Uterus

Uterus (uterus, Greek metra) is an unpaired hollow muscular organ in which the embryo develops and the fetus is hatched. The uterus is located in the middle of the pelvic cavity behind the bladder and in front of the rectum. Uterus pear-shaped, flattened in anteroposterior direction. The uterus distinguishes the bottom, body and neck.

The uterus (fundus uteri) is the upper convex part of the organ, protrudes above the line of flow into the uterus of the fallopian tubes, the corpus uteri, which forms the middle (large) part of the organ, is lower. The cone-shaped body of the uterus goes to the rounded part - the cervix uteri. The place of transition of the body of the uterus into the cervix is narrowed and is called the isthmus of the uterus (isthmus uteri). The lower part of the cervix extends into the vaginal cavity, therefore it is called the vaginal part (portio vaginalis [cervicis]), and the upper part of the cervix, which lies above the vagina, is called the supralaginal part of the cervix (portio supravaginal [cervicis]). On the vaginal part, you can see the opening of the uterus (ostium uteri), or uterine pharynx. This hole leads from the vagina into the cervical canal and continues into its cavity. In nulliparous women, the opening of the uterus is round or oval, and in those giving birth it has the shape of a transverse slit. The opening of the uterus is limited by the front lip (labium anterius) and the posterior lip (labium posterius). The posterior lip is thinner.

The uterus has a front and a back surface. The anterior surface of the uterus, facing the bladder, is called the facies vesicalis, and the posterior, facing the rectum, is the rectum (facies rectalis). These surfaces of the uterus are separated from each other by the margins of the uterus, the right and left (margo uteri dexster et margo uteri sinister). The dimensions and mass of the uterus vary individually. The length of the uterus in an adult woman is on the average 7-8 cm, width - 4 cm, thickness 2-3 cm. The weight of the uterus in nulliparous women varies from 40 to 50 g, and in those who give birth reaches 80-90 g. The volume of the uterus cavity is 4 -6 cm ³.

Structure of the uterus

The wall of the uterus differs in significant thickness and limits the narrow cavity of the uterus (cavitas uteri), which has a triangular shape on the cut in the frontal plane. The base of this triangle is turned towards the bottom of the uterus, and the vertex is directed downwards towards the cervix, where its cavity passes into the canalis cervicis uteri. The latter opens into the vaginal cavity with a hole in the uterus. The upper corners of the uterine cavity narrow in the form of funnel-shaped depressions into which the uterine openings of the tubes open.

The wall of the uterus consists of three layers. The surface layer is represented by the serosa (tunica serosa), which is also called perimetrium. This is a leaflet of the peritoneum, covering the uterus in front and behind. The subserous base (tela subserosa) in the form of a loose fibrous connective tissue is present only in the neck region and at the sides, where the peritoneum covering the uterus passes into the broad ligament of the uterus.

Connective tissue on either side of the uterus accommodating the blood vessels called parauterine fiber - parametrial (parametrium). The middle layer of the uterus wall is the muscle shell (tunica muscularis), or myometrium (myometrium), the thickest. Myometrium consists of complex intertwining bundles of smooth muscle tissue, as well as a small number of connective tissue bundles containing elastic fibers. In accordance with the preferential direction of the muscle bundles, three layers are distinguished in myometrium: the inner oblique, middle circular (circular) and outer oblique. The most powerful layer is the middle circular layer, which contains a large number of blood, lymphatic vessels and especially large veins, which is why this layer is called the vascular layer; The circular layer is most strongly developed in the cervical region. There is no submucosa in the walls of the uterus.

The mucosa (tunica mucosa), or endometrium (endometrium), forms the inner layer of the uterine wall, its thickness reaches 3 mm. The surface of the mucous membrane of the uterus is smooth. Only the cervical canal has one longitudinal fold and smaller palmoid folds (plicae palmatae) extending from it to both sides at an acute angle . These folds are located on the front and back walls of the cervical canal. In contact with each other, palmoid folds prevent penetration of the vaginal contents into the uterine cavity. The mucous membrane is lined with a single-layer columnar (prismatic) epithelium. It contains simple tubular uterine glands (glandulae utennae).

