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Anatomy yrtwo semone > Histology > Flashcards

Histology Flashcards

1
Q

Name the three layers of the skin

A
  1. Epidermis

Keratinised stratified squamous epithelium

Keratinocytes = true epithelial cells

  1. Dermis

Dense irregular connective tissue

  1. Hypodermis

Addipose tissue

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2
Q

Explain how you would distinguish between thick and thin skin?

A

Thick skin

  • lacks hair follicles
  • nasal planum, footpads
  • has both stratum lucidum and stratum corneum layers

Thin skin

  • most frequent and is usually haired
  • no strtum lucidum
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3
Q

Identify all five layers of the epidermis ?

A
  1. Stratum basale
  2. Stratum spinosum
  3. Stratum granulosum
  4. Stratum lucidum
  5. Stratum corneum
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4
Q

Identify and describe the Stratum basale ?

A

Stratum basale

  • single row of cells sitting on a basement membrane
  • stem cells undergo mitosis
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5
Q

Identify and describe the Stratum Spinosum ?

A

Spinosum

  • cells have spines projecting (cytoplasmic extension) and attach to each other via desomeres
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6
Q

Describe and identify the Stratum Granulosum ?

A

Stratum Granulosum

  • keratin accumulates in cells
  • contains keratohyaline granules - start to bind keratin together and Lamella granules - water proofing
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7
Q

Describe and identify the Stratum Lucidum ?

A

Stratum Lucidum

  • contains a protein which has a different staining affinity
  • above granulosa layer, only in thick skin
  • flattened dead cells of poor staining quality
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8
Q

Describe and identify the stratum corneum ?

A

Stratum Corneum

  • consisting of dead accumulated, anucleated squamous cells containg keratin
  • layers depend upon the site of tissue
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9
Q

Explain what the epidermis is composed of and where it is located ?

A

Epidermis

  • the most superficial layer of squamous epithelium
  • accompanied by other cell types for pigmentation, sensory perception and immune function
  • derived from ectoderm layer of the trilaminar germ disc.

Keratinocytes = true epithelial cells

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10
Q

Describe Langerhans cells their location, function and structure ?

A

Langerhans cells

  • found at the level of the stratum spinosum
  • involved in immune function
  • function as antigen presenting cells and may stimulate T cell responses in various allergic or inflammatory responses
  • well characterised in humans and rodents
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11
Q

Describe what melanocytes do, their location and function ?

A

Melanocytes

  • reside in the stratum basale layer of the epidermis
  • originate in the neural crest of the ectoderm
  • pigments may travel from basal layers to upper layers through specific processes - eventually phagocytosed by keratinocytes

They function to absorb and scatter UV radiation thus decreasing mutagenic effects

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12
Q

Describe the dermis, its location, composition and two layers ?

A

Dermis

  • Located beneath the epidermis
  • able to withstand certain mechanical stressers as it is both flexible and elastic
  • thick layer of connective tissue
  • dense irregular connective tissue
  • contains blood vessels, lymphatics and inflammatory cells (histamine and heparin).
  • develops from mesoderm of the trilaminar disc

Papillary layer = fine collagen fibres richly supplied with cappillaries

Reticular layer = Highly thick collagen bundles

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13
Q

Describe the location and composition of the Hypodermis ?

A

Hypodermis

The majority of the tissue is composed of adipose

but there are also, sweat glands, hair follicles, large vessels, nerves and lymphatics, skeletal muscle, mammary glands etc

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14
Q

Sebacious glands what do they produce, where are they located and what are they derived from ?

A

Sebacious glands (holocrine)

  • derived from the epidermis
  • solidly packed cells with a foamy appearance
  • produce sebum an oily product that waterproofs or softens the hair
  • glands empty into upper regions of hair follicles
  • all the contents of the cell are lost to the cells surface
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15
Q

Describe hair follicles origin, and accompanying cells.

A

Hair follicles

Specialised down growth of the epidermis that extends deeply into the dermis and hypodermis

  • hair growth originates at the bulb
  • melanocytes provide pigment to matrix cells which are eventually formed into hard keratine
  • arrector pilli muscles = smooth muscle attached to root sheath allow hair to become erect when cold
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16
Q

Identify the dermal root sheath, external root sheath, internal root sheath, hair and cuticle in a hair follicle ?

A
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17
Q

Describe the three stages of hair growth Anagen, Catagen and Telogen ?

A

Anagen

  • Growth phase
  • Dermal papilla (uppermost layer of the dermis) reattaches to a new hair follicle
  • older hair pushed out by the growth of a new hair follicle

Catagen

  • The dermal papilla detaches and rests, while the hair shaft is freed from the blood suplly and pushed upward

Telogen

  • Dermal papilla reattaches to new hair follicle (Dose not grow)
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18
Q

Describe Apocrine glands and what they produce ?

A

Apocrine glands

  • located throughout the skin of most domesticated animals
  • empties into upper part of hair follicle
  • simple cuboidal epithelium, coiled glands
  • not true sweat glands produce = viscous fluid, sexual attraction, communication, territorial marking
  • excretes a small portion of the cell contents and secretion
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19
Q

Describe Merocrine sweat glands and what they produce ?

A

Merocrine sweat glands ?

  • simple cuboidal or columnar epithelium
  • produce aqueous sweat for thermoregulation
  • open directly onto the surface of the skin
  • only secretion is lost to the cell surface

Found

  • footpad of dog and cat (picture attached)
  • frog of horse
  • planum rostrale and carpal glands of pig
  • nasolabial region in cattle
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20
Q

Describe the blood supply to the skin ?

A
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21
Q

Describe the formation of hooves, horns and claws ?

