Question

Estrogens are secreted by
A.Follicle cells
B.Ovary
C.Germinal epithelium
D.Stroma

Answer 1

Hint:Estrogens are a class of female hormones that influence the maturation, development, and functioning of female sexual characters. The level of estrogen gets elevated during ovulation and after the menstrual cycle. In ovaries, the egg follicle growth is stimulated by estrogen. The cells that turn into corpus luteum secrete estrogens.

Complete answer:Estrogens are an important class of three major female sex hormones. They comprise estradiol, estrone, and estriol. Estradiol is the key influencing hormone. The estrogens act on female sex organs and stimulate their growth and development. Also, estrogens stimulate the growth of primary follicle cells in the ovary. They influence the pituitary gland in the brain for the release of certain hormones that control follicle development. The estrogens also help in the transfer of eggs from the fallopian tube towards the uterus to meet sperm by developing a thick contracting wall.
The ovaries and the placenta are the major sources of estrogens. But it is believed that the actual secretion sites for estrogen are follicle cells and interstitial cells in the ovary. The follicle cells are those that make a sac-like structure and hold the immature egg until it is released during ovulation. After ovulation, the follicle cells degrade and turn into corpus luteum that secretes its own hormones. The interstitial cells are connective cells inside the ovary.

All of the ovarian steroid hormones are derived from cholesterol. Cholesterol is first converted into pregnenolone that is further converted into progesterone. Several androgens (male sex hormones) are made for the final conversion of progesterone into estrogens. This indicates that androgens act as precursors for estrogens. An enzyme named aromatase acts on androgens to convert them into estrogens in the follicular cells.
Hence, we can conclude that the right answer is option A.

Note:After being secreted in blood, the estrogens bind to a protein called sex hormone-binding globulin. Some of the estrogen hormones in serum stay in bound form and some in free form. The free hormone molecules penetrate the target cells by estrogen receptors inside the cytoplasm of the cell. This complex then enters the nucleus where it influences protein synthesis.