Question

Once a female reaches puberty, the uterus sheds an unfertilized egg along with the

Answer 1

It begins to shed the uterine tissue (also sometimes called lining or wall). Pretty sure that's the answer you're looking for haha.

Answer 2

The answer is the endometrium. The functional layer of the endometrium thickens in preparation for inception and implantation of the fertilized egg. When the released ova fail to be fertilized, the corpus luteum in the ovary disintegrates, and the subsequent drop in estrogen and progesterone levels results in menstruation as the endometrium also disintegrates.