The uterus or uterine ( lat. Uterus , matrix ; Greek. Mētra , Hystera , DELPHYS ; medium high German bërmuoter and short muoter ) is the part of the female sex organs in which after one, Conception the early embryonic stages ( blastocyst ) settle and birth tire Developing fetus . The fertilization of the haploid egg cell to form a diploid zygote had already taken place in the fallopian tube. The uterus extends from the external cervix to the opening to the fallopian tube and consists of three parts: the cervix, the isthmus, and the body of the uterus. With its pronounced muscle layer, it participates in the expulsion of the child during birth.
The technical term intrauterine means “within the uterus”. The opposite is extrauterine .
Construction and location
The uterus was first described in more detail, if not anatomically correct, by Galenus . Galen described a two-part uterus that was supposed to be warmer on the right than on the left and, in terms of humoral pathology , as can already be found in Parmenides and in the Hippocratic writings , the explanation for the development of male offspring in the right uterine chamber. From the 12th to the 15th centuries the scholastic idea of a seven-chambered uterus spread.
In principle, the uterus is a hollow organ that resembles an upside-down pear. It is about seven centimeters long, five centimeters wide, two to three centimeters thick and weighs 30 to 120 grams. However, size and weight can vary significantly. The uterus consists of three parts: the lowest part is the cervix ( cervix uteri ); it is joined by the isthmus and the actual body of the uterus ( corpus uteri ). The cervix surrounds the cervical canal ( Canalis cervicis ), which begins with the external cervix ( Ostium uteri externum ) and ends with the internal cervix ( Ostium anatomicum uteri internum ). The outer cervix is located at the portion of the cervix, into the vagina ( vaginal bulge), the vaginal portion of the cervix ( portio vaginalis uteri , or short cervix ). The part of the cervix that sits above the vaginal part is called the portio supravaginalis uteri (roughly German: uterine part above the vagina). At its end is the inner cervix, which is the narrowest point in the cervical canal with a diameter of two to three millimeters. The cervix is then connected to the body of the uterus via an equally narrow transition zone. This transition zone is called the isthmus uteri and is actually still included in the cervix. The isthmus is about five to ten millimeters long and surrounds the isthmus canal ( Canalis isthmi ) inside . The adjoining uterine body represents the largest part of the uterus with two thirds. The lumen (interior) of the uterine body ( Cavitas uteri ) is roughly triangular when viewed from the front with two lateral edges ( Margo uteri ). At the top laterally the body of the uterus merges into the fallopian tubes and at the top it ends with the tip of the uterus ( fundus uteri ). If you look at the body of the uterus from the side, however, it only resembles a narrow gap, as its anterior and posterior walls ( facies anterior and facies posterior ) lie against one another.
The front wall of the uterus lies on top of the neighboring (ventrally lying) urinary bladder , while the back wall points towards the rectum . Since the peritoneum ( the peritoneum ) covering all three organs, are formed due to the position of the organs two peritoneum pits: A between the bladder and the uterus ( vesicouterine pouch ), and between the uterus and rectum ( rectouterine pouch ). The pit between the rectum and the uterus is also known as the Douglas space and forms the deepest space in the woman's abdominal cavity . In addition, the location of the uterus is represented by three terms:
- Angle of the body of the uterus in relation to the cervix ("uterine body axis" flexio ): Normally, the body of the uterus is inclined slightly forwards in relation to the cervix ( anteflexion ). If the body of the uterus is tilted backwards, it is called retroflexio (uteri) .
- Angle between the cervix and vagina in the clinic, or with respect to the vertical body axis in anatomy (" cervix axis" Versio ): The cervix in turn bends forwards in relation to the vagina or the vertical body axis ( anteflexion ).
- Position of the portio in the pelvis ( positio ): The portio vaginalis uteri is usually located in a plane between the two ischial thorns ( interspinous plane ) and in the middle of the pelvis.
The exact location of the uterus, however, varies depending on the filling level of the surrounding organs, i.e. the urinary bladder and rectum.
Fastenings of the uterus
The uterus is anchored to the pelvis by a frontal plate made of connective tissue , the parametrium . The parametrium pulls from the lateral edges of the uterus - at the portions of the portio supravaginalis uteri to the top of the uterus ( fundus uteri ) - to the lateral pelvic wall and, like the uterus itself, is curved forward. It passes downwards ( caudally ) into the connective tissue next to the cervix ( paracervix ) and further down into the connective tissue next to the vagina ( paracolpium ). The parametrium is surrounded by peritoneum, especially at its upper, free end; this part, surrounded by the peritoneum, is called the broad ligament of the uterus ( ligamentum latum uteri ). Since these peritoneum duplicates are also called mesenteries , the part of the parametrium covered by the peritoneum is also called the mesometrium . The connective tissue that extends from the parametrium to the tube and ovaries is also referred to as mesosalpinx and mesovarium .
