Final Exam Flashcards
Pituitary
Froms from the roof of the oral cavity, grows upward as Ratheke’s pouch, lumen of pouch becomes the residual cleft between the pars distalis and pars nervosa
Hypophysis - pituitary is divided into an anterior pituitary (mostly pars distalis with along with pars tuberalis and pars intermedia) and posterior pituitary (pars nervosa and infundibular stalk)
Pars distalis of Pituitary
Cords or clusters of cells associated with sinusoids
Cords or clusters of cells seperated by many capillaries or sinusoids
Cells:
Chromophobes
Chromophils
a. Acidophils (produce growth hormone and prolactin)
b. Basophils (produce TSH, LH, FSH, and ACTH
Neurohypophysis
Contains numerus unmyelinated axons
Cell bodies are in the hypothalamus
Secrets oxytoicn and vasopressin
These travel down the hypothalamo-hypophyseal tract to pars nervosa
Swelling called Herring bodies are seen in the pars nervosa
Pituicytes are the cells in the pars nervosa
Thyroid
Cells origin from an outgrowth of buccal cavity
Thyroid follicles are hollow spheres filled with colloid
Colloid - Made up of thyroglobulin
Follicular cells - Cubodial epithelium, have microvili on apical edge, held together by tight junction to prevent leakabe of thyroglobulin
- Have a storage and endocrine phase
- In endocrine phase, stored thyroglobulin is taken up by follicular cels and broken down into T4 and T3 (active hormone)
Parafollicular cells - Isolated clusters of cells within the basal lamina of follicles. Larger paler cells and produce calcitonin
Parathyroid Gland
Located in or around thyroid
Capsule of internal parathyroids is areolar CT of thyroid
Parenchyma: Cords, cluster with numerous capillaries
Chief Cells - Predominant cel type. Light and dark cells. Dark chief cells produce parathyroid hormone (PTH).
Oxyphil Cell - Large cell with acidophilic cytoplasm of unknown fuction
PTH - Raise blood calcium levels, increases the activity of osteoclasts, wich tear down bone to release calcium
Adrenal Gland
Located on cranial pole of kidney
Capsule around adrenal sends trabeculae into the parenchyma. There are also fine reticular fibers within the parenchyma.
Cortex - divided into 3 regions
Zona glomerulosa - Produces mineralocorticoids (mainly aldosterone) which act on the kidney to keep more sodium and water in the blood instead of excreting them. Not influenced by ACTH.
Zona fasciculata - Widest zone. Cells have a foamy cytoplasm. Steroid producing cells: glucocorticoids such as cortisol, secreted when the pituitary secretes ACTH.
Has a large amount of SER and numerous lipid inclusions.
Zona reticularis - Closely packed cels in anastomosing cords; this zone produces some weak androgens and some glucocorticoids
Medulla - Made up of chromaffin cells. Pheochrome cells.
Paragnaglia
Small bodies containing chromafin cells that are found associated with abdominal aorta
Pineal Gland
Photoreceptor in lower vertebrates
Secretions of melatonin and serotonin.
