Structure




The uterus is located within the pelvic region immediately behind and almost overlying the bladder, and in front of the sigmoid colon. The human uterus is pear-shaped and about 7.6 cm (3.0 in) long, 4.5 cm (1.8 in) broad (side to side), and 3.0 cm (1.2 in) thick. A typical adult uterus weighs about 60 grams. The uterus can be divided anatomically into four regions: the fundus – the uppermost rounded portion of the uterus, the corpus (body), the cervix, and the cervical canal. The cervix protrudes into the vagina. The uterus is held in position within the pelvis by ligaments, which are part of the endopelvic fascia. These ligaments include the pubocervical ligaments, the cardinal ligaments, and the uterosacral ligaments. It is covered by a sheet-like fold of peritoneum, the broad ligament.

From outside to inside, regions of the uterus include:

  • Cervix uteri – "neck of uterus"
  • External orifice of the uterus
  • Cervical canal
  • Internal orifice of the uterus
  • Body (Latin: Corpus)
  • Uterine cavity
  • Fundus

Layersedit

Uterine wall thickness (cm)
Location Mean (mm) Range (mm)
Anterior wall 23 17 - 25
Posterior wall 21 15 - 25
Fundus 20 15 - 22
Isthmus 10 8 - 22

The uterus has three layers, which together form the uterine wall. From innermost to outermost, these layers are the endometrium, myometrium, and perimetrium.

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 functional layer thickens and then is sloughed during the menstrual cycle or estrous cycle. During pregnancy, the uterine glands and blood vessels in the endometrium further increase in size and number and form the decidua. Vascular spaces fuse and become interconnected, forming the placenta, which supplies oxygen and nutrition to the embryo and fetus.

The myometrium of the uterus mostly consists of smooth muscle. The innermost layer of myometrium is known as the junctional zone, which becomes thickened in adenomyosis.

The perimetrium is a serous layer of visceral peritoneum. It covers the outer surface of the uterus.

Surrounding the uterus is a layer or band of fibrous and fatty connective tissue called the parametrium that connects the uterus to other tissues of the pelvis.

Commensal organisms are present in the uterus and form the uterine microbiome.

  • Vertical section of mucous membrane of human uterus.

Supportedit

The uterus is primarily supported by the pelvic diaphragm, perineal body, and urogenital diaphragm. Secondarily, it is supported by ligaments, including the peritoneal ligament and the broad ligament of uterus.

Major ligamentsedit

It is held in place by several peritoneal ligaments, of which the following are the most important (there are two of each):

Name From To
Uterosacral ligaments Posterior cervix Anterior face of sacrum
Cardinal ligaments Side of the cervix Ischial spines
Pubocervical ligaments Side of the cervix Pubic symphysis

Axisedit

Normally, the uterus lies in anteversion and anteflexion. In most women, the long axis of the uterus is bent forward on the long axis of the vagina, against the urinary bladder. This position is referred to as anteversion of the uterus. Furthermore, the long axis of the body of the uterus is bent forward at the level of the internal os with the long axis of the cervix. This position is termed anteflexion of the uterus. The uterus assumes an anteverted position in 50% of women, a retroverted position in 25% of women, and a midposed position in the remaining 25% of women.

Positionedit

The uterus is in the middle of the pelvic cavity in frontal plane (due to ligamentum latum uteri). The fundus does not surpass the linea terminalis, while the vaginal part of the cervix does not extend below the interspinal line. The uterus is mobile and moves posteriorly under the pressure of a full bladder, or anteriorly under the pressure of a full rectum. If both are full, it moves upwards. Increased intra-abdominal pressure pushes it downwards. The mobility is conferred to it by musculo-fibrous apparatus that consists of suspensory and sustentacular part. Under normal circumstances the suspensory part keeps the uterus in anteflexion and anteversion (in 90% of women) and keeps it "floating" in the pelvis. The meaning of these terms are described below:

Distinction More common Less common
Position tipped "Anteverted": Tipped forward "Retroverted": Tipped backwards
Position of fundus "Anteflexed": Fundus is pointing forward relative to the cervix "Retroflexed": Fundus is pointing backward

The sustentacular part supports the pelvic organs and comprises the larger pelvic diaphragm in the back and the smaller urogenital diaphragm in the front.

