diplotene stage of prophase 1 and will resume at puberty
- at birth, all primary oocyte are in the diplotene stage of prophase 1 (resting Stage)
4. After puberty, a number of primary oocyte in each ovarian/estrous cycle resume its first meiotic division and leads to the formation of two daughter cells
- secondary oocyte and first polar body
- genetic material is equally divided, but cytokinesis (cell cytoplasm division) is unequal during the division
- the cell that received most of the cytoplasm is the secondary oocyte and the other smaller daughter cell is called the first polar body
5. The secondary oocyte is capable of completing the second meiotic division only after the stimulus of penetration of the sperm
6. The product of the second meiotic division is an ovum and a second polar body
- once again cytokinesis is unequal and the ovum retains most of the cytoplasm
304
What makes the cell membrane, or plasmalemma trilaminar?
- an outer and inner electron-dense lamina separated by an intermediate electron-lucent lamina
305
Hematoxylin and Eosin
1. Hematoxylin
- basic dye
- stains the nucleus (which is acidic, or basophilic) purple, or dark blue
2. Eosin
- acidic dye
- stains the cytoplasm (which is basic, or acidophilic) pink, or red
306
Olfactory Region of the Nasal Cavity
- Lined by ciliated pseudostratified columnar epithelium that has three types of cells.
- Mixed olfactory glands in the propria-submucosa.
- the dorsocaudal portion of the nasal cavity occupied by the ethmoidal labyrinth
1. *Neurosensory olfactory cells
- are bipolar cells (neurons) with dendrites extending to the lumen and axons reaching the olfactory bulb of the brain
- present in the retina and the olfactory region*
2. Sustentacular cells
- columnar cells.
3. Basal cells
307
Location Of: Simple Straight Tubular Gland, Simple Coiled Tubular Gland, and Simple Branched Tubular Gland
1. Simple Straight Tubular Gland
- large intestine
2. Simple Coiled Tubular Gland
- sweat gland
3. Simple Branched Tubular Gland
- stomach
308
Cardiac Valves
- are endocardial folds that consist of a central layer of dense CT covered by endothelium
309
Semen, or Ejaculate
- sperm + secretions of the accessory sex glands make up semen
- > spermatogenesis lasts about 50-70 days and another 2-3 weeks may be required for passage through the epididymis
310
Meninges and Cerebrospinal Fluid
1. Meninges
- layers that surround the central nervous system and the roots of the peripheral nerves
2. Cerebrospinal Fluid
- present in the cavities of the brain and spinal cord and in the space within the meninges
311
Cortex vs Medulla of the Thymus
1. Cortex (peripheral dark zone)
- outer layer, more compact
- lymphoblasts and lymphocytes predominate in the meshes of the peripheral epithelial reticulum
- > here they undergo mitotic divisions producing small lymphocytes that mainly occupy the deep cortex
2. Medulla (central light zone)
- inner layer, less compact
- *contains Hassal's, or thymic corpuscles which are concentrically arranged, flattened, degenerated epithelial reticular cells*
- macrophages containing phagocytosed lymphocytes are abundant here
- larger amount of epithelial reticular cells
312
*Sensory Ganglia vs Autonomic Ganglia*
1. Sensory, or Dorsal Root Ganglia
- *contain cell bodies of unipolar neurons with a single axon*
- associated with cranial nerves, or the dorsal root of the spinal nerve (spinal ganglia)
- each cell body is tightly encapsulated by ganglionic gliocytes (satellite cells)
2. Autonomic Ganglia
- *accumulations of multipolar nerve cell bodies along the course of autonomic nerves*
- each cell body is loosely encapsulated by ganglionic gliocytes (satellite cells)
313
Spermatogenesis
- the process of development of sperm
- takes place in the testis after puberty
- divided into spermatocytogenesis and spermiogenesis
314
Mast Cells
- common in loose CT
- abundant around blood vessels
- when stained with toluidine blue, the metachromatic granules stain a different color (red/purple)
- produce heparin (anticoagulant) and histamine (vasodilator to increase permeability)
- > histamine is active during an allergic reaction
315
Muscular System Development
```
- Three types of musculature (skeletal, cardiac and smooth muscle) are formed
during embryonic development
- muscles develop from mesoderm
1. Skeletal Musculature
- derived from the paraxial mesoderm
-> myotome of the somite
2. Cardiac and Smooth Muscles
- develop from the splanchnic mesoder
-> gut and respiratory tract
- Exception: the muscles of the iris (sphincter and dilataror pupillae) originate from the optic cup ectoderm