A

Hooves, horns and claws

Same structures as thick skin

They differ through the shape of the papillae / lamellae that extend from the dermis

Flat papillae = form flattish thick skin

Shaped papillae = form keratinised columns hooves, horns and claws

The hoof/ horn is held to underlying tissues through laminae

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22
Q

Identify the three layers of skin in a pigs ear, what features make this a thin skin classification ?

A

Pig ear thin skin

Thin skin as it lacks a stratum lucidum layer and contains many hair follicles

  • blue = hypodermis
  • pink = dermis
  • purple = epidermis
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23
Q

Identify the four layers of the epidermis in the thin skin of a pigs ear ?

A

Epidermis

yellow = stratum basale

blue = stratum spinosum

green = stratum lucidum

orange = stratum corneum

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24
Q

Identify the five skin layers in a dogs paw pad, what characteristics make this thick skin ?

A

Dog paw pad

This is thick skin as it has an incredable thick keratinous layer composed of stratum lucidum and stratum corneum (usually lacks hair follicles)

yellow = stratum basale

blue = stratum spinosum

green = stratum granulosum

purple = stratum lucidum

orange = starum corneum

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25
Q

Describe the nasal cavity regions and what structures maintain its shape ?

A

Nasal cavity

The structure is maintained by bone and cartilage of the nasal bones (maxillary, incisive, ethmoid and frontal) with the cartilage of the chonca. The left and right side is divided by the nasal septums.

Three regions of the nasal cavity

  • Rostral (Cutaneous) - comprised of stratified cuboidal to non - ciliated pseudostratified columnar
  • Respiratory (caudal to thirds) ciliated pseudostratified columnar epithelium
  • Olfactory (dorsocaudal) ciliated pseudostratified columnar epithelium with olfactory epithelium
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26
Q

Describe the specialisation of the ethmoid choncae within the respiratory system ?

A

The ethmoid choncae contains specialised olfactory epithelium

  • Respiratory epithelium specialised for olfaction
  • located near the ethmoid and the roof of the nasal cavity
  • Bowmans capsule = moistens olfactory mucosa
  • Olfactory cells long cilia contain receptors
  • Sustantacular cells = supportive cells of olfactory epithelium
  • Basal cells = stem cells
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27
Q

Describe the histology and identifying features of the trachea ?

A

Trachea

  • C rings of hyaline cartilage
  • pseudostratified columnar epithelium
  • Trachealis muscle contracts during coughing to increase intrathoracic pressure
  • large submuscosa contains specialised glands (seromucous glands)
  • goblet cells = secrete mucous
  • Cilia = moves mucous cranially
  • laminar prpria lie below the epithelium and is greatly vascularised.
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28
Q

Describe the distinctive histological features of the Bronchi?

A

Bronchi (primary to secondary)

  • irregular plates of cartilage in wall
  • smooth muscle which surrounds the laminar propar
  • depper the cartilage plates become less regular
  • the number of glands decrease with increasing depth into the long
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29
Q

Describe the histological features of the Bronchioles ?

A

Bronchioles

  • no cartilage in walls
  • deeper at this level the epithelium becomes simple columnar
  • contains club cells
  • terminal bronchioles transition to respiratory bronchioles when alveoli begin to appear on the slide.
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30
Q

What do club cells do and where are they located ?

A

Club cells are located within the bronchioles

  • dome shaped cells with short microvilli
  • detoxifies cytochrome P450 enzymes which break down air born toxins
  • act as stem cells to replenish bronchiloar epithelial cells
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31
Q

Describe the histological features of the alveolar, and the three cell types ?

A

Alveoli

  • honeycomb arrangement
  • abundant capillaries, supported by collagen and elastin fibres

Type one pneumocytes

  • simple squamous cells
  • thin to allow for diffusion
  • close opposition to capillaries

Type two pneumocytes

  • cuboidal cells
  • produce surfactant to decrease surface tension
  • stored in lamella bodies (granules)
  • can also act as stem cells replacing type one and two pneumocytes

Alveoli Macrophages

  • immunity against irritants, microbes and particulate matter via phagocytocis
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32
Q

Describe the three layers of the heart wall ?

A

Heart wall

  • Endocardium

simple squamous and dense irregular connective tissue

  • Myocardium

cardiac muscle - striated, single centered nucleus, intercalated disks, branching

under involuntary nervous control + contains perkinje fibres

  • Epicardium (visceral pericardium)

​squamous epithelium

loose connective tissue and elastic fibres containing the blood supply and nerves which innervate the heart

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33
Q

Identify the layers of a artery ?

A

Tunica intima

endothelium - simple squamous lines the entire vascular system

subendothelial layer

internal elastic lamina

Tunica media

smooth muscle layer

external elastic laminar

Tunica adventitia

contains vaso vasorum

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34
Q

What is the vaso vasorum and where is it located ?

A

Vaso vasorum

  • located in the Tunica adventitia
  • network of small blood vessels which supply oxygen and nutrition to large blood vessels.
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35
Q

What are purkinje fibres, and where are they located ?

A

Purkinje fibres

  • modified myocytes
  • observed between the endocardium and myocardium of the heart (also in myocardium)
  • transmit and distribute action potentials from the atrioventricular node
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36
Q

Describe the dfining histological features of an elastic artery ?

A

Type one, Elastic artery

  • The largest arteries including the aorta, common carotid
  • Tunica intima is thicker - than in other types of arteries (contains subendothelial layer)
  • Tunica media 10-40 layers fenestrated layers of elastin
  • Tunica adventitia contains vas vasorum.
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37
Q

Define the histological features of a muscular artery ?

A

Type two Muscular artery

  • Main distributing branches of the arterial tree eg radial, femoral, coronary artery
  • Tunica intima - very thin
  • obvious internal elastic lamina
  • Tunica media - contains alot of smooth muscle and less elastic fibres
  • obvious external elastic laminar
  • Tunica adventitia - variable thickness contains vaso vasorum
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38
Q

Define an arteriole through histological features ?

