Myometrium Health Dictionary

Myometrium: From 2 Different Sources


The muscular coat of the UTERUS.
Health Source: Medical Dictionary
Author: Health Dictionary
n. the muscular tissue of the uterus, which surrounds the *endometrium. It is composed of smooth muscle that undergoes small regular spontaneous contractions. The frequency and amplitude of these contractions alter in response to the hormones *oestrogen, *progesterone, and *oxytocin, which are present at particular stages of the menstrual cycle and pregnancy.
Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

Oxytocin

A short-lived, fast acting hormone, made by the hypothalamus of the brain, along with its close relative vasopressin (anti-diuretic hormone), stored in the posterior pituitary, and released into the blood as needed. It stimulates certain smooth muscle coats, constricts certain blood vessels and facilitates the sensitivity of some tissues to other hormones and nerves. The main tissues affected are the uterus, including endo­and myometriums, vagina, breasts (both sexes), erectile tissue (both sexes), seminal vesicles, and with special-case effects on uterine muscle contractions in both birth and orgasm, the vascular constriction that lessens placental separation bleeding, and the let­down reflex that nursing mothers have when babies cry (or kittens mew...or husbands whine)... oxytocin

Uterus, Diseases Of

Absence or defects of the uterus

Rarely, the UTERUS may be completely absent as a result of abnormal development. In such patients secondary sexual development is normal but MENSTRUATION is absent (primary amennorhoea). The chromosomal make-up of the patient must be checked (see CHROMOSOMES; GENES): in a few cases the genotype is male (testicular feminisation syndrome). No treatment is available, although the woman should be counselled.

The uterus develops as two halves which fuse together. If the fusion is incomplete, a uterine SEPTUM results. Such patients with a double uterus (uterus didelphys) may have fertility problems which can be corrected by surgical removal of the uterine septum. Very rarely there may be two uteri with a double vagina.

The uterus of most women points forwards (anteversion) and bends forwards (ante?exion). However, about 25 per cent of women have a uterus which is pointed backwards (retroversion) and bent backwards (retro?exion). This is a normal variant and very rarely gives rise to any problems. If it does, the attitude of the uterus can be corrected by an operation called a ventrosuspension.

Endometritis The lining of the uterine cavity is called the ENDOMETRIUM. It is this layer that is partially shed cyclically in women of reproductive age giving rise to menstruation. Infection of the endometrium is called endometritis and usually occurs after a pregnancy or in association with the use of an intrauterine contraceptive device (IUCD – see CONTRACEPTION). The symptoms are usually of pain, bleeding and a fever. Treatment is with antibiotics. Unless the FALLOPIAN TUBES are involved and damaged, subsequent fertility is unaffected. Very rarely, the infection is caused by TUBERCULOSIS. Tuberculous endometritis may destroy the endometrium causing permanent amenorrhoea and sterility.

Menstrual disorders are common. Heavy periods (menorrhagia) are often caused by ?broids (see below) or adenomyosis (see below) or by anovulatory cycles. Anovulatory cycles result in the endometrium being subjected to unopposed oestrogen stimulation and occasionally undergoing hyperplasia. Treatment is with cyclical progestogens (see PROGESTOGEN) initially. If this form of treatment fails, endoscopic surgery to remove the endometrium may be successful. The endometrium may be removed using LASER (endometrial laser ablation) or electrocautery (transcervical resection of endometrium). Hysterectomy (see below) will cure the problem if endoscopic surgery fails. Adenomyosis is a condition in which endometrial tissue is found in the muscle layer (myometrium) of the uterus. It usually presents as heavy and painful periods, and occasionally pain during intercourse. Hysterectomy is usually required.

Oligomenorhoea (scanty or infrequent periods) may be caused by a variety of conditions including thyroid disease (see THYROID GLAND, DISEASES OF). It is most commonly associated with usage of the combined oral contraceptive pill. Once serious causes have been eliminated, the patient should be reassured. No treatment is necessary unless conception is desired, in which case the patient may require induction of ovulation.

Primary amenorrhoea means that the patient has never had a period. She should be investigated, although usually it is only due to an inexplicable delay in the onset of periods (delayed menarche) and not to any serious condition. Secondary amenorrhoea is the cessation of periods after menstruation has started. The most common cause is pregnancy. It may be also caused by endocrinological or hormonal problems, tuberculous endometritis, emotional problems and severe weight loss. The treatment of amenorrhoea depends on the cause.

Dysmenorrhoea, or painful periods, is the most common disorder; in most cases the cause is unknown, although the disorder may be due to excessive production of PROSTAGLANDINS.