The pathological changes of the position of the uterus are:

  • retroversion/retroflexion, if it is fixed
  • hyperanteflexion – tipped too forward; most commonly congenital, but may be caused by tumors
  • anteposition, retroposition, lateroposition – the whole uterus is moved; caused by parametritis or tumors
  • elevation, descensus, prolapse
  • rotation (the whole uterus rotates around its longitudinal axis), torsion (only the body of the uterus rotates around)
  • inversion

In cases where the uterus is "tipped", also known as retroverted uterus, the person may have symptoms of pain during sexual intercourse, pelvic pain during menstruation, minor incontinence, urinary tract infections, fertility difficulties, and difficulty using tampons. A pelvic examination by a doctor can determine if a uterus is tipped.

Blood supplyedit

The uterus is supplied by arterial blood both from the uterine artery and the ovarian artery. Another anastomotic branch may also supply the uterus from anastomosis of these two arteries.

Nerve supplyedit

Afferent nerves supplying the uterus are T11 and T12. Sympathetic supply is from the hypogastric plexus and the ovarian plexus. Parasympathetic supply is from the S2, S3 and S4 nerves.

Developmentedit

Bilateral Müllerian ducts form during early fetal life. In males, anti-müllerian hormone (AMH) secreted from the testes leads to their regression. In females, these ducts give rise to the Fallopian tubes and the uterus. In humans the lower segments of the two ducts fuse to form a single uterus, however, in cases of uterine malformations this development may be disturbed. The different uterine forms in various mammals are due to various degrees of fusion of the two Müllerian ducts.

Various congenital conditions of the uterus can develop in utero. Though uncommon some of these are a double uterus, didelphic uterus, bicornate uterus and others.

Comments

Post a Comment

Popular posts from this blog

Function

Image
The reproductive function of the uterus is to accept a fertilized ovum which passes through the utero-tubal junction from the fallopian tube. The fertilized ovum divides to become a blastocyst, which implants into the endometrium, and derives nourishment from blood vessels which develop exclusively for this purpose. The fertilized ovum becomes an embryo, attaches to a wall of the uterus, creates a placenta, and develops into a fetus (gestates) until childbirth. Due to anatomical barriers such as the pelvis, the uterus is pushed partially into the abdomen due to its expansion during pregnancy. Even during pregnancy the mass of a human uterus amounts to only about a kilogram (2.2 pounds). The uterus also plays a role in sexual response, by directing blood flow to the pelvis and ovaries, and to the external genitals, including the vagina, labia, and clitoris. There is also some evidence that the uterus plays a role in cognition in a similar way to the ovaries. A study on rat models found
Read more

Twitter Marketing - How to Do it Right

Twitter Marketing isn't about spamming the system; it's about gaining useful relationships. With millions upon millions twitterers across the globe, there is an incredible potential to boost your business with targeted traffic. It is one of the most underutilized forms of internet marketing, but is definitely worth taking advantage of. Here are a few Twitter Marketing Tips to help increase your website/blog traffic: * Enhance Your Presence: While Twitter is primarily a social networking platform, it's an excellent platform for enhancing your presence. In particular, the mass-effectiveness of Twitter Marketing is a great way to build your brand and get in front of your target audience. As a social media platform, Twitter now has a lot has changed from its heyday years and even up to this present day. Much has evolved since its inception in late 2000s and early 2010s; however, you will never get far with that old list of Twitter advertising tips, for example. This current li
Read more

Uterus

Image
The uterus (from Latin "uterus", plural uteri ) or womb ( / w uː m / ) is a major female hormone-responsive secondary sex organ of the reproductive system in humans and most other mammals. In the human, the lower end of the uterus, the cervix, opens into the vagina, while the upper end, the fundus, is connected to the fallopian tubes. It is within the uterus that the fetus develops during gestation. In the human embryo, the uterus develops from the paramesonephric ducts which fuse into the single organ known as a simplex uterus. The uterus has different forms in many other animals and in some it exists as two separate uteri known as a duplex uterus. In medicine, and related professions the term uterus is consistently used, while the Germanic-derived term womb is commonly used in everyday contexts.
Read more