Note the sections showing coiled or tortuous glands and the dense lamina propria. If a pregnancy does not occur, the uterine lining breaks down about 2 weeks after ovulation. Spiral arteries supplying the outer region of the uterine lining constrict and deprive the region of oxygenated blood. The cells lose fluid and cease to function. The stroma is invaded by leukocytes.
Necrosis continues and the uterine lining is shed.
This is the Menstral phase of the uterine lining. After the third or fourth day, all of the lining is shed except basal regions containing glands that can regenerate during the proliferative phase of the subsequent cycle. The following photograph illustrates the endometrium in the menstral phase. Note the few remaining glands. The glands in the functionalis are the ones that become long during proliferative phase and tortuous during the secretory phase.