Final Exam Repro Flashcards
What happens to the ovulatory follicle?
Walls of ovulated follicle collapse, forming an ovulatory depression. The theca and granulosa cells proliferate, undergo hypertrophy, and initially form a corpus hemorrhagicum which matures into an actively secreting CL. (Day 1 through 4 in cattle)
What phase of the oestrus cycle does follicular waves of development and regression occur?
Diestrus
What happens after day 14 of the cattle oestrus cycle if no viable embryo is in close proximity to the uterus?
Pulsatile release of prostaglandin F2alpha from the uterus
What are the different paths follicles can take?
* Atresia- regression
* remain as primordial follicles with no sign of growth
* growing follicles- left the resting stage of primordial follicles and have begun growth but have not yet developed a thecal layer or antrum (cavity)
* mature, Graafian (tertiary) follicles- these are the follicles with the antrum or thecal layer
Graafian or tertiary follicle
Secondary follicles
Describe what happens with follicular waves? What do they occur in response to?
Follicular growth and regression cotninues in distinct waves throughout the estrous cycle in response to FSH secretion. Each wave consists of a cohort of follicles, one becomes dominant and the others remain subordinate. In cattle, 2-3 waves of follicles per oestrus cycle.
What induces the maturation of the Graafian follicle and ovulation 27 to 30 hours later in a cow?
Increasing LH levels promote a continual increase in estradiol secretion from the theca and granulosa cells of the dominant follicle, beginning about 4 days prior to estrus. Once the estradiol levels reach a threshold, a preovulatory surge of LH and FSH is triggered– and this causes the maturation of teh Graafian follicle and ovulation 27 to 30 hours later.
What happens immediately following ovulation in a cow?
The theca and granulosa cells proliferate and differentiate into small and large luteal cells, which secrete progesterone. They differ in their LH and prostaglandin receptor content. Small luteal cells contain most of the LH receptors and are more sensitive to LH stimulation, which leads to increase progesterone production. Large luteal cells secrete the majority of progesterone have few of the LH receptor sites and more prostaglandin receptors– Large also produce and store oxytocin.
What happens after the oocyte is fertilized?
- oocyte (fertilization)
- ootid
- zygote
- four cell stage
- eight cell stage
- Morula
- Early blastocyst
- Hatching blastocyst
What surrounds the yolk sac in embryogenesis?
Endoderm and blastocoel outside of that.
What surrounds the blastocoel?
Trophectoderm (ectoderm) becomes the allantochorion
What occurs with luteolysis in ruminants? What occurs with maternal recognition of pregnancy with ruminants?
Luteolysis: Progesterone loses its ability to downregulate oxytocin receptors. More oxytocin receptors, oxytocin from luteal cells of the ovary, when oxytocin binds to its receptor, prostaglandin released which goes to the ovary– triggers more oxytocin release– positive feedback loop.
** Critical thing in the ruminant for luteolysis to work: Uterine tissue has to be close to the CL. Close proximity of the uterine vein to the ovarian artery, so prostaglandin can diffuse across.
** Maternal recognition of pregnancy: blastocyst actively secretes interferon tau, which suppresses oxytocin receptor production, therefore even if oxytocin is around, prostaglandin will not be around– CL stays
Conceptus with necrotic tip- not a problem aseptic
Maternal recognition in the pig?
Luteolysis: Prostraglandin into the uterine veins–> goes systemically–> reaches the ovaries–> luteolysis
Conceptus present: PGF2alpha released–> will not go into the uterine vein–> will be redirected into the uterine lumen (prostaglandin is not suppressed, just redirected)
**For this to happen the conceptus has to produce ESTRADIOL–> change the secretion pattern of the prostaglandin from the vessels into the uterine lumen
** Can only happen if 2 conceptus’ in each horn (4 total)
Maternal recognition in a mare?
In the mare, the conceptus stays round, it does not elongate like in pigs and ruminants.
