A graph in which each dot represents paired values for two continuous variables, with the X axis representing one variable and the Y axis representing the other; used to display the relationship between two variables; also called a scattergram.
Structure Each suprarenal gland has an enveloping layer of ?brous tissue. Within this, the gland shows two distinct parts: an outer, ?rm, deep-yellow cortical (see CORTEX) layer, and a central, soft, dark-brown medullary (see MEDULLA) portion. The cortical part consists of columns of cells running from the surface inwards, whilst in the medullary portion the cells are arranged irregularly and separated from one another by large capillary blood vessels.
Functions Removal of the suprarenal glands in animals is speedily followed by great muscular prostration and death within a few days. In human beings, disease of the suprarenal glands usually causes ADDISON’S DISEASE, in which the chief symptoms are increasing weakness and bronzing of the skin. The medulla of the glands produces a substance – ADRENALINE – the effects of which closely resemble those brought about by activity of the SYMPATHETIC NERVOUS SYSTEM: dilated pupils, hair standing on end, quickening and strengthening of the heartbeat, immobilisation of the gut, increased output of sugar from the liver into the bloodstream. Several hormones (called CORTICOSTEROIDS) are produced in the cortex of the gland and play a vital role in the metabolism of the body. Some (such as aldosterone) control the electrolyte balance of the body and help to maintain the blood pressure and blood volume. Others are concerned in carbohydrate metabolism, whilst others again are concerned with sex physiology. HYDROCORTISONE is the most important hormone of the adrenal cortex, controlling as it does the body’s use of carbohydrates, fats and proteins. It also helps to suppress in?ammatory reactions and has an in?uence on the immune system.... adrenal glands
Types Inguinal hernia appears in the groin; less common is femoral hernia, which appears just below the groin. Incisional hernia may occur through a defect in any abdominal surgical scar, a paraumbilical hernia arising just to the side of the umbilicus and an epigastric hernia in the mid line above the umbilicus. In children, herniation may occur through the umbilicus itself, which is a natural weak spot. The commonest internal hernia is a hiatus hernia, when part of the stomach slips upwards into the chest through the DIAPHRAGM (see diagram).
Site of inguinal hernia (shaded).
Causes Hernias may be due to a defect present at birth (congenital), or may develop later in life (acquired). Acquired hernias arise due to the development of a defect or injury of the abdominal wall or due to increased pressure within the abdominal cavity, which forces the organ through a potential weakness. Such causes include chronic coughing or excessive straining due to constipation.
Complications Small hernias may cause no problems at all. However, some may be large and cumbersome, or may give rise to a dragging sensation or even pain.
Although most reduce spontaneously under the effects of gravity or gentle pressure, any organs that may have been displaced inside some hernias may become stuck, when they are said to be irreducible. If the contents become so trapped that their blood supply is cut o?, then strangulation occurs. This is a surgical emergency because the strangulated organs will soon die or rupture. When strangulation – usually of a loop of intestine – does occur, the hernia becomes irreducible, red, and very painful. If the hernia contains bowel, then the bowel may also become obstructed.
Treatment Conservative treatment with a compression belt, or truss, is now used only for those un?t for surgery or while awaiting surgery. Surgical repair can be at an open operation or by laparoscope, and consists of returning the herniated organs to their proper place and then repairing the defect through which the hernia occurred. This may be done safely under local or general anaesthetic, often as a day-case procedure, and most operative repairs result in a permanent cure.... hernia
K
Diagram of glomerulus (Malpighian corpuscle).
Fortunately the body has two kidneys and, as most people can survive on one, there is a good ‘functional reserve’ of kidney tissue.
