see Kegel exercises.
Structure of muscle Skeletal or voluntary muscle forms the bulk of the body’s musculature and contains more than 600 such muscles. They are classi?ed according to their methods of action. A ?exor muscle closes a joint, an extensor opens it; an abductor moves a body part outwards, an adductor moves it in; a depressor lowers a body part and an elevator raises it; while a constrictor (sphincter) muscle surrounds an ori?ce, closing and opening it. Each muscle is enclosed in a sheath of ?brous tissue, known as fascia or epimysium, and, from this, partitions of ?brous tissue, known as perimysium, run into the substance of the muscle, dividing it up into small bundles. Each of these bundles consists in turn of a collection of ?bres, which form the units of the muscle. Each ?bre is about 50 micrometres in thickness and ranges in length from a few millimetres to 300 millimetres. If the ?bre is cut across and examined under a high-powered microscope, it is seen to be further divided into ?brils. Each ?bre is enclosed in an elastic sheath of its own, which allows it to lengthen and shorten, and is known as the sarcolemma. Within the sarcolemma lie numerous nuclei belonging to the muscle ?bre, which was originally developed from a simple cell. To the sarcolemma, at either end, is attached a minute bundle of connective-tissue ?bres which unites the muscle ?bre to its neighbours, or to one of the connective-tissue partitions in the muscle, and by means of these connections the ?bre affects muscle contraction. Between the muscle ?bres, and enveloped in a sheath of connective tissue, lie here and there special structures known as muscle-spindles. Each of these contains thin muscle ?bres, numerous nuclei, and the endings of sensory nerves. (See TOUCH.) The heart muscle comprises short ?bres which communicate with their neighbours via short branches and have no sarcolemma.
Plain or unstriped muscle is found in the following positions: the inner and middle coats of the STOMACH and INTESTINE; the ureters (see URETER) and URINARY BLADDER; the TRACHEA and bronchial tubes; the ducts of glands; the GALL-BLADDER; the UTERUS and FALLOPIAN TUBES; the middle coat of the blood and lymph vessels; the iris and ciliary muscle of the EYE; the dartos muscle of the SCROTUM; and in association with the various glands and hairs in the SKIN. The ?bres are very much smaller than those of striped muscle, although they vary greatly in size. Each has one or more oval nuclei and a delicate sheath of sarcolemma enveloping it. The ?bres are grouped in bundles, much as are the striped ?bres, but they adhere to one another by cement material, not by the tendon bundles found in voluntary muscle.
Development of muscle All the muscles of the developing individual arise from the central layer (mesoderm) of the EMBRYO, each ?bre taking origin from a single cell. Later on in life, muscles have the power both of increasing in size – as the result of use, for example, in athletes – and also of healing, after parts of them have been destroyed by injury. An example of the great extent to which unstriped muscle can develop to meet the demands made on it is the uterus, whose muscular wall develops so much during pregnancy that the organ increases from the weight of 30–40 g (1–1••• oz.) to a weight of around 1 kg (2 lb.), decreasing again to its former small size in the course of a month after childbirth.
Physiology of contraction A muscle is an elaborate chemico-physical system for producing heat and mechanical work. The total energy liberated by a contracting muscle can be exactly measured. From 25–30 per cent of the total energy expended is used in mechanical work. The heat of contracting muscle makes an important contribution to the maintenance of the heat of the body. (See also MYOGLOBIN.)
The energy of muscular contraction is derived from a complicated series of chemical reactions. Complex substances are broken down and built up again, supplying each other with energy for this purpose. The ?rst reaction is the breakdown of adenyl-pyrophosphate into phosphoric acid and adenylic acid (derived from nucleic acid); this supplies the immediate energy for contraction. Next phosphocreatine breaks down into creatine and phosphoric acid, giving energy for the resynthesis of adenyl-pyrophosphate. Creatine is a normal nitrogenous constituent of muscle. Then glycogen through the intermediary stage of sugar bound to phosphate breaks down into lactic acid to supply energy for the resynthesis of phosphocreatine. Finally part of the lactic acid is oxidised to supply energy for building up the rest of the lactic acid into glycogen again. If there is not enough oxygen, lactic acid accumulates and fatigue results.
All of the chemical changes are mediated by the action of several enzymes (see ENZYME).
Involuntary muscle has several peculiarities of contraction. In the heart, rhythmicality is an important feature – one beat appearing to be, in a sense, the cause of the next beat. Tonus is a character of all muscle, but particularly of unstriped muscle in some localities, as in the walls of arteries.
