Estrous cycle
Estrous cycle
The Estrous cycle (pronounced: /ˈɛstrəs/ cycle) is a recurring physiological change that occurs in reproductive-age female mammals. The cycle involves changes in the reproductive system that make pregnancy possible.
Etymology
The term "estrous" is derived from the Latin word oestrus, which means "frenzy" or "gadfly". The term was used to describe the behavior of animals in heat. The word "cycle" comes from the Greek word kyklos, meaning "circle" or "wheel", referring to the cyclical nature of the process.
Description
The estrous cycle is characterized by changes in the female reproductive system, including the uterus and ovaries. These changes are driven by fluctuations in hormone levels, particularly estrogen and progesterone. The cycle is divided into several stages, including proestrus, estrus, metestrus, and diestrus.
Proestrus
During proestrus, the levels of estrogen increase, leading to the growth and development of follicles in the ovaries. This stage lasts for a few days.
Estrus
Estrus is the stage of the cycle when the female is receptive to mating. This is often referred to as being "in heat". During this stage, the levels of estrogen peak, triggering the release of an egg from the follicle in a process known as ovulation.
Metestrus
In metestrus, the follicle that released the egg transforms into a structure called the corpus luteum. This structure produces progesterone, which prepares the uterus for potential pregnancy.
Diestrus
During diestrus, the corpus luteum continues to produce progesterone unless pregnancy has occurred. If the egg has not been fertilized, the corpus luteum degenerates, leading to a decrease in progesterone levels and the start of a new cycle.
Related Terms
- Anestrus: A period of sexual inactivity between or during estrous cycles.
- Polyestrus: Having more than one estrous cycle in a breeding season.
- Monoestrus: Having only one estrous cycle in a breeding season.
External links
- Medical encyclopedia article on Estrous cycle
- Wikipedia's article - Estrous cycle
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