A

Arteriole

  • similar histologically as a muscular artery but the small size makes the various layers difficult to discern.
  • act as sphincters to regulate blood flow to various regions of the body
  • tunica media only 1-2 layers of smooth muscle
  • elastic laminae may be absent
  • tunica adventitia is thin
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39
Q

Define the histolical features of a capillaries?

A

Capillaries

  • Tunica intima only
  • endothelial cell enclosed by a basement membrane
  • lacks tunica media and tunica adventitia
  • slow blood flow
  • huge cross sectional surface area
  • caontain periocytes - contractive cell
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40
Q

Describe the three types of capillaries ?

A
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41
Q

Identify the histological features of a vein and how this compares to an artery.

A

Vein

  • returns blood to the heart
  • Tunica intima - contains endothelium and endothelial layer (connective tissue + basement membrane)
  • Tunica media - smooth muscle much thinner than in an artery
  • Tunica adventitia - layer of connective tissue containng the vaso vasorum in larger veins
  • > 2mm veins contain valves
    *
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42
Q

Describe the how various histological features varie as veins become closer to the heart ?

A

Variations

  • thickness of wall
  • pressence or absence of valves
  • amount of elastin and smooth muscle
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43
Q

Identify the structures (7) ? and tissue ?

A

Lymph node

  • afferent lymphatic vessels - entering the lymph node through the capsule
  • efferent lymphatic vessels - receive lymph from the medullary sinus eventually rejoining the lymphatic system
  • Subcapsular sinus - the space that encircles the lymph node beneath the capsule into which lymph from the afferent vessels drain
  • Trabecule - extensions of the outer capsule projecting into the the substance of the lymph node
  • lymphoid follicles
  • medullary sinuses - located in the central region they receive lymph from the subscapular and cortical sinusesand converge on the hilum of the node
  • hilum
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44
Q

What is a periocyte ?

A

Periocyte

Periocytes surround the endothelium of capillaries. They are contractile and regulate blood flow through the capillarie beds.

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45
Q

Identify the two layers of a lymphoid follicle ?

A

Lymphiod follicle

  • Mantle zone - outer layer
  • The darker staining periphery of the lymphoid follicle where there are numerous T - lymphocytes (cell mediated immunity)
  • Germinal centre - inner layer
  • The pale staining centre of the lymphoid follicle where B lymphocytes are stimulated to proliferate by contact with an antigen. (Humeral immune response produce antibodies.
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46
Q

Identify this organ and all its histological features ?

A

The spleen

Is a large lymphiod organ that receives a rich blood supply. It provides a region where the blood can come into contact with lymphocytes - similar to the lymph nodes for lymph.

  • Capsule - a thin fibroelastic coat surrounding the spleen
  • Trabeculae - extension of outer capsule projecting into the substance of the spleen
  • Red pulp - forms the bulk of splenic tissue filled with erythrocytes + rich in macrophages
  • White pulp - pale staining lymphoid aggregates simlar to follicle in lymph node

Two types

  • germinal layer - B lymphocytes
  • mantle layer - T lymphocytes
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47
Q

Identify this tissue and its distinctive histological features ?

A

Tissue = muco-cutaneous junction

Orange = muco-cutaneous junction

yellow = orbicularis oris (skeletal muscle)

green = hair follicle

Blue = keratinised stratified squamous epithelium

purple = non keratinised stratified squamous epithelium and seromucous salivary gland.

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48
Q

Describe the muco-cutaneous junction, and where is this found ?

A

Muco-cutaneous junction

Junction between the integument and the digestive system

  • found lips, nose, eyes and nose
  • in ruminants unlike other species the oral cavity is lined by keratinised stratified squamous epithelium - due to the large amounts of roughage in their diet
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49
Q

Identify this tissue, and its defining histological features ?

A

tongue

It is a muscular organ covered by a mucosa and can move in all directions.

  • dorsal thick keratinised stratified squamous epithelium
  • Ventral thin keratinised stratified squamous epithelium
  • intrinsic muscle fasicles run in all different directions.

Four types of lingual papillae

  • Filiform - mechanical
  • Fungiform
  • Foliate
  • Circumvallate
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50
Q

Describe structure, location and function of Filiform papillae ?

A

Type 1 = Filiform papillae

Covering dorsal surface of the toungue most common type

  • purly mechanical and protective
  • assist with prehension and grooming
  • move and shape food bolus for swallowing
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51
Q

Describe the structure, function and location of fungiform papillae ?

A

Type 2 Gustatory = Fungiform papillae

  • mushroom shaped
  • rise above the surface of the tongue
  • scattered amongst the filiform papillae on the dorasal surface of the tongue.
  • non-keratinised stratified epithelium
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52
Q

Describe the structure, location and function of Foliate papillae ?

A

Type 2 Gustatory Foliate papillae

  • These are leaf shaped
  • They are located around the sides of the tongue (parallel folds)
  • absent in ruminants, no taste bud contained within in the cat
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53
Q

Identify the structure, location and function of the Circumvallate papillae in the toungue ?

A

Type two gustatory Circumvallate papillae

  • surrounded by a mote
  • largest type of papillae
  • 3-6 rostral to the root of the tongue
  • taste buds located in the wall of the papillae
  • contains the majority of the taste buds
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54
Q

Provide the general structure of a tooth ?

A

Tooth

Outerlayer enamel

  • produced by ameloblasts (96% mineral hydroxyapatite crystals + 1% proteins amelogenins enamelins)

Inner layer dentine

  • avascular, acellular connective tissue - type one collagen
  • produced by odontoblasts external to the hard dentine
  • surrounds pulp cavity of the tooth
  • odontoblasts

Below the gum Cementum

  • cementoblasts
  • covers the root dentine
  • similar to bone

Periodontal ligament

  • anchors the tooth to the alveolar bone and absorbs shock
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55
Q

Describe the difference between a Brachydont and Hypsodont tooth ?