Irregular menstruation (variations from the woman’s normal menstrual pattern or changes in the duration of bleeding or the amount) can be the result of a disturbance in the balance of OESTROGENS and PROGESTERONE hormone which between them regulate the cycle. For some time after the MENARCHE or before the MENOPAUSE, menstruation may be irregular. If irregularity occurs in a woman whose periods are normally regular, it may be due to unsuspected pregnancy, early miscarriage or to disorders in the uterus, OVARIES or pelvic cavity. The woman should seek medical advice.

Fibroids (leiomyomata) are benign tumours arising from the smooth muscle layer (myometrium) of the uterus. They are found in 80 per cent of women but only a small percentage give rise to any problems and may then require treatment. They may cause heavy periods and occasionally pain. Sometimes they present as a mass arising from the pelvis with pressure symptoms from the bladder or rectum. Although they can be shrunk medically using gonadorelin analogues, which raise the plasma concentrations of LUTEINISING HORMONE and FOLLICLE-STIMULATING HORMONE, this is not a long-term solution. In any case, ?broids only require treatment if they are large or enlarging, or if they cause symptoms. Treatment is either myomectomy (surgical removal) if fertility is to be retained, or a hysterectomy.

Uterine cancers tend to present after the age of 40 with abnormal bleeding (intermenstrual or postmenopausal bleeding). They are usually endometrial carcinomas. Eighty per cent present with early (Stage I) disease. Patients with operable cancers should be treated with total abdominal hysterectomy and bilateral excision of the ovaries and Fallopian tubes. Post-operative RADIOTHERAPY is usually given to those patients with adverse prognostic factors. Pre-operative radiotherapy is still given by some centres, although this practice is now regarded as outdated. PROGESTOGEN treatment may be extremely e?ective in cases of recurrence, but its value remains unproven when used as adjuvant treatment. In 2003 in England and Wales, more than 2,353 women died of uterine cancer.

Disorders of the cervix The cervix (neck of the womb) may produce an excessive discharge due to the presence of a cervical ectopy or ectropion. In both instances columnar epithelium – the layer of secreting cells – which usually lines the cervical canal is exposed on its surface. Asymptomatic patients do not require treatment. If treatment is required, cryocautery – local freezing of tissue – is usually e?ective.

Cervical smears are taken and examined in the laboratory to detect abnormal cells shed from the cervix. Its main purpose is to detect cervical intraepithelial neoplasia (CIN) – the presence of malignant cells in the surface tissue lining the cervix – since up to 40 per cent of women with this condition will develop cervical cancer if the CIN is left untreated. Women with abnormal smears should undergo colposcopy, a painless investigation using a low-powered microscope to inspect the cervix. If CIN is found, treatment consists of simply removing the area of abnormal skin, either using a diathermy loop or laser instrument.

Unfortunately, cervical cancer remains the most common of gynaecological cancers. The most common type is squamous cell carcinoma and around 4,000 new cases (all types) are diagnosed in England and Wales every year. As many as 50 per cent of the women affected may die from the disease within ?ve years. Cervical cancer is staged clinically in four bands according to how far it has extended, and treatment is determined by this staging. Stage I involves only the mucosal lining of the cervix and cone BIOPSY may be the best treatment in young women wanting children. In Stage IV the disease has spread beyond the cervix, uterus and pelvis to the URINARY BLADDER or RECTUM. For most women, radiotherapy or radical Wertheim’s hysterectomy – the latter being preferable for younger women – is the treatment of choice if the cancer is diagnosed early, both resulting in survival rates of ?ve years in 80 per cent of patients. Wertheim’s hysterectomy is a major operation in which the uterus, cervix, upper third of vagina and the tissue surrounding the cervix are removed together with the LYMPH NODES draining the area. The ovaries may be retained if desired. Patients with cervical cancer are treated by radiotherapy, either because they present too late for surgery or because the surgical skill to perform a radical hysterectomy is not available. These operations are best performed by gynaecological oncologists who are gynaecological surgeons specialising in the treatment of gynaecological tumours. The role of CHEMOTHERAPY in cervical and uterine cancer is still being evaluated.

Prolapse of the uterus is a disorder in which the organ drops from its normal situation down into the vagina. First-degree prolapse is a slight displacement of the uterus, second-degree a partial displacement and third-degree when the uterus can be seen outside the VULVA. It may be accompanied by a CYSTOCOELE (the bladder bulges into the front wall of the vagina), urethrocoele (the urethra bulges into the vagina) and rectocoele (the rectal wall bulges into the rear wall of the vagina). Prolapse most commonly occurs in middle-aged women who have had children, but the condition is much less common now than in the past when prenatal and obstetric care was poor, women had more pregnancies and their general health was poor. Treatment is with pelvic exercises, surgical repair of the vagina or hysterectomy. If the woman does not want or is not ?t for surgery, an internal support called a pessary can be ?tted – and changed periodically.

Vertical section of female reproductive tract (viewed from front) showing sites of common gynaecological disorders.

