lisääntymissyklisten

Lisääntymissykli, or reproductive cycle, refers to the recurring physiological changes that occur in the reproductive system of many female animals, particularly mammals, which are controlled by hormones. This cycle prepares the female for potential conception and pregnancy. The most well-known example is the estrous cycle in mammals, often referred to as the heat cycle.

The estrous cycle typically involves several distinct phases. Follicular phase is characterized by the development of follicles in the ovary, which contain the eggs. During this phase, estrogen levels rise, stimulating the growth of the uterine lining. Ovulation, the release of a mature egg from the ovary, usually occurs at the peak of estrogen levels. The luteal phase follows ovulation, during which the ruptured follicle transforms into the corpus luteum. The corpus luteum produces progesterone, which further prepares the uterus for implantation of a fertilized egg.

If pregnancy does not occur, the corpus luteum regresses, leading to a drop in progesterone and estrogen levels. This hormonal decline triggers the breakdown and shedding of the uterine lining, a process called estrus or menstruation in primates. The cycle then restarts with the development of new follicles. The length and specific characteristics of the estrous cycle vary greatly among different species, influenced by factors such as genetics, environment, and season. Understanding these cycles is crucial for animal breeding, conservation efforts, and reproductive health research.