Placental physiology

Question 1

placental circulation

Answer 1

Question 2

pneumonic to remember placenta function

Answer 2

SERPENT

Question 3

placenta functions

Answer 3

storage
endocrine
respiration
protection
excretion
nutrition
transfer

Question 4

storage

Answer 4

metabolises glucose
stored as glycogen until required
synthesis and storage of cholesterol
iron and fat soluble vitamins

Question 5

endocrine

Answer 5

maintains pregnancy and prenatal development
Human chorionic gonadotrophin
Human chorionic somatomammotropin – maternal anti insulin effect, enhances fetal glucose use
Progesterone
Oestrogen

Question 6

respiration

Answer 6

Gaseous exchange occurs by diffusion

High Fetal haemoglobin levels - hemoglobin’s affinity for oxygen.

A slight maternal respiratory alkalosis in pregnancy, assists in the transfer of oxygen and carbon dioxide

Bohr effect

Haldane effect

Question 7

protection

Answer 7

Filters substances of high molecular weight - semi permeable membrane
Immunological function
Late pregnancy – naturally acquired passive immunity
Limited barrier to infection
Few bacteria can cross placental barrier
Many virus, parasitic & protozoal diseases can cross placental barrier e.g. HIV, human cytomegalovirus, rubella, toxoplasmosis
Medicines & drugs – some may be beneficial e.g. antibiotics
Poisons & carbon monoxide
Prevents antigen reactions (separate blood circulation)

Question 8

excretion

Answer 8

Diffusion

Carbon dioxide is the main substance excreted form the fetus

Small amount of Urea and uric acid excreted

Bilirubin

Question 9

nutrition

Answer 9

Fetal requirements for development obtained from maternal diet
amino acids & glucose – growth & energy
calcium & phosphorus – bones & teeth
iron & minerals – formations of blood

Depletes maternal supply (parasitic relationship)
Later stages of pregnancy, fats & fat soluble vitamins cross the placenta

Amino acids – active transport

Question 10

amino acids and glucose

Answer 10

growth and energy

Question 11

calcium and phosphorus

Answer 11

bones and teeth

Question 12

iron and minerals

Answer 12

formations of blood

Question 13

transfer of substances

Answer 13

Fetus dependant on mother

Facilitated by uteroplacental & fetoplacental circulation

diffusion 
water soluble substances
endocytosis of macromolecules 
active transport mechanisms e.g calcium. 

Rate of transfer influenced by increased maternal and fetal blood flow