A

Brachydont

  • short
  • stop growing post eruption
  • carnivore, human
  • low crown
  • narrow canal

Hypsodont

  • long teeth
  • grow for a portion or throughout the entire life of the animal
  • high crown
  • horses, cheek ruminant
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56
Q

Describe the development of the teeth ?

A

Tooth development

Enamel can not be repaired but dentin is repairable

Ameloblasts

  • produce enamial
  • lie external to the enamel
  • degenerate when tooth erupts, so repair to damaged enamel later in life is impossible

Odontoblasts

  • are external to the hard dentine
  • have long slender cytoplasmic processes that penetrate the width of the dentin and run in canals (tubules)
  • these processes are embedded in the secreted matrix

Cementoblasts

  • cementocytes live with in the lucunae within the lower root
  • cementum is laid down through out life
  • collagen fibres laid down with in the cementum which eventually forms the peridontal ligamnet.
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57
Q

Describe the location of the four major salivary glands ?

A
58
Q

Describe a serous secretion and where it is produced ?

A

Serous secretion from a salivary gland

  • protein and water
  • adjust PH, aid taste and moisten dry food stuffs
  • Parotid gland mostly produces a serous secretion

Note - secretion exits through the intercalated duct then the striated duct.

59
Q

Moucous secretion where is it produced and what is its function?

A

Moucous secretion

second type of salivary secretion

  • slippery secretion
  • aid in bolus formation and lubrication
  • The buccal salivary gland mostly produces a mucous secretion
60
Q

What is a mixed salivary gland, identify the two types of acini below ?

A

A mixed salivary gland

  • identify serous acinus and mucous acinus
  • produce bothe a serous saliva, and a mucous saliva
  • sublingual and mandibular gland
61
Q

Describe the salivary duct system ?

A

Salivary duct system

  • acinar cells produce the secretion
  • open into intercalated duct - simple cuboidal
  • Interlobular duct - simple cuboidal
  • Large, terminal ducts - striated columnar epithelium
62
Q

Describe the endocrine system ?

A

Endocrine system

  • it is ductless
  • secretory products are known as hormones and released into the blood circulation
  • high affinity for specific receptors
  • negative feed-back loops
63
Q

Describe the structure of the pituitary gland ?

A

Structure of the pituitary gland

  • Derived from the ectoderm
  • Pars distilis is the anterior pituitary no connection to the hypothalamus
  • Pars nervosa posterior pituitary contains the axons nerve fibres from the hypothalamus
  • Pars intermedia is a simple columnar or pseudostratified columnar epithelium between the pars distilis and pars nervosa
  • Pars Tuberalis surrounds the infundibulum stalk
64
Q

Describe how the pituiatry gland is derived ?

A

Pituitary gland

  • The pituitary gland is derived from ectoderm
  • The pars distilus (ventral) develops from oral ectoderm by an upgrowth of the diverticulum from the root of the oral cavity
  • Rathke’s pouch
  • The pars nervosa develops by a downgrowth of a part of the dicephelon that eventully forms the floor of the third ventricle
65
Q

Describe the cell types of the Pars distalis ?

A

Pars distalis anterior pituitary

Three distinct cell types

Acidophils

  • acidophilic secretory cells
  • somatotrophs, lactotrophs

Basophils

  • basophilic secretory cells
  • TSH Thyrotrops, Gonadotrophs FSH, LH

Chromophobes

  • between acidophils and basophils
  • poor staining
  • either old cells / post secretory or stem cells
66
Q

Describe the histology of the the pars intermedia ?

A

Pars intermedia

  • Inbetween the anterior and posterior pituitary galnd
  • simple columnar or pseudostratified columnar epithelium
  • melanotrophs most common cell type alph melanocyte stimulating hormone
    *
67
Q

Describe the histolical features of the pars Tuberalis ?

A

Pars tuberalis

  • Composed of cell clusters that form a folded tissue with small cyst
  • traversed by the hypophyseal venules (blood vessels)
  • Paraenchymal cells have melatonin receptors and are believed to be involved in seasonal regulation of the reproductive cycle in animals.
68
Q

Describe the histology of the pineal gland ?

A

Pineal gland

  • flattened cone shaped organ
  • derived from ectoderm
  • contain pinalocytes and astrocytes
  • visual light pinalocytes release serotonin
  • in the dark serontonin is converted to melotonin
69
Q

Describe the histology of the pars nervosa ?

A

Pars Nervosa

posterior pituitary

  • Contains axons from the hypothalamus - no nerve cell bodies
  • Herring bodies - dilations of nerve cell fibres
  • Pituicytes - are glial cells that store and release neurohypophysial hormones
  • hormones are peptieds released from the hypothalamus bound to carrier proteins and stored in axon terminals
  • oxytocin, antidiuretic hormone (ADH)
70
Q

Describe the histology and structure of the thyroid gland ?

A

Thyroid gland

  • derived from endoderm
  • Bi-lobed structure containing numerous follicles with cuboidal to simple columnar epithelium
  • lumen contains “colloid”
  • thyroid hormones T3 and T4 controls metabolism

C cells (parafollicular cells

  • located between the follicles
  • derived from neural crest cells
  • produce calcitonin for bone reabsorption
  • lowers calcium and phosphate levels within the blood
71
Q

Describe the histology and structure of the parathyroid gland ?

A

Parathyroid gland

  • derived from endoderm
  • consist of cell clusters
  • Chief cells - small cuboidal cells with pale cytoplasm secrete PTH
  • Oxyphil cells - esoinophilic cells (stain red) unknown function maby aged chief cells

Parathyroid hormone - bone reabsorption and excretion of Ca2+ activates vitamin D

72
Q

Describe the adrenal glands structure ?