3 lobes:
Pinealocytes - large cells; open nucleus
Astrocytes
Brain sand (corpora arenacea)
Thyroid Follicles
NA/I symporter - NA help iodine move in against the concentration gradient
Oxidation of iodine occurs in the follicle colloid
Iodination can then occur of thyroglobulin to break it down int T4 and T3
Thyroid System
TRH is released from the hypothalamus and stimulates release of TSH to act on the thyroid gland
The thyroid hormone releases T3 and T4
T3 and T4 work to increase metabolism, growth and development, increase catecholamine effect
Parafollicular Cells
Produce calcitonin which lower serum calcum
Cells of the Parathyroid
Chief - smaller and bluer
- Produce PTH
- PTH -> increase serum CA
(osteoclasts/kidney/gut (vitamin D))
- PTH -> slightly lowered serum PO4
(complicated interaction between gut/kidney/bone)
Oxyphil - bigger and redder
Regulation
- One of the very few endocrine systems not regulated by the pituitary gland
- Calcium concentratioins in blood provide direct feedback to parathyroid, stimulating or restricting PTH production
- Calcium sensitity is through the CaSR (calcium sensing receptor) protein
Adrenal Gland
Zona glomerulosa
- Not much influenced by ACTH
Incluenced more by Angiotensin II
Produces mineralocorticoids: aldosterone
Causes increase Na and water retention by kidney
Zona fasciculata
Is stimulated to produce glucocorticoids by ACTH
- Cortisol
Glucocorticoids suppress inflammation and outside liver are catabolic (increase gluconeogenesis)
Zona reticularis
Is stimulated to produce adrogens by ACTH
- Androstenedione
Medulla
Chromafin (aka pheochrome) cells produce catecholamines
Stimulated by preganglionic fibers of the sympathetic nerous system
Pineal Gland
Light Sensitive
- Acts as a light sensing organ in lower animals
Produces melatonin
- May regulate/restrict puberty through action on the pituitary
- May afect seasonal breeding cycles
- May affect circadian rythm
Cells
Pinealocytes - produce melatonin
Brain sand (corpora arenacea)
Testes
- Male gametes
- Spermatozoa
- Testosterone
Dick Ducts
- Ductuli efferents
- Epididymus
- Ductus (vas) deferens
- Ejaculatory duct
Collects, stores spermatozoa from each testis and conducts their maturation
Dick Glands
- Seminal vesicles
- Prostate gland: Secretes seminal fluid
- Semen: Consists of seminal fluid and spermatozoa
Penis
- The organ of copulation
- Bulbourethral glands of Cowper: Secrete a fluid which lubricates the urethra for the passage of semen during ejaculation
Testes
- Exocrine component: Produces spermatoza
- Endocrine component: Leydig cells produce testoerone and sertoli cells produce estrogen
- Capsule forms tunica albuginea
- Stroma: Mediastinum tesis at the anterior pole surround the “rete testis”
- The tunica albuginea is surrounded by tunica vaginalis
Testis Parenchyma
Seminiferous tubules
- Basal lamina around seminiferous tubules
- Myoid cells, smooth muscle outside basal lamina
- Stratified epithelium cells: The various stages of developing germ cells + Sertoli cells inside the tubules
- Sertoli cells: Supporting or sustentacular cells are nurse cells, tall triangle shaped cells (hard to see cell outlines)
- Sertoli cells function as physical and nutitional support, phagocytosis, secretion of estrogen, androgen-biding protein, activin, and inhibin
Sertoli Cells
Support spermatogenesis nutritonally and hormonally
Sertoli cells create blood-testis barier
Held together by tight junctions
THE ADLUMINAL COMPARTMENT IS THE IMMUNE PRIVILEGED AREA
Spermatogensis
3 phases
Mitosis, meiosis, metamorphosis
Spermatocytogenesis (mitotic state) - Spermatogonia divide and eventually give rise to spermatocytes
Meiosis - Spermatocyte become a haploid spermatid
Spermatogonia Cell Division
- A cells: stem cells that have round nucleus with condense chromatis
Primary spermatocytes: largest cells, begining of meiosis, 4N DNA, chromosoam cross-over occurs
Secondary spermatocytes: Smaller with 2N DNA, undergo 2nd meiotic division
Spermatids: Small round cells, nuclei become flattend and heterochromatic and are haploid (1N DNA)
Mature spermatozoa: Formed during the metamorphosis stage. Development of the acrosome, flagellum, and nuclear condensation. Head is covered by acrosomal cap with cointains hyaluronidase.
Testicular Stroma and Ducts
- Leyding cells: acidophilic foamy cytoplasm and produce testosterone (lightly eosinophilic large cytoplasm). Endocrine cells - produce testosterone (controlled by LH).
