Extra-embryonic/fetal membrane

Question 1

Extra-embryonic/fetal membranes

Answer 1

• Structure or tissues that develop from the zygote, but do not form a part of the embryo, and have functional importance only in embryonic life
• Present solely during the development and shed/lost at birth/hatching

Question 2

Function of extra-embryonic/fetal membranes

Answer 2

• Supply/storage of nutrients
• Respiratory exchange
• Excretion and mechanical protection of the embryo
• Production of hormones
• Formation of placenta

Question 3

Yolk sac formation

Answer 3

• Formed by the folding and migration of embryonic cells
• From splanchnopleure (endoderm and mesoderm)
• Develops into a bilaminar, trilaminar, and definitive yolk sac

Question 4

Function of yolk sac

Answer 4

Helps with nutrition and gaseous exchange

Question 5

Formation of the amnion

Answer 5

Develops from inner somatopleure

Question 6

Formation of the chorion

Answer 6

Develops from the outer somatopleure

Question 7

Extra-embryonic coelom

Answer 7

The space between the amnion and the chorion

Question 8

What is the amnion?

Answer 8

A thin, tough membrane which forms the walls of a fluid filled sac in which the embryon develops

Question 9

Function of the amnion

Answer 9

The primary role of amnion is the protection of the embryo

Question 10

Formation of allantois

Answer 10

• Develops as a diverticulum of the splanchnopleure, that grows into the extra-embryonic coelom
• Fuses with the allantoic mesoderm to form chorioallantoic membrane which forms part of the chorioallantoic placenta

Question 11

Function of allantois

Answer 11

• Fluid filled
• Vascularization of the chorion to facilitate nutrition and respiration of the developing embryo
• Stores renal waste

Question 12

Fetal fluids

Answer 12

• Amniotic and allantoic fluids that increase during gestation at varying rates
• Secreted from cells that form the amnion and allantois
• Composition similar to fetal plasma (in early pregnancy)

Question 13

What causes variation in fetal fluids?

Answer 13

Depends on species and embryonic physiology

Question 14

Function of fetal fluids

Answer 14

Aqueous medium for the fragile embryo to grow, prevents adhesion of the embryo into the amniotic membrane

Question 15

What is conceptus?

Answer 15

Embryo/fetus + fluid-filled membranes

Question 16

Umbilical cord

Answer 16

• A structure that connects the fetus and placenta
• Comprised of fetal mucoid connective tissue (Wharton’s jelly), surrounding two umbilical arteries, two umbilical veins, urachus and vestigial yolk sac

Question 17

Urachus

Answer 17

Fibrous tissue of the allantois that forms a canal, which drains urine from the fetus

Question 18

Function of umbilical cord

Answer 18

• Helps the transfer of oxygen and nutrients from the maternal circulation to the fetal circulation
• Removal of waste from the fetal circulation

Question 19

Fetal circulation

Answer 19

• Fetal vein will have oxygenated blood
• Fetal artery will have deoxygenated blood