Symptoms Many patients with kidney disorders do not have any symptoms, even when the condition is quite advanced. However,
others experience loin pain associated with obstruction (renal colic) or due to infection; fevers; swelling (oedema), usually of the legs but occasionally including the face and arms; blood in the urine (haematuria); and excess quantities of urine (polyuria), including at night (nocturia), due to failure of normal mechanisms in the kidney for concentrating urine. Patients with chronic renal failure often have very di?use symptoms including nausea and vomiting, tiredness due to ANAEMIA, shortness of breath, skin irritation, pins and needles (paraesthesia) due to damage of the peripheral nerves (peripheral neuropathy), and eventually (rarely seen nowadays) clouding of consciousness and death.
Signs of kidney disease include loin tenderness, enlarged kidneys, signs of ?uid retention, high blood pressure and, in patients with end-stage renal failure, pallor, pigmentation and a variety of neurological signs including absent re?exes, reduced sensation, and a coarse ?apping tremor (asterixis) due to severe disturbance of the body’s normal metabolism.
Renal failure Serious kidney disease may lead to impairment or failure of the kidney’s ability to ?lter waste products from the blood and excrete them in the urine – a process that controls the body’s water and salt balance and helps to maintain a stable blood pressure. Failure of this process causes URAEMIA – an increase in urea and other metabolic waste products – as well as other metabolic upsets in the blood and tissues, all of which produce varying symptoms. Failure can be sudden or develop more slowly (chronic). In the former, function usually returns to normal once the underlying cause has been treated. Chronic failure, however, usually irreparably reduces or stops normal function.
Acute failure commonly results from physiological shock following a bad injury or major illness. Serious bleeding or burns can reduce blood volume and pressure to the point where blood-supply to the kidney is greatly reduced. Acute myocardial infarction (see HEART, DISEASES OF) or pancreatitis (see PANCREAS, DISORDERS OF) may produce a similar result. A mismatched blood transfusion can produce acute failure. Obstruction to the urine-?ow by a stone (calculus) in the urinary tract, a bladder tumour or an enlarged prostate can also cause acute renal failure, as can glomerulonephritis (see below) and the haemolytic-uraemia syndrome.
HYPERTENSION, DIABETES MELLITUS, polycystic kidney disease (see below) or AMYLOIDOSIS are among conditions that cause chronic renal failure. Others include stone, tumour, prostatic enlargement and overuse of analgesic drugs. Chronic failure may eventually lead to end-stage renal failure, a life-threatening situation that will need DIALYSIS or a renal transplant (see TRANSPLANTATION).
Familial renal disorders include autosomal dominant inherited polycystic kidney disease and sex-linked familial nephropathy. Polycystic kidney disease is an important cause of renal failure in the UK. Patients, usually aged 30–50, present with HAEMATURIA, loin or abdominal discomfort or, rarely, urinary-tract infection, hypertension and enlarged kidneys. Diagnosis is based on ultrasound examination of the abdomen. Complications include renal failure, hepatic cysts and, rarely, SUBARACHNOID HAEMORRHAGE. No speci?c treatment is available. Familial nephropathy occurs more often in boys than in girls and commonly presents as Alport’s syndrome (familial nephritis with nerve DEAFNESS) with PROTEINURIA, haematuria, progressing to renal failure and deafness. The cause of the disease lies in an absence of a speci?c ANTIGEN in a part of the glomerulus. The treatment is conservative, with most patients eventually requiring dialysis or transplantation.
Acute glomerulonephritis is an immune-complex disorder due to entrapment within glomerular capillaries of ANTIGEN (usually derived from B haemolytic streptococci – see STREPTOCOCCUS) antibody complexes initiating an acute in?ammatory response (see IMMUNITY). The disease affects children and young adults, and classically presents with a sore throat followed two weeks later by a fall in urine output (oliguria), haematuria, hypertension and mildly abnormal renal function. The disease is self-limiting with 90 per cent of patients spontaneously recovering. Treatment consists of control of blood pressure, reduced ?uid and salt intake, and occasional DIURETICS and ANTIBIOTICS.
