Placentation Flashcards
What are the four functions of the placenta?
- Exchange.
- Endocrine.
- Chemical Protection.
- Physical Protection.
What is the exchange function of the placenta?
- O2 and CO2 exchange.
- Waste products.
- Nutrients.
What is the endocrine function of the placenta?
- Estrogen.
- P4.
- eCG (equine).
- hCG (human).
- Placental lactogen (PL).
*Transient.
What is the chemical protection function of the placenta?
- Immunosuppression.*
- Prevents infiltration by maternal defenses.*
- Filter toxins and microorganisms.
*Prevents the maternal immune system from attacking the embryo.
What is the physical protection function of the placenta?
Shock absorber.
What is gastrulation?
When the single-layer blastula becomes a three-layer structure.
List the gastrulation layers in the order in which they form.
- Endoderm.
- Ectoderm.
- Mesoderm.
What is the endoderm?
The layer that lines the trophoblast cells and gives rise to the yolk sac.
What is the ectoderm?
The layer that covers the trophectoderm.
What is the mesoderm?
The layer that forms between the ectoderm and the yolk sac. Becomes the allantoic portion of the placenta.
What tissues are formed by the ectoderm?
- CNS.
- External repro. anatomy (penis, scrotum, Cowper’s gland, posterior vagina, clitoris).
- Sense organs.
- Hooves.
- Mammary glands.
- Hair.
- Sweat glands.
- Skin.
What tissues are formed from the mesoderm?
- Circulatory system.
- The rest of the reproductive tract.
- Skeletal.
- Urinary ducts.
- Muscle.
- Kidneys.
- Reproductive tracts.
What tissues are formed from the endoderm?
- Primordial germ cells.
- Digestive.
- Other glands.
- Liver.
- Thyroid.
- Lungs.
- Pancreas.
List the four placental membranes from innermost to outermost.
- Yolk Sac.
- Amnion.
- Allantois.
- Chorion.
What is the function of the yolk sac in birds?
To nourish the embryo.
What is the function of the yolk sac in mammals?
Acts as a source of blood cells and primordial germ cells.
*Atrophies.
What are the characteristics of the amnion?
- Non-vascular* and fluid-filled.
- Protective cushion.
- Ruptures at birth.
- Contains fluid produced by the fetus.
*Except equines.
What are the characteristics of the allantois?
- Contains blood vessels that attach to the umbilical cord.
- Fuses with the chorion to form the allantochorion or the chorioallantois. When ruptured at birth, fluid leaks out.
- Brings blood vessels to the chorion.
What are the characteristics of the chorion?
- Attachment to the mother.
What are the four types of placental attachment, and which animal(s) does each belong to?
- Cotyledonary: Cattle, sheep.
- Discoid: Human, non-human primate.
- Zonary: Dog, cat.
- Diffuse: Horse, pig.
How many cotyledons do cows have?
70-120.
How many cotyledons do ewes have?
90-100.
What is the shape of the cow placentome?
Convex.
What is the shape of the ewe placentome?
Concave.
What is the placentome?
Fetal cotyledon + Maternal caruncle.
What does the placentome allow?
Allows for the exchange of waste and nutrients.
What are binuclear giant cells?
Cells from the fetal placenta that burrow into the endometrium. Secrete placental lactogen and pregnancy-specific protein B.
*20% of the fetal placenta.
What is the biochemical classification of placental lactogen?
Protein.
What hormones is PL similar to?
PRL and growth hormone.
What are the functions of PL?
- Stimulates milk synthesis.
- May regulate the maternal metabolism to facilitate fetal growth.
When is PL highest?
The last 1/3 of gestation.
Which two domestic animals do not possess PL?
- Swine.
- Equines.
How does diffuse placental attachment occur?
Using millions of microcotyledons.
*Increases placental surface area.
What two tissues form endometrial cups?
- Trophoblast.
- Endometrium.
When do endometrial cups begin forming?
Day 35.
What do endometrial cups produce?
eCG.
* stimulates the ovaries to create excess CLs, increasing P4 production.
When do endometrial cups slough off?
Day 100-140
True or False: All the pups or kittens share a single placenta.
False. Each pup or kitten has their own.
What animals have a zonary placental attachment?
- Bitches.
- Queens.
What animals have discoid placental attachment?
- Non-human primates.
- Some rodents.
- Humans.
What are the maternal layers of the epitheliochorial placenta?
- Endometrial capillaries.
- Endometrial interstitium (a basement membrane).
- Endometrial epithelium.
What are the fetal layers of the epitheliochorial placenta?
- Chorionic epithelium.
- Chorionic interstitium.
- Chorionic capillaries.
What are the maternal layers of the endotheliochorial placenta?
- Enodmetrial capillaries.
- Endometrial interstitium (a basement membrane).
What are the fetal layers of the endotheliochorial placenta?
- Chorionic epithelium.
- Chorionic interstitium.
- Chorionic capillaries.
What are the maternal layers of the hemochorial placenta?
- Endometrial capillaries.
What are the fetal layers of the hemochorial placenta?
- Chorionic epithelium.
- Chorionic interstitium.
- Chorionic capillaries.
True or False: Binucleate giant cells become part of the endometrium region when they burrow into it.
False. Binucleate giant cells form their own region.
When should fetal and maternal blood first mix?
At parturition.
What does the mixing of fetal and maternal blood result in if the fetus and mother have different blood types?
The mother could form antibodies against the fetus’s blood type. This could threaten future fetuses that possess the same blood type.
What is erythroblastosis fetalis (human)?
When antibodies cross the placenta and cause fetal red blood cells to lyse.
*Happens if the maternal and fetal Rh factors are not the same.
What is neonatal isoerythrolysis (Horses and cats)?
Antibodies in the colostrum that are absorbed in the 24 hours following birth cause the red blood cells to lyse.
What are the three types of implantation?
- Superficial.
- Eccentric.
- Interstitial.
What animal(s) is superficial implantation found in?
Farm animals.
What animal is eccentric implantation found in?
Rodent.
What animal is interstitial implantation found in?
Humans.
What is superficial implantation?
When the chorion lies opposed to the uterine wall. Like a ball resting on the sidewalk.
What is eccentric attachment?
When the chorionic sac sits in a uterine fold. Like a ball sitting in a hole in the ground.
What is interstitial attachment?
When the embryo digests part of the uterine wall. Like a ball that is buried underground.
What are the two degrees of tissue loss?
- Deciduate (High).
- Indeciduate or nondeciduate (low).
What form(s) of placental attachment fall under deciduate tissue loss?
- Eccentric(rodent).
- Interstitial (human).
What form(s) of placental attachment fall under indeciduate tissue loss?
- Superficial (farm animals).
