Umbilical vesicle

Umbilical Vesicle

The Umbilical Vesicle (also known as the yolk sac) is a vital component of the embryo during the early stages of pregnancy. It is one of the three embryonic appendages, along with the amnion and the allantois.

Formation

The Umbilical Vesicle forms during the second week of embryogenesis from the hypoblast cells. These cells proliferate and migrate to form a layer that lines the blastocyst cavity, creating the primitive yolk sac. Later, the yolk sac splits into two layers: the outer layer fuses with the chorion to form the choriovitelline placenta, while the inner layer remains with the embryo.

Function

The Umbilical Vesicle serves multiple functions during embryonic development. It is the first site of blood cell and vascular formation, a process known as hematopoiesis. It also contributes to the formation of the gut and provides nutrients to the developing embryo before the placenta is fully formed.

Clinical Significance

Abnormalities in the Umbilical Vesicle can lead to various birth defects. For example, an enlarged yolk sac is associated with miscarriage and chromosomal abnormalities. On the other hand, a small or absent yolk sac can indicate ectopic pregnancy or embryonic death.

See Also

• Embryo
• Embryogenesis
• Amnion
• Allantois
• Blastocyst
• Chorion
• Placenta
• Birth defect
• Miscarriage
• Ectopic pregnancy