What is the structure and function of the corpus luteum?

The corpus luteum is a temporary endocrine structure in female ovaries that produces progesterone after ovulation.

The corpus luteum, Latin for 'yellow body', is a temporary endocrine structure that forms in the ovary of female mammals after ovulation. It is a crucial part of the menstrual cycle and early pregnancy. Its primary function is to produce and secrete the hormone progesterone, which is vital for maintaining pregnancy.

The formation of the corpus luteum occurs after the mature ovarian follicle ruptures and releases its egg during ovulation. The remaining follicular cells undergo luteinisation, a process involving morphological and physiological changes, to form the corpus luteum. This structure is characterised by a highly vascularised, glandular, and yellowish appearance due to the accumulation of lipids and carotenoids.

The corpus luteum's main function is to produce progesterone, a hormone that prepares the uterus for implantation of a fertilised egg and supports early pregnancy. Progesterone does this by thickening the endometrium, the lining of the uterus, and suppressing further ovulation during pregnancy. The corpus luteum also produces a small amount of oestrogen, another hormone that supports pregnancy.

If fertilisation does not occur, the corpus luteum degenerates into a structure known as the corpus albicans, a process called luteolysis. This leads to a decrease in progesterone levels, triggering the onset of menstruation. If fertilisation does occur, the corpus luteum is maintained by the hormone human chorionic gonadotropin (hCG), produced by the developing embryo. This ensures the continued production of progesterone, necessary for maintaining the pregnancy until the placenta is fully formed and can take over this role.

In summary, the corpus luteum is a vital structure in the female reproductive system. Its primary role is to produce progesterone, a hormone necessary for preparing the uterus for pregnancy and supporting its early stages. Its existence and function are closely tied to the menstrual cycle and the process of fertilisation.