The uterus, or the womb, is the female sexual organ in which the fertilised ova mature to an embryo foetus before the birth. All female mammals have a uterus. In the following, only the human uterus will be considered.
From a developmental perspective, the uterus is created from two channels (Paramesonephric ducts), which fuse together. If this fusion is incomplete, the uterus may have a pronounced septum. In rare cases, it can may even be duplicated (see anomalies).
Before puberty, the uterus is relatively small. It then becomes approx. 5–10 cm large. During pregnancy, it expands upwards and to the sides. It can then be positioned above the naval. After childbirth, the muscles of the uterus strongly contract, thereby causing a rapid reduction of the organ. After menopause, the uterus becomes even smaller.
The uterus is shaped like an upside-down pear. At the upper end of the uterus, the Fundus uteri, are two lateral branches, the fallopian tubes. The uterus is a muscular hollow organ which is approx. 7 cm long and 5 cm wide. It weighs approx. 30–120 g. Understandably, the size and weight can vary significantly depending on previous pregnancies. The uterus can be anatomically divided into the following sections:
The position of the uterus can vary between individuals. If the uterus is curved forward, this is referred to as "anteflexion". This is the most common positional variant. If the uterus is curved backwards, this is referred to as "retroflexion". Other variants include "anteversion" and "retroversion". The uterus is surrounded by the following structures:
The peritoneum folds back from the bladder to the front wall of the uterus, covers these to a large extent, and then folds back from the rear wall of the uterus to the rectum. In the middle of these three organs, two peritoneal pits form. These are referred to as the vesicouterine pouch (ventral) and he rectouterine pouch (dorsal). The latter peritoneum pit simultaneously forms the deepest point of the female peritoneal cavity (Douglas space) and extends to just above the posterior vaginal fornix – formed by the Cervix uteri with the vagina. It should be noted that the cervix uteri is free of peritoneum.
The supporting structures of the uterus include the connective tissue structures surrounding the uterus. These are collectively referred to as the "Parametria". Other structures include the pelvic floor muscles, which are found caudally. The ligaments in the parametrium allow the uterus to move in the pelvis.
The pelvic floor muscles ensure that the uterus does not sink the Levator ani plays the most important role.
The uterine artery, which originates as a visceral branch from the Internal iliac artery, is responsible for the arterial supply. In the broad ligament, it approaches the uterus at the height of the cervix and emits branches to the vagina (Rami vaginal). It then extends along the lateral lower margin and emits numerous branches (helicine arteries), which are also tortuous, upward to the fundus. Once there, they each emit a tubal branch to the fallopian tube and ovarian branch to the ovary. The latter anastomoses between the uterine artery and the ovarian artery. The tortuosity of the uterine artery allows it to adapt to changes in the size of the uterus during pregnancy.
Venous drainage is accomplished by the pronounced uterine venous plexus. It often takes takes the blood of the vagina and then flows through the uterine veins into the internal iliac veins. An additional outflow into the ovarian plexus is also possible.
Together with the inferior hypogastric plexus, the inferior mesenteric plexus is responsible for the sympathetic supply of the uterus. The fibres originating from these nerve plexus extend along Uterovaginal plexus (Frankenhäuser plexus, pelvic ganglion) to the organ. The parasympathetic fibres originate from the S2-S4 and also extend along the uterovaginal plexus . The parasympathetic system is also responsible for the contraction of the uterus. It also dilates vessels. The effect of the sympathetic system is hormone-dependent. Depending on the situation, it leads to either contraction or relaxation.
From a histological perspective, the uterus is composed of several layers. From outside to inside you will find:
The uterus provides a space for the development of embryos or the foetus. In a monthly cycle the endometrium is assembled and disassembled under the control of hormones. If no fertilisation occurs during this period, the woman enters a menstrual cycle (menstruation). If an egg cell (zygote) is fertilised and the embryo is successfully implanted (nidation), the endometrium continues to grow. Together with the trophoblast, it forms the placenta which ensures the supply of the growing embryo. After the birth, it is expelled as afterbirth.
The complex processes of organogenesis may lead to abnormalities of the uterus. These abnormalities can also effect the development of other female sexual organs. The uterus is formed by the fusion of the paramesonephric ducts . A disturbed fusion may lead to abnormalities of the uterus:
The ICD codes of some common diagnoses concerning the uterus are listed below:
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