```
316
*What are the Components of the Air-Blood Barrier?*
1. Pneumocyte I Cell
2. The Basal Lamina of Pneumocyte I and the Basal Lamina of Capillary Endothelial Cells, separated by a sparse CT
- These two basal laminae may be fused
3. The Capillary Endothelial Cell.
4. The Plasmalemma of a Red Blood Cell
317
Persistent Truncus Arteriousus
No spiral septum, so the aorta and pulmonary arteries are not formed
318
Pericardium
1. Visceral Pericardium
- simple squamous epithelium
- closely attached with epicardium
2. Pericardial Cavity
- space between the parietal and visceral pericardium
- contains serous fluid lubricating the surfaces for frictionless cardiac movement
- serous pericardial fluid
3. Parietal Pericardium
- first mesothelium layer
- then collagen and elastic fibers
319
Conceptus
- used to describe the embryo/fetus and its membranes
320
Muscles of the Body Wall
- Myogenic cells are separated into a smaller dorsal portion (epimere) and a larger ventral portion called the hypomere
321
Lungs
- Covered by visceral, or pulmonary pleura
- The pleura consists of simple squamous epithelium and a layer of connective tissue which is continuous with that of interalveolar septa
- *The pleura is thickest in ruminants and thinnest in the dog and cat*
- The lungs are small and do not change volume during respiration
- Lung is divided into:
1. Intrapulmonary Conducting Airways
- Bronchi and Bronchioles
2. *Gas Exchange Area (parenchyma)
A. Respiratory Bronchioles
B. Alveolar Ducts and Alveolar Sacs
C. Alveoli*
322
Holoblastic Cleavage
- total cleavage
- in mammals
- a small amount of yolk is present and equally distributed
- > isolecithal egg
- there is a complete division of the zygote
323
Eccentric Implantation
- The embryonic sac lies in a fold or pocket of uterine wall Ex: rat and squirrel
324
Astrocytes
- star-shaped cells with multiple radiating processes that contain glial filaments
- provides structural support by binding neurons to capillaries and to the pia mater
- largest and most numerous
- *in grey matter is protoplasmic astrocytes
- in white matter is fibrous astrocytes*
- astrocyte processes terminate at an expansion called end feet
- > they cover the endothelium of blood vessels within the brain and spinal cord and form the blood brain barrier
- > helps to maintain the flow of oxygen and nutrients in the CNS
325
*Multinucleated vs. Multilobulated*
1. Multinucleated
- osteoclasts and skeletal muscles
2. Multilobulated
- Barr Body, or sex chromatin in the female
- Neutrophil
326
Placenta
- As a result of implantation, fetal membranes are embedded into the uterine wall and establish the contact with fetus and mother
- Thus the composite structure formed by the close contact of fetal membranes and maternal tissue for the purpose of physiological exchange between the fetus and mother is termed placenta
- Nutrients and oxygen from the maternal blood diffuses from the uterine artery into the umbilical vein
- Excretory products from the embryo diffuse from umbilical artery into uterine vein
327
Spinal Nerve
- formed by the union of dorsal and ventral roots
| - whenever a nerve is divided, it carries both afferent and efferent fibers
328
Differentiation of Different Cells
```
1. Blood Cells (pluripotent stem cell) proliferate into
A. Lymphoid Stem Cells
- T cells
- B cells
-> plasma cells that produce antibodies
- Natural Killer Cells
B. Myeloid Stem Cells
- granulocyte
-> neutrophils, eosinophils, and basophils
- monocyte
- megakaryocytes
-> thrombocyte (platelets)
- erythrocytes
```
329
Elastic Cartilage
- same as the hyaline cartilage, but has a large amount of elastic fibers present in the ground substance
- *present in the pinna of the ear and the epiglottis*
330
Vomeronasal Organ
- function is in sexual behavior by detection of odor of the opposite sex
- a paired duct, located on either side of the nasal septum which opens into the incisive duct
- is crescent shaped with a medial concave and lateral convex mucosa
- > medial has pseudostratified columnar epithelium and consists of neurosensory, sustentacular and basal cells
- > lateral has pseudostratified columnar epithelium and consists of ciliated and non-ciliated columnar, goblet and basal cells
- propria-submucosa contains vomeronasal glands (mucous, or mixed) and vomeronasal cartilage (hyaline) that encloses the organ
331
Bone Repair
- Osteogenic (osteoblast) cells of the periosteum and endosteum proliferate
- Those nearest to the bone fragment form bony trabeculae
- Those away from the bone differentiate into chondroblasts and produce cartilage
- Later, cartilage is replaced by bone
- Osteoclasts invade for bone remodeling
332
Primary Centers of Ossification
- develop in the diaphysis (shaft)
- begins as the periosteal collar which is an osseous tissue formed around the shaft of the cartilage model by chrondroblasts differentiating into osteoblasts
- cartilage in the central regions of the shaft undergoes degeneration (erosion of cartilage)
- replaced by mesenchymal cells that differentiate into osteoblasts which deposit osseous tissue on the degenerating cartilage