- Straight tubules: simple squamous or cuboidal epitheium, connect seminiferous tubules to rete testis
- Rete testis: anastomonic tubules located in mediastinum
- Ductuli efferets - Connect rete testes to epididymis; epithelium is ciliated, simple columnar
Rete Testis & Ductuli Efferents
Move non-motile spermatozoa to epididymis
Lined by a single layer of cuboidal epithelial cels with microvilli and single cilicum at rete tests or cilia at ductuli efferents
Genital Ducts
Ductus Epididymis - Coiled tube that stores sperm while it matures
- Divided into head, body, and base
- Epithelium is pesudostratified columnar with sterocilia
- Connects to ductus deferens
- Takes about 10 - 15 days
Ductus Deferens - Epithelium becomes pseudostratified columnar, gradually loses sterocilia
- Lumen contains spermatozoa in the mature male animal
- Tunica muscularis is very thick
Epididymis
Maturation of spermatozoa
Stay in epididymis for 2 weeks
Pseudostratified columnar epithelial cells with seterocilia lined with a sing smooth muscle laery
Ductus deferens
Three layers of smooth muscle. Peristatic contration is controlled by sympathetic nervous system during ejaculation
Seminal vescile
Associated with ductus deferens and secrete seminal fluid
Seminal fluid is alkaline and helps neutralize the acidity of the vaginal tract
Contains proteins, fructose, mucus, vitamin C, flavins, phosphorylcholine, and prostaglandins
Vesicular glands are absent in carnivores
Simple columnar epithelium have lipofuscin granules in cytoplasm
Accessory Organs
- Ampulla: Terminal part of vas deferns
- Prostate: Body surround urethra. Concentrically laminated concentrations of secretory product
- Have ejaculatory ducts, a sort part of the vas deferns joins with the duct of the seminal vesicles
- Produces half of the seminal fluid which cointains fibrinolysin and ciric acid. Helps liquify coagulated semen. Tall columanr secretory epithelial cells with round nuclei.
Urethra
Transition epithelium
Pelvic part has colliculus seminalis, an area where deferens ducts, seminal vesicles, and prostatic ducts empty into the urethra
Penis
Has a capsule of tunica albuginea
Ereticle tissue: Vascular sinuses in the CT
- Corpus cavernosum penis
- Corpus cavernosum urehra
Glans: Extension of corpus spongiosum and covered with stratified squamous eithelium of prepuce
Ovary
Has a cortex and a medulla and a tunica albuginea
Has both endocrine (hormones) and exocrine (oocytes) fuction
The hormones are produced by the developing follices
Follicles are transformed after ovulation to corpora lutea
Ovary responds to pituitary hormones, including FSH and LH
Cortex is where follices developed and is peripherally located
Tissue between follices is the stoma (fibroblast-like with lipid droplets)
Tunica Albuginea and Serosa
Tunica albuginea is the CT around the outer edge of the cortex
Tunica serosa covering the ovary has simple cuboidal epithelium (outer most layer)
Ovarian Medulla
Contains the blood vessels for the ovary
Contains a system of channels lined by cuboidal epithelium called the rete ovarii
Oogenesis
Oogonia divide mitotically until birth and give rise to primary oocytes which become arrested in meiotic prophase I
When simulated to divide the primary oocyte complete meiosis I dividing to form the secondary oocyte and 1st polar body
The secondary oocyte is formed just prior to ovulation
The secondary oocyte undergoes the 2nd meiotic division right after fertilization
Ovarian Follicles
The oocytes are inside follicles, surrounded by a capsule-like structure called the zona pellucida and a layer of epithelial cells called granulosa cells
The zona pellucida is a thick glycoprotein layer secreted by both the oocyte and the granulosa cells
There is a basement membrane around the follicular epithelial cells and a theca around the follicle outside the basement membrane
Stages of development are described based on their apperance
Primordial Follicle
Oocyte is surrounded by a single layer of squamous cells.
These follicles are quiescent.
