Fetal Membranes + Umbilical Chord

Question 1

When does the amniotic cavity form and how?

Answer 1

Day 8

• when the embryoblast differentiates to epi- and hypo-, the amniotic cavity forms above the epiblast and is surrounded by amnioblasts which come from the epiblast

Question 2

What are the functions of the amniotic cavity and its fluid?

Answer 2

• Protection (from infection + physical shock)
• Adherence Prevention - ???
• Temperature Control
• Homeostasis - (fluid + electrolytes)
• Movement - permits movement

Question 3

When does the chorion form and how?

Answer 3

during the 2nd week

• the extraembryonic mesoderm differentiates into somatic and splanchnic when the ex.emb. coelom forms
• the outer, somatic extraembryonic mesoderm and both layers of the trophoblast (cyto- + syncytio-)

Question 4

When does the umbilical cord form and how?

Answer 4

around the 5th week

• the connecting stalk, omphalo-enteric duct and allantois are “pinched” off by the lateral folding of the amniotic cavity

Question 5

What is the approximate diameter and length of the umbilical chord?

Answer 5

d = 1-2 cm

length = avg. 55 cm

Question 6

What are the contents of the umbilical chord?

Answer 6

• umbilical vein - carries O2 rich blood
• umbilical arteries - paired, contain O2 poor blood
• Wharton’s Jelly - mucopolysacc. substance (w/ hyal. acid + chondroitin sulfate) from ext.emb. meso w/ fibroblasts + macrophages