Vitelline Cavity

**The yolk cavity, or yolk sac, or calum vitellinum** is located in the abdominal cavity of the anterior part of the human body, containing a reserve of yolk and immersed in it after leaving the oviduct, a fertilized egg or eggs, from which the embryo is then formed. It has the shape of a truncated cone and opens at one end into the lumen of the oviduct, and at the other into the cavity of the yolk sac. The yolk sac is a simple sac, consisting of two layers - inner and outer. In humans, it reaches the size of a bean, so it is difficult to get an unambiguous idea about it. The vitelline cavity lies to the left of the midline and behind the left kidney, located next to the splanchnic flexure of the duodenum.

Yolk sac: physiological significance and functions

The main source of yolk for the embryo is the ovarian follicles, which do not have blood vessels. From them, the contents flow into the vitelline ducts, which open into the yellow field in the plane of the inner layer of the vitelline vesicle (cavity). This layer has a relief pattern of a dense plexus of cellular processes - the “embryonic” epibolus, which is a cluster of ciliary cilia covering the developing embryo.

At the beginning of egg migration in the germinal endometrium, morula cells penetrate the yolk, washing the membranes with yolk. In this case, the epithelium of the yolk sac breaks through the mucous membrane of the embryo. During this operation, the female sex hormone progesterone penetrates from the germ cell blastema into the yolk sac. All this happens at the stage of 6-8 weeks of embryo development