Uterus as an organ is largely mobile. Depending on the condition of neighboring organs can occupy a different position. Normally, the longitudinal axis of the uterus is oriented along the axis of the pelvis. When the bladder is emptied, the uterus bottom is directed forward - the uterus is tilted anteriorly (anteversio uteri). Leaning forward, the uterus body forms in the neck an angle, open anteriorly, - the bend of the uterus in front (anteflexio uteri). When the bladder is full, the uterus's bottom goes back and the uterus straightens slightly. The uterus is slightly deflected to the right (more often) or to the left (lateropositio literi). In rare cases, the uterus is tilted back (retroversio uteri) or curved posteriorly (retroflexio uteri).

Ratio of uterus to peritoneum

Most of the surface of the uterus is covered with the peritoneum (with the exception of the vaginal part of the cervix). From the area of the uterine fundus, the peritoneum continues to the vesicle (anterior) surface and reaches the cervix, then passes to the bladder. This deep pocket, not reaching the front of the vaginal vault and formed by the peritoneum, which also covers the posterior surface of the bladder, has received the name of a vesicoureteral cavity (excavatio vesicouterina). The peritoneum covering the rectum (posterior) surface of the uterus reaches the posterior wall of the vagina, from where it rises upwards to the front wall of the rectum. When moving from the uterus to the rectum, the peritone forms the rectum-uterine cavity (excavatio rectouterina), the Douglas space. On the right and left, this indentation is limited to the rectal-uterine folds of the peritoneum, which extend from the cervix to the rectum. The rectum-uterine cavity is lowered (extended) into the pelvic cavity deeper than the vesicle-uterine cavity. It reaches the back of the vaginal vault. At the base of the rectum-uterine folds of the peritoneum there is a rectum-uterine muscle (m.hötouterinus) with bundles of fibrous fibers. This muscle begins on the posterior surface of the cervix in the form of flat beams, passes through the thickness of the folds of the peritoneum, bypassing the rectum and attached to the periosteum of the sacrum.

Ligament of the uterus

At the edges of the uterus, the peritoneal sheets that cover its vesicular and rectum surfaces converge and form the right and left broad ligament of the uterus. A wide ligament of the uterus (lig. Latum uteri) consists of two sheets of the peritoneum - the anterior and posterior. In its structure and purpose, it is a mesentery of the uterus (mesometrium). The right and left broad ligament of the uterus are directed to the side walls of the small pelvis, where they pass into the parietal peritoneal sheet. In the free upper edge of the broad ligament of the uterus, between the leaves of the uterus, the uterine tube is located. The site of the broad ligament, adjacent to the fallopian tube, was called the mesentery of the tube (mesosalpinx). Between the leaves of the mesentery are appendages of the ovary. Somewhat below the attachment of the ovary's own ligament to the uterus from the anterolateral surface of the uterus, a ligamentous uterine ligament (lig.teres uteri) begins. This ligament is a round, dense fibrous throat 3-5 mm thick, containing muscle bundles. The round ligament of the uterus is located between the leaves of the broad ligament of the uterus, is directed downwards and anteriorly, to the deep opening of the inguinal canal, passes through it and, in the form of separate fibrous bundles, is woven into the cellulose of the pubis. To the posterior leaf of the broad ligament of the uterus is attached by its mesenteric margin the ovary. The site of the broad ligament of the uterus adjacent to the ovary is called the mesenteric mesentery. At the base of the broad ligament of the uterus between the cervix and the pelvic walls lie bunches of fibrous fibers and smooth muscle cells, which form cardinal ligaments (ligg. Cardinalia). Their lower edges connect these ligaments with the fascia of the urogenital diaphragm and keep the uterus from lateral displacements.