A

Structure adrenal glands

Located above the kidney

Composed of two endocrine components

Cortex

  • derived from intermediate mesoderm
  • zona glomerulosa (outer thin)
  • Zona Fasciculata (middle
  • Zona reticularis (inner)

Medulla

  • modified sympathetic neurons
  • derived from neural crest ectoderm
  • Chromaffin cells and storage granules
73
Q

Describe the layers of the adrenal cortex in detail ?

A

Outer layer adrenal cortex composed of three layers

Zona glomerulosa

  • outer layer, thin
  • secretes aldosterone reabsord water

Zona Fasciculata

  • 70% of cortex
  • large cells with lipid inclusions
  • secretes glucocorticoids (cortisol)

Zona reticularis

  • small eosinophil cells (red)
  • secrte weak androgen characteristics
74
Q

Describe the histology of the adrenal gland medulla?

A

Adrenal gland medulla - inside

  • modified sympathetic neurons
  • derive from neural crest ectoderm
  • Chromaffin cells organised into nest and cords, with a rich vascular network
  • Storage granules - contain catecholomines (epinephrine, noreepinephrine)
75
Q

Describe the four layers of the gut ?

A

The four layers of the gut

Mucosa

  • epithelium
  • lamina propria (thin layer of connective tissue)
  • muscularis mucosa

Submucosa

  • submucosa glands
  • blood vessel
  • nerves
  • connective tissue

Muscularis externa

  • inner circular muscle layer
  • outer longitudinal muscle layer

Serosa

  • serosa covers an organ
  • adventitia attaches an organ to the surrounding tissues
76
Q

Describe the mucosa of the oesophagus ?

A

Mucosa oesophagus

epithelium =

  • stratified squamous epithelium
  • may be keratinised in ruminants and horses
  • functions to protect underlying structures

Lamina Propria

  • dense irregular connective tissue

Muscularis mucosa

  • longitudinal orientated smooth muscle
77
Q

Describe the histological features of the submuscosa, muscularis externa and adventitia within the oseophagus ?

A

Oesophagus

submucosa

  • loose connective tissue
  • large arteries, veins, lymph vessels and nerves
  • seromucous glands

Muscularis externa

  • inner circular muscle
  • outer longitudinal muscle
  • the amount of skeletal muscle and smooth muscle varies depending on species

Adventitia

  • loose connective tissue
  • blood vessels, lymph vessels and nerves
78
Q

Describe this organ?

A

Stomach

mucosa

  • simple columnar epithelium
  • surface contains goblet cells - mucous producing cells
  • produces a thick alkaline mucous to protect the mucosa from the acid stomach contents

Gastric pits

  • numerous funnel like depressions within the mucosa
  • the cells that line the base and neck of these pits are responsible for gastric secretions
  • parietal cells secrete HCL and intrinsic factor
  • Chief cells secrete pepsinogen
  • neck mucous cells secrete mucous to protect against auto digestion

Submucosa

  • loose connective tissue

Muscularis externa

  • three muscle layer - but three layers are rarely visable
  • oblique
  • inner circular
  • outer longitudinal layer

Serosa

  • thin and barely visable

submucosa = contains numerus

79
Q

Distinguish between chief cells, neck cells, enteroendocrine cells and parietal cells ?

A

Distinguish between chief and parietal cells of the stomach

Parietal cells

  • eosinophilic cytoplasm lots of pink
  • secrete HCL and intrinsic factor which binds vitamin B12 making it readily available for digestion

Chief cells

  • secrete pepsinogen - once unfolded becomes pepsin which acts to break down proteins into polypeptide fragments.

Neck cells

  • mucous secretion to prevent autodigestion

Enteroendocrine cells

  • stain silver
    *
80
Q

Describe this structure?

A

Small intestine

Three parts which are similar histologically duodenum, jejunum and ileum

Mucosa

  • Plicae circulares - folds in the mucosa / submuscosa
  • intestinal villi - the lamina propia extends into the folds of each villus
  • Muscularis mucosa has two layers and also extends into the intestinal villi, where the smooth muscle cells form a longitudinal bundle in their core.

Crypts of lieberkuhn

  • openings of glands between the villi run through the lamina propria
  • lined with simple columnar epithelial cells
  • Paneth cells located at the bottom of the crypts secrete an antibacterial components
  • enteroendocrine cells secrete gastrin and secretin (full)
81
Q

How to distinguish the duodenum histologically ?

A

Duodenum

  • the duodenum, jujenum and ileum all have the same intestinal mucosa with villi
  • Only the duodenum has a submucosa packed with Brunners glands
  • submucosa glands
  • secrete alkaline mucins into the lumen
  • acts to neutralise acid from the stomach
82
Q

Identify the paneth and goblet cells of the small intestine ?

A

Identify the paneth and goblet cells of the small intestine ?

Paneth cells

  • located at the bottom of the crypts of lieberkuhn
  • secrete antimicrobial agents (lysozyme)

Goblet cells

  • located within the endothelium
  • secrete mucous for protection from chyme acid
83
Q

What is an lacteal ?

A

Lacteal

  • A single lymphatic vessel within the lamina propria of the villis
  • blind terminal end
  • contraction of smooth muscle in villis aids in movement of lymph
  • carries lipids (chylomicrons) bypassing the portal system of the liver
84
Q

Describe how to identify the ilium from other sections of the small intestine?

A

Identification of the iluim

Only the ilum has Peyers patches

small masses of lymphatic tissue found throughout the ilium within the submucosa layer.

85
Q

Describe the unique histology of the below structure ?