Hysterectomy Many serious conditions of the uterus have traditionally been treated by hysterectomy, or removal of the uterus. It remains a common surgical operation in the UK, but is being superseded in the treatment of some conditions, such as persistent MENORRHAGIA, with endometrial ablation – removal of the lining of the uterus using minimally invasive techniques, usually using an ENDOSCOPE and laser. Hysterectomy is done to treat ?broids, cancer of the uterus and cervix, menorrhagia, ENDOMETRIOSIS and sometimes for severely prolapsed uterus. Total hysterectomy is the usual type of operation: it involves the removal of the uterus and cervix and sometimes the ovaries. After hysterectomy a woman no longer menstruates and cannot become pregnant. If the ovaries have been removed as well and the woman had not reached the menopause, hormone replacement therapy (HRT – see MENOPAUSE) should be considered. Counselling helps the woman to recover from the operation which can be an emotionally challenging event for many.... uterus, diseases of

Couvelaire

n. the appearance of the uterus following a massive placental abruption (*abruptio placentae) when blood has extravasated (leaked) through the *myometrium to the subserosal surface of the uterus. The uterus is hard and tender and a bruised discoloration can be seen at the time of Caesarean section.... couvelaire

Endometrial Cancer

a malignant tumour of the lining (*endometrium) of the uterus. Risk factors are nulliparity (never having given birth), obesity, and tamoxifen use as chemotherapy for breast cancer. The presenting symptom is usually *postmenopausal bleeding, but this cancer may present with postmenopausal discharge or *pyometra. The tumour invades the *myometrium and spreads down to the cervix and through the Fallopian tubes to the ovaries and peritoneal cavity and through the lymphatics to pelvic and aortic nodes. Prognosis depends on tumour differentiation, depth of myometrial invasion, extent of tumour spread, and involvement of retroperitoneal nodes. Treatment is laparoscopic abdominal *hysterectomy and bilateral *salpingo-oophorectomy, with *lymphadenectomy and radiotherapy if indicated.... endometrial cancer

Endometriosis

n. the presence of fragments of endometrial tissue at sites in the pelvis outside the uterus or, rarely, throughout the body (e.g. in the lung, rectum, or umbilicus). It is thought to be caused by retrograde *menstruation. When the tissue has infiltrated the wall of the uterus (myometrium) the condition is known as adenomyosis. Symptoms vary, but typically include pelvic pain, severe *dysmenorrhoea, *dyspareunia, infertility, and a pelvic mass (or any combination of these). Medical treatment is aimed at suppressing ovulation using *gonadorelin analogues, combined oral contraceptives, or the intrauterine system (see IUS). High-dose progestogens suppress *gonadotrophins (FSH and LH), shrink implanted endometrial tissue, and reduce retrograde menstruation. They have a similar efficacy to other medical treatments, are cheaper, and have fewer side-effects than gonadorelin analogues. Surgical treatment may also be necessary, usually by laser or ablative therapy via the laparoscope. More radical surgical treatment in the form of a total hysterectomy and bilateral salpingo-oophorectomy is sometimes required.... endometriosis

Myometritis

n. inflammation of the muscular wall (myometrium) of the uterus.... myometritis

Placenta Accreta

a condition in which the placenta is abnormally strongly attached to the wall of the uterus with superficial penetration of chorionic *villi into the underlying *myometrium. Women with *placenta praevia and at least one previous Caesarean delivery are considered to be at high risk for placenta accreta. When placenta accreta is thought to be likely, consultant obstetric and anaesthetic input are vital in planning and conducting the delivery. Radiological input with temporary uterine balloon tamponade may be considered, and methotrexate has been used. The risk of haemorrhage, blood transfusion, and hysterectomy should be discussed. In placenta increta the chorionic villi extend into the myometrium; a placenta percreta occurs where the chorionic villi penetrate through the myometrial wall and can invade the bladder. An emergency hysterectomy is usually necessary in these rare cases.... placenta accreta

Uterus

(womb) n. the part of the female reproductive tract that is specialized to allow the embryo to become implanted in its inner wall and to nourish the growing fetus from the maternal blood. The nonpregnant uterus is a pear-shaped organ, about 7.5 cm long. It is suspended in the pelvic cavity by means of peritoneal folds (ligaments) and fibrous bands. The upper two-thirds of the uterus (body) is connected to the two *Fallopian tubes, and the narrower lower third (*cervix, or neck) projects at its lower end into the vagina. The uterus has an inner mucous lining (*endometrium) and a thick wall of smooth muscle (*myometrium). During childbirth the myometrium undergoes strong contractions to expel the fetus through the cervix and vagina. In the absence of pregnancy the endometrium undergoes periodic development and degeneration (see menstrual cycle). —uterine adj.... uterus



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