Corpus Luteum: The Yellow Body

Corpus Luteum

The corpus luteum (plural corpora lutea) word is from the Latin language which means "yellow body" and the yellow colouration of the corpus luteum is due to the pigment, lutein.

During ovulation, an secondary oocyte is released from a graafian or dominant follicle. After its release, the remaining cells of the granulosa and theca interna form the corpus luteum. The center contains the remains of the blood clot that formed after ovulation. Surrounding the clot are glanulosa lutein cells (large luteal cells) and on the outside theca lutein cells (small luteal cells). These cells temporarily act as a endocrine gland that produces progesterone, estrogen, inhibin and to a lesser extent cholesterol.

When Egg Isn't Fertilized

If the egg is not fertilized, the corpus luteum stops secreting progesterone and decays (after approximately 10-12 days in humans). It then degenerates into a corpus albicans, which is a mass of fibrous scar tissue.

The uterine lining (endometrium) is expelled through the vagina (in mammals that go through a menstrual cycle). In an estrous cycle, the lining degenerates back to normal size.

When Egg Is Fertilized

If the egg is fertilized and implantation occurs, the syncytiotrophoblast (derived from trophoblast) cells of the blastocyst secrete the hormone human chorionic gonadotropin (hCG).

Human chorionic gonadotropin signals the corpus luteum to continue progesterone secretion, thereby maintaining the thick lining (endometrium) of the uterus and providing an area rich in blood vessels in which the zygote(s) can develop. From this point on, the corpus luteum is called the corpus luteum graviditatis.

Corpus luteum in pregnancy has a long life. In conception cycles, The corpus luteum generally lives for approximately 7 to 10 weeks of gestational age, and continues to produce and secrete progesterone. After 7-10 weeks of gestational age, the corpus luteum is replaced by the placenta in terms of progesterone production.