Tilting-disc valve Health Dictionary

The ?brous disc that acts as a cushion between the bony vertebrae (see SPINAL COLUMN), enabling them to rotate and bend one on another. The disc tends to degenerate with age and may get ruptured and displaced – prolapsed or slipped disc – as a result of sudden strenuous action. Prolapsed disc occurs mainly in the lower back; it is more common in men than in women, and in the 30–40 age group.... intervertebral disc

The mitral valve, so-called because of its resemblance to a bishop’s mitre, is the valve which guards the opening between the ATRIUM and VENTRICLE on the left side of the HEART.... mitral valve

Otherwise known as the blind spot of the EYE, the disc is the beginning of the optic nerve – the point where nerve ?bres from the retina’s rods and cones (the light- and colour-sensitive cells) leave the eyeball.... optic disc

The valve, with three cusps or ?aps, that guards the opening from the right atrium into the right ventricle of the HEART.... tricuspid valve

The valve that controls the ?ow of blood from the AORTA to the left ventricle of the HEART.... aortic valve

An anatomical term describing a rounded ?attened structure. Examples are the cartilagenous disc positioned between two vertebrae (see SPINAL COLUMN) and the optic disc (see EYE).... disc

The SPINAL COLUMN is built up of a series of bones, known as vertebrae, placed one upon the other. Between these vertebrae lies a series of thick discs of ?bro-cartilage known as intervertebral discs. Each disc consists of an outer portion known as the anulus ?brosus, and an inner core known as the nucleus pulposus. The function of these discs is to give ?exibility and resiliency to the spinal column and to act as bu?ers against undue jarring. In other words, they are most e?cient shock-absorbers. They may, however, PROLAPSE, or protrude, between the two adjacent vertebrae. If this should happen they press on the neighbouring spinal nerve and cause pain. As the most common sites of protrusion are between the last two lumbar vertebrae and between the last lumbar vertebra and the sacrum, this means that the pain occurs in the back, causing LUMBAGO, or down the course of the sciatic nerve causing SCIATICA. The prolapse is most likely to occur in middle age, which suggests that it may be associated with degeneration of the disc involved, but it can occur in early adult life as well. It usually occurs when the individual is performing some form of exercise which involves bending or twisting, as in gardening. The onset of pain may be acute and sudden, or gradual and more chronic in intensity. (See also INTERVERTEBRAL DISC.)

Treatment varies, depending (amongst other things) on the severity of the condition. In the acute phase, rest in bed is advisable, along with ANALGESICS. Later, exercise and physiotherapy are helpful, and in some cases manipulation of the spine brings relief by allowing the herniated, or prolapsed, disc to slip back into position. The injection of a local anaesthetic into the spine (epidural ANAESTHESIA) is yet another measure that often helps the more chronic cases. If those measures fail, surgery to remove the prolapsed disc may be necessary, but the patient’s condition should be carefully reviewed before surgery is considered since success is not certain. An alternative form of treatment is the injection into the disc of chymopapain, an ENZYME obtained from the paw-paw, which dissolves the disc.... prolapsed intervertebral disc

The popular name for a PROLAPSED INTERVERTEBRAL DISC. (See also SPINAL COLUMN; SCIATICA.)... slipped disc

A structure that allows fluid or semi-fluid material to flow in 1 direction through a tube or passageway but closes to prevent reflux in the opposite direction. The valves at the exits from the heart chambers and in the veins are essential to the circulatory system. There are also small valves in the vessels of the lymphatic system.... valve

These cup-like structures are found in the HEART, VEINS, and lymphatic vessels (see LYMPH); they ensure that the circulation of the blood and lymph goes always in one direction.... valves

A flat, circular, plate-like structure containing cartilage that lines the joints between adjacent vertebrae (bones) in the spine. Each intervertebral disc is composed of a fibrous outer layer and a soft gelatinous core. It acts as a shock absorber to cushion the vertebrae during movements of the spine. With increasing age, intervertebral discs become less supple and more susceptible to damage from injury.

Fibrous covering disclosing agents Dyes that make the plaque deposits on teeth more visible so that they can be seen and removed. discoid lupus erythematosus A form of the chronic autoimmune disorder lupus erythematosus.... disc, intervertebral

See disc prolapse.... disc, slipped

See mitral valve prolapse.... floppy valve syndrome

See disc prolapse.... herniated disc

A common, slight deformity of the mitral valve, in the left side of the heart, that can produce a degree of mitral incompetence. The prolapse is most common in women and causes a heart murmur. It may be inherited, but the cause is often unknown.Usually, there are no symptoms, and treatment is not needed. Occasionally, the condition may produce chest pain, arrhythmia, or, rarely, heart failure. Often, no treatment is required for mitral valve prolapse, but some people may be treated with beta-blocker drugs, diuretic drugs, antiarrhythmic drugs, or, rarely, heart-valve surgery.... mitral valve prolapse

A surgical operation to replace a defective or diseased heart valve. (See also heart-valve surgery.)... valve replacement

A common disorder of the spine, in which an intervertebral disc ruptures and part of its pulpy core protrudes. It causes painful and at times disabling pressure on a nerve root or, less commonly, on the spinal cord. The lower back is most commonly affected. A prolapsed disc may sometimes be caused by a sudden strenuous action, but it usually develops gradually as a result of degeneration of the discs with age. If the sciatic nerve root is compressed, it causes sciatica, which may be accompanied by numbness and tingling, and, eventually, weakness in the muscles of the leg. A prolapsed disc in the neck causes neck pain and weakness in the arm and hand.