333
*Euchromatin vs. Heterochromatin vs. Nucleolus*
1. Euchromatin
- lightly stained and relatively active
- uniformly dispersed
2. Heterochromatin
- darkly stained and relatively less active
- basophilic clumps
3. Nucleolus
- darkly stained and granules
- has DNA and rRNA
- rRNA synthesis and its packaging into precursors of ribosomes
334
**Gap Junctions**
- also called communicating junctions
- the intercellular space is bridged by interlocking transmembrane proteins
- *major in cardiac muscles*
- permits the direct passage of inorganic ions and other H20 soluble molecules from cell to cell
335
Blood Vessels
- the blood islands outgrowths link up with neighboring islands to form the actual blood vessels
- subsequently, the surrounding mesenchyme differentiates into the connective tissue and the muscular layer of the blood vessels
336
Ganglion
- aggregations of nerve cell bodies along the course of peripheral nerves
337
Muscular Venules
- Pericyte layer is replaced by one or two smooth muscle layers
- the tunica externa also becomes more prominent
338
*Species Differences of the Spleen*
1. Sinusual Spleen
- abundant venous sinuses in the dog
2. Nonsinusal Spleen
- poorly developed sinuses in the cat, horse, pig and ruminant
339
Skeletal Muscle
- strong, quick discontinuous voluntary contraction
- striated and voluntary
- *multinucleated
- > nucleus peripherally located*
- contains myofibrils
- myofiber (entire cell) -> myofibrils(Bundles of myofilaments) -> myofilaments (actin and myosin)
340
Beginning of Implantation
- sow
- bitch
- queen
- ewe
- cow
- mare
1. Sow = 13-14 days
2. Bitch = 17-18 days
3. Queen = 13-14 days
4. Ewe = 15-20 days
5. Cow = 25-30 days
6. Mare = 35-40 days
341
Rough Endoplasmic Reticulum vs. Smooth Endoplasmic Reticulum
- ER is a network of tubules
1. Rough Endoplasmic Reticulum
- has the presence of ribosomes
- > therefore basophilic
- involved in protein synthesis
2. Smooth Endoplasmic Reticulum
- without ribosomes
- synthesis of cholesterol based lipids
- drug detoxification
- the release and recapture of calcium ions during contraction and relaxation of muscles
342
Types of Capillaries: location
1. Continuous Capillaries
- muscles
2. Fenestrated Capillaries
- visceral capillaries
- *occur in the GIT*
3. Porous Capillaries
- kidney glomerulus
4. Sinusoidal Capillaries
- are the fenestrated capillaries present in endocrine glands
343
Development of the Conducting System
- develops by differentiation of myocardial tissue
| - AV node, SA node and purkinje fibers are all modified cardiac muscle
344
Neutrophils
- heterochromatic segmented nuclei with 3-5 lobes joined by thin strands
- Barr Body (extra chromatin lobe), or sex body in females
- *are called heterophils in chickens
- immature neutrophils (band, or nonsegmented cells) are present during disease*
- cytoplasm is pale grayish blue
- Cytoplasmic Granules play a major role in defending the body against bacteria by phagocytosis
- > roll along the walls of blood vessels
- > remain in circulation only for 10-14 hours and after migrate to tissue
- > reach at the site of inflammation immediately by chemotaxis
- chemotaxis steps are rolling -> arrest -> adhesion -> crawling -> transmigration
- > interstitial migration -> phagocytosis
- contains two types of cytoplasmic granules:
1. Specific Granules
- bactericidal compound
2. Azurophilic Granules
- hydrolytic enzymes
345
Bone Marrow Blood Supply
1. Nutrient arteries enter through the midshaft/diaphysis in long bones and provide blood supply to the marrow
2. These arteries divide and give branches throughout the marrow
3. Their branches terminate on the periphery of marrow and join with the venous vessels
4. Bone marrow on its periphery has venous or vascular sinuses that anastomose and drain blood to the central vein
5. Blood cells, produced in bone marrow, cross the wall of these sinuses to reach the peripheral circulation
346
Infundibulum
- the first part of the uterine tube
- funnel shaped
- site of fertilization in dogs and birds
347
Similarities Between Veins and Arteries
1. Large veins have abundance of elastic fiber in the Tunica Media
2. Medium sized veins have abundance of smooth muscle in the Tunica Media
3. Small sized veins, or venules have 2-3 layers of smooth muscles in Tunica Media
348
Cytoplasmic Inclusions
- structural part of the cell, not living/storage material
1. Glycogen
- in liver cell and muscle
- seen using PAS reaction
2. Lipids
- in adipose cells
- seen using osmic acid fixation
3. Melanin
- in skin and retina/eye pigment
4. Hemosiderin
- result of hemoglobin degradation
5. Lipofuscin
- commonly found in cardiac muscle, liver and nerve cells
349
Adipocytes
- adipose, or fat cells
- two types
1. Unilocular Adipocyte
- majority
- yellow, or white fat
- adipocytes filled with large lipid droplets
2. Multilocular Adipocyte
- brown fat
- very active
- important in young, or hibernating animals
- multiple lipid droplets
- high concentration of mitochondria in the cytoplasm
350
How is transport of the sperm achieved?
