Placentation

monotremes

egg laying mammals

marsupial placenta

Choriovitelline

Simple contact with maternal cells

Most nourishment from yolk

eutherian mammals

mammals with placenta

why is the placenta considered a transient organ?

has both metabolic and endocrine functions

T/F: There are two parts of the placenta: fetal and maternal.

true

what extra-embryonic structures create the umbilicus?

yolk sac and allantois

which extra-embryonic structure eventually becomes the mature placenta?

allatnochorion

maternal fetal interface

Region where maternal and fetal tissues interact via interdigitating microvilli

what is the functional unit of the placents?

chorionic villus to maximize exchange between conceptus and dam

How are placentas classified?

based on distribution of chorionic villi

which placenta is characteristics of all carnivores?

zonary

what animals have a diffuse placenta?

horse, pig

Explain diffuse placenta in sows

chorionic villi are closely spaced and uniformly distributed

penetrate into endometrium to form maternal-fetal interface

Explain diffuse placenta in mares

made up of microzones called microcotyledons

what is a unique structure of the mare placenta that helps maintain pregnancy?

endometrial cups via chorionic girdle

what is the purpose of endometrial cups?

To produce ECG/PMSG, which stimulates ovulation and thus forms a secondary CL in the ovary, which maintain the pregnancy by continuing to produce progesterone until about D100 when the placenta takes over as the main P4 producer

T/F: eCG in mares can be tracked to determine progression of pregnancy

FALSE, endometrial cups continue to produce eCG for entire life span of cup - regardless of pregnant or non-pregnant

Which animals have a zonary placenta?

dogs and cats

explain zonary placenta (HINT describe regions)

1. bandlike zone of chorionic villi aka transfer zone

2. second region on either end on original band called paraplacenta (iron transport)

3. clear regions for direct absorption of materials from uterus

what animals have a discoid placenta?

humans, rodents, primates

explain discoid placenta

round disc containing all chorionic villi in one place forming maternal fetla interface

which placenta type interacts directly with maternal blood?

discoid

what animals have a cotyledonary placenta?

ruminants

A cotyledonary placenta has different parts:

a. _______________ = fetal portion

b. _____________ = maternal contact site

cotyledon

caruncle

_________ is the cotyledon-caruncle complex

placentome

Explain how the cotyledons of cows and ewes are different.

cows are convex and sheep are concave

Placentas can also be classified based on the type of intimacy between maternal and fetus. explain

number of placental layers that separate fetal blood from maternal blood

epitheliochorial is found in what animals?

cow, pig, horse

epitheliochorial placenta

6 layers

intact layer of fetal and maternal epithelium

endotheliochorial placenta is found in what animals?

dogs and cats

endotheliochorial placenta

5 layers

semi-invasive

complete erosion of endometrial epithelium and underlying interstitium - maternal capillaries are directly exposed

what animals have a hemochorial placenta?

primates and rodents

hemochorial placneta

3 layers

most invasive

chorionic epithelium in direct apposition to maternal pools of blood

Pig

a. chorionic villus patterning

b. maternal fetal barrier

c. loss of maternal tissue at birth

diffuse

epitheliochorial

none

Mare

a. chorionic villus patterning

b. maternal fetal barrier

c. loss of maternal tissue at birth

diffuse

epitheliochorial

none

Sheep, goat, cow

a. chorionic villus patterning

b. maternal fetal barrier

c. loss of maternal tissue at birth

cotyledonary

epitheliochorial

none

dog, cat

a. chorionic villus patterning

b. maternal fetal barrier

c. loss of maternal tissue at birth

zonary

endotheliochorial

moderate

primate, rodent

a. chorionic villus patterning

b. maternal fetal barrier

c. loss of maternal tissue at birth

discoid

hemochorial

extensive

Method of transfer in the placenta for:

a. gases and water

b. sodium and potassium

c. glucose and amino acids

simple diffusion

active transport

facilitated diffusion

Antibody transfer only occurs in which type of placenta?

hemochorial placenta because antibodies can cross placenta border and enter fetal circulation

T/F: The placenta serves as an endocrine organ. in most species the placenta takes over P4 production

true, however bitch, sow, and queen gestation is so short the CL maintains P4 entire pregnancy

What hormone rises at the beginning of the parturition period?

estradiol