Anatomy Of Pregnancy 2: Anatomical features of pregnancy in the sow, mare, ruminant and carnivores Flashcards
Which species are of only litter bearing?
Carnivores, rodents & pigs
What shape are the blastocysts in the sow initially? (Post fertilisation)
Spherical
Describe the movement of the blastocysts post fertilisation in uterus in the sow and all that occurs at the same time
-Spherical Blastocysts come into uterine horn from uterine tube/oviduct
-remain mobile at initial stage and disperses along uterine horn due to peristaltic movement
-as blasocysts expand and start growing, become elongated- long thin tubes
-allows surface of whole of blastocyst to make contact with endometrium
-this initiates arterial recognition; preventing release of prostaglandin
What does the peristaltic movement of the sow blastocyst in uterine horn allow
Allow blastocysts to evenly distribute themselves across both uterine horns
How long are the blastocyst tubes in the sow after changing shape from speherical to elongated?
1m each
In what occasion would maternal recognition not take place in a sow? what does this mean for pregnancy?
If there are less than 3 conceptuses (embryos)- this means pregnancy is terminated as release of prostaglandin will not be prevented. (If there is not enough blastocyst covering endometrium surface area, body doesn’t recognise the pregnancy as “worth it”)
What types of placenta are found in the sow?
1.Diffuse;
-placental zone- with villi
-paraplacnetal zone- no villi (the edges of placenta)
2.Epithelial-chorial;
-no invasion of endometrium i.e will have 6 layers to pass through for exchange of nutritional material
3.Non-deciduate;
This means no loss of maternal tissue meaning afterbirth placenta shed cleanly with no loss of maternal tissue
What is avascular extremity of placenta
Occurs in what kind of animals
2 embryos neighbouring the avascular extremities of one placenta link up and fuse together
-occurs in litter bearing animals
Survival of piglet embryos depends on…
What do the embryos do in the uterus?
Survival depends on nutrition which is directly correlated with surface area of endometrium being covered by the embryos
-embryos compete for nutritional support; as they grow each embryo tries to take up a such space as they can which means there’s only so many pregnancies that sow can support
-this means surplus embryos die & reabsorbed at early stage of development
Blastocyst in the mare
-enters uterus when
-remains what shape
-protected by what?
-initially very…
-approx 6 days
-remains spherical protected by a protective capsule called embryonic vesicle
Initially very mobile; covers the full length of the uterus by movement of uterine contractions
Describe what happens to the blastocyst in the mare post fertilisation
—Embryonic vesicle covering blastocyst enlarges
-at day 16 enlarges to the point of it being unable to pass through body horn junction
—at day 30 becomes palpable
—day 28-33 continues to ^ in size
-allantois begins enlarage whilst yolk sac regresses
-embryo begins to move dorsally in vesicle
—at day 40
• Chorio-allantois engulfs yolk sac
• Umbilical cord forms
• Contains remnant of yolk sac
• Foetus moves ventrally as it elongates
—at day 60-100
• Foetus too deep in abdomen to identify
What type of placenta is found in the mare?
Diffuse, epitheliochorial, non-deciduate placenta
Placenta in mare is fully formed around what day?
Day 140
What are the microcotyldeons
What species are they found in
Microscopic microvillous tufts present only during pregnancy- help increase S.A to improve transfer of material between foetal and maternal circulation
Found in mare
How long after birth should the mare shed the placenta? What if it doesn’t in this time period?
<6 hours after
Can be life-threatening if doesn’t- mare can develop infections if it doesn’t shed it in time
What are hippomanes
Soft lobs of material- accumulations of waste product of the Allantois that are sometimes shed after birth- of no concern
Found in mare
Describe the action/process of blastocyst in the cow
-Morula enters uterus approx day 4
-Becomes blastocyst approx day 8
-blastocyst elongates significantly; occupies most of uterine horn; means not very mobile. Elongation however still allows good cover of S.A and exchange of nutrients
-starts off at side of corpus luteum but then blastocyst expands to other side as well (when looking for pregnancy in cow, will be initially looking at same side as CL)
Name the type of placenta found in the cow
Cotyledonary, epithelio-chorial, non-deciduate placenta
Cotyledonary-> patches of villi found around the placenta. Develop on surface of chrorion
What is the placentome (found in cow)
Linking of the cotyledon of foetal side to the caruncle of maternal side
Around what day can you identify a pregnancy in the cow?
Using what?
Day 21
Using rectal US
What can you start seeing on ultrasound in a cow/other species when looking for pregnancy
-Can start seeing heartbeat of embryo
-corpus luteum
-fluid filled structure in the uterus
What type of placenta is found in the ewe
Cotyledonary, epithelio-chorial, non-deciduate placenta
In ewe there is much higher incidence of ______ than in other species
Twins
What is transuterine migration?
When an embryo moves from one uterine horn (containing the CL) to the other uterine horn
What is freemartinism
-which animal is it most common in
Occurs in females carrying one female and male embryo twins. The placental blood vessels of the twins link. This fusion results in the transfer of male hormones to the female fetus, which can lead to various developmental abnormalities of the reproductive tract and the female’s inability to reproduce.
-cow
Is freemartinism a problem in ewes?
Nope
Techniques used to detect pregnancy in ewe
-Abdominal ballotment- feeling the foetus through the abdominal wall (towards end of pregnancy)
-US; 70-105 days into pregnancy