Fatigue occurs when a muscle is made to act for some time and is due to the accumulation of waste products, especially sarcolactic acid (see LACTIC ACID). These substances affect the end-plates of the nerve controlling the muscle, and so prevent destructive overaction of the muscle. As they are rapidly swept away by the blood, the muscle, after a rest (and particularly if the rest is accompanied by massage or by gentle contractions to quicken the circulation) recovers rapidly from the fatigue. Muscular activity over the whole body causes prolonged fatigue which is remedied by rest to allow for metabolic balance to be re-established.... muscle
The infection may be silent – with no obvious symptoms – or symptoms may be troublesome, for example, vaginal discharge and sometimes a palpable mass in the lower abdomen. If a LAPAROSCOPY is done – usually by endoscopic examination – overt evidence of PID is found in around 65 per cent of suspected cases.
PID may be confused with APPENDICITIS, ECTOPIC PREGNANCY – and PID is a common cause of such pregnancies – ovarian cyst (see OVARIES, DISEASES OF) and in?ammatory disorders of the intestines. Treatment is with a combination of ANTIBIOTICS that are active against the likely pathogens, accompanied by ANALGESICS. Patients may become seriously ill and require hospital care, where surgery is sometimes required if conservative management is unsuccessful. All women who have PID should be screened for sexually transmitted disease and, if this is present, should be referred with their partner(s) to a genito-urinary medicine clinic. Up to 20 per cent of women who have PID become infertile, and there is a seven-to ten-fold greater risk of an ectopic pregnancy occurring.... pelvic inflammatory disease(pid)
forearm. The biceps femoris at the back of the thigh bends the leg at the knee and extends the thigh.... biceps muscle
and plays an important role in breathing. There are openings in the diaphragm for the oesophagus and major nerves and blood vessels. To inhale, the diaphragm’s muscle fibres contract, pulling the whole diaphragm downwards and drawing air into the lungs. (See also breathing.)... diaphragm muscle
After examination of the external genitalia, a speculum is inserted into the vagina to allow a clear view of the cervix.
A cervical smear test may be performed.
The doctor inserts 2 fingers into the vagina and, with the other hand, feels the abdomen to evaluate the position and size of the uterus and the ovaries and to detect any tenderness or swelling.... pelvic examination
The patient is connected to a recording instrument that measures one of the unconscious body activities, such as blood pressure, heart-rate, or the quantity of sweat on the skin. The patient receives information (feedback) on the changing levels of these activities from changes in the instrument’s signals. Using relaxation techniques, the patient learns to change the signals by conscious control of the body function. Once acquired, this control can be exercised without the instrument.... biofeedback training
The drugs may cause muscle weakness and drowsiness. In rare cases, dantrolene causes liver damage.... muscle-relaxant drugs
These muscles and ligaments support the uterus, vagina, bladder, urethra, and rectum. Performing the exercises may help to prevent prolapse of the uterus (see uterus, prolapse of) and urinary stress incontinence (see incontinence, urinary). They may also help women who find achieving orgasm difficult.
The pelvic floor muscles are those that tighten when urine flow is stopped midstream. The exercises involve stopping and starting urine flow several times by contracting and relaxing the muscles. Ideally, they should be performed for 5 minutes every hour throughout the day. They can be done standing, sitting, or lying down, by imagining that urine is being passed, contracting and holding the muscles for 10 seconds, and then slowly releasing them, repeating 5–10 times as often as possible.... pelvic floor exercises
There are 2 parts: psoas major and psoas minor.
Psoas major acts to flex the hip and rotate the thigh inwards.
Psoas minor bends the spine down to the pelvis.... psoas muscle
The most common disorder of the quadriceps is a haematoma caused by a direct blow.... quadriceps muscle
This is an important part of rehabilitation for people with mental handicap or those with chronic psychological disorders, such as schizophrenia.
Role-playing is a commonly used technique in which various social situations are simulated in order to improve the individual’s confidence and performance.... social skills training
A child is unlikely to be completely toilet-trained before age 3 and may normally take much longer to remain dry at night (see enuresis).... toilet-training
It is attached to the top and back of the shoulderblade and to the outermost part of the collarbone.
The trapezius helps support the neck and spine and is involved in moving the arm.... trapezius muscle
Health Encyclopedia