Embryogenesis and placentation Flashcards
Which structures produce progesterone at different stages of pregnancy?
Early = corpus luteum
Followed by the placenta
Which hormone induces luteolysis?
Prostaglandin
What happens to the uterus when there is a decrease in progesterone?
Will no longer allow attachment of the embryo
How is luteolysis stopped in cattle and sheep?
The blastocyst produces interferon which blocks synthesis of oxytocin receptors so prostaglandin isn’t produced
How does maternal recognition occur in pigs?
Oxytocin is still produced but prostaglandin is re-routed into the uterine lumen where it cannot cause luteolysis
What is the time for attachment of the placenta longer in mares than other species?
It has to migrate rather than elongate itself
When in pregnancy does most pregnancy loss occur?
In the first few weeks when maternal recognition of pregnancy and placental attachment is occuring
What 3 types of cell are found in the inner cell mass of the blastocyst?
- Endoderm
- Mesoderm
- Ectoderm
What are the 2 bags of fluid that form during pregnancy around the foetus?
Amnion
Allantochorion
When the primitive endoderm has completed its growth it forms a cavity, what is this?
Yolk sac
What is the name of the functional part of the foetal placental?
Chorionic villus - increase SA for exchange
How is the primate embryos different to other species?
The embryo implants into the uterus whereas in other species the embryo attaches to the uterus
What are the functions of the placenta?
- allows metabolic exchange between the dam and foetus
- maintains pregnancy
- stimulates maternal mammary gland
- promotes foetal growth
Which cells induce local tissue to differentiate into sex cords?
Primitive germ cells
What determines if an embryo becomes male or female?
The sex chromosome within the spermatozoa