Thre is a basement membrane between the follicle and the ovarian stroma.
Primary Follicle
Oocyte is surrounded by cuboidal granulosa cells
Zona pellucida forms around oocyte
Theca may be forming
Secondary Follicle
Small pockets of follicular fluid appear between granulosa cells
The pockets have not yet coalesced into 1 large fluid cavity
The theca become obvious
Tertiary Follicle
Has 1 large fluid-filled cavity with a layer of cranulosa cells around the stratum granulosum
The oocyte is surrounded by granulosa cells called the cumulus oophorus
The corona radiata is the layer of granulosa cells immediately in concat with the zona pellucida
The cumulius oophorus is attached to the wall of the follicle by a mass of granulosa cells called the hilus
Granulosa Cells
Follicles are divided into special areas including:
Cumulus oophorus
Corona radiata
Stratum granulosum
Atretic Follicle
Follicular atresia - follicles degenerate and become atretic
Ovarian Cycle - Luteal Phase
The corpus luteum (CL) is a transiet endocrine gland derived from an ovulated follicle that produces progesterione which helps maintain pregnancy
Eventually regressing and ability to produce progesterone and involutes to become a CT scar
PGF2alpha lyses
Ovarian Cycle - Follicular Phase
The CL is regressing
The follicle is maturing
Estrogen is being produced by granulosa cells in response to FSH
Rising estrogen in the late follicular phase initiate the LH surge which triggers ovulation
Endometrium is proliferating
Theca cells have LH receptors which cause produce androgens that diffuse into the follice
Granulosa cells have FSH recepors and produce estrogen and will later develop LH receptors
Pre-Ovulatory LH Surge
Rising estrogen levels during the follicular phase stimulate the release of LH from the pituitary and the high estrogen at the end of the follicular phase causes an LH surge which:
- Stimulates primary oocyte to complete meiosis I
- Starts process of ovulation
- Indues formation of the CL in the ovulated follicle
Events at Ovulation
The LH surge causes release of collagenase and other enzymes to digest tissues at the ovulation site
The stroma overlying the follice becomes avascular and degenerates
Tecal layers thin
The oocyte and the cumulus oophorus break free from antral wall
The follicle protrudes from wall of ovary at the “stigma”
The oocyte is released from the follicle
After ovulation, a CH forms as blood fills in the follicle lumen. The wall of follicle collapses and creats folds.
Luteal Phase
The CL forms from the granulosa and the theca cells after ovulation:
- Granulosa cells proliferate, enlarge and become granulosa lutein cells.
- Theca interna cells convert to theca lutein cells.
- Progesterone is produced by the CL.
- The uterine glands are secreting.
- LH secretion maintains function of the CL.
- Progesterone stimulates the development of uterine endometrium.
- Progesterone (and estrogen) produced by the CL inhibit FSH and LH release.
CL Regression
The fate of the CL depends on wheter copulation and/or fertilization occurs.
