The corpus luteum (

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

for "yellow body"; plural corpora lutea) is a temporary

endocrine The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neur ...

structure in female

ovaries The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...

involved in the production of relatively high levels of

progesterone Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the majo ...

, and moderate levels of

estradiol Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous and menstrual female reproductive cycles. Estradiol is responsible for the development o ...

, and

inhibin A Activin and inhibin are two closely related protein complexes that have almost directly opposite biological effects. Identified in 1986, activin enhances FSH biosynthesis and secretion, and participates in the regulation of the menstrual ...

. It is the remains of the ovarian follicle that has released a mature ovum during a previous ovulation. The corpus luteum is colored as a result of concentrating

carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, ...

s (including

lutein Lutein (;"Lutein"

) from the diet and secretes a moderate amount of

estrogen Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal ac ...

that inhibits further release of

gonadotropin-releasing hormone Gonadotropin-releasing hormone (GnRH) is a releasing hormone responsible for the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. GnRH is a tropic peptide hormone synthesized and released ...

(GnRH) and thus secretion of

luteinizing hormone Luteinizing hormone (LH, also known as luteinising hormone, lutropin and sometimes lutrophin) is a hormone produced by gonadotropic cells in the anterior pituitary gland. The production of LH is regulated by gonadotropin-releasing hormone (GnRH) ...

(LH) and

follicle-stimulating hormone Follicle-stimulating hormone (FSH) is a gonadotropin, a glycoprotein polypeptide hormone. FSH is synthesized and secreted by the gonadotropic cells of the anterior pituitary gland and regulates the development, growth, pubertal maturation, ...

(FSH). A new corpus luteum develops with each

menstrual cycle The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that make pregnancy possible. The ovarian cycle controls the production and release of eggs ...

Development and structure

The corpus luteum develops from an

ovarian follicle An ovarian follicle is a roughly spheroid cellular aggregation set found in the ovaries. It secretes hormones that influence stages of the menstrual cycle. At the time of puberty, women have approximately 200,000 to 300,000 follicles, each with ...

during the luteal phase of the

or oestrous 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 refers to the visible collection of blood, left after rupture of the follicle, that secretes progesterone. While the

oocyte An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ...

(later the

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicell ...

if fertilization occurs) traverses the

Fallopian tube The fallopian tubes, also known as uterine tubes, oviducts or salpinges (singular salpinx), are paired tubes in the human female that stretch from the uterus to the ovaries. The fallopian tubes are part of the female reproductive system. In o ...

into the

uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...

, the corpus luteum remains in the

ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. ...

. 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 5 cm in diameter. Its cells develop from the follicular cells surrounding the ovarian follicle. The follicular

theca cell The theca folliculi comprise a layer of the ovarian follicles. They appear as the follicles become secondary follicles. The theca are divided into two layers, the theca interna and the theca externa. Theca cells are a group of endocrine cells ...

s luteinize into small luteal cells (thecal-lutein cells) and follicular granulosa cells luteinize into large luteal cells (granulosal-lutein cells) forming the corpus luteum. Progesterone is synthesized from cholesterol by both the large and small luteal cells upon luteal maturation. Cholesterol- LDL complexes bind to receptors on the plasma membrane of luteal cells and are internalized. Cholesterol is released and stored within the cell as cholesterol ester. LDL is recycled for further cholesterol transport. Large luteal cells produce more progesterone due to uninhibited/basal levels of protein kinase A (PKA) activity within the cell. Small luteal cells have LH receptors that regulate PKA activity within the cell. PKA actively phosphorylates

steroidogenic acute regulatory protein The steroidogenic acute regulatory protein, commonly referred to as StAR (STARD1), is a transport protein that regulates cholesterol transfer within the mitochondria, which is the rate-limiting step in the production of steroid hormones. It i ...

(StAR) and translocator protein to transport cholesterol from the outer mitochondrial membrane to the inner mitochondrial membrane. The development of the corpus luteum is accompanied by an increase in the level of the steroidogenic enzyme P450scc that converts cholesterol to

pregnenolone Pregnenolone (P5), or pregn-5-en-3β-ol-20-one, is an endogenous steroid and precursor/metabolic intermediate in the biosynthesis of most of the steroid hormones, including the progestogens, androgens, estrogens, glucocorticoids, and mineralocor ...

in the mitochondria. Pregnenolone is then converted to progesterone that is secreted out of the cell and into the blood stream. During the bovine estrous cycle, plasma levels of progesterone increase in parallel to the levels of P450scc and its electron donor adrenodoxin, indicating that progesterone secretion is a result of enhanced expression of P450scc in the corpus luteum. The mitochondrial P450 system electron transport chain including adrenodoxin reductase and adrenodoxin has been shown to leak electrons leading to the formation of superoxide radical. Apparently to cope with the radicals produced by this system and by enhanced mitochondrial metabolism, the levels of antioxidant enzymes catalase and superoxide dismutase also increase in parallel with the enhanced steroidogenesis in the corpus luteum.

