The cavity of the uterus is covered by a specialised lying. It is so important it got it's own scientific name. The scientific name is the endometrium.

The early pregnancy attach itself to the endometrium and than literally burries itself in the endometrium to obtain contact with the mother's blood vessels. See Early Pregnancy.

The endometrium's thickness is influenced by the female hormones estorgen and progesterone , and its reponse to the hormones causes menstruation.(See Normal menstruation )

The next drwawing illustrates the uterus with it's front part cut away.