A

Colon, caecum and rectum

primary function is the reabsorption of water and inorganic salts

Mucosa

  • No plicae circulares or intestinal villi (this means the epithelium is much smoother)
  • many crpts of Lieberkuhn packed with goblet cells
  • laminar propria is very thin.
  • muscularis mucosa is very thick

Sumbmucosa

  • contains a varyable amount of fat and blood vessels

Muscularis externa

  • the two layers are much thicker when compared to other sections of the gastrointestinal tract
86
Q

Describe how the intestine changes as it progresses along from the small to large intestine ?

A
87
Q

Discuss the three overlapping periods of Haematopoiesis (blood cell formation)

A

Blood cell formation, Haematopoiesis

Blood cell fromation is started by haemangioblast in the visceral mesoderm. (Splanchnic mesoderm of the yolk sac wall).

Three periods

Mesoblastic = blood island - formation of blood vessels and first blood cell erthrocyte (vasculogenesis and erythropoiesis)

Hepato - lienal period = The liver becomes the main heematopoietic organ at about f months of gestation, at 3-7 months the spleen in ruminants.

Medullary period = Bone marrow begins haematopoetic activity around 4 months of gestation.

88
Q

Describe the formation of the cardiac tube, and the first fold?

A

Blood islands (cardiogenic field).

During embryo folding the blood islands fold to become two dorasl and ventral aortae, and venous system

In parallel the blood islands undergo a lateral folding to form the cardiac tube.

  • Blood islands/endothelial tubes move to the midline to fuse forming the cardiac tube. (lateral fold)
  • Endothelial tube
  • At its posterior end the heart will be joined with the venous system, then heart formation occurs. (cranial fold)
  • embryonic heart beat begins at day 22 pig, day 23 dog and day 24 horse.
89
Q

Name the three overlapping periods of blood cell formation ?

A

Three overlapping periods of blood cell formation

  1. Mesoblastic
  2. Hepato-lienal
  3. Medullary period
90
Q

Describe the segmentation of the cardiac tube ?

A

Segmentation of the heart

Too develop into a four chambered heart it first develops into a loop formation than undergoes an internal division.

91
Q

Name the segments of the heart tube ?

A

Bulbous cordis = becomes the ventricular septum

sinus venosus

truncus arteriosus

92
Q

Describe the embryonic loop formation of the heart ?

A

Loop formation

  • primitive atrium loops around ontop of the primitive atrium
  • the bolbus cordis moves inbetween
93
Q

Describe the development of the sinus venosus ?

A

Heart formation sinus venosus

  • Three pairs of veins are connected to the sinus venosus (vitelline vein, umbilical vein and cardinal vein.
  • The three veins form left and right horns
  • The right horn is favored and merges with the atrium develops into the cranial and caudal vena cava
  • The left sinus horn develops into the coronary sinus
94
Q

Name the structures of the right ventricle and right atrium ?

A
95
Q
A
96
Q

Describe the septum formation in the atrium ?

A

Septum formation in the atrium

septum primum, foramen primum, septum secundum, foramen secundum

foramen ovale

  • Septum primum develops from the roof of the atrium
  • The Foramen primum provides passage for the blood between right and left atrium
  • Before the foramen primum seals over, holes develop called the foramen secundum

A septum secundum grows to the left of the septum primum, and grows until it completely covers the foramen secundum,

but retains the foramen ovale during embryonic development.

97
Q

Describe the two atrial defects of the Foramen secundum, and septum secundum ?

A

Atrial defects

  1. Foramen secundum and septum primum develop too large. When the two septa joined at birth the two overlap the holes.
  2. Septum secundum secondum failed to develop, thus septum primum cannot seal and the deoxygenated and oxygenated blood mix.
98
Q

Describe how the four chambers of the heart are formed ?

A

Formation of the septums

Septum intermedium

  • endocardial cushions in the cardiac wall grow until they meet and fuse forming the septum intermedium.
  • division between atria and ventricles

Interventricular septum

  • Transition between the bulbus cordis and ventricule is marked by a mascular fold which develops into the interventricular septum.
  • grows dorsally towards the septum intermedium

Now we have a four chambered heart

99
Q

Describe the formation of the pulmonary and aortic trunks (aorticopulmonary septum) ?

A

Aorticopulmonary septum

The trunks arise from the bulbous cordis and truncus arteriosus

  • these are then divided into two oposing channels by bulbar/truncal cushions in the walls of the heart
  • these fuse in the midline to form a spiralling septum
  • base of right ventrical of the heart giving rise to the left and right pulmonary arteries
100
Q

Describe the development of the atrioventricular valves ?

A

Atrioventricular valves

  • The atrioventricular valves arise from the edges of atrioventricular channels and are suspended by muscular cords
  • the left has two valves the mitral/ bicupsid valve
  • the right has three valves the tricupsid valve
  • The muscular cords which attach to the valves are replaced by the connective tissues (chordae tendinae), and the rest becomes papillary muscle.
101
Q

Describe the development of the semilunar valves ?

A

Describe the formation of semilunar valves ?

  • The semilunar valves develop as swellings of the truncus arteriosus, into the ventral aorta and pulmonary trunk via growing cushions.
  • Upon completion of the aorticopulmonary septum, the swellings give rise to three half moon shaped valves in each aortic and pulmonary outlet.
102
Q

Describe the development of the arterial and venous systems ?

A

Arterial and venous systems

Arterial system

  • Cranial; six aortic arches, dorsal and ventral aorta
  • Caudal; at first they extend as a pair then fuse to form a single aorta, and develop into internal and exdternal iliac arteries.

