The corpus luteum is a temporary yellow body structure that occurs in all female mammals. The structure develops from the follicle on the ovary during the second half of the menstrual cycle (period) after the egg has been released. In humans the corpus luteum has a diameter of approximately 2-5 cm (0.8-2 in). The corpus luteum has a very important role to play in the mammal reproduction.
What is the function of the corpus luteum?
The first role of corpus luteum is to secrete the hormone progesterone, which is responsible for the changes and development of the endometrium (inner lining of the uterus) that allow, and maintain, a healthy pregnancy. When the egg is not fertilized the corpus luteum stops releasing the hormone. In humans, and some other mammals, this causes the uterine lining to be shed and in other mammals the uterine lining simply returns back to a regular size.
When the egg is fertilized and implants in the wall of the uterus a special hormone called human chorionic gonadotropin (in humans, but a similar hormone is released in other mammals) is released. This hormone tells the corpus luteum to continue to produce progesterone and this ensures the lining of the uterus remains thick so that the fertilized egg has a place to develop. At this time the structure becomes known as the corpus luteum graviditatis. In humans, and other animals with a placenta, the placenta eventually takes over the role progesterone production and the corpus luteum degrades.
Did you know?
After it has served its purpose the structure is broken down by macrophages and collagen is laid down by the fibroblasts. At this time the structure is known as corpus albicans and in some cases this will remain as a scar on the ovary.