Lisääntymissyklet

Lisääntymissyklet refer to the recurring physiological changes that occur in the reproductive systems of many female animals, preparing them for potential reproduction. These cycles are often influenced by hormonal fluctuations and are essential for the release of eggs and the creation of an environment conducive to fertilization and implantation.

The duration and characteristics of reproductive cycles vary significantly across different species. In some mammals, the cycle is referred to as the estrous cycle, which involves distinct phases such as proestrus, estrus (heat), metestrus, and diestrus or anestrus. Estrus is the period of sexual receptivity, when the female is most likely to conceive. In primates, including humans, the reproductive cycle is called the menstrual cycle, characterized by a monthly shedding of the uterine lining if pregnancy does not occur.

Key hormones involved in regulating these cycles include gonadotropins like follicle-stimulating hormone (FSH) and luteinizing hormone (LH), as well as ovarian hormones such as estrogen and progesterone. FSH stimulates the development of ovarian follicles, which produce estrogen. Estrogen, in turn, triggers the LH surge, leading to ovulation—the release of a mature egg from the ovary. Progesterone prepares the uterus for potential pregnancy.

The timing of reproductive cycles can be influenced by environmental factors such as photoperiod (daylight hours), temperature, and social cues from other individuals. These cycles are a fundamental aspect of sexual reproduction, ensuring that females are fertile at opportune times, thereby increasing the chances of successful reproduction and species survival. Disruptions to these cycles can indicate reproductive health issues.