endometrium

Endometrium
Uterus and uterine tubes. (Endometrium labeled at center right.)
Opened uterus with cat fetus in midgestation: 1 umbilicus, 2 amnion, 3 allantois, 4 Yolk sac, 5 developing marginal hematoma, 6 maternal part of placenta (endometrium)
Latintunica mucosa uteri
subject #268 1262
MeSH Endometrium
Dorlands/Elsevier t_22/12832078
The endometrium is the inner membrane of the mammalian uterus.

Function

The endometrium functions as a lining for the uterus, preventing adhesions between the opposed walls of the myometrium, thereby maintaining the patency of the uterine cavity. During the menstrual cycle or estrous cycle, the endometrium grows to a thick, blood vessel rich, glandular tissue layer. This represents an optimal environment for the implantation of a blastocyst upon its arrival in the uterus.

During pregnancy, the glands and blood vessels in the endometrium further increase in size and number. Vascular spaces fuse and become interconnected, forming the placenta, which supplies oxygen and nutrition to the embryo and fetus.

Cycle

The endometrial lining undergoes cyclic regeneration. Humans and the great apes display the menstrual cycle, whereas most other mammals are subject to an estrous cycle. In both cases, the endometrium initially proliferates under the influence of estrogen. However, once ovulation occurs, in addition to estrogen, the ovary will also start to produce progesterone. This changes the proliferative pattern of the endometrium to a secretory lining. Eventually, the secretory lining provides a hospitable environment for one or more blastocysts.

If no blastocyst is detected, the progesterone level drops and the endometrial lining is either reabsorbed (estrous cycle) or shed (menstrual cycle). In the latter case, the process of shedding involves the breaking down of the lining, the tearing of small connective blood vessels, and the loss of the tissue and blood that had constituted it through the vagina. The entire process occurs over a period of several days. Menstruation may be accompanied by a series of uterine contractions; these help expel the menstrual endometrium.

In case of implantation, however, the endometrial lining is neither absorbed nor shed. Instead, it remains as decidua. The decidua becomes part of the placenta; it provides support and protection for the gestation.

If there is inadequate stimulation of the lining, due to lack of hormones, the endometrium remains thin and inactive. In humans, this will result in amenorrhea. After menopause, the lining is often described as being atrophic. In contrast, endometrium that is chronically exposed to estrogens, but not to progesterone, may become hyperplastic.

In humans, the cycle of building and shedding the endometrial lining lasts an average of 28 days. The endometrium develops at different rates in different mammals. Its formation is sometimes affected by seasons, climate, stress and other factors. The endometrium itself produces certain hormones at different points along the cycle. This affects other portions of the reproductive system.

Histology

The endometrium consists of a single layer of columnar epithelium, resting on a layer of connective tissue which varies in thickness according to hormonal influences - the stroma. Simple tubular uterine glands reach from the endometrial surface through to the base of the stroma, which also carries a rich blood supply of spiral arteries. In a woman of reproductive age, two layers of endometrium can be distinguished. These two layers occur only in endometrium lining the cavity of the uterus, not in the lining of the Fallopian tubes:[1]
  • The functional layer is adjacent to the uterine cavity. This layer is built up after the end of menstruation during the first part of the previous menstrual cycle. Proliferation is induced by progesterone (follicular phase of menstrual cycle), and later increased by the progestrone from the corpus luteum (luteal phase). It is adapted to provide an optimum environment for the implantation and growth of the embryo. This layer is completely shed during menstruation.
  • The basal layer, adjacent to the myometrium and below the functional layer, is not shed at any time during the menstrual cycle, and from it the functional layer develops.
In the absence of progesterone, the arteries supplying blood to the functional layer constrict, so that cells in that layer become ischaemic and die, leading to menstruation.

It is possible to identify the phase of the menstrual cycle by observing histological differences at each phase:

PhaseDaysThicknessEpithelium
menstrual phase1-4thinabsent
proliferative phase4-14intermediatecolumnar
secretory phase15-28thickcolumnar. Also visible are helicine branches of uterine artery

Pathological conditions

Adenomyosis is the growth of the endometrium into the muscle layer of the uterus (the myometrium).

Endometriosis is the growth of endometrial tissue outside the uterus.

Endometrial cancer is the most common cancer of the human female genital tract.

See also

Additional images


Vertical section of mucous membrane of human uterus.

Histopathologic representation of endometrioid adenocarcinoma demonstrated in endometrial biopsy. Hematoxylin-eosin stain.

Blastocyst with an inner cell mass and trophoblast.

microscopic slide of the endometrium.