- CL of pregnancy
Corpus albicans: The CL is gradually replaed by a CT scar
Oviduct Divisions
- Infundibulum - funnels shaped, with fimbriae
- Ampulla - extends caudally from infundibulum
- Isthmus - a narrow, muscular segment joining the uterus
Oviduct Layers
- Mucosa - the epithelium and the underingly CT tissue
- Tunica muscularis - irregularly arranged smooth muscle
- Tunica serosa
Oviduct Mucosa
- Mucosa is folded
- Epithelium is simple columnar ciliated
- Non-ciliated secretory cells
Uterus
Layers:
- Endometrium: Equivalent to the tunica mucosa and submucosa and contains uterine glands
- Myometrium: Equivalent to the tunica mscularis, it is the inner circular layer, outer longitudinal layer
- Perimetrium: Tunica serosa, a thin layer of fibroelastic CT covered by a mesothelium
Cervix
Epithelium is columnar mucous cells
Tunica muscularis has inner circular and outer longitudinal layers
Vagina and Vestibule
Vagina
Stratifed squamous non-keratinized epithelium
No muscularis mucosa, therefore the lamina propria is joined to the submucosa
Tunica muscularis: inner circular, outer longitudinal
Vestibule
Contains major and minor vestibular glands
Proestrus
Beginning of endometrial growth
CL from previous cycle is regressing
New follices are growing: theca cells and granulosa cells
Estrus and Metestrus
Estrus
- Ovulation occurs during this phase in most species
- CL develops during this phase in the dog
Metestrus
- Defined as the period of CL development
- Progesterone levels climbing
- No metestrus in dog since CL develops in estrus
Diestrus
Phase of active CL
Uterus reaches maximal endometiral gland development and activity
CL regresses toward end if no implantation
Anestrus - prolonged period of sexual inactivity
Vaginal Smear
Anestrus - Mainly non-keratinized cells, few PMNs
Proestrus - PMNs early, numerous RBCs, keratinized cells increasing
Estrus - Some RBCs, mainly keratinized cells
Metestrus - Diestrus: PMNs reappear, RBCs variable
Mammary Gland
Compound gland with large ducts in the interlobular CT (modified sweat gland - apocrine and merocrine)
Both the alveoli and the intralobular ducts are secretory, with simple cuboidal to columnar epithelium
Corpora amylacea are concentrations of secretory materal found scattered in alveoli
Alveoli regress when the gland is inactive
Myoepithelial Cells - Contractile cells that surround alveoli and respond to oxytocin to cause milk “letdown”. Found between basal lamina and alveolar cells.
Non-secretory portion: Interlobular ducts, lobar ducts, and lactiferous sinus
Mammary Glands Ducts & Stroma
Ducts
Epithelium: bein as simple cuboidal, lobar ducts have bistratified columnar epithelium. Smooth muscle and elastic fibers surround large ducts.
Stroma: the loose collagenous and adipose tissue stroma is a major component of non-lactating glands. Stroma become very scant during lactation.
Mammary Gland Sinus System
Lactiferous sinus = Teat sinus + Gland sinus
Bistratified columnar epithelium
Streak canal (lactiferous duct): Transition from bistratified columnar epithelium to the skin of the teat
Unilobar Kidney
Found in dog, cat, horses, and small ruminants
Broad papilla forms renal crest
Collecting ducts feed into renal pelvis
Multilobar Kidney
Found in cow, pig, and primate
Renal Lobe
Outer Cortex:
- Pars convoluta
- Pars radiata
Inner Medulla:
- Loops of Henle
- Collecting ducts - Open through tiny openings in papilla called area cribosa
Area Cribosa
Collecting ducts open through tiny opening in papilla called area cribosa
Uriniferous Tubules
Uriniferous Tubule - The functional unit of each kidney is the microscopic uriniferous tubule
Includes:
A. Nephron - produces urine
B. Collecting duct - collects, concentrates, and transports urine
Nephron
Includes:
A. Renal corpuscle
a. Glomerulus
b. Glomerular capsule
B. Renal tubule
a. Proximal and distal convoluted tubules
b. Loops of Henle
c. Connecting tubule
Renal Corpuscle
Glomerulus - Tuft of capillaries
Glomerular (Bowman’s) Capsule - Houses the glomerulus
The glomerulus connects the afferent arteriole to the efferent arteriole
Capsule consists on an internal (visceral) and an external (parietal) lined by epithelial cels
Podocytes - Epithelial cells that line the visceral layer
- Have cytoplasmic processes called foot processes or pedicles