* Embryo has to move all over the mares uterus– otherwise that part of the uterus will secrete prostaglandin which will go systemically into the circulation
* this means imaging will change every time you look
When the does the conceptus look like at day 14 in a mare, why? When does it start to change?
Anechoic- black
* Fluid filled
* Intercell mass is there but so tiny, you can only start seeing the developing embryo at day 21
What does ecG do? what happens after day 100?
** ecG is LH like.
Initially stimulates the primary CL to produce more progesterone. Then high circulatory ecG concentrations lead to the luteinisation of more follicles resulting in accessory CLs. After day 100 the placenta takes over the role for the main production of prosteragens
What does relaxin do in the horse? What secretes relaxin?
Relaxin is secreted by the placenta.
Promotes uterine and cervical growth and remodeling that is essential for normal fetal growth and parturition.
*Decreases collagen content in the pubic symphysis and cervix
* inhibits uterine contractility
*Plays a role in mammary gland development.
* Angiogenic and vasodilatory effects on endometrial and mammary tissues.
Why might a mare not return to estrus if termination of pregnancy occurs between >34 and 37 days?
Persistence of endometrial cups may delay return to regular cycles for 3 to 4 months (the cups continue to function and produce ecG; they will survive until the time of their normal demise)
What does placental lactogen do? What produces placental lactogen?
Somatotropic- (growth of fetus)
Lactogenic- (Groth effect on mammary gland)
** Binucleate giant cells (of trophoblastic origin that invade the endometrium)
** it is thought that the sire has an impact on the degree to which a fetus can produce placental lactogen, therefore it might be possible for the sire to influence milk production of the dam. “Sire-on-fetus-hypothesis”
What is the level of oestrogen in most species? What are the two different species in this regard?
Oestrogen levels in most species increase at the end of gestation (progestagens are converted to oestrogens). Only in women oestrogen is high throughout pregnancy and the mare has significant amounts throughout the second half of gestation.
What are progestagens?
Class of steroid hormones that activate the progesterone receptor. Most important is progesterone (P4). Others are 17 alpha-hydroxyprogesterone, 20alpha-dihydroprogesterone, etc.
Where does spermatogenesis take place?
Seminiferous tubules
What transports sperm to the epididymis?
Efferent ducts and rete testes
How long is the gestation of cattle, sheep, dog, cat, horse, pig?
Cattle- 280 days
Sheep- 150 days
Dog- 65 days post LH surge; 63 days post ovulation
Cat- 62 days
Horse- 335-345 days
Pig- 114 days (3 months, 3 weeks, 3 days)
What are the sources of nutrition for a foetus before 17 days approximately?
Yolk sac, histotrophic (uterine milk) secretion via areolae glands
What is the sinus terminalis?
Large fetal blood vessel forms around teh placental zone– where the yolk sac comes in contact with the chorion opposite the embryo forming a marginal annular zone of vascular choriovitelline placentation
What is the chorionic girdle?
A band of elongate trophoblast cells forms around day 35 of gestation at the junction of the developing allantois and regressing yolk sac. The trophoblast cells invade the endometrium at about 36 to 38 days to give rise to the endometrial cups– which secrete equine chorionic gonadotropic (eCG)
When is amniogenesis complete?
By day 21– which is about the time when the allantois enters the extra-embryonic coelum (completely surrounding the amnion and the yolk sac by day 40)
In males what does the mesonephric duct form? What do the gonadal cords form?
* mesonephric duct forms the epididymis
* gonadal cords forms the seminferous tubules originally the gonads
In females, what do the paramesonephric (Mullerian) ducts form?
Body of teh uterus and the uterine tubes and horns. The vagina is made up of paramesonephric ducts (mesoderm) and urogenital sinus (endoderm)
Problem with the female reproductive tract from a calf on the left?
Freemartin- more than 90% of heifers who are born as a twin to a bull calf are sterile due to becoming XX/XY chimeras from placental anastomoses in which blood crosses from one twin to the other. The XY now preset in the heifer calf prevents development of paramesonephric ducts.
