Which endometrial layer regenerates to rebuild the functional layer after menses?

• A. Stratum basalis
• B. Stratum functionalis
• C. Myometrium
• D. Stratum compactum

Answer: (A)

Endometrial regeneration comes from the stratum basalis, the permanent basal layer. After menses, the functional layer (stratum functionalis) is shed, but the basal layer remains intact. The cells in this basalis proliferate and differentiate to rebuild the glands, stroma, and blood vessels, restoring the functional layer to its thick, receptive state. The myometrium is the muscular layer beneath the endometrium and does not rebuild the endometrial lining. Stratum compactum is part of the functional layer and is shed with it, so it isn’t the source of regeneration.