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?
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
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?
1. oocyte (fertilization)
4. four cell stage
5. eight cell stage
7. Early blastocyst
8. 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?
* 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?
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.
3. Abdominal opening of uterine tube
6. Ovarian bursa
5, 7, 9, 10, 12, 13?
5. Intercornual ligaments
9. Vaginal part of the cervix
12. External urethral opening
13. Opening of major vestibular gland
1, 2, 4, 10, 12, 13, 15
4. Tunica albuginea
12. atretic follicle
13. Corpus luteum
15. 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?
6. Mesovarium- most cranial part of broad ligament, attaches to ovary at hilus
* cranial free border of the mesovarium is the suspensory ligament
7. mesosalpinx- appears to attach to the infundibulum & uterine tube portion
8. 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
9. 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.
1. Ovarian artery
2. Uterine branch of ovarian artery
3. Uterine artery
5. 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?
5. Rete testis
11. 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 expands distally to form the ampulla in the horse, dog, and ruminant?
What makes up the spermatic cord?
* Ductus deferens, testicular vessels and nerves (including the pampiniform plexus), supporting mesenteries- mesorchium, mesoductus deferens, visceral vaginal tunic.
* Extends from the deep inguinal ring to the testis.
From an endocrine point of view, what is the onset of puberty?
Relies on the secretion of GnRH at the appropriate frequency and in sufficient quantities to stimulate gonadotropin release by the anterior pituitary lobe (even before puberty low amounts of GnRH are released)
* in the female- age at first oestrus, age at first ovulation, age at which female can support pregnancy without deleterious effect
* In the male- age when behavioral traits are expressed, age at first ejaculation, age when spermatozoa first appear in ejaculate, age when ejaculate contains threshold number of spermatozoa
What happens with oestradiol and GnRH as puberty approaches in the male? What about the female?
* Male- no surge center. Testosterone--> oestadiol-->negative feedback on GnRH neurons--> as puberty approaches GnRH neurons become less and less sensitive to oestradiol--> therefore more GnRH neurons can fire and more LH/FSH
* Female- oestradiol in low levels has a negative feedback on the tonic center to GnRH--> as puberty approaches negative feedback is not as strong--> GnRH release and therefore FSH/LH release--> leading to HIGH oestradiol--> HIGH oestradiol levels lead to POSITIVE feedback on the surge center--> massive GnRH release and LH surge and OVULATION
General age range for puberty? What animal is the oldest? What animal is the youngest? What is something to consider with when guessing the age of onset of puberty in a particular species?
* about a year generally, or a bit less
* Female horse takes 18 months to hit puberty on average
* Female pig takes 6 months to hit puberty on average
** considerable breed differences occur!
What does the paraventricular nucleus (PVN) produce? Where is it deposited and why?
* Posterior lobe is not connected via the hypothalamo-hypophyseal portal system therefore oxytocin and GnRH (neurohormones) are deposited directly through capillaries
What does GnRH do? What happens with GnRH over time?
* GnRH leads to the release of pituitary hormones-- LH and FSH.
* GnRH is prone to downregulation if the animal is exposed to it for long periods of time (GnRH implants can result in a decrease of FSH and LH release, and sperm production ceasing in males)
What hormones comes from the ovaries?
* Oestrogens, progesterone, inhibin, oxytocin, relaxin, some testosterone
What are the two major phases of the oestrus cycle?
1. Follicular phase (Proestrus & Oestrus)- regression of corpora lutea to ovulation (20%)-- dominant follicle producing oestradiol
2. 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
What are the four events of the follicular phase?
1. Gonadotropin release from AL of pituitary (follicular development in response to FSH and LH= INCREASE OESTRADIOL)
2. Follicular preparation of ovulation
3. Sexual receptivity
4. Ovulation (when a threshold of HIGH OESTRADIOL is reached a positive feedback will be exerted on the surge center and a high amplitude, high frequency pulse of GnRH will be released in a short period of time- hours)
What are the four processes in the dynamics of antral follicles?
1. Recruitment- a cohort of follicles are selected and start growing
2. Selection- a few undergo atresia and some are selected
3. Dominance- one (in monotocuous species) reaches dominance and starts producing inhibin
4. Atresia- the others undergo atresia because of lack of FSH (due to negative feedback from inhibin)
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
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)**
Why does the CL cease to be?
PGF2alpha binds to specific receptors on the luteal cells--> Ca channels are opened --> intracellular Ca concentration increases--> high Ca is throught to cause apoptotic effects
(Progesterone is also inhibited because Protein Kinase C is activated and acts on the progesterone)
What phase of oestrus is progesterone high? What stage of oestrus is oestradiol high?
Diestrus progesterone is high, oestrus oestradial is high
What hormones add to spermatogenesis in the male?