- Pedicles interdigitate to form filtration slits
Vascular pole - Afferent and eferent arterioles enter/leave
Urinary pole - Where proximal tubule originates
Mesangial Cells
Phagocytic cell found between capilarries of glomerulus
Cytoplasmic processes extend between endothelial cells
Function is to clean the GBM (glomeular basement membrane) of the particulate matter
Renal Function
- Filtration
- Tubular reabsorption
- Tubular secretion
Glomerular Basement Membrane
Lamina rara externa - adjacent to podocyte processes - heparan sulfate - filters by charge
Lamina densa - central zone - type IV collagmen - fliters by size
Lamina rara interna - adjacent to endothelial cells - heparan sulface - filters by charge
Glomerular Filtration
~ 20% - 25 of cardiac output
Glomeular Filtration Rate (GFR)
Tubular Reabsorption
- Substances are reabsorved selectively in different parts of the uriniferous tubules
- Active Transport: Glucose, amino acids, Na+
- Glucose passes freely through the filtration barrier (PCT)
- Na+ (PCT and Loope of Henle)
- Passive Diffusion: Water and urea
- Urea passes frely across the filtration barier by diffusion and passively absorbed in PCT
- The extent of water reabsorptioin influence the amount of urea in the urea
- Hormones like parathyroidhormone (PTH), aldosterone, antidiuretic hormone (ADH) also influence the rabsorption process
Tubular Secretion
1. Endogenous compounds
- Creatinine, histamine, metabolic products of hormones
2. Exogenous compounds
- Antibiotics, asprin, other drugs
3. Water, cations, and anions pass into tubular lumen by passive or active mechanisms
General Features of Tubular Epithelium
Function of epithelium is determine by:
- The asymmetric distribution of channels and transporters in the apical and basolateral membranes
- The permeability of the zona occludens (paracellular transport)
Proximal Convoluted Tubule (PCT)
Simple cuboidal epithelium with brush border
Loop of Henle
- U shaped structure with a thin descending limb and a thick ascening, both composed of simple squamous epithelia
- Function: Passive reabsorption of Na+ and Cl-
- The thin ascending limb of the loop become the thick ascending limb which is composed of simple cuboidal epitheium
- Function: Active reabsorption of varous electrolytes
Distal Convoluted Tubue (DCT)
- Zone of transition
- More empty lumens
Collecting Duct
Has 2 types of cells:
- Principal cells
- Intercalated cells
JG Apparatus
Consists of 3 types of cells:
-
Macula densa of the DCT
a. Taller epithelium with more apparent nuclei
b. Chemoreceptors for Na+ and Cl- -
Juxtaglomerular cells
a. Located in the wall of afferent arteriole
b. Have cigar shaped nuclei
c. Secrete renin - Extraglomerular mesangial cells
a. Lacris or Polkissn cells
b. Located outside glomerulus
Urothelium
Called transitional epithelium
Found only in the urinary tract
Fluid Transport in the Urinary System
Upon delivery at a minor calyx, filtrate is no longer modified by rabsorption or secretion and is called urine
It flows passively into the renal pelvis but moves by peristalsis along the ureters for temporary storage in the bladder, which is emptied through the urethra
Review
Gray Matter
- Made up of nerve cell bodies
- Fibers (mostly unmyelinated)
- Glial cells
- Neuropil is the background of gray matter, composed of glial processes and unmyelinated nerve processes
Review
White Matter
- Made up of myelinated fibers and glia
- Divided into dorsal, lateral, and ventral funiculi
- Funiculi contain ascending and descending tract
Meninges
3 meningeal layers:
- Dura mater
a. Fused to the periosteum of the cranial cavity
b. Seperated from the periosteum in the vertebral cana by the epidural space - Arachnoid
a. Membrane + trabeculae
b. Space below is subarachnoid space - Pia mater
a. Closely associated with nervous tissue
Pia + Arachnoid = Leptomeninges
CNS Vasculature
Pericytes in the perivascular space are responsible for formation and maintenance of vessel basement membrane as well as phagocytosis after injury
Astrocytes processes from a sheath around CNS vessels
The most important vascular adaptation is the tight junctions between vascular endothelial cells. This forms the blood-brain barrier.
Ventricular System
Ventricles are large cavities inside the brain, lined by ependymal cells, and filled with CSF.