- Mesovarium
- Mesosalpinx
- Abdominal opening of uterine tube
- Infundibulum
- Ovary
- Ovarian bursa
5, 7, 9, 10, 12, 13?
- Intercornual ligaments
- caruncles
- Vaginal part of the cervix
10’. fornix
- External urethral opening
- Opening of major vestibular gland
1, 2, 4, 10, 12, 13, 15
- Medulla
- Mesovarium
- Tunica albuginea
- oocyte
- atretic follicle
- Corpus luteum
- Corpis albicans
Who has more coiled shape and more ventral/ close to or at pelvic inlet ovaries/ uterus?
Cows and sows
What species have semen deposited in the uterine body or cervix? What species have semen deposited in the vagina?
* dog, pig, and horse
* ruminants- vagina
What makes it difficult to catheterise bitches?
Urethral orifice opens on hummock (cows and sows opens in roof of suburethral diverticulum)
Broad Ligament: Mesovarium, Mesosalpinx, Mesometrium
6? What is the cranial free border of 6? 7, 8, 9?
- Mesovarium- most cranial part of broad ligament, attaches to ovary at hilus
* cranial free border of the mesovarium is the suspensory ligament
- mesosalpinx- appears to attach to the infundibulum & uterine tube portion
- mesometrium- continuous with perimetrium (serosal surface), fold from lateral surface near tip of horn– runs to inguinal canal– the cranial free border is the ROUND LIGAMENT OF THE UTERUS
- arrow indicates entrance to ovarian bursa
What is the thickening between the uterine pole of ovary and ipsilateral horn? What makes up the ovarian bursa?
Proper ligament of ovary
* Ovarian bursa: medial wall of mesovarium & lateral wall of mesosalpinx
What ligament does the ovarian a run in? Uterine a?
Ovarian aa. runs in the mesovarium, uterine a. runs in the mesometrium
Blood supply to carnivore ovary and uterus
1, 2, 3, 5?
Aorta–> ovarian a. branches to uterus and uterine tube
Aorta–> internal iliac a.–> internal pudendal a.–> vaginal a.
- Ovarian artery
- Uterine branch of ovarian artery
- Uterine artery
- Vaginal artery
What cells produce oestrogens under what influence? What kick starts this production?
Membrana granulosa cells produce oestrogens (from androgens produced by theca interna cells after the influence of LH) under the influence of FSH
What happens with the LH surge? Explain what it actually is?
The LH surge from the theca interna cells producing androgens–> membrana granulosa cells producing oestrogens under the influence of FSH–> ovulation
* also oocyte–> maturation (completion of 1st meiotic division)–> secondary oocyte
** Ovulation involves the destruction of the follicular wall and the release of the oocyte, swept into the uterine tube– brought about with an increase in the secretion of follicular fluid (including collagenase and the initiation of an inflammatory response and the degradation of the cumulus oophorus holding the oocyte in)
How is the GnRH surge center eliminated in the male?
By testosterone converted to oestradiol during embryogenesis. (it is not eliminated inthe female because oestradiol cannot cross the BBB since in a female it is bound by alpha-fetoprotein)
2, 5, 11?
- Mediastinum
- Rete testis
- pampiniform plexus
How does the body cool down testicular temperature?
Counter current heat exchange
* the highly convoluted testicular artery has an intimate relationship with the veins of the pampiniform plexus–> this intimate relationship cools down the arterial blood by exposing it to the cooler venous vlood from the testes
Phases of spermatogenesis?
Occur in cycles over time within a given segment of a seminiferous tubule- 50 days in a bulld, 74 days in a human. Needed: correct interaction of hormones and maintenance of optimal testicular temperature
* Spermatocytogenesis- spermatogonia give rise to spermatocytes (joined until spermatocytes where they lose contact with basal lamina and pass through the blood-testis barrier into the adluminal compartment of the tubule)
* Meiosis- spermatocytes give rise to spermatids
* Spermiogenesis- spermatids transform into spermatozoa (formation of the acrosome and loss of excess cytoplasmic material)
What produces seminal plasma?
