Estrous cycle

Estrous cycle is a recurring physiological change that occurs in reproductive-age female mammals. The estrous cycle is characterized by changes in the female reproductive system that prepare the body for potential pregnancy. The cycle is regulated by hormones, including estrogen and progesterone, and involves several stages, including proestrus, estrus, metestrus, and diestrus.

Overview

The estrous cycle is the female reproductive cycle in mammals that are not primates, including rodents, cows, and dogs. It is similar to the menstrual cycle in humans and primates, but there are some key differences. For example, in the estrous cycle, the endometrium (the lining of the uterus) is reabsorbed if pregnancy does not occur, whereas in the menstrual cycle, the endometrium is shed as menstrual flow.

Stages of the Estrous Cycle

The estrous cycle consists of several stages:

• Proestrus: This is the stage after the end of the previous cycle and before the next ovulation. The levels of estrogen start to increase, which causes the endometrium to thicken in preparation for potential pregnancy.

• Estrus: This is the stage when the female is receptive to mating (also known as "in heat"). Ovulation occurs during this stage.

• Metestrus: This stage occurs after ovulation. The corpus luteum, which is the structure that the egg was released from, starts to produce progesterone.

• Diestrus: This is the stage when the corpus luteum is fully functional. If pregnancy does not occur, the corpus luteum degenerates and the cycle starts again.

Hormonal Regulation

The estrous cycle is regulated by several hormones, including:

• Gonadotropin-releasing hormone (GnRH): This hormone is released by the hypothalamus and stimulates the pituitary gland to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

• Follicle-stimulating hormone (FSH): This hormone stimulates the growth of follicles in the ovaries.

• Luteinizing hormone (LH): This hormone triggers ovulation and the formation of the corpus luteum.

• Estrogen: This hormone is produced by the follicles and prepares the body for ovulation.

• Progesterone: This hormone is produced by the corpus luteum and prepares the body for pregnancy.

See Also

• Menstrual cycle
• Ovulation
• Reproductive system
• Hormones

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