NEET BIOLOGY

Detailed explanation-1: -The normal endometrium increases in thickness during the proliferative phase of the menstrual cycle in response to estrogen. Following ovulation, the endometrium provides an attachment site for and a source of nourishment to an early embryo until the placenta develops.

Detailed explanation-2: -Estrogens act through specific receptors located in the nuclei of epithelial and stromal cells of the endometrium. Estrogens stimulate the synthesis of these receptors and the progesterone inhibits their synthesis. Estrogens induce the proliferation of the mucosa during the proliferative phase.

Detailed explanation-3: -During the first part of the cycle, the hormone estrogen is made by the ovaries. Estrogen causes the lining to grow and thicken to prepare the uterus for pregnancy.

Detailed explanation-4: -So, the correct answer is ‘Oestrogen’.

Detailed explanation-5: -When the follicular phase begins, levels of estrogen and progesterone are low. As a result, the top layers of the thickened lining of the uterus (endometrium) break down and are shed, and menstrual bleeding occurs.