References

1. ^ Blue Histology - Female Reproductive System. School of Anatomy and Human Biology - The University of Western Australia [1] Accessed 20061228 20:35

External links

F. s. catus

Trinomial name
Felis silvestris catus
(Linnaeus, 1758)

Synonyms
Felis lybica invalid junior synonym
Felis catus invalid junior synonym[2]

The cat (
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Umbilicus may refer to:
  • Umbilicus (mollusk), a feature of gastropod shell anatomy
  • Umbilicus (genus), a genus of 15-20 species of flowering plants
  • Umbilicus urbis Romae, the designated centre of the city of Rome from which and to which all distances in Rome

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This article or section may be confusing or unclear for some readers.
Please [improve the article] or discuss this issue on the talk page. This article has been tagged since December 2006.
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Allantois (plural allantoides or allantoises) is a part of a developing animal conceptus (which consists of all embryonic and extra-embryonic tissues). It helps the embryo exchange gases and handle liquid waste.
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The yolk sac is the first element seen in the gestational sac during pregnancy, usually at 5 weeks gestation.

It is a critical landmark, identifying a true gestation sac.

It is quite echogenic (light) to ultrasound, and reliably seen early.
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hematoma, or haematoma, is a collection of blood, generally the result of hemorrhage, or, more specifically, internal bleeding. Hematomas exist as bruises (ecchymoses), but can also develop in organs.

It is not to be confused with hemangioma.
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The placenta is an ephemeral (temporary) organ present in placental vertebrates, such as some mammals and sharks during gestation (pregnancy).

The placenta develops from the same sperm and egg cells that form the fetus, and functions as a fetomaternal organ with two
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Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
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Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
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Elsevier, the world's largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. Based in Amsterdam, the company has substantial operations in the UK, USA and elsewhere.
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Mammalia
Linnaeus, 1758

Subclasses & Infraclasses
  • Subclass †Allotheria*
  • Subclass Prototheria
  • Subclass Theria

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uterus or womb is the major female reproductive organ of most mammals, including humans. One end, the cervix, opens into the vagina; the other is connected on both sides to the fallopian tubes.
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myometrium is the middle layer of the uterine wall consisting of smooth muscle cells and supporting stromal and vascular tissue.

The inner layer of the uterine wall is the endometrium or uterine lining, and the outer layer the serosa or peritoneum.
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The menstrual cycle is a recurring cycle of physiologic changes that occurs in the females of several mammals, including human beings and other apes.[1] Humans are the only species that has a menstrual cycle with concealed ovulation.
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Oestrus is also the biological genus name of the gadfly.


The estrous cycle (also oestrous cycle; originally derived from Latin oestrus
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Implantation is an event that occurs early in pregnancy in which the embryo adheres to the wall of uterus. At this stage of prenatal development, the embryo is a blastocyst. It is by this adhesion the fetus receives the oxygen and the nutrients from the mother to be able to grow.
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The blastocyst is an early stage of the human (or other mammal) development early in pregnancy. It is the structure formed in early human embryogenesis, after the formation of the blastocele, but before implantation.
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Pregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the body of a female mammal such as a human. In a pregnancy, there can be multiple gestations (for example, in the case of twins or triplets).
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The blood vessels are part of the cardiovascular system and function to transport blood throughout the body. The most important types, arteries and veins, carry blood away from or towards the heart, respectively.
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The placenta is an ephemeral (temporary) organ present in placental vertebrates, such as some mammals and sharks during gestation (pregnancy).

The placenta develops from the same sperm and egg cells that form the fetus, and functions as a fetomaternal organ with two
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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This article or section is in need of attention from an expert on the subject.
Please help recruit one or [ improve this article] yourself. See the talk page for details.
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fetus (or foetus, or fœtus) is a developing mammal or other viviparous vertebrate, after the embryonic stage and before birth. The plural is fetuses (foetuses, fœtuses) or, very rarely, foeti.
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The menstrual cycle is a recurring cycle of physiologic changes that occurs in the females of several mammals, including human beings and other apes.[1] Humans are the only species that has a menstrual cycle with concealed ovulation.
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Oestrus is also the biological genus name of the gadfly.


The estrous cycle (also oestrous cycle; originally derived from Latin oestrus
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Estrogens (alternative spellings: oestrogens or œstrogens) are a group of steroid compounds, named for their importance in the estrous cycle, and functioning as the primary female sex hormone.
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Ovulation is the process in the menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum (also known as an oocyte, female gamete, or casually, an egg) that participates in reproduction.
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Progesterone is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species. Progesterone belongs to a class of hormones called progestogens, and is the major naturally occurring human
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The vagina, (from Latin, literally "sheath" or "scabbard" ) is the tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles.
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