Functions of the Placenta

Question 1

Outline the 5 main functions of the placenta.

Answer 1

1. Respiration
2. Nutrition
3. Excretion
4. Endocrine
5. Immunity

Question 2

Why does oxygen pass from maternal haemoglobin to foetal haemoglobin?

Answer 2

Foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin.

Question 3

When do hCG levels plateau before they fall?

Answer 3

~10 weeks gestation

Question 4

What causes symptoms of nausea and vomiting in early pregnancy?

Answer 4

hCG

Question 5

Name two instances when there are higher levels of hCG.

Answer 5

1. Multiple pregnancy (e.g. twins)

2. Molar pregnancy

Question 6

Why does they placenta produce oestrogen?

Answer 6

Helps soften tissues and make them more flexible.

Allows muscles and ligaments of uterus and pelvis to expand.

Allows cervix to become soft and ready for birth.

Enlarges and prepares breasts and nipples for breastfeeding.

Question 7

When does the placenta mostly take over the production of progesterone?

Answer 7

~5 weeks gestation

Question 8

What is the role of progesterone in pregnancy?

Answer 8

Maintains pregnancy:

1. Relaxes uterine muscles to prevent contraction
2. Maintains endometrium

Question 9

What sides effects does progesterone cause in pregnancy and why?

Answer 9

Relaxes other muscles e.g.:

1. Lower oesophageal sphincter causing heartburn
2. Bowel causing constipation
3. Blood vessels causing hypotension, headaches and skin flushing
4. Raises body temperature 0.5-1 degree celsius

Question 10

Give an example of immunity to a certain disease being given to foetus through the placenta.

Answer 10

Recurrent genital herpes - mother’s antibodies to the herpes virus cross the placenta and protect the baby during labour and delivery, preventing infection during birth.

This protection does not occur during an initial episode of genital herpes, as the mother has not yet started producing sufficient antibodies against the herpes virus to offer the fetus protection.