Placenta Flashcards
What is a transient endocrine organ and produces a variety of hormones that enter maternal and fetal blood supply?
Placenta
What are the major function untis of the placenta?
Chorionic villi
What are chorionic villi?
Major functional unit of placenta - projection on the surface of the chorion that intimately interact with maternal tissue
What is placenta classification based on
Chorionic villi distribution
What is placenta classification “diffuse”?
Chorionic villi located over the entire uterine luminal epithelium
- pig and horse
How is the pig placenta classification?
Diffuse placenta that is velvety in appearance with closely spaced chorionic villi
What is the horse placenta classification?
Organized as microzones of villi named microcotyledons.
Microtyledons are distributed over the entire surface of the chorion as discrete regions of fetal maternal interfaces
What is mare unique specialization?
Unique to mare is presence of endometrial cups derived from narrow band of thick trophoblast that develop around fetus
What does the mare chorionic girdle begin?
~d25
What occurs at ~d40 of mare endometrial cups?
Girdle peels off fetal membranes and trophoblast invade the endometrium to form the cups and produc eCG
What occurs to mare endometrial cups at ~d70?
They begin to be destroyed due to maternal immune attack
What is cotyledonary?
Chorionic vascularized villous trophoblasts and uterine endometrial structures termed caruncles come together like a spot weld
- ruminants
combined structure called placentomes
What occurs at ~30d in sheep and ~36d in cattle?
Villous processes of trophoblast form in the chorionic membrane opposite the caruncular tissue.
What does further branching of the villi in cotyledonary help?
Further branching of the villi helps the trophoblast fit into the caruncular tissue - fingers into a glove
How does Cow, giraffe cotyledonary differ from sheep, goat?
Cow and giraffe - Convex
Sheep and goat - Concave
What is difference between zonary and discoid placenta classification based on chorionic villi distribuition?
Zonary - an invasive band of the chorion surrounds the middle of the fetus (dog and cat)
Discoid - a disc-like structure of chorion interacting with maternal tissue ( higher primates and rodents
What occurs to chorioallantoic placenta at ~18d cats and ~20d in dogs?
Chorion fuses with allantois
- zonal villi invade the endometrium with some villi pushing into gland openings
- maternal blood vessels become completely surrounded by trophoblast
Four placenta classifications based on cell layers at maternal-fetal interface?
Epitheliochorial
Syneptheliochorial
Endotheliochorial
Hemochorial
Epitheliochorial?
Least invasive as epithelium of chorionic villi and uterine luminal epthelium are intact
6 - layers
Capillary wall
Basement Membrane
Endometrium Layer
Chorion
Basement Membrane
Capillary Wall
What are the 6 layers of epitheliochorial starting at maternal side?
Capillary wall
Basement Membrane
Endometrium Layer
Chorion
Basement Membrane
Capillary Wall
Synepitheliochorial?
Specialized binucleate giant trophoblast cells (BNGC) migrate into the uterin epithelium
6 layers
Synepitheliochorial
1 Cows
- Sheep and goats
- Cows trinucleated cells are formed but are short lived
- Continued production of binucleate trophoblast can produce an extensive fetal-maternal syncytial layer
What is placental lactogen?
Hormone important in mammary gland development for prodcution of lactose
Endotheliochorial?
Trophoblasts move through uterin epithelium, stroma and are in contact with maternal endothelia (cats, dogs)
5 layers
Hemochorial?
Highly invasive trophoblast pass through the maternal uterine epithelium, stroma and endothelium of maternal vasculature becoming directly in contact with maternal blood
- rodents, higher primates
5 functions partially or completely accomplished throughout pregnancy?
Gastrointestinal (fetal nutrition)
Endocrine (Hormone/enzyme production)
Respiratory (Transfer of O2 and CO2)
Renal (Hormone/Enzyme Production)
Relatively Uncharacterized (Immunologic Functions)
5 forms of plactenal transport?
Simple Diffusion - gasses and simple molecules
Facilitate diffusion - glucose, carrier system operates with a chemical gradient
Active transport - essential a.a., water soluble vitamins; maintain higher concentration in fetus than in mother
Receptor-mediated endocytosis - immune bodies, protein and fat
Leakage - intact cells
What does the umbilical cord consist of?
Surrounds two umbilical arteries
Surrounds two umbilical veins
Urachus
Vestige of yolk sac
How do the umbilical arteries move within umbilical cord?
Move in spiral pattern around the urachus giving off branches to the amniotic sac and ending in chorioallantoic membrane
