During the menstrual phase, which layer of the endometrium is shed?

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

Answer: (B)

In menstruation, the endometrium that is shed is the functional layer (stratum functionalis). This layer thickens under the influence of estrogen and progesterone during the cycle and contains the glands and spiral arteries. When hormone levels fall if pregnancy doesn’t occur, the functional layer becomes ischemic and sloughs off, producing menses. The basal layer (stratum basalis) remains intact and serves to regenerate a new functional layer in the next cycle. The myometrium, the muscular layer beneath, is not shed.