ANATOMY - Placenta Development Flashcards
What are the functions of the placenta?
Protection of the foetus
Provision of maternal oxygen and nutrients
Removal of foetal metabolic waste products
What are the four foetal membranes which make up the placenta?
Yolk sac
Amnion
Allantois
Chorion
Describe the formation of the amnion from the somatopleure
As the embryo begins to sink into the somatopleure, the folds of the somatopleure meet dorsally and fuse to form the amnion
When the amnion has formed, what is the somatopleure now known as?
When the amnion has developed, the somatopleure is known as the chorion
What is contained within the amnion?
Suspended foetus
Amniotic fluid
What is the main function of the amnion?
The main function of the amnion is shock absorption and thus protection of the developing foetus
What are amniotic pustules?
Amniotic pustules are glycogen accumulations that appear as white spots on the surface of the ruminant amnion
What is the chorio-vitelline placenta?
The chorio-vitelline placenta is the temporary fusion of the yolk sac with the chorion to allow the diffusion of nutrients during development
What is the allantois?
The allantois is an extra-embryonic diverticulum of the hindgut
What is the main function of the allantois?
Collects foetal metabolic waste products such as urine, secretions and blood transudate
What is the chorio-allantoic placenta?
The chorion-allantoic placenta is the final form of the placenta formed by the fusion of the allantois with the chorion
What is the function of chorionic villi?
Chorionic villi increase the surface area of the chorion to increase nutrient absorption from the maternal endometrium
What are the four possible distributions of chorionic villi on the placenta?
Diffuse
Cotyledonary
Zonary
Discoid
What are cotyledons and caruncles?
Cotyledons: regions of chorionic villi on the foetal chorion
Caruncles: structures on the endometrium which interdigitate with the cotyledons
What are placentomes?
Placentomes are the interdigination of the foetal cotyledons and the endometrial caruncles
Which species have placentomes?
Ruminants
What is the difference between placental and paraplacental?
Placental: regions of the placenta covered in chorionic villi
Paraplacental: regions of the placenta with no chorionic villi
What is the name for the paraplacental regions which have no vasculature as well as no chorionic villi?
Avascular extremity
What is an epithelio-chorial placenta?
An epithelio-chorial placenta is when there is direct contact between the foetal chorion and the maternal endometrial epithelium
What are the six histological layers of an epithelio-chorial placenta?
- Maternal endometrial endothelium
- Maternal connective tissue
- Maternal endometrial epithelium
- Foetal chorion
- Foetal mesoderm
- Foetal endothelium