* Ampullary glands or Seminal vesicles (in ram and bull)- potassium, fructose, citric acid (in the stallion ergothionine and sialic acid adding a gel component)
* Bulbourethral glands: Sialoprotein (mucinous gelatinous material prominent in boar and stallion semen) and galactosamine- small in cats and absent in dogs
* Prostate gland- Colourless, slightly acid fluid, high concentration of proteolytic enzymes, zinc and copper (especially dog)
Main role of ischiocavernosus m., bulbospongiosus m., retractor penis m.?
* ischiocavernosus m. - pumps blood into corpus cavernosum, positions penis during intromission and coitus
* bulbospongiosus m. - pulses during ejaculation to assist in expulsion of semen
* retractor penis mm.- retraction of the penis into the prepuse following coitus
Layers of the scrotum- external to internal
Skin, tunica dartos, scrotal fascia, parietal vaginal tunic, visceral vaginal tunic
* Closer to the are where the scrotum inserts to the body- the cremaster muscle is between the scrotal fascia and the parietal vaginal tunic
What makes up the testicular parenchyma?
Seminferous tubules and interstitial endocrine cells
What are the two major phases of the oestrus cycle?
- Follicular phase (Proestrus & Oestrus)- regression of corpora lutea to ovulation (20%)– dominant follicle producing oestradiol
- Luteal phase (Dioestrus)- from ovulation until corpora lutea regression (80%)– CL producing progesterone… Dioestrus ends with luteolysis
What effects does luteolysis have?
Luteolysis removes the negative feedback on the hypothalamus, resulting in GnRH release in higher amplitudes and frequencies. FSH and LH are released at higher concentrations–> Follicular development. When a dominant follicle is selected, it will produce inhibin leading to a decrease in FSH release
During ovulation, what physically happens for ovulation to occur?
Destruction of follicular tissue due to: Hyperaemia (histamine in response to LH surge)–> oedema (histamine in response to LH surge)–>elevated hydrostatic pressure
(angiogenic factors have been found in follicles, suggesting that they control their own blood flow)
LH SURGE LEADS TO:
* histamine= hyperemia and edema
* PGE2= increased blood flow to ovary and dominant follicle
PGF2alpha= release of lysosomal enzymes to weaken follicle wall & increased contraction of ovarian smooth muscle which increases follicular pressure
* shift from E2 to P4 by dominant follicle = collegase
* Tumour necrosis factor alpha= kills granulosal cells
* gap junction breakdown between granulosal cells and oocyte= removal of meiotic inhibition= first polar body= haploid oocyte= fertilization
What does the luteal phase consist of?
* Corpora lutea formation (after follicle ruptures, blood vessels also rupture so Corpus Haemorrhagicum forms first–> theca interna and granulosa cells get thrown into folds and mix–> undergo LUTEINIZATION (transform into luteal tissue)–> CL is a mixture of large (former granulosa cells) and small Luteal (former theca interna cells) cells
* Production of progesterone
* Luteolysis
Effects of progesterone?
* Negative feedback on GnRH neurons–> less LH and FSH produced
* Positive effect on endometrium (gland secretion increases, contractility decreases), cervix closes
Why is the uterus necessary for luteolysis? What are requirements for luteolysis?
* PGF2alpha enters uterine drainage, diffuses from Uterine- ovarian vein (UOV) to ovarian artery (OA)–> transported directly to the ovary where it causes luteolysis
* Requirements for luteolysis: Oxytocin receptors on endometrial cells, presence of critical level of ovarian oxytocin (LARGE LUTEAL CELLS PRODUCE OXYTOCIN), PGF2alpha synthesis by endometrium **(Positive feedback loop between PGF2alpha and Oxytocin)**
What phase of oestrus is progesterone high? What stage of oestrus is oestradiol high?
