Placenta

Question 1

What are the main tissue types in the placenta

Answer 1

fetal and maternal tissue
- chorion and allantois - mammal placenta
- chorion and yolk sac - domestic animals
- endometrium - rodents and humans

Question 2

what are functions of the placenta

Answer 2

• transfer oxygen and carbon dioxide (respiratory)
• fetal nutrition (gastrointestional)
• excretory functions (water balance, pH and renal)
• hormone/enzyme production (endocrine)
• immunological functions

Question 3

what type of transport is used

Answer 3

simple diffusion (water gases simple molecules)
facilitated diffusion - glucose
active transport - essential amino acids, water soluable vitamines, sodium, potassium calcium (higher concentrations in the fetus)
receptor mediated endocytosus - immunoglobulins some proteins fat and visuses

Question 4

how do you classify placentas

Answer 4

chorionic villi distribution
- cotyledonary - chorionic vascularized villous trophoblasts and uterine endometrial structures termed caruncles come together
- zonary - invasive band of the chorion surrounds middle of fetus (dog and cat)
discoid - a disc like structure of chorion interacting with maternal tissue (higher primates and rodents

Question 5

what hormones are produced by the placenta

Answer 5

progesterone - stimulates endometrial (uterine lining) growth and particularly gland secretions
estradiol - also important product of placenta - especially during the last part of pregnancy (peak estradiol secretion in most species indicates it is close to parturition period and increases levels promote labour
relaxin - in humans, mares, cats dogs pigs and rabbits - softening or relaxation of pelvic ligaments for delivery of baby (unknow what stimulates it) acts with progesterone to maintain pregnancy

Question 6

what is progesterone block

Answer 6

inhibiting uterine contractions
absolute levels vary wildly among species

Question 7

what removes progesterone block

Answer 7

estradiole - becasue progesterone in the placenta gets converted to estradiol in domestic species (except equine)
this is driven by fetal corticoids - also stimulates releaseof prostaglandin that also helps reduce progesterone levels by stimulating regression of corpus luteum

Question 8

what are two ways we classified placentas

Answer 8

chorionis villi distributions ex zonary - invasie band of the chorion surrounds the middle of the fetus (dog and cat)
based on cell layers - epitheliochorial, least invasive as epithelium of chorionic villi and uterine luminal epithelium are intact
sow- no erosion of luminal epithelium occurs
mare - small group of trophoblasts cells chorionic girdle trophoblasts moderately and transeiently invade the luminal epithelium