Like the previous theca cells, the theca lutein cells lack the

aromatase Aromatase (), also called estrogen synthetase or estrogen synthase, is an enzyme responsible for a key step in the biosynthesis of estrogens. It is CYP19A1, a member of the cytochrome P450 superfamily, which are monooxygenases that catalyze many ...

enzyme that is necessary to produce estrogen, so they can only perform steroidogenesis until formation of

androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This in ...

s. The granulosa lutein cells do have aromatase, and use it to produce estrogens, using the androgens previously synthesized by the theca lutein cells, as the granulosa lutein cells in themselves do not have the

17α-hydroxylase Cytochrome P450 17A1 (steroid 17α-monooxygenase, 17α-hydroxylase, 17-alpha-hydroxylase, 17,20-lyase, 17,20-desmolase) is an enzyme of the hydroxylase type that in humans is encoded by the ''CYP17A1'' gene on chromosome 10. It is ubiquitously exp ...

or 17,20 lyase to produce androgens. Once the corpus luteum regresses the remnant is known as corpus albicans.

Function

The corpus luteum is essential for establishing and maintaining pregnancy in females. The corpus luteum secretes

, which is a

steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the adrenal cortex, hence ''cortico-'') and sex steroids (typically made in the gonads or placenta). Withi ...

responsible for the decidualization of the

endometrium The endometrium is the inner epithelial layer, along with its mucous membrane, of the mammalian uterus. It has a basal layer and a functional layer: the basal layer contains stem cells which regenerate the functional layer. The functional layer ...

(its development) and maintenance, respectively. It also produces

relaxin Relaxin is a protein hormone of about 6000 Da first described in 1926 by Frederick Hisaw. The relaxin family peptide hormones belong to the insulin superfamily and consists of seven peptides of high structural but low sequence similarity; re ...

, a hormone responsible for softening of the

pubic symphysis The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attaches to the pubi ...

which helps in parturition.

Unsuccessful fertilisation

If the egg is not fertilised, the corpus luteum stops secreting progesterone and decays (after approximately 10 days in humans). It then degenerates into a corpus albicans, which is a mass of fibrous

scar A scar (or scar tissue) is an area of fibrous tissue that replaces normal skin after an injury. Scars result from the biological process of wound repair in the skin, as well as in other organs, and tissues of the body. Thus, scarring is a ...

tissue. The uterine lining (endometrium) is expelled through the vagina (in mammals that go through a

). In an

estrous cycle The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females. Estrous cycles start after sexual maturity in females and are interrupted by anestro ...

, the lining regenerates back to normal size.

Successful fertilisation

If the egg is fertilised and implantation occurs, the syncytiotrophoblast (derived from

trophoblast The trophoblast (from Greek : to feed; and : germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the p ...

) cells of the

blastocyst The blastocyst is a structure formed in the early embryonic development of mammals. It possesses an inner cell mass (ICM) also known as the ''embryoblast'' which subsequently forms the embryo, and an outer layer of trophoblast cells called th ...

secrete the hormone

human chorionic gonadotropin Human chorionic gonadotropin (hCG) is a hormone for the maternal recognition of pregnancy produced by trophoblast cells that are surrounding a growing embryo (syncytiotrophoblast initially), which eventually forms the placenta after implantatio ...

(hCG, or a similar hormone in other species) by day 9 post-fertilisation. 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 vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide awa ...

s in which the

(s) can develop. From this point on, the corpus luteum is called the ''corpus luteum graviditatis''. The introduction of

prostaglandin The prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are deriv ...

s at this point causes the degeneration of the corpus luteum and the

abortion Abortion is the termination of a pregnancy by removal or expulsion of an embryo or fetus. An abortion that occurs without intervention is known as a miscarriage or "spontaneous abortion"; these occur in approximately 30% to 40% of pre ...

of the

fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal dev ...

. However, in placental animals such as humans, the

placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...

eventually takes over progesterone production and the corpus luteum degrades into a corpus albicans without embryo/fetus loss.

Luteal support Luteal support is the administration of medication, generally progesterone, progestins, hCG or GnRH agonists, to increase the success rate of implantation and early embryogenesis, thereby complementing and/or supporting the function of the corpus ...

refers to the administration of medication (generally

progestin A progestogen, also referred to as a progestagen, gestagen, or gestogen, is a type of medication which produces effects similar to those of the natural female sex hormone progesterone in the body. A progestin is a ''synthetic'' progestogen. Pro ...

s) for the purpose of increasing the success of implantation and early

embryogenesis An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

, thereby complementing the function of the corpus luteum.

Content of carotenoids

The yellow color and name of the corpus luteum, like that of the macula lutea of the retina, is due to its concentration of certain

s, especially

lutein Lutein (;"Lutein"

. In 1968, a report indicated that beta-carotene was synthesized in laboratory conditions in slices of corpus luteum from cows. However, attempts have been made to replicate these findings, but have not succeeded. The idea is not presently accepted by the scientific community. Rather, the corpus luteum concentrates carotenoids from the diet of the mammal.

In animals

Additional images

File:Order_of_changes_in_ovary.svg, Order of changes in ovary File:Human Ovary with Fully Developed Corpus Luteum.jpg, Human ovary with fully developed corpus luteum File:Luteinized follicular cyst.jpg, Luteinized follicular cyst.

H&E stain Hematoxylin and eosin stain ( or haematoxylin and eosin stain or hematoxylin-eosin stain; often abbreviated as H&E stain or HE stain) is one of the principal tissue stains used in histology. It is the most widely used stain in medical diag ...

Pathology

* Corpus luteum cyst: hemorrhage into persistent corpus luteum. Commonly regresses spontaneously.

References

Bibliography

* *

External links

* * – "The Female Pelvis: The Ovary"
CT of the abdomen showing a ruptured hemorrhagic copus luteal cyst
{{DEFAULTSORT:Corpus Luteum Histology Mammal female reproductive system Pelvis Human female endocrine system Theriogenology