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Flashcards in Histo Deck (97):
1

What are the functions of the tight junction or blood testes barrier?

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* Barrier: TJs formed between adjacent cells play an essential role in compartmentalization by creating a barrier to restrict the diffusion of solutes through the paracellular pathway

* Fence: TJs also create a boundary between the apical and basolateral domains of a cell, which differe in protein and lipid composition. This in turn creates and maintains epithelial and endothelial cell polarity.

** The BTB also creates an immunological barrier that sequesters antigenic determinants residing on germ cell surfaces from the systemic circulation. This barrier also excludes the entry of circulating immunoglobulins and lymphocytes into the adluminal compartment.

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How does the size of the oocyte vary between primordial and secondary follicles?

The oocyte (imature ovum) larger in secondary follicles

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follicle cells (membrana granulosa)

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What is follicular atresia?

Degeneration of follicles at any stage of their development. The majority of follicles undergo atresia, while those that mature to ovulate are relatively few. The oocyte may degenerate prior to the onset of degeneration of follicular wall or visa versa. During atresia the membrane granulosa and theca interna cells exhibit signs of degeneration such as pyknosis and chromatolysis.

** they may undergo hypertrophy, luteinization, fibrosis, or hyalinisation-- which the theca interna and basement membrane may become amorphous and resemble a glassy structure.

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What is the function of the endocrine cells of the theca interna?

The membrana ganulosa cells possess FSH receptors and in late tertiary follicles, LH receptors. The endocrine cells of the theca interna possess LH receptors. LH acts on the endocrine cells of the theca interna to facilitate PRODUCTION OF ANDROGENS. Then passes to the membrana granulosa to produce oestrogens under the influence of FSH. Causing signs of oestrus.

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What is in the theca interna layer of the follicle?

Blood vessels

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What is meant by luteinization?

Formation of the corpus luteum

* follicle ruptues, wall collapses, walls fold inward and antral cavity is nearly obliterated. Haemorrhage may occur forming CORPUS HEMORRHAGICUM-- mostly in the mare, cow, and sow.

* the cells of membrana granulosa and theca interna hypertrophy and multiply to form luteal cells that comprise the corpus luteum

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What hormones are produced by the corpus luteum?

* oestrogens, oxytocin, relaxin, progesterone

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What is a corpus albicans?

Scar tissue left behind from the regression of the corpus luteum

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What biological purpose is served by recurrent formation and regression of corpora lutea?

* prepares the uterus "just in case"-- relaxes the muscle, increases uterine secretion

* progesterone and oestrogen are always at opposite ends of the spectrum- progesterone dominates

 

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What hormone is primarily responsible for the structure of teh epithelium seen in this slide?

Oestrogen

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What two potential animals could this be? Why?

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Cords of epithelioid cells occur throughout the stroma of the cortex in bitches and queens.

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What does Follicle-stimulating hormone (FSH) do in the male and female?

1. Increase ovarian growth

2. Proliferation of granulosa cells requires the presence of FSH

3. In the presence of LH, FSH, increase oestrogen secretion

4. Promote spermatogenesis

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What does Luteinizing Hormone do in the male and female?

1. aka interstitial cell stimulating hormone (ICSH)

2. Stimulating the interstitial cells of both ovary and testes

3. Induce ovulation

4. Induce formation of the corpus luteum

5. Stimulate steroid secretion in both the ovary and the testes

6. Some gonadotrophs secrete only LH, but the others secrete both FSH and LH

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What does LH act directly on? Follow on effects?

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Ovarian and uterine changes during the estrous cycle in the cow

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What hormones are affecting the follicle? What cells possess FSH receptors? What cells possess LH receptors? Then what happens

*gonadotrophins: LH and FSH incluences the follicle (from the pars distalis of the hypophysis cerebri)

* Membrana granulosa cells possess FSH receptors and in late tertiary  follicles LH receptors too

* Endocrine cells of the theca interna possess LH receptors

** LH acts on the theca interna cells to produce androgens--> passed into the membranosa granulosa to produce oestrogens under the influence of FSH --> therefore favorable local environment, act on the reproductive tract, and cause signs of oestrus

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What are rete ovarii?

In the medulla irregular tubules, lined by cuboidal epithelium or solid cords of cuboidal cells that comprise rete ovarii- vestiges of embryonic development (especially in carnivores and ruminants)

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What is the difference between a primary and secondary follicle? Tertiary follicle (antral)?

* Primary follicle- primary oocyte surrounded by simple cuboidal follicular epithelium and basement membrane (changes to simple columnar).