Chronic glomerulonephritis is also due to immunological renal problems and is also classi?ed by taking a renal biopsy. It may be subdivided into various histological varieties as determined by renal biospy. Proteinuria of various degrees is present in all these conditions but the clinical presentations vary, as do their treatments. Some resolve spontaneously; others are treated with steroids or even the cytotoxic drug CYCLOPHOSPHAMIDE or the immunosuppressant cyclosporin. Prognoses are generally satisfactory but some patients may require renal dialysis or kidney transplantation – an operation with a good success rate.
Hydronephrosis A chronic disease in which the kidney becomes greatly distended with ?uid. It is caused by obstruction to the ?ow of urine at the pelvi-ureteric junction (see KIDNEYS – Structure). If the ureter is obstructed, the ureter proximal to the obstruction will dilate and pressure will be transmitted back to the kidney to cause hydronephrosis. Obstruction may occur at the bladder neck or in the urethra itself. Enlargement of the prostate is a common cause of bladder-neck obstruction; this would give rise to hypertrophy of the bladder muscle and both dilatation of the ureter and hydronephrosis. If the obstruction is not relieved, progressive destruction of renal tissue will occur. As a result of the stagnation of the urine, infection is probable and CYSTITIS and PYELONEPHRITIS may occur.
Impaired blood supply may be the outcome of diabetes mellitus and physiological shock, which lowers the blood pressure, also affecting the blood supply. The result can be acute tubular necrosis. POLYARTERITIS NODOSA and SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) may damage the large blood vessels in the kidney. Treatment is of the underlying condition.
Infection of the kidney is called pyelonephritis, a key predisposing factor being obstruction of urine ?ow through the urinary tract. This causes stagnation and provides a fertile ground for bacterial growth. Acute pyelonephritis is more common in women, especially during pregnancy when bladder infection (CYSTITIS) spreads up the ureters to the kidney. Symptoms are fever, malaise and backache. Antibiotics and high ?uid intake are the most e?ective treatment. Chronic pyelonephritis may start in childhood as a result of congenital deformities that permit urine to ?ow up from the bladder to the kidney (re?ux). Persistent re?ux leads to recurrent infections causing permanent damage to the kidney. Specialist investigations are usually required as possible complications include hypertension and kidney failure.
Tumours of the kidney are fortunately rare. Non-malignant ones commonly do not cause symptoms, and even malignant tumours (renal cell carcinoma) may be asymptomatic for many years. As soon as symptoms appear – haematuria, back pain, nausea, malaise, sometimes secondary growths in the lungs, bones or liver, and weight loss – urgent treatment including surgery, radiotherapy and chemotherapy is necessary. This cancer occurs mostly in adults over 40 and has a hereditary element. The prognosis is not good unless diagnosed early. In young children a rare cancer called nephroblastoma (Wilm’s tumour) can occur; treatment is with surgery, radiotherapy and chemotherapy. It may grow to a substantial size before being diagnosed.
Cystinuria is an inherited metabolic defect in the renal tubular reabsorption of cystine, ornithine, lysine and arginine. Cystine precipitates in an alkaline urine to form cystine stones. Triple phosphate stones are associated with infection and may develop into a very large branching calculi (staghorn calculi). Stones present as renal or ureteric pain, or as an infection. Treatment has undergone considerable change with the introduction of MINIMALLY INVASIVE SURGERY (MIS) and the destruction of stone by sound waves (LITHOTRIPSY).... kidneys, diseases of
Astigmatism (See ASTIGMATISM.)
Blepharitis A chronic in?ammation of the lid margins. SEBORRHOEA and staphylococcal infection are likely contributors. The eyes are typically intermittently red, sore and gritty over months or years. Treatment is di?cult and may fail. Measures to reduce debris on the lid margins, intermittent courses of topical antibiotics, steroids or systemic antibiotics may help the sufferer.
Blepharospasm Involuntary closure of the eye. This may accompany irritation but may also occur without an apparent cause. It may be severe enough to interfere with vision. Treatment involves removing the source of irritation, if present. Severe and persistent cases may respond to injection of Botulinum toxin into the orbicularis muscle.