- by muscular contraction of the cervix and uterus
- by the motility of the sperm themselves
- > flagellum
351
Structure of the Nuclear Envelope
- has two concentric membranes (outer/inner) separated by a 25 nm wide perinuclear space
- > 2.5/3.5x larger than the cell membrane
- has numerous pores for transport (rRNA transport)
352
*Pseudostratified Columnar Epithelium*
- composed of a single layer of cells, but due to different cell shapes and nuclei locations at various levels gives a fake impression of having more than one layer
- columnar and ciliated
- mainly present in its ciliated form in the trachea and bronchi
353
Lateral aortic branches
- Supply the derivatives of the intermediate mesoderm
| - form the renal, testicular or ovarian arteries
354
External Morphogenesis of the Cardiac Tube
- the cardiac tube becomes spiraled
- bulbus and ventricle shift caudally and ventrally
- atrium and sinus shift cranially and dorsally
- the atrium grows rapidly in the lateral direction and differentiates into the left and right atria
- sinus venosus becomes incorporated into the right atrium
- the ventricle differentiates into the left and right ventricle around the truncus arteriosus
355
Glycocalyx Coat
- present in the external leaflet of the cell membrane to provide protection to the cell from mechanical and chemical damage
- glycolipids and glycoproteins
356
Exocrine vs Endocrine Pancreas
1. Exocrine Pancreas
- abundance of rER (darker stain bc basophilic)
- contains ribosomes
2. Endocrine Pancreas
- abundance of sER
- no ribosomes
357
Arteriovenous Anastomoses
- Direct connections between arterioles and venules without an intervening capillary bed
- Thick muscular layer, that receives a dense vasomotor nerve supply
- > sympathetic and parasympathetic
- Present in skin, lip, intestine, nasal mucosa, male and female reproductive tract
- Functions to regulate blood pressure, thermoregulate and erection
358
Relationship of Sclerotomes with other structure and intersegmental arrangement
- somites and spinal nerves have a segmental arrangement
- arteries lie in an intermediate location (intersegmental)
- Each sclerotome splits into cranial and caudal portions
- the caudal portion of one sclerotome unites with the cranial portion of the next to form a vertebra
359
Macrophage
- phagocytic cells
- large, ovoid or spherical cells that contain cytoplasmic vacuoles and numerous lysosomes
- derived from monocytes
360
Hyaline Cartilage
- present on the articular surfaces of the bones, nose and trachea
- surrounded by perichondrium which is composed of:
a. An outer fibrous layer
- collagen fibers and fibroblasts
b. An inner cellular, or chondrogenic layer
- chrondroblast
361
What is the Cytoskeleton composed of?