* FSH acts to stimulate Sertoli cells (fSh)
* LH acts on the Leydig/interstitial cells
* Testosterone initiates spermatogenesis in conjunction with FSH
* Oestrogen and inhibin also play a role in spermatogenesis)
Who in this picture does not have a prostate gland?
Ram does not have a prostate gland
During embryogenesis, what causes development of the gonad into testis?
Testis Determining Factor (TDF) which is probably synonymous with sex determining Y gene (SRY)
Mechanism of erection
* engorgement of cavernous tissue--> compression of veins and lack of venous drainage--> walls of coiled (helicine) arterys of deep artery of penis and bulb relax--> additional blood is pumped in by contraction of ischiocavernosus and bulbospongiosus muscles
What are the functions of the epididymis?
* Water absorption
* Spermatozoal transport
* Blood- epididymis barrier
* Spermatozoal maturation (motility and changes acrosomal molecules, alterations in sperm metabolism, etc.)
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
Once the sperm gets through, where is it? What happens?
In the perivitelline space in close proximity to the oocyte's cortical granules.
* The sperm's membrane fuses with the oocyte's plasma membrane and the sperm is engulfed
* Cortical block is initiated- critical to prevent polyspermy-- when cortical granules are released into the perivitelline space they bring about a chemical change in the zona pellucida that makes it impenetrable for other sperm
After membrane fusion with the sperm and the oocyte's plasma membrane, what happens?
The sperm's nuclear membrane disappear and the nucleus decondenses and the male pronucleus is formed. The male pronucleus subsequently fuses with the female pronucleus (called syngamy) and marks successful fertilization--> embryogenesis can proceed.
What are the 8 steps undergone once the sperm reaches the uterine tube?
When does foetal skeletal mineralisation occur in the bitch? Queen? Why is this important?
From 45 days after the LH peak in a bitch, 36 to 45 days of gestation in the queen
* When they would show up on a radiograph if taking a radiograph is justified
* You could still see uterine enlargement after day 30 (though could be pyometra or hydrometra), you can see spherical gestational sacs 30-40 days
What imaging modality can help determine litter size?
* radiograph of bitch or queen in final week of gestation
* Does not confirm whether alive or dead
* Findings of intra-foetal gas, disorganization of skeletal structures, overlap of skull bones indicates the foetuses are dead
What is the preferred method of pregnancy diagnosis?
Ultrasound- permits earlier confirmation of pregnancy- early pregnancy- round gestational sac and later conceptus enlarges developing poles etc.
* Ultrasound allows evaluation of foetal internal structures, heart rate, viability, and estimation of foetal age.
What heart rate would a non-stressed, normal foetus have?
Approximately 1.5 to 2 times the heart rate of the dam, a higher heart rate indicates foetal stress
With ultrasound, when can you confirm pregnancy in a bitch and queen?
* 19-20 days post LH peak in bitch
* 11-14 days post LH peak in queen
* At this early stage the round, anechoic gestational sacs are visible
** sonogrpahic pregnancy diagnosis becomes reliable from about 30 days gestation in bitch
How can foetal age be estimated? Why isn't foetal sexing done in dogs and cats?
First appearance of visible structures, measuring certain foetal parameters such as gestational sac diameter, crown-rump length or head diameter
** foetuses are too small to sex dog and cat foetuses
Who doesn't have seminal vesicles?
What makes up the ejaculatory duct?
* Ejaculatory duct- ruminants and horses- vesicular gland enters the ductus deferens before it enters the urethra-- in other species the ducts enter the urethra separately
What is an important consideration when contemplating intervention of parturition?
* Be very afraid of intervening based on dates alone, elective caesarians in most animals are not at all routine
General warning signs of dystocia?
* Excessive straining without results
* Haemorrhagic or foul smelling discharge
* Excessive interval between or within stages
* Active labour > 4 hours and no pup produced
* Odd coloured or malodorous vaginal discharge, bleeding
* Interval between pups > 30 min or > 2 hours (without myometrial contractions)
When to intervene with parturition?
* Follow general principles
* There are a wide range of normals
* if an owner is concerned, then monitor parturition/ check foetus
* Don't assume foetus is dead until there is proof
When does the embryo have cardiac activity in a pup foetus?
Considerations in ultrasound in a mare
* ultrasound probe introduced per rectum
* mare standing and restrained in stocks-- potentially sedation to avoid injury
* conceptus can be IDed as early as 10 days after ovulation, sonographic pregnancy diagnosis becomes reliable from about 14 days after ovulation in the mare-- this early ID allows non-pregnant mares to be re-bred ASAP
* recall the equine conceptus is mobile from day 6 to 16-- where it fixes at the base of a uterine horn-- detection of twin pregnancies is preferred before fixation at day 16
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
What are some problems with ultrasound exam in cattle and sheep? Advantages?