* Secondary follicle (pre-antral)- primary oocyte surrounded by stratified follicular epithelium of membrana granulosa cells. (formation of zona pellucida and differentiation of the thecal layer and caviation of follicular epithelium)

* Tertiary follicle (antral): formation of antrum (follicular fluid), cumulus oophorus, and corona radiata... with wall comprising membrana granulosa, bm, capillary wreath, theca interna, theca externa

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What is the purpose of the corona radiata?

The cells nourish the oocyte

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What actually happens with ovulation?

LH surge--> acts on membrana granulosa cells to initiate ovulation--> destruction of the follicular wall--> release of oocyte--> swept into uterine tube by an increase in secretion of follicular fluid--> due to collagenase and the initiation of an inflammatory repsonse and degradation of ground substance, the wall collapses--> the oocyte is released from cumulus oophorus and now may complete the 1st meiotic division depending on the species

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What happens after the rupture of the follicle?

Formation of the corpus luteum. Following rupture of the follicle and follicular wall copase--> wall folds inwards obliterating the antral cavity--> haemorrhage may occur (corpus haemorrhagicum)--> cells of the membranosa granulosa and theca interna hypertrophy and multiply to form luteal cells that comprise the corpus luteum--> large luteal cells develop from the membrana granulosa cells and the small luteal cells develop from the theca interna cells-->following ovulation mitosis and hypertrophy of cells continues for 7 to 10 days, CL reached mature size--> CL cells secrete progesterone which suppresses follicular development and promotes uterine secretion and formation of the placenta

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Where does the vasculature of the corpus luteum come from?

Theca interna

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When does luteolysis occur? What causes luteolysis? What is left behind?

Corpora lutea degenerate if there is no pregnancy or at the end of gestation. This is generally due to prostaglandins F2alpha released from teh uterus.

** the capillaries degenerate and the luteal cells accumulate large lipid droplets and then degenerate... macrophages phagocytose debris-- corpus albicans is left

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What is in the uterine tube to assist in transport of ovum or zygote (zygote= ovum and sperm)? What is in the isthmus to help propel ovum?

* cilia and/or microvilli

* ciliated cells predominate in the ampulla and decrease towards the isthmus. All cells possess microvilli.

** in the isthmus, muscular activity predominates of the tunica muscularis

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What are caruncles in ruminants?

Vascular endometrial thickenings forming raised mounds on the luminal surface.

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What causes endometrial glands to increase secretion? What is the secretion?

Oestrogen & progesterone especially (markedly increased)-- the secretion is called histotroph, supplying nutrients to the conceptus, influx of lymphocytes.

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What is the cervix made up of?

Thick walled muscular tube

* cells produce cervical mucus which contributes the bulk of the vaginal and vestibular mucus present at oestrus and parturition-- thickens to form a cervical plug between cycles and during gestation.

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What happens to the stratified squamous epithelium at oestrus? What other structures are in the vagina?

Thickens & influx of lymphocytes

Lymphatic nodules

serosa with extensive vascular plexuses and highly innervated

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vagina vs. vestibule structure

* more sub-epithelial lymphatic nodules in vestibule

* lamina propria/ submucosa contains cavernous tissue which undergoes congestion during oestrus

** vestibule- major vestibular glands and tubular mucus glands- lubrication for copulaton and parturition

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What line seminiferous tubules?

Stratified epithelium of spermatogenic cells (which give rise to spermatozoa) and Sertoli cells.

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What is the function of interstitial cells? What is another name for them?

Interstitial endocrine cells aka Leydig cells

* Interstitial cells occur within the intralobular loose connective tissue surrounding the seminiferous tubules in company with blood and lymph vessels.

PRODUCE ANDROGENS (testosterone)

 

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What is important to note about the differences between spermatogenic cells of the seminiferous epithelium?

They are not identical from one tubule to the next or from different locations along the same tubule. There are various combinations of cells in certain stages of development that are always associated with each other.

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What are the phases of spermatogenesis?

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What is the epithelium from the testis, epididymis, and ductus deferens?

* Simple columnar epithelium with some cilia for motility, some with microvilli (absorptive/ secretory). this epithelium is supported and surrounded by 3-6 layers of myofibroblasts and connective tissue.

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What type of gland is the prostate gland?

Compound tubuloalveolar gland. One of the functions of the glands secretion is to neutralize seminal plasma. Simple cuboidal or columnar epithelium lines the tubules, alveoli and majority of the ducts. Smooth muscle cells are abundant in the capsule and outer regions of the trabeculae.

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Where is elastic tissue most abundant in the glans penis?