Choroid Plexus
Found in roof and wall of all ventricles of brain.
Covered in ependymal cells
Secrete CSF
Tight junctions between these ependymal cells form the blood-CSF barrier.
Capillaries here ARE fenestrated.
Cerebrospinal Fluid
Produced by choroid plexuses in lateral, third, and fourth ventricles
Circulates through central canal
Exits via the lateral foramina to the subarachnoid space
Reabsorbed to the vascular system via the arachnoid villi
Brainstem
Gray matter in the brain is distributed in the form of nuclei instead of columns
Nuclei: collection of cell bodies within the brain stem, and deep within the cerebrum and cerebellum
Many nuclei are sensory or motor from the cranial nerves
Some are relay areas
Cerebellum
Coordinates motor activity
Zones:
- Molecular: Most superficial
- Purkinje cells: Large flask-like cells. Provide the only efferent route from the cortex to deeper cerebellar nuclei
- Granular layer
Cerebrum
Layers of the cortical gray matter:
- Molecular layer
- Small pyramidal
- Large pyramidal
- Polymorphic
White Matter
ANS
Visceral part of the nervous system.
- Important in homeostasis.
- Regulates smooth muscle, cardiac muscle, and glands
- Mainly motor, but also has sensory components
- Efferent is a 2 neuron system
1. First ganglion is preganglionic located in the CNS
2. Second neuron is postganglion located in a peripheral ganglion
Sympathetic (thoracolumbar)
- The ganglion are large and near the vertebrae
- Preganglionic neurotransmitters: ACH
- Postganglion neurotransmitters: Norepinephrine
Parasympathetic (craniosacral)
- Parasympathetic ganglia innervate single organs; the ganglia are microscopic (usually) and are in or near the organ
- Neurotransmitter of both pre- and postganglionic fibbers is ACH
Key Words
Anterior Compartment
- Anterior chamber: between cornea and iris
- Iris: contains ciliary body
- Posterior chamber: between iris and lens
Posterior compartment: Filled with vitreous humor
Cornea
- Devoid of blood vessels and lymphatics
- Has remarkable healing power
Epithelium
- Turnover time of 7 days
- Germinal cells in the basal layer at limbus-cornea junction
Bowman’s membrane
- Basal lamina that support epithelium
Substantia propria (stroma)
- Avascular
- Keratocytes
Descemet’s Membrane
- Basement membrane
Corneal Endothelium
- Mesenchymal epithelium
Sclera
Sclera proper
- Dense irregular CT
Limbus
- Germinal cell center for cornea
Vascular Coat or Uvea
The vascular rich midle layer of the eye constituting the iris, ciliary body, and choroid
Choroid
- Vascular rich layer most prominent layer of middle tunic
Tapetum lucidum
- Found in choroid between vascular layer and pigment epithelium
- Night vision
Ciliary Body
- Anterior continuation of the choroid
- Zonular fibers extend to lens
Ciliary Body
- Classified as bistratified columnar
Ciliary Muscle Controls Lens Thickness
- Under parasympathetic innervation
- When it contracts it removes tension from zonules, lens “round up” to accomate for near vision
Iris
- Circular diaphragm in front of lens (extension of choroid)
- Heavily pigmented myoepithelial cell lining
2 types of muscles
- Pupillary sphincter muscle (constriction) - parasympathetic innervation
- Pupillary dialator muscle - sympathetic innervation
Corpora nigra (iris granules)
- Found in the horse and ruminants
Aqueous Humor
- Drained away at filtration angle into endothelial spaces between trabeculae and then to the Canal of Schlemm
Retina
Ora serrata
- Transition from optic to blind part of retina, closer to lens
Pigmented Epithelium
- Has phagocytic ability
- Dehydrate retina
- Creat immune privilege space of inner eye
Layers of Rods and Cones
- Contains membranous vesicles stacked like coins in the processes of rods and cones
In rods these membranous stacks contain a pigment called rhodopsin
- In cones there is a pigment called iodospin
- Rhodopsin and iodopsin are photoreceptor proteins
Retinal Photoreceptors
Two visual system: scotopic & photopic
- Dark adapted (night) vision is called scotopic and is ruled by rods
- Rods have rhodopsin
- Light adapted (daylight) is called photoic and uses cones (color vision)
- Cones have iodopsin
Three Neuron System of Nuclear Layers of the Retina
1st neuron
- Nuclei of rods and cones
2nd neuron
- Inner nuclear layer of bipolar cells, horizontal cells, and amacrine cells
3rd neuron
- Layer of ganglion cells
Plexiform layers are seen between these nuclear layers as lighter areas not containing many nuclei
Fovea
- The foveal retina is modified to obtain the maximum photoreceptor sensitivity and the greatest visual discrimination.
