Group 3 - set 1/3 - Implantation and Placentation function - Revision Period stuff COMPLETE **** Flashcards
How is the placenta formed?
when foetal membranes become closely attached to the uterine wall
to facilitate physiological exchange of gases nutrients and waste products
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
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
What is the function of the Amnion? 4
allows symmetrical growth
allows foetal movement
protects the foetus
temperature control
What is the function of the Yolk Sac in different species? 3
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
What is the function of the Allantois?
the connection to the hindgut becomes the umbilical cord
What is the function of the chorion?
it becomes the foetal contribution to the placenta
State the names of the 3 stages of implantation
apposition
adhesion
firm attachment or invasion
Implantation: What happens during apposition?
the foetal membranes become closely apposed to the uterine epithelium
Implantation: What happens during Adhesion?
a complex interaction occurs between molecules of the trophoblast and the uterine epithelium
Implantation: What happens during Firm attachment or invasion?
non-invasive or invasive implantation of the trophoblast into the uterus depending on the species
Implantation: Describe what happens with Non-invasive implantation 4
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
Implantation: Describe what happens with Invasive Implantation 5
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
Classification of Placental Structure: State the 5 ways we can classify a placenta
foetal extra embryonic membranes
source of nutrition
whether maternal tissue is shed with foetal tissue at birth
histological structure
nutrient exchange area
Placental Classification: How can we classify a placenta by Foetal extra embryonic membranes?
- Give examples of different types 3
depending on the layers involved in the placental structure
chorionic
yolk sac
allantoic
Placental Classification: How can we classify placental structure by source of nutrition? 2
haemotrophic placenta obtains nutrition form circulating maternal blood
histotrophic placenta obtains nutrition form endometrium
Placental Classification: How can we classify placentas based on whether maternal tissue is shed with foetal tissue at birth?
deciduate means that some maternal tissue is shed at birth
non-deciduate means no maternal tissue is shed at birth
Placental Classification: How can we classify placentas based on thew Macroscopic nutrient exchange area?
- Give example of different types 3
by looking at the distribution of chorionic villi on the chorionic sac and their relationship with the endometrium
diffuse
cotyledonary
zonary
Placental Classification: How can we classify placentas based on Histological structure?
by looking at the number of tissue layers interposed between maternal and foetal circulations
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
3 possible foetal layers
foetal endothelium
foetal connective tissue
foetal trophoblast
3 possible layers
maternal endothelium
maternal connective tissue
maternal epithelium
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
epitheliochorial
foetal endothelium
foetal connective tissue
foetal trophoblast
maternal epithelium
maternal connective tissue
maternal endothelium
mare and sow
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
endotheliochorial
foetal endothelium
foetal connective tissue
foetal trophoblast
maternal epithelium
maternal endothelium
bitch and queen
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
haemochorial
foetal endothelium
foetal connective tissue
foetal trophoblast
rabbits, humans, primates
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
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
Macroscopic Placental Classification: Distribution of Chorionic Villi
- Which species have a Cotyledonary placenta?
- What does this mean?
cow and ewe
chorionic villi are distributed in clusters called cotyledons over the surface of the chorioallantoic membrane
Macroscopic Placental Classification: Distribution of Chorionic Villi
- Which species have Zonary Placentas?
- What does this mean?
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
Placental Classification: Classify the sow placenta
epitheliochorial
diffuse
non-deciduate
Placental Classification: Classify the cow and ewe placenta
synepitheliochorial
cotyledonary
non-deciduate
Placental Classification: Why are cow and ewe placentas called as SYNepitheliochorial instead of just epithaliochorial is there are 6 layers? 6
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
Placenta: How do placentomes form?
- In which species do they form and why?
- What is the function of a placentome?
when cotyledons align with coruncles
ewes and cows as they have cotyledonary placentas
nutrient exchange
Classify the horse placenta
epitheliochorial
diffuse
non-deciduate
Describe how the development of horse foetal membranes differs from that of other species 5
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
Describe the development of Endometrial cups in the horse 3
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
Equine Endometrial Cups: When do they form?
- What starts to happen from about day 70?
between days 40 and 60
they are surrounded and destroyed by immune cells
Classify the placenta of a dog
endotheliochorial
zonary
deciduate
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?
the pigmented zone
the transfer zone
Classify the human placenta
haemochorial
invasive
decidate
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?
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
Umbilical cord: what structures make up the umbilical cord?
the umbilical arteries wrapped around the umbilical vein