1. Microfilaments
2. Intermediate Filaments
3. Microtubules
362
Heart Wall Layers
1. Endocardium
- inner
2. Myocardium
- middle
3. epicardium
- outermost
363
Microvilli
- also called Brush Border
- cytoplasmic evagination, or infolding
- increases the SA for absorption
- in the small intestine and kidney (for absorption)
- they are NOT composed of microtubules
364
*Bone develops from*
1. Sclerotome
- vertebrae and ribs
2. *Somatic Mesoderm
- appendicular skeleton*
365
*What do all intercellular junctions have in common?*
- they are all connected by transmembrane proteins
366
Secondary Centers of Ossification
- in long bones, these appear in both epiphyses
| - the process of ossification is the same as in primary centers
367
Settled, or Centrifuge Blood
1. The Uppermost layer
- plasma
- > water = 92%
- > plasma proteins = 7%
- > other solutes = 1%
2. Middle Layer
- 1% Buffy Coat
- > thrombocytes and leucocytes
3. Lowest Layer
- 45% PCV (packed cell volume), or hemocrit (erythrocytes)
368
Tonsils
- lies beneath, or in contact with the epithelium
- > stratified squamous epithelium (oropharynx)
- > pseudostratified epithelium (nasopharynx)
- The tonsilar surface may be smooth
- > the palatine tonsil of dog and cats
- Or it may have deep invaginations, referred to as tonsillar fossulae
- > the lingual tonsil in the horse and the palatine tonsil in horses and ruminants
- > These invaginations allow a high concentration of lymphatic tissue
- epithelium is infiltrated with lymphocytes, neutrophils and macrophages
- beneath the epithelium, diffuse lymphatic tissue with plasma cells surrounds lymphatic nodules, which frequently posses a germinal center
- the tonsil is surrounded by a distinct CT capsule
369
Neural Tube Formation
- **The notochord induces the ectoderm to form the neural ectoderm, or neural plate
- Later the notochord regresses and persists in adult as the nucleus pulposus of the intervertebral disc**
- notochord induces ectoderm to form the neural plate -> neural groove forms -> two ends come together -> form epidermis and neural tube (brain and spinal cord) -> releases neural crest cells
370
Peroxisomes
- abundant in the liver and kidney
- oxidizes specific organic substrates which produces hydrogen peroxides (toxic) that is eliminated by catalase
- > contains oxidase and catalase enzymes
- detoxifies certain substances
- > alcohol (ethanol)
371
Duct System (Smallest to Largest)
1. Intralobular Duct
- within lobes
2. Interlobular Duct
- in between lobes
3. Lobar Ducts
- duct of a lobe
4. Main Ducts
- duct of a gland
372
**Intracartilaginous, or Endochondral Ossification**
- appendicular skeleton, vertebral column and bones at the base of the skull
1. Bones are first formed as hyaline cartilage models, which later is replaced by bone tissue
- Mesenchymal cells differentiate into chrondroblasts which produce the intercellular matrix characteristic of hyaline cartilage
- The cartilage model is surrounded by perichondrium and further growth occurs by proliferation of chrondroblasts
373
Fibrocartilage
- present in the intervertebral disc and menisci
- *the perichondrium is poorly developed, although it is surrounded by collagen fibers*
- Stained blue with trichrome Stain
374
Trachea
- *Lined by pseudostratified ciliated columnar epithelium with goblet cells, neuroendocrine cells, and migratory cells*
- Neuroendocrine cells
- > APUD cells, or Amine Precursor Uptake and Decarboxylation
- > typically pyramidal shaped
- > *abundant in young animals*
- > identified by histochemical methods
- Migratory cells
- > lymphocytes, globular leukocytes and mast cells
- The Propria-submucosa consists of loose CT and a subepitheial layer of longitudinally elastic fibers
- *Has C or U-shaped hyaline cartilage
- > The dorsal free ends of the cartilage are bridged by smooth muscle
- -> it is external in carnivores and internal in other domestic animals*
- the external perichondrium is surrounded by loose connective tissue of the adventitia
375
Lymph Capillaries
- endothelium lined tubes that are usually larger than blood capillaries
- basal lamina is either absent or discontinuous
* - valves are present in ALL TYPES of lymph vessels except lymph capillaries*
376
Bronchioles
- Lined with simple columnar, or cuboidal epithelium with ciliated and Clara cells
- *Clara (bronchiolar exocrine) cells secrete proteins to protect bronchiolar lining against oxidative pollutants and inflammation