- Surrounding the fovea is an ovid yellow area about 1 mm wide called the macula lutea.
- Retinal blood vessels are absent at the fovea. AT the fovea, the photoreceptors are almost exclusively cones which are elongated an closely packed.
Optic Nerve
The afferent fibers from the retina converge at a point medial to the fovea, at the optic disc. The fibers then penetrate the sclera through the lamina cribosa to form the optic nerve.
Retina blind spot: Absence of photoreceptor cells from the optic nerve
The afferent fibers are not myelinated
The main blood supply of the retina is provided by the central artery of the retina
Lens
Lens Capsule
- Thick basement membrane
- Produced by epithelial lens cells
- Is on the very outside of the lens
Lens Epithelium
- Cuboidal, present only on anterior aspect in the adult lens
Eyelids
Palpebral conjunctiva
Tarsal glands
- Large sebaceous glands that produce an oily film which covers the tear film and prevents evaporation
Orbicularis oculi muscle
Third Eyelid: Nictating memrane
- Protection and moisten the eye while keeping visibility
Glands of the Eyes
Lacrimal glands
- Contain serous antibacterial enzymes
Superficial glands of the 3rd eyelid
- Help produce lacrimal secretion
- Cherry eye is a prolapse of this gland
Deep Gland of 3rd Eyelid
- Lacrimal gland
Ear Organization
External Ear
Middle Ear
- Tympanic membrane transmits vibrations to oval window via ossicles
Inner Ear
- Impulses generated, transmitted to brain by cochlear nerve for hearing; by vestibular nerve for equilibrium
External Ear
Ceruminous glands
- Modified apocrine sweat glands that make cerumen.
Middle Ear
Tympanic cavity
- Simple squamous epithelium
Ossicles: 3 small bones in the midle ear
Malleus
Incus
Stapes
Auditory (Eustachian) Tube
- Line by pseudo stratified columnar epithelium with goblet cells
- Connects tympanic cavity and pharynx
- Guttural pouches: In equine, are large diverticuli of the auditory tubes which functon to cool brain during exercise
Inner Ear
A system of canals and cavities in the petrous temporal bone (osseous labyrinth).
Inside this system is a membranous system (membranous labyrinth)
Osseous Labrynth: 3 Compartments
- Vestibule
- Utricle (horizontal linear acceleration)
- Saccule (vertical linear accleration)
- Semicircular canals
- 2 verticle and 1 horizontal
- Each canal has a bulge at one extremility “ampulla” where sensory epithelium is located - Cochlea
Sensory Epithelium
Accleration
rotational accleration - cristae ampullares
Cupula - gelatinous body
horizontal liner accleration - macula utriculus
vertical linear accleration - macula sacculus
- Otoliths - calcium protein
Vibration
Organ of Corti
Cochlea
Dorsal - contains perilymph
Middle (scala media) - contains endolymph
Ventral - contains perilymph
Scala Media
Stria vascularis produces endolymph
Organ of Corti - Has supporting cells and sensory “hair cells”
Tectorial memrane - gelatinous body structure
