Everything about The Corpus Luteum totally explained
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.
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 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:
Function
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 isn't fertilized
If the egg isn't 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
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.
Additional images
Image:Order_of_changes_in_ovary.svg|Order of changes in ovary
Image:MenstrualCycle.png|Menstrual Cycle
Further Information
Get more info on 'Corpus Luteum'.
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