Diestrus progesterone is high, oestrus oestradial is high
Who in this picture does not have a prostate gland?
Ram does not have a prostate gland
During the immediate transport phase where sperm enter the cervix or uterus, what are ways sperm are lost?
Retrograde loss (gravity is against them) and phagocytosis by neutrophils
If semen are deposited into the vagina, what are the hurdles the cervix throws at them?
* Oestrogens lead to the production of sulfomucins from the cervical mucosa–> sperm are flushed out if they get into it as it is flowing caudal.
* Sialomucin is produced in the cervical crypts and facilitates easier transport route for sperm “privileged pathway”. The sperm have to actively swim through this mucus.
Where is capacitation undergone? What is capacitation of sperm?
In the uterus.
* Capacitation- plasma membrane of epididymal spermatozoa contains surface molecules (carbohydrates and proteins)– if ejaculated sperm get in contact with seminal plasma, these surface molecules get coated by seminal plasma proteins. When sperm are exposed to the female tract environment, the seminal plasma molecules and part of the plasma membrane molecules are removed. They then expose portions of molecules which are able to bind to the zona pellucida. (can become incapacitated if incubated in seminal plasma)
How is sperm transported within the female reproductive tract?
Via strong uterine contractions brought on by the dam’s oestradiol and by prostaglandins in the semen. And by the spem simply getting through the reservoirs in the cervix and uterotubal junction.
What allows the sperm to bind to the zona pellucida? What happens when binding occurs?
Sperm’s zona binding region (ZBR) reacts with Zona Pellucida Protein 3 (ZP3)– when this happens the acrosome reaction is initiated
What is the acrosomal reaction?
* Pore formation occurs so that the acrosomal contents can reach the zona pellucida and facilitate the sperm’s penetration
What are the 8 steps undergone once the sperm reaches the uterine tube?
When does the embryo have cardiac activity in a pup foetus?
23-25 days
Typical schedule for equine pregnancy scanning
Day 14 post ovulation- pregnancy & twin ID
Day 25-28 post ovulation- assess foetal viability (heart beat)
Day 40 post ovulation- confirm pregnancy (stud fee is usually due around this time)
Day 60-70 post ovulation- foetal sexing
In a mare and a cow, when is gestational sac reliably IDed? Foetal movement? Foetal sexing?
In a bitch and a queen: radiograph: when is skeletal mineralization? Litter size estimated? Ultrasound: gestational sac? foetal heart beat in bitch?
What are the layers between an epitheliochorial? Who has this?
* Allantoic endothelium, connective tissue, chorionic epithelium, uterine epithelium, uterine connective tissue, uterine endothelium, maternal blood
* sow and mare
Amniotic plaques (mineral deposits) are found on amniotic ectoderm around umbilical stalk
What are the areas in between chorionic villi in equine placentation? What is so important about day 35?
* areas between villi are called arcades
* At day 35 trophoblast cells have divided into invasive and non-invasive components- the invasive, binucleate trophoblast cells make endometrial cups which produce ecG–> aid in recruitment, development, and luteinization of additional follicles (ecG peaks between 60-80 days, is gone by day 120) but this means they will be present and making the horse think she is pregnant even if the foetus dies
Chorionic girdle- where the endometrial cups develop
Sinus terminalis- a vein encircling the vascular area of the blastoderm
Hippomanes- amorphous, khaki-brown colored lumps; formed from fetal waste products
Areolae- small, round, grey, thickened foci on Chorion; formation starts in 2nd month of gestation; focal accumulations of secretory gland products (histiotroph)
What events occur before embryonic attachment to the uterus? When is attachment complete in cats, cattle, dogs, horses, sheep, and swine?
* development within zona pellucida
* hatching of blastocyst from the zona pellucida
* maternal recognition of pregnancy
* formation of extraembryonic membranes
