FORM & FUNCTION (Extraembryonic/Fetal Membranes)

Question 1

Extra-embryonic/fetal membranes:

Answer 1

-structures or tissues that develop from the zygote, but do NOT form a part of the embryo
-have functional importance in embryonic life

Question 2

Extra-embryonic/fetal membranes functions:

Answer 2

-supply/storage of nutrients
-respiratory exchange
-excretion
-mechanical protection of the embryo
-production of hormones
-formation of placenta

Question 3

Extra-embryonic/fetal membranes development:

Answer 3

-in a similar manner in avians and mammals
*present solely during the development and shed/lost at birth/hatching

Question 4

Yolk sac:

Answer 4

-formed by folding and migration of embryonic cells
-develops into bilaminar, trilaminar and definitive yolk sac
-splanchopleure (lateral mesoderm and endoderm) forms the yolk sac

Question 5

Function of yolk sac:

Answer 5

-helps with nutrition and gaseous exchange

Question 6

Amnion and chorion develop from:

Answer 6

-the somatopleure
>inner membrane: becomes the amnion
>outer membrane: becomes the chorion
*space between the amnion and chorion forms the extra-embryonic coelom

Question 7

Amnion:

Answer 7

-thin, tough membrane
-forms the walls of a fluid filled sac in which the embryo develops

Question 8

Function of amnion:

Answer 8

-protection of the embryo

Question 9

Allantois:

Answer 9

-develops as a diverticulum of the splanchonopleure, that grows into extra-embryonic coelom
-fuses with allantoic mesoderm to form the chorioallantoic membrane
-forms a part of the chorioallantoic placenta
-contains a fluid filled in allantoic cavity

Question 10

Allantois functions:

Answer 10

-vascularization of the chorion to facilitate nutrition and respiration of the developing embryo
-store renal waste

Question 11

Fetal fluids:

Answer 11

-amniotic and allantoic fluid increases during gestation at vary rates
-increase is dependant on species and embryonic physiology
-composition is very much similar to fetal plasma (in early pregnancy)
-secreted from the cells that form the amnion and allantois

Question 12

Functions of fetal fluids:

Answer 12

-aqueous medium for the fragile embryo to grow
-prevents adhesion of the embryo into the amniotic membrane

Question 13

Conceptus:

Answer 13

-embryo/fetus + fluid-filled membranes

Question 14

Umbilical cord:

Answer 14

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

Question 15

Urachus:

Answer 15

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

Question 16

Functions of umbilical cord:

Answer 16

-helps the transfer of oxygen and nutrients from the maternal circulation to the fetal circulation
-removal of waste from the fetal circulation

Question 17

Umbilical cord circulation:

Answer 17

-umbilical vein carries oxygenated blood from the mother to the fetus
-umbilical artery carries unoxygenated blood from the fetus to the mother