Group 3 - set 1/3 - Implantation and Placentation function - Revision Period stuff COMPLETE ****

Question 1

How is the placenta formed?

Answer 1

when foetal membranes become closely attached to the uterine wall
to facilitate physiological exchange of gases nutrients and waste products

Question 2

Describe the development of the extra embryonic membranes and state functions - you may find drawing on a whiteboard helps
* dont worry about getting it word for word

Answer 2

the inner cell mass is surrounded by the trophoblast
the inner cell mass gives rise to ectoderm, mesoderm and endoderm
the inner cell mass will become the embryo
the yolk sac is formed by the endoderm

the mesoderm grows upwards towards the embryo forming amniotic folds and downwards to surround the yolk sac
the amniotic folds grow closer together and meet, forming the amniotic cavity in which the developing embryo sits

the chorion forms where the trophoblast meets the mesoderm
the amnion forms around the embryo where the trophoblast meets the mesoderm

the yolk sac regresses
the allantois begins to develop from the hindgut

the connection between the hindgut and allantoid will become the umbilical cord
the allantois grows bigger
the chorioallantoic membrane is formed where the chorion meets the allantois

Question 3

What is the function of the Amnion? 4

Answer 3

allows symmetrical growth
allows foetal movement
protects the foetus
temperature control

Question 4

What is the function of the Yolk Sac in different species? 3

Answer 4

in birds and reptiles it surrounds the yolk
in marsupials it forms the definitive placenta
in high mammals it has a nutritional role in early pregnancy

Question 5

What is the function of the Allantois?

Answer 5

the connection to the hindgut becomes the umbilical cord

Question 6

What is the function of the chorion?

Answer 6

it becomes the foetal contribution to the placenta

Question 7

State the names of the 3 stages of implantation

Answer 7

apposition
adhesion
firm attachment or invasion

Question 8

Implantation: What happens during apposition?

Answer 8

the foetal membranes become closely apposed to the uterine epithelium

Question 9

Implantation: What happens during Adhesion?

Answer 9

a complex interaction occurs between molecules of the trophoblast and the uterine epithelium

Question 10

Implantation: What happens during Firm attachment or invasion?

Answer 10

non-invasive or invasive implantation of the trophoblast into the uterus depending on the species

Question 11

Implantation: Describe what happens with Non-invasive implantation 4

Answer 11

elongation and apposition of the pre-implantation embryo
epithelial cells stop expressing MUC1 proteoglycan during implantation window
trophoblast layer attaches to the uterine epithelial layer

Question 12

Implantation: Describe what happens with Invasive Implantation 5

Answer 12

no elongation of pre-implantation embryo
embryo aligns itself with endometrium
epithelial cells stop expressing MUC1 proteoglycans during implantation window
trophoblast layer attaches to the uterine epithelial layer
trophectoderm invades maternal tissue

Question 13

Classification of Placental Structure: State the 5 ways we can classify a placenta

Answer 13

foetal extra embryonic membranes
source of nutrition
whether maternal tissue is shed with foetal tissue at birth
histological structure
nutrient exchange area

Question 14

Placental Classification: How can we classify a placenta by Foetal extra embryonic membranes?
- Give examples of different types 3

Answer 14

depending on the layers involved in the placental structure

chorionic
yolk sac
allantoic

Question 15

Placental Classification: How can we classify placental structure by source of nutrition? 2

Answer 15

haemotrophic placenta obtains nutrition form circulating maternal blood

histotrophic placenta obtains nutrition form endometrium

Question 16

Placental Classification: How can we classify placentas based on whether maternal tissue is shed with foetal tissue at birth?

Answer 16

deciduate means that some maternal tissue is shed at birth

non-deciduate means no maternal tissue is shed at birth

Question 17

Placental Classification: How can we classify placentas based on thew Macroscopic nutrient exchange area?
- Give example of different types 3

Answer 17

by looking at the distribution of chorionic villi on the chorionic sac and their relationship with the endometrium

diffuse
cotyledonary
zonary

Question 18

Placental Classification: How can we classify placentas based on Histological structure?