Cataract A term used to describe any opacity in the lens of the eye, from the smallest spot to total opaqueness. The prevalence of cataracts is age-related: 65 per cent of individuals in their sixth decade have some degree of lens opacity, while all those over 80 are affected. Cataracts are the most important cause of blindness worldwide. Symptoms will depend on whether one or both eyes are affected, as well as the position and density of the cataract(s). If only one eye is developing a cataract, it may be some time before the person notices it, though reading may be affected. Some people with cataracts become shortsighted, which in older people may paradoxically ‘improve’ their ability to read. Bright light may worsen vision in those with cataracts.
The extent of visual impairment depends on the nature of the cataracts, and the ?rst symptoms noticed by patients include di?culty in recognising faces and in reading, while problems watching television or driving, especially at night, are pointers to the condition. Cataracts are common but are not the only cause of deteriorating vision. Patients with cataracts should be able to point to the position of a light and their pupillary reactions should be normal. If a bright light is shone on the eye, the lens may appear brown or, in advanced cataracts, white (see diagram).
While increasing age is the commonest cause of cataract in the UK, patients with DIABETES MELLITUS, UVEITIS and a history of injury to the eye can also develop the disorder. Prolonged STEROID treatment can result in cataracts. Children may develop cataracts, and in them the condition is much more serious as vision may be irreversibly impaired because development of the brain’s ability to interpret visual signals is hindered. This may happen even if the cataracts are removed, so early referral for treatment is essential. One of the physical signs which doctors look for when they suspect cataract in adults as well as in children is the ‘red re?ex’. This is observable when an ophthalmoscopic examination of the eye is made (see OPHTHALMOSCOPE). Identi?cation of this red re?ex (a re?ection of light from the red surface of the retina –see EYE) is a key diagnostic sign in children, especially young ones.
There is no e?ective medical treatment for established cataracts. Surgery is necessary and the decision when to operate depends mainly on how the cataract(s) affect(s) the patient’s vision. Nowadays, surgery can be done at any time with limited risk. Most patients with a vision of 6/18 – 6/10 is the minimum standard for driving – or worse in both eyes should
E
bene?t from surgery, though elderly people may tolerate visual acuity of 6/18 or worse, so surgery must be tailored to the individual’s needs. Younger people with a cataract will have more demanding visual requirements and so may opt for an ‘earlier’ operation. Most cataract surgery in Britain is now done under local anaesthetic and uses the ‘phaco-emulsi?cation’ method. A small hole is made in the anterior capsule of the lens after which the hard lens nucleus is liqui?ed ultrasonically. A replacement lens is inserted into the empty lens bag (see diagram). Patients usually return to their normal activities within a few days of the operation. A recent development under test in the USA for children requiring cataract operations is an intra-ocular ?exible implant whose magnifying power can be altered as a child develops, thus precluding the need for a series of corrective operations as happens now.
Chalazion A ?rm lump in the eyelid relating to a blocked meibomian gland, felt deep within the lid. Treatment is not always necessary; a proportion spontaneously resolve. There can be associated infection when the lid becomes red and painful requiring antibiotic treatment. If troublesome, the chalazion can be incised under local anaesthetic.
Conjunctivitis In?ammation of the conjunctiva (see EYE) which may affect one or both eyes. Typically the eye is red, itchy, sticky and gritty but is not usually painful. Redness is not always present. Conjunctivitis can occasionally be painful, particularly if there is an associated keratitis (see below) – for example, adenovirus infection, herpetic infection.
The cause can be infective (bacteria, viruses or CHLAMYDIA), chemical (e.g. acids, alkalis) or allergic (e.g. in hay fever). Conjunctivitis may also be caused by contact lenses, and preservatives or even the drugs in eye drops may cause conjunctival in?ammation. Conjunctivitis may addtionally occur in association with other illnesses – for example, upper-respiratory-tract infection, Stevens-Johnson syndrome (see ERYTHEMA – erythema multiforme) or REITER’S SYNDROME. The treatment depends on the cause. In many patients acute conjunctivitis is self-limiting.