Tunica albuginea (which has dense irregular connective tissue, smooth muscle, and elastic fibres depending on the species)

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What makes up the bulk of the tunica albuginea and septa of the glans penis?

* dense irregular connective tissue (smooth muscle and elastic fibres)

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What is the nature of the tissue between the blood channels (cavernous spaces) in the areas of the erectile tissue?

The erectile or cavernous tissue comprises large endothelia-lined spaces within a supporting matrix of loose to dense fibrous connective tissue depending on the species. The loose connective tissue has a somewhat mesenchyme-like appearance.  In the horse, the blood spaces are enveloped by longitudinally oriented smooth muscle fascicles which are able to constrict spaces on contraction.  In the ruminant and boar, the fibrous and elastic connective tissue elements predominate.

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What are the functions of tight junctions, or blood testis barrier?

* Barrier: TJs formed between adjacent cells play an essential role in compartmentalization by creating a barrier to restrict the diffusion of solutes through the paracellular pathway

*Fence:  TJs also create a boundary between the apical and basolateral domains of a cell, which differ in protein and lipid composition. this in turn creates and maintains epithelial and endothelial cell polarity.

* BTB also creates an immunological barrier that sequesters antigenic determinants redising on germ cell surfaces from the systemic circulation. This barrier excludes the entry of circulating immunoglobulins and lymphocytes into the adluminal compartment.

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What is histotrophe? Vs. haemotroph nutrition

Aka uterine milk- during the time before the placenta is functional the embryo receives nutrition through fluid secreted by endometrial glands

* haemotroph nutrition- essential metabolites are provided by maternal circulatory system

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What is the amnion? What is the purpose of amniotic fluid?

Made up of trophoblast and embryonic mesoderm;  amniotic fluid protects the embryo/fetus from any impacts and provides the fetus with an environment it can move its limbs and body-- freedom to develop, prevents attachment between fetal skin and the amnionic membrane-- assists cervical dilation and lubricates the birth passage at parturition

* amniotic and allantoic fluids contain metabolites, electrolytes, hormones, enzymes, cells and other structures e.g. caliculi

* the fetus swallows amniotic fluid, creating complete turnover every 3 hours

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What is the allantois? What is it filled with?

Diverticulum of the hindgut. Fills with fetal waste fluids; grows in between amnion and chorion.  Allantois is vascularized by allantoic arteries (branches of the aorta), allantoic veins that enter the fetus via the umbilicus

* amniotic and allantoic fluids contain metabolites, electrolytes, hormones, enzymes, ecells and other structures e.g. caliculi

* mesonephric formed urine passes into the allantoic cavity until 90 days after gestation, after this time, urine passes into the amnion due to closure of the urachus and development of a patent urethra

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What makes up the chorion?

Trophoectoderm and embryonic mesoderm

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Who has epitheliochorial, endotheliochorial, hemochorial, and synepitheliochorial?

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1. allantoic blood vessel

2. chorioallantoic membrane

3. chorioallantoic villus

10. microplacentome

13. uterine gland

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4. chorioallantoic villus, epithelium

7. crypt, epithelium

9. maternal blood vessel

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What is the difference between the surface of the fetal vs. the maternal areolus?

Fetal portion of the areolus has the appearance of a rosette or villus, the maternal portion appears as a smooth surfaced cup surrounding the opening of the uterine gland.

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What is the syncytium?

A layer of caruncular epithelium in which cell boundaries are difficult to define

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What type of gland is a lactating mammary gland of a sheep?

What type of secretion?

Modified cutaneous sweat glands; compound tubuloalveolar glands

* Alveolar epithelial cells secrete lipid and casein (milk protein): the lipid is by the apocrine mode; the casein by the merocrine mode

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Binucleate cells in both the maternal and foetal epithelium -- what is the origin and function of these cells?

Function is the production of placental lactogen. These binucleate trophoblast cells invade the maternal endometrium and often form syncytia with the epithelial cells (trinucleate cells) which justifies the classification synepitheliochorial. Around 7 to 10 days post partum the crypts within each caruncle undergo necrosis and epithelial cells are sloughed. Therefore, the placenta can be classified as partially deciduate.

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Differences between the umbilical cord of a sheep vs. a pig?

Pig has 1 vein- ruminants have 2 veins. Ruminants is short and only traverses the amnion.  Both contain 2 arteries (deoxygenated blood back to Mom) and urachus.

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How long does the yolk sac placenta function for?

17- 20 days depending on the species in the extraembryonic coelom-- as the allantois expands, the yolk sac degenerates leaving no visible remnant at term