Embryonic Development and Placentation

Question 1

what are the 4 parts of the blastocyst

Answer 1

Inner cell mass
Zona pellucida
Trophoblast
Bastocoele

Question 2

what are the 3 layers of the blastocyst and the function

Answer 2

ectoderm- CNS, sweat glands, sense organs, skin, mammary gland, hair, hooves
Mesoderm- circulatory, repro, skeletal system, kidneys, muscle, urinary ducts
Endoderm- GI, pancreas, liver, thyroid, lungs, Endocrine

Question 3

what are the 4 membranes

Answer 3

yolk sac
amnion
allantois
chorion

Question 4

where do blood vessels grow and attach
how does this make the placenta ready

Answer 4

blood vessels grow in the chorio-allantois and attach to the embryo to form the umbilical cord
the placenta is now ready to be formed via attachment to the uterine endometrium

Question 5

what are the 4 membranes and their functions

Answer 5

yolk sac- early nutrient supply for early embryo
amnion- protects fetus from injury, provides lubrication for parturition, reservoir for urine and waste
allantois- fuses with chorion (chorio-allantoic placenta) carries blood vessels of placenta, reservoir for nutrition and wastes. umbilical cord attaches fetus to allantois
chorion- attaches to uterus, absorbs nutrients from uterus, allows maternal/fetal gas Exhange, produces hormones

Question 6

how does maternal recognize pregnancy

Answer 6

chemical message from embryo
results in maintenance of CL
PGF2a production from the endometrium is inhibited or re-directed
CL is protected from the effects of PGF2a

Question 7

what are the 2 types of implantation (placenta)

Answer 7

superficial- chorion fuses to the uterine endometrium
interstitial- embryo invades endometrium and develops in the endometrium

Question 8

how long does it take for placenta attach to the uterus in cow, sow, ewe, mare, bitch, queen, human

Answer 8

cow- 30-35 days
sow- 12-20
ewe- 18-20
mare- 50-60
bitch- 14-16
queen- 12-14
human- 8-10

Question 9

what are the 4 types of placental types and which animals have it

Answer 9

diffuse- mare and sow
zonary- dogs and cats
cotyledonary- cow and ewe
discoidal- primates

Question 10

explain diffuse type of placenta

Answer 10

villi will cover the surface of the chorion

Question 11

explain zonary type of placenta

Answer 11

villi will form a band around the chorion

Question 12

explain cotyledonary type of placenta

Answer 12

villi become localized at cotyledons

Question 13

explain discoidal type of placenta

Answer 13

villi cover about 1/2 of surface of placenta

Question 14

what are the 3 types of fusion for placenta and which animals have it

Answer 14

epitheliochorial- pigs, horses, and ruminants
endotheliochorial- dogs and cats
hemochorial- primates and rodents

Question 15

what is epitheliochorial fusion in placenta

Answer 15

has 6 layers
endometrial capillary- basement membrane- maternal endometrium- fetal chorion- basement membrane- chorionic capillary

Question 16

what is endotheliochorial type of fusion in placenta

Answer 16

5 layers
endometrial capillary- maternal endometrium- fetal chorion- basement membrane- chorionic capillary

Question 17

explain hemochorial fusion of placenta

Answer 17

3 layers
maternal RBC
fetal chorion
chorionic capillary

Question 18

how does the placenta provide fetal nutrition

Answer 18

blood gas exchange at chorion
placenta highly permeable to water and electrolytes
placenta converts glucose to fructose
fetal fat formed from fatty acids transferred acrss the placenta
fetus makes proteins from transferred AA
water soluble vitamins cross the placenta easier than fat soluble
minerals are transferred across the placenta
antibodies to fight disease do not cross the placenta- newborn must have colostrum

Question 19

how does the placenta serve as an endocrine organ

Answer 19

progesterone is the main hormone which causes uterine quiescence and histotrophic production