Dacryocystitis In?ammation of the lacrimal sac. This may present acutely as a red, painful swelling between the nose and the lower lid. An abscess may form which points through the skin and which may need to be drained by incision. Systemic antibiotics may be necessary. Chronic dacryocystitis may occur with recurrent discharge from the openings of the tear ducts and recurrent swelling of the lacrimal sac. Obstruction of the tear duct is accompanied by watering of the eye. If the symptoms are troublesome, the patient’s tear passageways need to be surgically reconstructed.
Ectropion The lid margin is everted – usually the lower lid. Ectropion is most commonly associated with ageing, when the tissues of the lid become lax. It can also be caused by shortening of the skin of the lids such as happens with scarring or mechanical factors – for example, a tumour pulling the skin of the lower lid downwards. Ectropion tends to cause watering and an unsightly appearance. The treatment is surgical.
Entropion The lid margin is inverted – usually the lower lid. Entropion is most commonly associated with ageing, when the tissues of the lid become lax. It can also be caused by shortening of the inner surfaces of the lids due to scarring – for example, TRACHOMA or chemical burns. The inwardly directed lashes cause irritation and can abrade the cornea. The treatment is surgical.
Episcleritis In?ammation of the EPISCLERA. There is usually no apparent cause. The in?ammation may be di?use or localised and may affect one or both eyes. It sometimes recurs. The affected area is usually red and moderately painful. Episcleritis is generally not thought to be as painful as scleritis and does not lead to the same complications. Treatment is generally directed at improving the patient’s symptoms. The in?ammation may respond to NON-STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) or topical CORTICOSTEROIDS.
Errors of refraction (Ametropia.) These will occur when the focusing power of the lens and cornea does not match the length of the eye, so that rays of light parallel to the visual axis are not focused at the fovea centralis (see EYE). There are three types of refractive error: HYPERMETROPIA or long-sightedness. The refractive power of the eye is too weak, or the eye is too short so that rays of light are brought to a focus at a point behind the retina. Longsighted people can see well in the distance but generally require glasses with convex lenses for reading. Uncorrected long sight can lead to headaches and intermittent blurring of vision following prolonged close work (i.e. eye strain). As a result of ageing, the eye becomes gradually long-sighted, resulting in many people needing reading glasses in later life: this normal process is known as presbyopia. A particular form of long-sightedness occurs after cataract extraction (see above). MYOPIA(Short sight or near sight.) Rays of light are brought to a focus in front of the retina because the refractive power of the eye is too great or the eye is too short. Short-sighted people can see close to but need spectacles with concave lenses in order to see in the distance. ASTIGMATISMThe refractive power of the eye is not the same in each meridian. Some rays of light may be focused in front of the retina while others are focused on or behind the retina. Astigmatism can accompany hypermetropia or myopia. It may be corrected by cylindrical lenses: these consist of a slice from the side of a cylinder (i.e. curved in one meridian and ?at in the meridian at right-angles to it).
Keratitis In?ammation of the cornea in response to a variety of insults – viral, bacterial, chemical, radiation, or mechanical trauma. Keratitis may be super?cial or involve the deeper layers, the latter being generally more serious. The eye is usually red, painful and photophobic. Treatment is directed at the cause.
Nystagmus Involuntary rhythmic oscillation of one or both eyes. There are several causes including nervous disorders, vestibular disorders, eye disorders and certain drugs including alcohol.
Ophthalmia In?ammation of the eye, especially the conjunctiva (see conjunctivitis, above). Ophthalmia neonatorum is a type of conjunctivitis that occurs in newborn babies. They catch the disease when passing through an infected birth canal during their mother’s labour (see PREGNANCY AND LABOUR). CHLAMYDIA and GONORRHOEA are the two most common infections. Treatment is e?ective with antibiotics: untreated, the infection may cause permanent eye damage.