Vessels and nerves of the uterus

The blood supply to the uterus is aa. Et w. Uterinae et ovaricae. Each a. The uterinae usually departs from the anterior branch of the internal iliac artery, most often along with the umbilical artery. The beginning of the uterine artery is usually projected on the lateral edge of the pelvis, at a level of 14-16 cm below the nameless line. Further, the uterine artery is guided medially and forward under the peritoneum over the fascia covered with muscle, lifting the anus, into the base of the broad ligament of the uterus, where the branches to the bladder (rami vesicales) usually leave from it. They participate in the blood supply of not only the corresponding parts of the wall of the bladder, but also the area of the vesicle-uterine fold. Then the uterine artery crosses the ureter, settling over it and giving it a small twig, and then comes close to the side wall of the uterus, often at the level of the isthmus. Here a. Uterinae gives the descending, or vaginal (one or more), artery (a. Vaginalis). Continuing further up the lateral wall of the uterus to its corner, the uterine artery all over extends from 2 to 14 branches to the anterior and posterior walls of the uterus. In the area of the ovary's own ligament a. The uterina sometimes gives a large branch to the bottom of the uterus (from which the tube branch often leaves) and twigs to the round uterine ligament, after which the uterine artery changes its direction from the vertical to the horizontal one and goes to the ovary gates where it divides into the ovarian branches that anastomose with the ovarian artery .

The veins of the uterus have thin walls and form the uterine venous plexus, which is located mainly in the region of the lateral walls of the cervix and periarticular tissue. It extensively anastomoses with the veins of the vagina, the external genitalia, urinary-vesicle and rectal venous plexuses, and the ovarian groin-like plexus. The uterine venous plexus collects blood mainly from the uterus, vagina, fallopian tubes and a wide ligament of the uterus. Through the veins of the circular ligament, the uterine venous plexus communicates with the veins of the anterior abdominal wall. Blood from the uterus flows down the uterine vein into the internal iliac vein. Uterine veins in their lower divisions often consist of two trunks. It is important to note that of the two uterine veins, one (smaller) is usually located in front of the ureter, the other behind it. Blood from the bottom and upper part of the uterus flows, in addition, and through the veins of the round and broad ligament of the uterus into the groinlike plexus of the ovary and then through v. Ovarica in the lower vena cava (right) and renal (left); from the lower body of the uterus and the upper part of the cervix, the outflow of blood is carried out directly in v. Iliaca interna; from the lower part of the cervix and vagina - to the system v. Iliaca interna through the internal hollow vein.

The innervation of the uterus is carried out from the lower hypogastric plexuses (sympathetic) and the pelvic internal nerves (parasympathetic).

The lymphatic system of the uterus is conventionally divided into intraorganic and extraorganic, and the first gradually passes into the second.

Lymphatic vessels of the first group that divert lymph from about two upper third of the vagina and the lower third of the uterus (mainly the cervix) are located at the base of the broad ligament of the uterus and pour into the internal iliac, external and general iliac, lumbar sac and anal spine.

Lymphatic vessels of the second (upper) group divert lymph from the body of the uterus, ovaries and fallopian tubes; they begin mainly from large subserous lymphatic sinuses and pass mainly in the upper part of the broad ligament of the uterus, heading for the lumbar and sacral lymph nodes, and partly (mainly from the bottom of the uterus) - along the round uterine ligament to the inguinal lymph nodes. Regional lymph nodes of the uterus are located in various parts of the pelvic cavity and abdominal cavity: from the iliac arteries (general, external, internal) and their branches to the point of divergence of the mesenteric artery from the aorta.

X-ray anatomy of the uterus

For X-ray examination of the uterus, a contrast medium (metrosalpingography) is introduced into its cavity. On the roentgenogram the shadow of the uterine cavity has the appearance of a triangle with slightly concave sides. The base of the triangle is facing upward, and the vertex is down. The upper corners of the uterine cavity correspond to the openings of the fallopian tubes, the lower corner to the inner opening of the cervical canal. The uterine cavity accommodates 4 to 6 ml of contrast fluid.