Placentation, Gestation and Parturition Flashcards
Placenta
transient organ of pregnancy that provides an interface for metabolic exchange between mother and foetus
How are placentas classified?
morphologically based on villi distribution and the amount of seperation between the maternal and fetal blood
Which animals have a diffuse placenta?
mare and sow
Diffuse placenta
uniform distribution of chorionic villi that cover the entire surface of the chorion
zonary placenta
band like zone of chorionic villi, made up of three distinct zones (transfer, pigemented and allantochorion)
Which animals have a zonary placenta?
dogs and cats
Which animals have a discoid placenta?
rodents and primates
Discoid placenta
round-patch of chorionic tissues that forms the fetal-maternal interface
Cotyledon
Placental unit of trophoblastic origin with abundant blood vessels and connective tissue
placentome
interphase point formed fetal cotyledon and maternal part (caruncular region)
Which animals have an Epitheliochorial placenta?
bovine, mare and sow
Which animals have an endothelichorial placenta?
dogs and cats
Which animals have an hemochorial placenta?
humans, primates and rodents
Binucleate giant cells
migrate in the ruminant placenta, secrete lactogen and protein B, progesterone and estrogens
What are the modes of transportation across the placenta?
simple diffusion, facilitated diffusion and active transport
How does gas and water cross the placenta?
simple diffusion
How does K, Na and CL cross the placenta?
active transport
What is the main energetic component most important to the fetus attained from the mother
Glucose
When do glucose requirements increase in the fetus?
during the last 1/3 of gestation
What molecules cannot cross the placenta?
proteins (some IG’s), lipids and liposoluble vitamins
What hormones does the placenta secrete?
hCG/eCG- stimulates ovaries
progesterone- maintain pregnancy
placental lactogens- fetus growth
prostglandins, oxytocin and relaxin- parturition
What are the stages of parturition?
- myometrial contractions initiated by the fetus
- expulsion of the fetus
- expulsion of the fetal membranes
What initiates parturition?
pressures on the cervix causes the release of oxytocin, stimulating myometrial contractions
