Development & Ageing - Pregnancy, Parturition and late fetal development Flashcards
What is histiotrophic nutrition and when does this occur?
Nutrition derived of nutrients from the breakdown of surrounding tissue
Occurs in the first trimester
What is haemotrophic nutrition and when does this occur?
Nutrients derived from maternal blood
Occurs in the second trimester
What is meant by a haemochorial-type placenta?
The maternal blood directly contacts the fetal membranes
What is the function of the connecting stalk?
Links developing embryo unit to the chorion
What are trophoblastic lacunae?
Large spaces filled with maternal blood formed by the breakdown of maternal capillaries and uterine glands
How is the amniotic sac made and explanded?
The accumulation of fluid causes the amnion the come into contact with the outer, chorion, layer, which fuse together forming the amniotic sac
What are primary chorionic villi?
The cytotrophoblast forms finger-like projections through the syncitiotrophoblast layer into the maternal endometrium
What are the 3 stages of chorionic villi development?
Primary:
- Outgrowth of the cytotrophoblast and branching of these extensions
Secondary:
- Growth of the fetal mesoderm into the primary villi
Tertiary:
- Growth of the umbilical artery and umbilical vein into the villus mesoderm, providing vasculature
What is the process of conversion?
Extra-villus trophoblast cells coating the villi invase down into the maternal spiral arteries, forming endovasculat EVT
Endothelium and smooth muscle is broken down - EVT coats the inside of the vessel
Why does conversion occur?
Turns spiral arteries into a low pressure, high capacity conduit for maternal blood flow to the embryo
What are the maternal changes that occur with pregnancy?
- Cardiac output increases 30% in first trimester
- Peripheral resistance decreases up to 30%
- Maternal blood volume increases to 40%
- Pulmonary ventilation increases 40%