- > Also produce surfactant to keep lumen patent*
- The propria-submucosa consists of sparse loose C.T
- > *NO cartilage and glands here*
- Tunica adventitia comprised of loose CT with elastic fibers orientated circularly
377
Endocardium
- innermost layer of the heart
- lines the atria and ventricles
- three layers
1. Endothelium
- lined by simple squamous epithelium
2. Inner Subendothelial Layer
- dense irregular CT
- with collagen and elastic fibers
3. Outer Subendothelial Layer
- loosely arranged collagen and elastic fibers
- Purkinje fibers may be present
378
Capillaries
- composed of endothelial cells, basal lamina, pericytes and a thin adventitial CT layer that is lacking around brain capillaries
- forms networks, called capillary beds, where exchange takes place between circulating blood and interstitial fluid
379
Acrosomal Reaction
- follows capacitation
- Involves the release of the enzymes, hyaluronidase and trypsin like substance, in the acrosome
- The action of these enzymes facilitate the penetration of the oocyte barriers
- > such as the corona radiata, zona pellucida and oocyte cell membrane
380
Gametogenesis
- refers to the process by which germplasm are converted into highly specialized sex cells (gametes) that are capable of uniting at fertilization and producing a new being
- production of gametes
- > spermatozoa (male) and ovum (female)
381
orula
- After 4 to 6 divisions, the zygote results in the formation of a solid cluster of cells termed as morula
- > mulberry shaped
- the zona pellucida is still intact
- In most domestic animals it consists of 16-64 cells
- in man, the morula consists of 16 cells by the fourth day of development
382
**Howel-Jolly Bodies**
- DNA fragments
- them
- during maturation erythroblasts normally expel their nuclei, but in some cases a small portion of DNA remains
- normally seen in dog and cat
- NOT seen in horses and ruminants
383
MALT (Mucosa Associated Lymphoid Tissue)
- Lymphoid aggregations present in the submucosa of the Digestive and Respiratory system organs
- > also GALT and RALT
384
Peripheral NS Layers
1. Endoneurium
- a single nerve fiber consists of an axon enveloped by neurolemmocytes and surrounded by a thin layer of these connective tissue fibers
2. Perineurium
- nerve fibers are organized into fascicles (bundles) that are enveloped by collagenous connective tissue
3. Epineurium
- multiple bundles, or fascicles of nerves are bounded together by this
385
GALT (Gut Associated Lymphoid Tissue)
- Large aggregates of single lymphatic nodules (Ileal Peyer’s patch) are present in the distal jejunum, and ileum in young ruminants, pigs and carnivores
- Its role is maturation of B-lymphocytes
- Solitary lymph nodules in the colon and rectum.
386
Dense Connective Tissue
- Adult CT
- mainly composed of thick collagenous fibers and a few fibroblast cells
1. Dense Irregular CT
- present in the deeper layer of dermis and capsules of the organ
2. Dense Regular CT
- present in tendons and ligaments
387
*Lipofuscin*
- indigestible residue of phagocytosis
- commonly found in cardiac muscle, liver and nerve cells
- important in the nerve cell because it is long lasting
- > neurons do not multiply, only grow
- this pigment increases with age
388
*Vitelline Artery*
- left side regresses
| - *right side forms the cranial mesenteric artery*
389
Chorion
- It is a outermost membrane
- develops from the extraembryonic somatopleure
- The finger-like projection, called chorionic villi, develops over the surface of the chorion to make contact with the uterus of mother
- The chorion fuses with allantois to form chorio-allantoic placenta
- > in the ox and pig
390
Ovulation is controlled by:
1. FSH (follicle stimulating hormone)
2. LH (luteinizing hormone)
- > both are produced by the adenohypophysis
391
Seromucous, or Mixed Gland
- has both serous and mucous acini
| Ex: mandibular salivary gland
392
The shape of the nucleus..
- determines the shape of the cell
Example:
Flat nucleus = flat cell
Round nucleus = oval, cuboidal, or hexagonal cellular shape
393
Large Sized Lymph Vessels
* - 3 distinct layers are present*
| - internal elastic membranes are usually absent
394
*Reticulocytes*
- immature RBCs that have ribosomal RNA in them
- 1-2% normal in dog and cat
- NOT seen in horses and ruminants
- has nothing to do with reticular fibers, or cells!