Venous system

  • returns blood to the heart
  • vitteline vein (veins from yolk sac and abdominal organs)
  • Umbilical vein (veins from placenta oxygenated blood)
  • Cardinal veins (veins from the cranial part of the developing embryo)
103
Q

Describe foetal circulation

A

Foetal circulation

  • Circulation in the foetus is designed so that blood bypasses the liver (ductus venosus), due to there being no requirement to metabolise nutrients
  • Foetal circulation also bypasses the lungs (ductus arteriosus), as the lungs are undeveloped
  • the foetus meets all its nutrient and oxygen requirments from the maternal blood across the placenta.
104
Q

Describe the major changes to foetal circulation that occur at birth ?

A

Two major events occur to the circulation at birth

Placental blood flow ceases

Lung respiration begins

  • Unbilical arteries closes to form ligamentum teres vesicae
  • umbilcal veins closes to form ligamentum teres hepatis
  • ductus venosus closes to form ligamentum venosum
  • ductus arteriosus closes to form ligamentum arteriosum
  • foramen ovale closes to form the fossa ovalis
105
Q

Describe the formation of the gut tube ?

A

Gut tube formation

  • endoderm
  • the trilaminar germ disc undergoes a lateral folding of the developing embryo
  • the disc starts to resemble a tube
  • internal layer of endoderm lies on the innermost aspect of this tube to form a primitive gut tube from mouth to anus
  • endoderm forms the respiratory and digestive system
106
Q

Classifcation of the primitive gut ?

A

The primitive gut can be classified into free sections

  • the endoderm lined tube may be classified into the foregut, midgut and hindgut
  • the respiratory system develops from a region known as the foregut
  • respiratory diverticulum
107
Q

Describe how the respiratory diverticulum develops ?

A

Respiratory diverticulum

  • The respiratory oesophagus is seperated from the trachea and oesophagus by the tracheo-oesophageal groove.
  • that results in the edevlopment of the tracheo-oesophageal septum which defines the respiratory diverticulum
  • The respiratory diverticulum has branched to form left and right lung buds as the precursors of left and right lung tissues.
108
Q

Identify two Trachea-oesophageal defects which occur during development?

A

Tracheal oesophageal defects

Altresia

  • an abnormal closure of a tube orifice
  • often associated with oesophageal atresia

Fistula

  • an abnormal opening between two tubes
  • occurs when the oesophgeal septum fails to develop correctly
109
Q

Name the four periods of the lung maturation ?

A

The four periods of lung maturation

  1. Pseudo-glandular period
  2. Canalicular period
  3. Saccular period
  4. Alveolar period
110
Q

Describe the pseudoglandular period of lung development ?

A

Pseudoglandular period of lung development

  • terminal bronchioles form
  • lungs resemble glands under the microscope, as tubules lined by columnar endodermal epithelium.
  • structures often mistook for glands
111
Q

Describe the canicular period of lung development ?

A

Canicular period

  • second stage of lung development
  • terminal bronchioles branch too form two or more respiratory bronchiloes
  • lined by columnar endodermal epithelium
  • surrounding capillaries grow intensely from the mesoderm, and make close contact with the epithelium

A foetus born during this period would not survive as respiration is impossible.

112
Q

Describe the saccular period of lung development ?

A

Saccular period

  • Alveoli sacs develop as the last birufication as blind saccules
  • alveolar sacs begin to thin from columnar to squamous epithelium

A premature birth at this stage may result in respiratory distress syndrome and the baby has a slime chance of survival.

113
Q

Describe the alveolar period of development ?

A

Alveolar period of lung development

  • Final compartment development for gas exchange
  • capillaries bulge into the alveoli sacs forming immature aveoli
  • epithelial cells differentiate into type one and two pneumocytes

A foetus born during the alveolar stage would have a good chance of survival

114
Q

Describe the formation of the pleural cavities ?

A

Pleural cavities

  • Lateral folds of the lateral mesoderm differentiate into the parietal and vsiceral layers of the pleura
  • the space between is the intraembryonic mesoderm
  • Intraembryonic coelom = pleural and peritoneal cavities
  • extraembryonic coelom = develops into the chorionic cavity that is outside of the developing embryo, to form the placenta.

The result is the splanchnic mesoderm touches the lungs directly and runs in all the fissures (Visceral pleura)

The somatic mesoderm is reflected at the lung root and adhers to the thoracic wall and diaphragm (parietal pleura)

115
Q

Name the three embryonic components that give rise to the diaphragm ?

A

The three embryonic components of the diaphragm

  1. pleuro-peritoneal membrane
  2. body wall musculature
  3. septum transversum
116
Q

Describe how the septum transversum contributes to the diaphragm ?

A

Septum transversum - diaphragm

  • formed during the head and tail folds of the embryo
  • thick mass of mesenchymal cells
  • it forms a partial shelf seperating the thorax and abdomen
117
Q

Describe the contribution of the pleuro-peritoneal membrane to diaphragm development ?

A

Pleuro-peritoneal membrane

  • The thorax communicates with the abdomen through pericardial peritonial canals
  • Pleuro-peritoneal membrane grows from the dorsal body wall to seal off the canals and form tendinous part of the diaphragm.
118
Q

Describe the contribution of the body wall masculature to diaphragm development ?

A

Body wall masculature

  • The lungs grow in size and push some of the lateral wall inwards as a final musculature component of the diaphragm
  • This ingrowth forms the final part of the diaphragm.
119
Q

Describe the embryological origins of the oral cavity, anus and urogenital openings.

A

Embryological origins

Oral cavity

  • ectodermal depression
  • stomoderm (oral pharyngeal membrane)

Anus and urogenital opening

  • ectodermal depression
  • proctoderm (cloacal membrane)
120
Q

Describe the blood supply to the gut during embryonic development ?

A

Gut blood supply

Foregut = coeliac artery

Midgut = cranial mesenteric artery

Hindgut = caudal mesenteric artery

121
Q

Describe the embryonic origins of a mesentary ?