The connective tissue of the cervix but not homogeneous, but has several reinforcements that are as bands ( ligaments called). The sum of all these retaining straps, described in 1895 by the Berlin gynecologist Alwin Mackenrodt (1859-1925) as reinforcements, which pull towards the portio supravaginalis uteri , is called the Mackenrodt strap ( ligamentum transversum cervicis , or ligamentum cardinale ). These hold the uterus in a kind of springy, floating position, which is additionally secured by the pelvic floor muscles. There are also ligaments that extend from the pubic symphysis and from the sacrum to the uterus: the pubic-urinary bladder ligament ( ligamentum pubovesicale ), the urinary bladder-uterine ligament ( ligamentum vesicouterinum ), the sacrum-uterine ligament ( ligamentum sacrouterinum ) and the rectum-uterus Ligament ( ligamentum rectouterinum ). The latter, together with smooth muscles ( musculus rectouterinus ), form the structural basis for a fold on the back of the uterus, the plica rectouterina . This delimits the Douglas room to one side. The round uterine ligament ( ligamentum teres uteri , or ligamentum rotundum ) also extends from the top of the uterus, first in an arc shape into the inguinal canal and then to the large labia.
Blood supply and lymph drainage
The blood supply to the organ takes place on each side via the uterine artery ( Arteria uterina ). The uterine arteries emerge from the internal iliac artery ( internal iliac artery ) and run in the ligamentum latum , where they cross the ureter , to the cervix. There it gives off some branches to the vagina ( rami vaginales ) and otherwise meanders along the lateral edge of the uterus up to the top of the uterus. This meandering is important so that the artery can stretch sufficiently if the uterus enlarges during pregnancy. Once at the top of the uterus, the uterine artery gives off one branch to the tube ( Ramus tubarius ) and one to the ovaries ( Ramus ovaricus ). This Ramus ovaricus connects ( anastomoses ) with the ovarian artery ( Arteria ovarica ).
The blood first flows into a wide-meshed network of veins in the uterine wall ( plexus uterinus ), which often also absorbs the venous blood from the vagina. The ureteric plexus opens into the uterine vein ( vena uterina ) and further into the inner pelvic vein ( vena iliaca interna ).
The lymph drains off somewhat differently depending on the section: Lymph from the cervix and body usually first reaches lymph nodes , which are located in the connective tissue next to the uterus ( Nodi lymphoidei parauterini ). The cervix then conducts its lymph into the internal pelvic lymph nodes ( Nodi lymphoidei iliaci interni ) and into the sacral lymph nodes ( Nodi lymphoidei sacrales ), from where they connect to the lumbar lymph nodes ( Nodi lymphoidei lumbales ). The body of the uterus also directs its lymph into the internal pelvic lymph nodes, or directly into the lumbar lymph nodes. The top of the uterus drains its lymph just like the body of the uterus, but can also drain into the superficial inguinal lymph nodes ( Nodi lymphoidei inguinales superficiales ) via the ligamentum teres uteri .
The uterus is innervated by nerves from the lower abdominal plexus ( inferior hypogastric plexus ). The branches of this plexus form the uterovaginal plexus ( Franckhauser plexus ) on both sides of the uterus . The sympathetic parts originate from the small visceral nerve ( Nervus splanchnicus minor ), the lowest visceral nerve ( Nervus splanchnicus imus ) and the Nervi splanchnici lumbales . These fibers are switched partly in the ganglia mesenterica ( ganglion mesentericum superius and ganglion mesentericum inferius ), partly in ganglion cells , which lie directly in the nerve plexus itself. The parasympathetic components, on the other hand, come from the pelvic splachnic nerves and switch either directly in the organ wall or in the plexus .
Like all hollow organs, the uterus is made up of three layers. Outside is the perimetrium, a smooth, shiny coating of the serosa . The main part of the wall is a layer of smooth muscle called the myometrium. The inner lining is a mucous membrane called the endometrium . The inner cavity is called the Cavum uteri .
Cyclic changes in the endometrium
In humans, the endometrium can be divided into a stratum basale (also called basalis ) and a stratum functionalale (also called functionalalis ). In the stratum functionale, a stratum compactum facing the inner cavity and a loosely built stratum spongiosum can also be divided. The stratum functionalale is built up and broken down under hormonal control in a monthly cycle .
In the proliferation phase , controlled by the hormone estrogen, the build-up of the stratum functionalale starts from the stratum basale. The glands proliferate and arteries grow in a spiral shape into the newly emerging layer, one speaks of spiral arteries .
The proliferation phase is followed by the secretion phase, initiated by the hormone progesterone . The glands in the endometrium take on a serrated, saw-blade shape and the gland cells begin to secrete proteins and mucus. In the first half of the secretion phase, a retronuclear vacuole is visible in the lower half of the cell under the nucleus when viewed in a normal microscopic specimen . There was before the tissue fixed was glycogen . Furthermore, in the vicinity of the arteries in the stratum compactum, pre-decidual cells, precursors of decidual cells, develop in the placenta that forms when an embryo is implanted.
If fertilization does not occur during this period, the desquamation phase follows, which is triggered by falling estrogen and progesterone levels. The spiral arteries contract, causing ischemia in the stratum functionalale . This layer is broken down and detached through an inflammatory reaction.
