Reproduktsioonitsükkel

Reproduktsioonitsükkel, often translated as reproductive cycle or estrous cycle in English, refers to the recurring physiological and behavioral changes that occur in sexually mature, non-pregnant female mammals in preparation for reproduction. This cycle is regulated by hormones, primarily estrogen and progesterone, secreted by the ovaries and the pituitary gland.

The cycle is typically divided into several phases. Proestrus is characterized by the development of ovarian follicles and rising estrogen levels, leading to behavioral changes and physical swelling in some species. Estrus, or heat, is the period of sexual receptivity, where the female is most fertile and willing to mate. This phase is driven by peak estrogen levels.

Ovulation, the release of an egg from the ovary, usually occurs during estrus. Following estrus, if fertilization does not occur, the corpus luteum forms and secretes progesterone, which prepares the uterus for potential pregnancy. This phase is known as metestrus. If pregnancy does not occur, the corpus luteum regresses, progesterone levels drop, and the cycle begins anew, entering diestrus. In some species, the cycle may not involve a distinct diestrus phase, and the animal may return to estrus directly.

The duration of the reproductive cycle varies significantly among different species, ranging from a few days to several months. Factors such as age, nutrition, and environmental conditions can also influence the cycle. Understanding the reproductive cycle is crucial for animal breeding, reproductive health management, and conservation efforts.