395
Fetal, or Extraembryonic Membranes
A. Develop from the extraembryonic Somatopleure
1. Amnion
2. Chorion
B. Develop from the extraembryonic Splanchnopleure
3. Yolk Sac
4. Allantois
396
Meroblastic Cleavage
- partial cleavage
- In birds
- the massive amount of yolk present
- > polylecithal egg
- prevents the complete division of the zygote
397
Syndesmochorial Placenta
- Based on Histological Layers
- Chorionic epithelium is in contact with uterine connective tissue
- Five layers are present
Ex: Ruminants (cow, sheep, goat)
398
Limb Morphogenesis order of development
- regions of the limb develop in proximo-distal order
| - the distal end of the limb, or footplate is flattened like a paddle along its outer margin ectoderm
399
Lymph Vessels of the Spleen
- *NO afferent lymph vessels*
| - Efferent capsular and trabecular lymph vessels originate in the white pulp and drain into splenic lymph nodes
400
Muscular Arteries Structure
1. Tunica Intima
2. Internal Elastic Membrane
* 3. Tunica Media
- thickest layer
- predominance of elastic laminae (fibers)
- composed mainly of smooth muscle cells arranged in a circular, or helical pattern
- elastic and collagen fibers*
4. External Elastic Membrane
5. Tunica Externa (tunica adventitia)
401
Functions of the Placenta
1. Nutrition
2. Respiration through gaseous exchange
3. Excretion
4. Placental Barrier
- impermeable to bacteria
5. Synthesis of hormones
- estrogen, progesterone and gonadotrophins
402
**Cytocrine**
- secretory material from one cell is transferred to the cytoplasm of another cell
Ex: transfer of melanin pigment from the melanocytes into the keratinocytes
403
Neuromuscular Synapse (Efferent Termination)
- consists of a presynaptic neuronal motor end plate overlaying a postsynaptic muscle sole plate in the mid region of the muscle
fiber
- each motor end plate lies in the corresponding trough of the muscle sole plate with about a 40-50nm neuromuscular gap
- the motor end plate cytoplasm has many mitochondria and synaptic vesicles that contain Acetylcholine
-> ACh releases at the active sites, diffuses across the neuromuscular gap and binds to postsynaptic receptor site, leading to muscle fiber depolarization
404
Endocrine Gland vs. Exocrine Glands
- develops from the epithelium
1. Endocrine Glands
- a ductless gland
- secretions are released into the intercellular fluid and are transported to the site of action by the blood
- not attached
2. Exocrine Glands
- has ducts
- attached
405
Result of Fertilization
- Prior to the fusion of the male and female pronuclei, they duplicate their DNA content and immediately on fusion their chromosomes split in the course of a normal mitotic division which results in the formation of a 2-cell zygote
- Restoration of the diploid chromosomal number
- Determination of the sex , XX of female and XY of male
- > reverse in birds (XX-male, XY-female)
- Initiation of cleavage, or further division
406
Fetus
- the developing offspring during the fetal period
407
Insemination
- is the deposition of sperms into the female genital tract
- Insemination is naturally performed during mating (coitus), or by means of artificial insemination (AI)
- at insemination, millions of male cells or spermatozoa are deposited into the vagina
408
Fetal, or Extraembryonic Membrane Functions
1. Protection
| 2. Nutrition
409
Axon
- originates from the axon hillock of the cell body and ends in terminal branches (telodendrites)
- the cytoplasm (axoplasm) is devoid of chromatophilic substances, or Nissl Substances
- each terminal branch ends in an expansion called a terminal bulb where neurotransmitter molecules are packaged and stored within the synaptic vesicle
- the terminal branches may also contain secretory vesicles that store neuromodulators and neurohormones
410
Prenatal Period
1. Pre-embryonic Period
- the period of development of the gametes (gametogenesis) up to implantation
2. Embryonic Period
- period from implantation to the origin of the primordia of the organs and the formation of the basic body form
- most important period because the majority of the development occurs here
- embryo
3. Fetal Period
- period of growth and maturation of the organ system to become competent to assume their specialized functions
- fetus
411
Polyspermy
- zona reaction prevents this
- Occasionally more than one sperm may penetrate the female germ cell
- This occurs more commonly in the pig and birds
- > normally rare
- The great majority of such conceptus die at a very early stage of development
412
Interventricular Septal Defect
- Interventricular septal defect
| with primary hypertrophy of the left ventricle and secondary right ventricular dilation and hypertrophy
413
Bone
- a specialized connective tissue composed of intercellular calcified material (bone matrix) and three cell types (osteoblasts, osteocytes and osteoclasts)
- organic matter : Inorganic matter = 1:2
- organic matter can be removed by boiling
- > courses in a spiral direction
- inorganic matter can be removed by putting bone in acid
- > calcium and phosphorous are abundant
414
Principles of Cleavage
- the first division occurs at the long axis of the cytoplasm
- the second, or subsequent division tends to be at a right angle to the previous one
- the speed of division is inversely proportional to the amount of yolk present
- > birds divide slower than mammals
415
Ampullary region of the uterine tube
- The ampulla is the second part of the uterine tube where fertilization occurs
- site of fertilization for most animals
- 12 to 24 hours after fertilization
416
Patent Ductus Arteriosus (PDA)
- typical metallic murmur
- failure of the ductus arteriosus to close
- Oxygenated blood from the aorta passing through PDA goes to:
1. The right ventricle which causes turbulence, hence a typical metallic murmur
2. Also goes to lungs, thus reducing its efficiency
- The lower part of the body and the hind limb don’t get a lot of oxygenated blood, therefore they become weaker
417
Golgi Complex Functions
- provides the site for accumulation, concentration and packaging of secretory proteins into membrane bound vesicles
- cis = receiving side
- trans = shipping side
- biosynthesis of glycoproteins, glycolipids, phospholipids and neutral lipids
- stained with silver salt, or osmium and appears as a black network of cisternae
418
*Stratified Squamous Epithelium (Keratinized vs Non-keratinized)*
- several layers of cells with the most superficial cells being squamous, or flat
1. Keratinized
- mainly found in the skin
2. **Non-keratinized
- mainly found in the cornea and vagina**
419
Receptors (afferent terminations)
- by location
- type of stimulus
1. By Location:
- Exteroreceptors
-> body surface
- Enteroreceptors
-> viscera
- Proprioceptors
-> musculoskeletal structures
2. Type of stimulus:
- Mechanoreceptors,
- Chemoreceptors
- Thermoreceptors
3. Anatomically:
A. Nonencapsulated receptors
- Free nerve ending
- Tactile corpuscles
B. Encapsulated receptors:
- Encapsulated tactile (Meissner’s) corpuscles
- Lamellar (Paccinian) corpuscles
- Bulbous (Krause’s) or genital corpuscles
- Neurotendinous and neuromuscular spindles.
