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The corpus luteum (Latin for "yellow body") (plural corpora lutea) is a temporary endocrine structure in mammals, involved in the production of the progestogens that are needed for the maintenance of a pregnancy.
Additional recommended knowledge
Development and structure
The corpus luteum develops from an ovarian follicle during the luteal phase of the menstrual cycle or estrous cycle, following the release of a mature ovum (egg) from the follicle during ovulation. The follicle first forms a corpus hemorrhagicum before it becomes a corpus luteum, but the term simply refers to the visible collection of blood left after rupture of the follicle, and has no functional significance. While the oocyte (later the zygote) traverses the Fallopian tube into the uterus, the corpus luteum remains in the ovary.
The corpus luteum is typically very large relative to the size of the ovary; in humans, the size of the structure ranges from under 2 cm to 6 cm in diameter. 
Its cells develop from the follicular cells surrounding the ovarian follicle:
The corpus luteum is essential for establishing and maintaining pregnancy in females.
When egg is not fertilized
If the egg is not fertilized, the corpus luteum stops secreting progesterone and decays (after approximately 14 days in humans). It then degenerates into a corpus albicans, which is a mass of fibrous scar tissue.
The uterine lining sloughs off without progesterone and is expelled through the vagina (in humans and some great apes, which go through a menstrual cycle). In an estrus cycle, the lining degenerates back to normal size.
When egg is fertilized
Human chorionic gonadotropin signals the corpus luteum to continue progesterone secretion, thereby maintaining the thick lining (endometrium) of the uterus, and providing an area rich in blood vessels in which the zygote(s) can develop. From this point on, the corpus luteum is called the corpus luteum graviditatis.
The introduction of prostaglandins at this point causes the degeneration of the corpus luteum and the abortion of the fetus. However, in placental animals such as humans, the placenta eventually takes over progesterone production and the corpus luteum degrades into a corpus albicans without embryo/fetus loss.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Corpus_luteum". A list of authors is available in Wikipedia.|