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[edit | edit source]

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[edit | edit source]

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[edit | edit source]

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.