Now common practice, but:
* time required for examination
* Accuracy of examination
* technological limitations
* Level of experience of the operator
* early pregnancy diagnosis
* determination of twinning
* foetal viability
* 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?
Even though ultrasound is the gold standard, in a mare what are two other methods of determining pregnancy? Which is better to hint at viability, while the other does not at all indicate viability?
* eCG detectable in serum from approximately 40-110 days post ovulation
* Oestrone sulphate- urinary oestrogens- commercially available from approximately 80 days gestation-- the levels of oestrogen peaks around 7-8 months and decline rapidly if foetus dies
What is the only reliable assay used in a bitch to determine pregnancy?
Relaxin- detectable protein in blood-- after day 20 post LH surge and reaches peak levels day 45 to 50 of gestation.
* relaxin is of placental origin, which explains its absence in non-pregnant animals.
** palpation after day 25 post LH peak can also be helpful without equipment
What does the placenta consist of?
* maternal endometrium
* extra-embryonic fetal membranes: allantois, amnion, chorion, yolk sac
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
What is a synepitheliochorial placenta? Who has this?
There is migration of trophectodermal binucleate cells into the endometrial epithelium and fusion with these to form syncytia to varying degrees
* present in ruminants
Who has endotheliochorial? What are the layers?
* allantoic endothelium, connective tissue, chorionic epithelium, uterine endothelium- NO uterine epithelium and NO uterine connective tissue
What layers for hemochorial? Who?
* allantoic endothelium
* connective tissue
* chorionic epithelium
* primates and rodents
What are binucleate and trinucleate cells?
Binucleate cells are- Trophoblast cells (cells that provide nutrients to the embryo (transfer complex molecules: proteins, oestrogens, and progesterone)- called trophoectoderm after gastrulation (when the three germ layers are present)) -- that produce placental lactogen (somatotropic & lactogenic). They invade the maternal endometrium and often form syncytia (FUSION of CELLS) with epithelial cells (TRINUCLEATE CELLS)
From bigger surface area & more layers to the least layers, name the contact surfaces between mother and baby?
* Epitheliochorial--> synepitheliochorial--> endothelialchorial--> haematochorial
The degree of invasion/ implantation-- potential loss of maternal tissue at parturition-- there are two basic types?
* Non- deciduate- maternal tissue is NOT lost when placenta is discontinued (epitheliochorial)
* Deciduate- Maternal tissue is lost when placenta is discontinued (endothelialchorial, haemochorial)
(ruminants are partially deciduate)
Placentation in a ruminant
Synepitheliochorial, cotyledonary, villous, partially deciduate
Placentation in sows
* Epitheliochorial, diffuse, folded, non-deciduate
Placentation in equine
Epitheliochorial, diffuse (microcotyledonary), villous, non-deciduate
Placentation in a carnivore
Endotheliochorial, zonary, labyrinthine, deciduate
What is a cotyledon and placentome?
* cotyledon- form where trophoblast is in touch with caruncle- abundant vessels and connective tissue
* placentome- placental unit; consists of fetal cotyledon and maternal caruncle (attachment starts day 16, well established day 30)
When does amniogenesis occur in ruminants? How about formation of the allantois?
* amniogenesis between days 13 and 16 (with mesamnion that attaches amnion and chorion)
* the allantois forms between 2nd and 3rd week of gestation-- fills the extra-embryonic coelom by the 4th week
Equine: amniogenesis: between day 17 and day 22
* allantois starts to form around day 22- vascularized by day 25
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)
If you saw a green band on the extra-embryonic membranes in a bitch, what would that be?
Marginal hematoma- hemophagous regions where extravasated maternal blood is phagocytosed by fetal trophoblast cells (green because of uteroverdin)-- not as prominent in the cat
Where does the umbilical cord in a horse run?
In the amnionic part of the cord for 3/5s, the remainder in the allantoic part of the cord
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
Where does the embryo receive nutrition from before the placenta is functional? What is it called after the placenta is functional?
* histotrophe & after- haemotroph
What is the amnion made up of? allantois? chorion?
Amnion- Trophoblast and embryonic mesoderm; allantois- mesderm; chorion- trophoectoderm and embryonic mesoderm
Where is there more fluid- amnion or allantois?
Allantois- except in the ewe at mid gestation
Gestation in the pig, horse, cattle, sheep, dog, cat?
pig- 114 days (3 months, 3 weeks, 3 days)
horse- 335-345 days
Cattle- 280 days
Sheep- 150 days
dog- 65 days post LH surge; 63 days post ovulation
cat- 62 days
Where does progesterone come from throughout gestation in the horse?
Primary CL, then ecG stimulates primary CL to produce more progesterone, high circulatory ecG concentrations then lead to luteinisation of more follicles resulting in accessory CLs