A

Mesentary

  • Formas when a layer of peritoneum lies against each other a double layer of peritoneum, - lateral mesoderm
  • contains blood vessels, nerves and lymphatics
  • attaches an organ to the body wall

Lesser mesentary - lesser curvature of stomach, dudenum and liver

Greater mesentary - spleen and the greater curvature of the stomach

122
Q

Describe the embryological origin of the foregut ?

A

Foregut

Oesophagus

  • extends developing pharynx to stomach
  • start wide + short to long and narrow
  • stratified squamous epithelium

Stomach

  • forms from a dilated region of the foregut
  • rotates 90degress clockwise with dorsal surface on the left
  • dorsal surface grows faster than the ventral surface forming the greater and lesser curvatures of the stomach respectively
  • finally 45-90 degree clockwise rotation to form the pylorus - to raise the pylorus and lower the cardia

descending duodenum and accessory organs are also a part of the fore gut.

123
Q

Describe the embryological orgin of the liver ?

A

Foregut accessory organ liver?

  • Hepatic diverticulum = consist of hepatic cords, cystic diverticulum, and the ventral pancreatic bud of cells from the endoderm
  • they envade to the mesoderm of the septum transversum of the diaphragm to form the cellular component of the liver
  • endoderm forms the tubular part of the liver
124
Q

Describe the embryological development of the midgut ?

A

Midgut

the midgut develops into the ascending duodenum, jejunum,iliem, caecum, ascending colon and 2/3 along the transverse colon

The midgut is suspended from the dorsal wall by the root of the mesentary

It communicates or opens to the yolk sac via the vitelline gland.

125
Q

Describe the embryological origins of the gallbladder ?

A

Gall bladder

  • Develops from the hepatic diverticulum - cystic diverticulum
  • forming the gall bladder and cystic duct

The cystic portion fails to develop in the horse, whale and rat

126
Q

Describe the embryological origin of the pancreas ?

A

Pancreas

  • A ventral pancreatic bud is derived from the hepatic diverticulum
  • a dorsal pancreatic bud emerges from the foregut dorsally

The ventral pancreas rotates with the stomach and eventually fuses with the dorsal pancreatic bud.

127
Q

Describe the developments and differential growth of the midgut ?

A

Midgut

Development

  • R vitelline artery gives rise to the cranial mesenteric artery (blood circulation to/ from yolk sac of foetus) which becomes internalised in the loop
  • proximal descending part becomes small intestine
  • distal ascending part becomes the large intestine

Mid gut differentiation

  • a rapid extension of the proximal part pushes to the right and wraps around the cranial mesenteric
  • 180 degree rotation around dorsal axis
  • continues to move through to the left then cranially again (completed 360 degree rotation)
128
Q

Describe the positioning of the midgut after final development ?

A

Mid gut positions once developed

Ascending duodenum and descending colon = right

jejunum = ventral left

caecum and iliem = right

ascending colon = right, two dimensional loops ruminants, spiral coil pig, narrow U shape loop horse

Transverse colon = becomes localised right to left and continues into descending colon

129
Q

Describe the branches of the cranial mesenteric artery ?

A
130
Q

Describe the development of the hind gut ?

A

Hind gut = distal 1/3 transverse colon, desending colon, rectum and anal canal

Cloacal membrane = Forms the terminal part of the hindgut where the endoderm comes to lie in contact with the ectoderm.

Urorectal septum - develops into perineal body - to divide the rectum and cloaca

131
Q

Identify the three generations of kidney primordia ?

A

Three kidney primordia

  • pronephros (early nephrons)
  • mesonephrons (middle nephrons)
  • metanephrons (later nephros)
132
Q

Describe the development of the pronephrons ?

A

Pronephrons

form from intermediate mesoderm in the cervical region

  • early development
  • cranial region
  • consist of 7-8 pairs pronephric tubules
  • in lower vertebrates - amniotes (tetrapods) comprising reptiles, birds and mammals
  • only 1-3 tubules form and connect to archinephric duct

Duct will continue to develop caudally to the cloaca.

  • mammals = degenerate without function
  • fish =persist and functions in immature fish
  • amphibians = persist and function in larvae
133
Q
A
134
Q

Describe the development of the mesonephrons ?

A

Mesonephrons

  • forms glomeralus, tubules and bowmans capsule
  • size correlates to placenta type - big with high placenta layers
  • cranial mesophrinic tubules connect with the developing gonads
  • mesonephric duct connected to epididymis and vas deferens in male

Forms by intermediate mesoderm in the lumbar and thoracic area

  • mammals function as temporary embryonic kidney
  • birds reptiles function until hatching
  • fish + amphibians function as adult kidney
135
Q

Describe the development of the metanephros ?

A

Metanephros

Derives from the metanephric diverticulum

Derived from intermediate mesoderm in the pelvic region

  • branches from archinephric duct and mesoephric duct
  • loacted sacral region
  • induces differentiation of renal tubules

Become the permanent functional kidneys in mammals

136
Q

Describe the development of the ureteric duct

A

Ureteric duct

Suquential division of the ureteric duct forms the

  • collecting ducts
  • major calyces
  • minor calyces
  • renal pelvis
  • ureter
137
Q

Describe the devlopment of the metanephric blastema ?

A
138
Q

Describe the ascent of the kidneys ?

A

Ascent of the kidneys

  • kidneys move cranially into the lumbar region
  • rotate 90 degress to face the veertebrae
  • initially hilum is the entry area of blood vessels
  • blood supply from aorta changes as the kidneys ascend
139
Q

Describe the formation of the bladder ?

A

Formation of the bladder

  • terminal part of hindgut extends into the cloaca
  • divided into the anus and urogenital sinus
  • urinary bladder derived from endoderm
  • canal near the cloaca called urachus and pelvic region of urogenital pelvis
140
Q

Describe Leydig and Sertoli cells

A

Anatomy yrtwo semone (10 decks)

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