The Placenta And Umbilical Cord

Question 1

Describe the structure of the placenta.

Answer 1

The placenta connects the baby to the uterus wall. Trophoblastic villi becomes chorionic villi which are bigger and acquire blood capillaries which are connected to the umbilical artery and vein. These are the blood vessels connecting the embryo to the uterus wall via the umbilical cord.

Question 2

What are the 5 roles of the placenta?

Answer 2

• endocrine system producing hormones
• exchange
• physical barrier between foetal and mother circulation
• provides passive immunity
• protection from the immune system

Question 3

Describe the exchange between mother and foetal blood.

Answer 3

Intervillous spaces called lacunae surround chorionic villi and contain mothers blood. Chorionic villi have microvilli for max exchange. There is a small distance which is good for D, FD, AT, pinocytisis and osmosis. A countercurrent flow maintains the gradient. Exchange materials include nutrients, waste products and respiratory gases.

Question 4

Describe why there needs to be a physical barrier between the mother and foetal circulation.

Answer 4

• protects from high blood pressure

- protects from changes in BP

Question 5

Describe passive immunity

Answer 5

Maternal antibodies cross the placenta to attack antigens, but not the foetal cells even though they contain the fathers antigens.

Question 6

Describe how the placenta protects the foetus from the immune system of the mother.

Answer 6

The mother doesn’t make an immune response to the foetus or placenta even though they have foreign antigens. The cell walls of the chorionic villi fuse to make the syncitium so there aren’t spaces between them; so migratory immune cells like granulocytes can’t get through.

Question 7

How does the placenta not always provide immunological protection?

Answer 7

• spontaneous abortions like organ rejection
• rhesus disease; where the mother is rhesus negative and the foetus is rhesus positive so blood cells destroyed
• pre eclampsia = high BP
• microoganisms like rubella can get through to baby, as can nicotine/ heroin

Question 8

What is the umbilical cord?

Answer 8

Has 2 umbilical arteries away from foetus and 1 umbilical vein to the foetus, carries blood between mother and foetus.