Lisääntymiskierto

Lisääntymiskierto, often referred to as the reproductive cycle, is a recurring sequence of physiological events in sexually reproducing organisms that leads to the potential for conception. In females, this cycle is typically characterized by hormonal fluctuations that prepare the body for pregnancy. In mammals, the most well-known example is the menstrual cycle in primates and the estrous cycle in many other mammals. These cycles involve the maturation and release of an egg cell from the ovary, known as ovulation, and the subsequent changes in the uterus to receive a fertilized egg. If fertilization does not occur, the uterine lining is shed, leading to menstruation in some species or reabsorption in others, and the cycle begins anew.

The timing and duration of the reproductive cycle vary significantly across species. Hormones such as estrogen, progesterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) play crucial roles in regulating these complex processes. In males, the reproductive cycle is less distinctly defined but involves the continuous production of sperm and male hormones, primarily testosterone. The overall purpose of the reproductive cycle is to ensure the continuation of the species by facilitating the production and development of offspring. Understanding the intricacies of these cycles is fundamental to reproductive biology, endocrinology, and the development of contraceptive and fertility treatments.