420
Sinusoids (blood spaces)
- present in the liver parenchyma
- larger than capillaries
- their shape changes with the surrounding parenchyma
- large openings and pores in the endothelial cells provide a maximum exchange
421
Primary vs Secondary Lymphoid Organs
1. Primary Lymphoid Organs
- produce lymphocyte precursors
- > "training academy of lymphocytes"
- Embryonic yolk sac
- Bone marrow
- Thymus
- Cloacal Bursa
- > birds
- GALT
- > Peyer’s patches
2. Secondary Lymphoid Organs
- Site of immune response
- Houses mature immunocytes
- > "battle field of lymphocytes"
- Lymph Nodes
- Spleen
- MALT, or Mucosa Associated Lymphatic Tissue
- Diffuse lymphatic tissue
422
Abnormalities of the Heart
1. Ectopic Cordis
2. Interventricular, interatrial and spiral septal defects
3. Transposition of the great vessels
4. Dextroaorta
5. Pulmonary and aortic stenosis (narrowing)
6. Tetrology Fallot
7. Eisenmenger Complex
423
Implantation
- A free-living blastocyst is nourished by the secretion from endometrial gland.
- Later, it develops fetal membranes and gradually attaches to the endometrial epithelium and thereby establishes a close relationship between the fetal and maternal circulatory system for physiological exchange
- This process of attachment is called implantation
424
Brain White/Grey Matter Locations
- cerebrum
- cerebellum
- brain stem
- spinal cord
1. Cerebrum and Cerebellum
- grey matter outside (peripheral)
- white matter inside (central)
* 2. Brain Stem
- patches of grey matter called nuclei that are embedded in white matter*
3. Spinal Cord
- grey matter inside (central)
- white matter outside (peripheral)
425
Lysosomes
- contain hydrolytic enzymes that digest things like food, or bacteria
- enzymes are synthesized in the rER, then go to the golgi complex where they are modified and packaged as primary lysosomes
- primary lysosomes fuse with phagocytosed material, or obsolete cellular organelles (autophagic vacuoles).. they are dead... and become secondary lysosomes
- > primary lysosomes + phagocytosed material = secondary lysosomes
- after digestion, the indigestible contents of the secondary lysosomes are retained as residual bodies called lipofuscin (age pigment)
- > lipofuscin can not be broken down
- > associated with system of phagocytosis
426
Conducting Portion vs Respiratory Portionof respiratory system
1. Conducting Portion - conducts air
- trachea
- primary bronchi
- secondary bronchi
- bronchiole
- a terminal bronchiole
2. Respiratory Portion - gas exchange
- respiratory bronchiole
- alveolar duct
- alveolar sac (termination of alveolar duct)
Histology and Embryology
flashcards
Decks in class (17)
# Cards
-
Midterm426
-
Embryology Midterm54
-
Digestive System192
-
Urogenital System87
-
Endocrine Glands72
-
Male Genital System67
-
Integument (skin)92
-
Female Genital System69
-
Embryo Digestive System and Respiratory86
-
Embryology Urogenital System54
-
Special Organ Embryo Abnormalities8
-
Development of the Pharynx + Thyroid Gland24
-
Development of the Ear11
-
Development of the Eye, Tongue, and Tooth16
-
Species Differences of Pancreatic Duct7
-
Embryology Derivations76
-
Indifferent Stage Female and Male derivatives19