Symptoms improve with time and analgesic drugs. However, in severe cases, surgical techniques, such as decompression of the spinal canal or removal of the protruding material and repair of the disc, may be necessary.... disc prolapse

A structure at the exit of a heart chamber that allows blood to flow out of the chamber, but prevents backwash. There are 4 heart valves: aortic, pulmonary, mitral, and tricuspid. Their opening and closing during each heart cycle produces heart sounds.

Any of the 4 heart valves may be affected by stenosis (narrowing), which causes the heart to work harder to force blood through the valve, or by incompetence or insufficiency (leakiness), which makes the valve unable to prevent backwash of blood. These defects cause characteristic heart murmurs.

Heart-valve defects may be present at birth (see heart disease, congenital), or they may be acquired later in life. The most common congenital valve defects are aortic stenosis and pulmonary stenosis. Acquired heart-valve disease is usually the result of degenerative changes or ischaemia affecting part of the heart and leading to aortic stenosis or mitral incompetence. Rheumatic fever can cause mitral stenosis, mitral incompetence, aortic valve defects, tricuspid stenosis and tricuspid incompetence. The heart valves may also be damaged by bacterial endocarditis.

Heart-valve disorders commonly lead to heart failure, arrhythmias, or symptoms resulting from reduced blood supply to body tissues.

Heart-valve defects may be diagnosed by auscultation, chest X-ray, ECG, or echocardiography and may be corrected by heart-valve surgery.... heart valve

An operation to correct a heart valve defect or to remove a diseased or damaged valve. A heart valve may have to be repaired, widened, or replaced because it is either incompetent (leaky) or stenotic (narrowed). Widening of a valve may involve valvotomy or valvuloplasty. A damaged valve can be replaced by a mechanical one (fashioned from metal and plastic), a valve constructed from human tissue, a pig valve, or a valve taken from a human donor after death. A heart–lung machine is used during replacement.After heart-valve surgery, symptoms such as breathlessness may take weeks to improve and require medication to be continued. Some people need longterm treatment with anticoagulant drugs to prevent the formation of blood clots around the new valve.... heart-valve surgery

a *shunt used in the treatment of *glaucoma to reduce and control intraocular pressure. The device works by bypassing the *trabecular meshwork and redirecting the outflow of aqueous humour through a small tube into an outlet chamber.... ahmed valve

a form of mechanical prosthesis commonly used in the past for replacing damaged heart valves. Currently, most mechanical valve replacements are of the tilting-disc variety.... ball-and-cage valve

see mitral valve.... bicuspid valve

an abnormal enlargement of the central depression of the *optic disc due to loss of nerve fibres, as occurs in glaucoma.... disc cupping

displacement of an intervertebral disc through a tear in the fibrous outer coat of the disc. See prolapsed intervertebral disc.... disc herniation

the early embryo before the formation of *somites. It is a flat disc of tissue bounded dorsally by the amniotic cavity and ventrally by the yolk sac. The formation of the *primitive streak and *archenteron in the embryonic disc determines the orientation of the embryo, which then becomes progressively elongated.... embryonic disc

a valve at the junction of the small and large intestines consisting of two membranous folds that close to prevent the backflow of food from the colon and caecum to the ileum.... ileocaecal valve

a valve in the heart lying between the right ventricle and the pulmonary artery. It is a *semilunar valve that prevents blood returning to the ventricle from the pulmonary artery.... pulmonary valve

either of the two valves in the heart situated at the origin of the aorta (see aortic valve) and the pulmonary artery (see pulmonary valve). Each consists of three flaps (cusps), which maintain the flow of blood in one direction.... semilunar valve

a one-way valve used to drain cerebrospinal fluid in order to control *hydrocephalus. The device is inserted into the ventricles of the brain and passes via a subcutaneous tunnel to drain into either the right atrium or the peritoneum.... spitz–holter valve

(TAVI) replacement of the aortic valve in patients with *aortic stenosis using a catheter-delivered prosthesis rather than open heart surgery. Usually the catheter is passed via the femoral artery, but sometimes it can be passed via the subclavian artery or through the wall of the left ventricle via a localized *thoracotomy.... transcatheter aortic valve implantation