Changes in the endometrium during pregnancy
With fertilization and successful implantation of the fertilized egg cell ( zygote ), more precisely the blastocyst , the uterine lining continues to grow and ensures the supply of the growing embryo . After birth , the uterine lining in primates is expelled with the placenta as the afterbirth .
If this fusion does not take place completely, this is the cause of various uterine malformations . Failure to fuse leads to double formation of the uterus, accompanied by a malformation of the vagina with the formation of a partition there as well ( uterus duplex et vagina duplex ). An incomplete fusion (with no fusion of the upper section of the Müller ducts) leads to a bicornuate uterus ("two-horned uterus") with a single or double cervix and with or without a vaginal septum. The so-called uterus arcuatus can be seen as a weakened form of a uterus bicornis .
The uterus is relatively small prepubertal, becomes 5–10 cm in size after puberty and expands strongly upwards and to the sides during pregnancy . At the end of pregnancy, it reaches to the ribs. After the delivery, it will shrink again. After menopause , it gets smaller again.
Studies on animal and especially mouse models have shown that transcription factors of the HOX gene groups, especially HOX A9, A10, A11 and A13, play an important role in the development of the urogenital tract . HOX A10 and HOX A11 are relevant for the development of the uterus and cervix . The upper vagina is assigned to HOX A13 , the fallopian tubes HOX A9 .
The uterus as an organ is established according to Leyendecker et al. (1998) and Noe et al. (1999) composed of two different tissue systems, the inner "archimetra" facing the cavum uteri and the outer "neometra". Phylogenetically and ontogenetically, the inner archimetra or the endometrial-subendometrial unit represents the oldest part of the uterus. It consists of the epithelial and stromal part of the endometrium and the muscles immediately below with smooth muscle fibers that are predominantly circular. This layer of smooth, circular muscle fibers begins caudally at the level of the lower cervix uteri and runs through the corpus uteri as a stratum subvasculare and continues over the uterine horns (cornua uteri) as tubular ring muscles in the fallopian tubes . The "archimetra" is formed relatively early in the embryonic development through the melting of the Müllerian ducts . This fusion process creates a zone of intersecting muscle fibers in the midline, also known as "fundo-cornual raphe", i.e. exactly where the circular muscle fibers diverge from the middle part of the uterus into the respective uterine horns and continue into the fibers of the fallopian tubes. The archimetra is a functional unit controlled by the ovary and consisting of the endometrium and subendometrial muscles. The “archimetra” is already present as a functional layering of the uterus in the basal terrestrial vertebrates. They are very old in tribal and evolutionary terms. The archimetra takes on functionally tasks in the early stages of reproduction. In addition to the implantation of the fertilized egg with the necessary structure of the uterine lining, it is also about uterine peristalsis and the defense against inflammation in the internal female genitalia.
The "neometra" consists of the outer muscle layer, the stratum supravasculare with mainly longitudinally arranged, smooth muscle fibers that radiate into the uterine ligaments and fix the uterus to the bony pelvic wall and the stratum vasculare. The function of the neometra is to expel it during childbirth . While the functions of the "archimetra" are mainly regulated by the ovary , the functions of the "neometra" are mainly controlled by the embryo or fetus .
The first living donor a uterus in humans was in 2013 at the Sahlgrenska University Hospital in Gothenburg ( Sweden performed). Since then, several children have been born in different countries who were carried to term in a transplanted uterus. Sometimes women have had two children after a transplant.
In December 2018, it was first announced that the uterus would be transplanted from a dead woman to a woman who was born without a uterus. Eight egg cells from this woman were fertilized and frozen using in vitro fertilization , then her uterus was implanted, and her eggs were inserted months later. The child she carried was born by caesarean section and the implanted uterus was removed at the same time.
Uterus of non-primates
In most mammals merges only a part of during fetal development Mueller courses into a compact body of the uterus ( corpus uteri ). The part referred to as the front section in animals is created in pairs from the start, which is also referred to here as the bicornuate uterus ("two-horned uterus"). Such a bicornuate uterus with two uterine horns ( cornua uteri ), for example, is possessed by all predatory and ungulate animals .
Possible signs or illnesses
Diseases of the uterus are called metropathies . In detail, this means:
- Bleeding abnormalities
- Aplasia and dysplasia (malformations)
- Tumors (growths)
- Uterine prolapse (uterine prolapse)
- Uterine atony ( weak contraction of the uterus after birth)
- Accumulation of liquids
- Physometra (accumulation of gas in the uterus after birth)
- Endometriosis (growth of the endometrium - the lining of the uterus)
- Therapy in utero (medical treatment of an unborn child inside the uterus)
- Flexible transgastric peritoneoscopy
- Bandl ring
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- Anteflexio uteri, the natural forward flexion of the uterus. A retroflexio uteri is a backward sloping uterus that can be either mobile or fixed. Schematic representation of ante- and retroflexion of the uterus   
- Angle of the body of the uterus in relation to the cervix (flexio) 
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