The corpus luteum
for "yellow body") (plural corpora lutea
) is a temporary endocrine
structure in mammals, involved in production of progestogen
, which is needed to maintain pregnancy.
Development and structure
develops from an ovarian follicle
during the luteal phase
of the menstrual cycle
or estrous cycle
, following the release of a secondary oocyte 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 mm to 5 mm 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.
In the ovary, the corpus luteum secretes oestrogens and progesterone, which are steroid hormones responsible for the thickening of the endometrium and its development and maintenance, respectively.
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
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
If the egg is fertilized and implantation
occurs, the trophoblast
cells of the blastocyst
secrete the hormone human chorionic gonadotropin
(hCG, or a similar hormone in other species).
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.
- - "The Female Pelvis: The Ovary"