Answer 18

by looking at the number of tissue layers interposed between maternal and foetal circulations

Question 19

Histological Placental classification: State and name the maximum possible number of foetal layers starting from closest to the foetal blood supply
- do the same for maternal

Answer 19

3 possible foetal layers
foetal endothelium
foetal connective tissue
foetal trophoblast

3 possible layers
maternal endothelium
maternal connective tissue
maternal epithelium

Question 20

Histological Placental classification: State the name of the Placenta with all 6 layers
- state which layers these are starting from foetal side
- which species have this structure? 2

Answer 20

epitheliochorial

foetal endothelium
foetal connective tissue
foetal trophoblast
maternal epithelium
maternal connective tissue
maternal endothelium

mare and sow

Question 21

Histological Placental classification: State the name of the Placenta with 4 layers
- state which layers these are starting from foetal side
- which species have this structure? 2

Answer 21

endotheliochorial

foetal endothelium
foetal connective tissue
foetal trophoblast
maternal epithelium
maternal endothelium

bitch and queen

Question 22

Histological Placental classification: State the name of the Placenta with 3 layers
- state which layers these are starting from foetal side
- which species have this structure? 3

Answer 22

haemochorial

foetal endothelium
foetal connective tissue
foetal trophoblast

rabbits, humans, primates

Question 23

Macroscopic Placental Classification: Distribution of Chorionic Villi
- Why is the distribution of chorionic villi important?
- Give examples of species with a diffuse distribution of chorionic villi and explain what this means

Answer 23

because the chorionic villi are areas of nutrient exchanges so are the functional units of the placenta

sow and mare

chorionic villi are distributed over the entire surface of the chorioallantoic membrane so nutrient exchange occurs over the entire surface

Question 24

Macroscopic Placental Classification: Distribution of Chorionic Villi
- Which species have a Cotyledonary placenta?
- What does this mean?

Answer 24

cow and ewe

chorionic villi are distributed in clusters called cotyledons over the surface of the chorioallantoic membrane

Question 25

Macroscopic Placental Classification: Distribution of Chorionic Villi
- Which species have Zonary Placentas?
- What does this mean?

Answer 25

bitch and queen

chorionic villi are gathered in a wide band on the section of the chorioallantoic membrane that surrounds the middle of the foetus

Question 26

Placental Classification: Classify the sow placenta

Answer 26

epitheliochorial
diffuse
non-deciduate

Question 27

Placental Classification: Classify the cow and ewe placenta

Answer 27

synepitheliochorial
cotyledonary
non-deciduate

Question 28

Placental Classification: Why are cow and ewe placentas called as SYNepitheliochorial instead of just epithaliochorial is there are 6 layers? 6

Answer 28

on the foetal side some chorionic cells undergo nuclear division without cytokinesis
this forms some binucleate cells
granules form within these cells
they migrate to and fuse with the maternal epithelial cells
this forms a maternal-foetal hybrid cell with 3 nuclei
the granules are emptied into maternal circulation

Question 29

Placenta: How do placentomes form?
- In which species do they form and why?
- What is the function of a placentome?

Answer 29

when cotyledons align with coruncles

ewes and cows as they have cotyledonary placentas

nutrient exchange

Question 30

Classify the horse placenta

Answer 30

epitheliochorial
diffuse
non-deciduate

Question 31

Describe how the development of horse foetal membranes differs from that of other species 5

Answer 31

by day 30 we have both a yolk sac placenta and a allantoic placenta
the junction between the 2 placentas is called the chorionic girdle
the chorionic girdle is the initial point of attachment of the membranes to the maternal uterus
the yolk sac shrinks and the allantois grows
by day 50 the allantois is the main placenta

Question 32

Describe the development of Endometrial cups in the horse 3

Answer 32

endometrial cup cells originate from the chorionic girdle
they invade the uterus and form ulcer-like structures called endometrial cups
they secrete equine chorionic gonadotrophin

Question 33

Equine Endometrial Cups: When do they form?
- What starts to happen from about day 70?

Answer 33

between days 40 and 60

they are surrounded and destroyed by immune cells

Question 34

Classify the placenta of a dog

Answer 34

endotheliochorial
zonary
deciduate

Question 35

Dog Placenta: What are the 2 bands of pigmented tissue on the edges of the placenta called?
- What do we call the middle bit in-between?

Answer 35

the pigmented zone

the transfer zone

Question 36

Classify the human placenta

Answer 36

haemochorial
invasive
decidate

Question 37

Umbilical Cord: which blood vessels does oxygenated nutrient rich blood leaving the placenta travel in?
- Where does the umbilical vein go?
- what happens immediately to this blood?
- describe the origin of the umbilical arteries
- what do they carry?

Answer 37

the umbilical vein

it mostly bypasses the liver and empties into the right atrium of the heart

it is shunted from the right atrium to the left atrium through the foramen ovale

they are branches of the internal iliac arteries

deoxygenated blood to the placenta

Question 38

Umbilical cord: what structures make up the umbilical cord?

Answer 38

the umbilical arteries wrapped around the umbilical vein