Pinguecula A benign degenerative change in the connective tissue at the nasal or temporal limbus (see EYE). This is visible as a small, ?attened, yellow-white lump adjacent to the cornea.
Pterygium Overgrowth of the conjunctival tissues at the limbus on to the cornea (see EYE). This usually occurs on the nasal side and is associated with exposure to sunlight. The pterygium is surgically removed for cosmetic reasons or if it is thought to be advancing towards the visual axis.
Ptosis Drooping of the upper lid. May occur because of a defect in the muscles which raise the lid (levator complex), sometimes the result of ageing or trauma. Other causes include HORNER’S SYNDROME, third cranial nerve PALSY, MYASTHENIA GRAVIS, and DYSTROPHIA MYOTONICA. The cause needs to be determined and treated if possible. The treatment for a severely drooping lid is surgical, but other measures can be used to prop up the lid with varying success.
Retina, disorders of The retina can be damaged by disease that affects the retina alone, or by diseases affecting the whole body.
Retinopathy is a term used to denote an abnormality of the retina without specifying a cause. Some retinal disorders are discussed below. DIABETIC RETINOPATHY Retinal disease occurring in patients with DIABETES MELLITUS. It is the commonest cause of blind registration in Great Britain of people between the ages of 20 and 65. Diabetic retinopathy can be divided into several types. The two main causes of blindness are those that follow: ?rst, development of new blood vessels from the retina, with resultant complications and, second, those following ‘water logging’ (oedema) of the macula. Treatment is by maintaining rigid control of blood-sugar levels combined with laser treatment for certain forms of the disease – in particular to get rid of new blood vessels. HYPERTENSIVE RETINOPATHY Retinal disease secondary to the development of high blood pressure. Treatment involves control of the blood pressure (see HYPERTENSION). SICKLE CELL RETINOPATHY People with sickle cell disease (see under ANAEYIA) can develop a number of retinal problems including new blood vessels from the retina. RETINOPATHY OF PREMATURITY (ROP) Previously called retrolental ?broplasia (RLF), this is a disorder affecting low-birth-weight premature babies exposed to oxygen. Essentially, new blood vessels develop which cause extensive traction on the retina with resultant retinal detachment and poor vision. RETINAL ARTERY OCCLUSION; RETINAL VEIN OCCLUSION These result in damage to those areas of retina supplied by the affected blood vessel: the blood vessels become blocked. If the peripheral retina is damaged the patient may be completely symptom-free, although areas of blindness may be detected on examination of ?eld of vision. If the macula is involved, visual loss may be sudden, profound and permanent. There is no e?ective treatment once visual loss has occurred. SENILE MACULAR DEGENERATION (‘Senile’ indicates age of onset and has no bearing on mental state.) This is the leading cause of blindness in the elderly in the western world. The average age of onset is 65 years. Patients initially notice a disturbance of their vision which gradually progresses over months or years. They lose the ability to recognise ?ne detail; for example, they cannot read ?ne print, sew, or recognise people’s faces. They always retain the ability to recognise large objects such as doors and chairs, and are therefore able to get around and about reasonably well. There is no e?ective treatment in the majority of cases. RETINITIS PIGMENTOSAA group of rare, inherited diseases characterised by the development of night blindness and tunnel vision. Symptoms start in childhood and are progressive. Many patients retain good visual acuity, although their peripheral vision is limited. One of the characteristic ?ndings on examination is collections of pigment in the retina which have a characteristic shape and are therefore known as ‘bone spicules’. There is no e?ective treatment. RETINAL DETACHMENTusually occurs due to the development of a hole in the retina. Holes can occur as a result of degeneration of the retina, traction on the retina by the vitreous, or injury. Fluid from the vitreous passes through the hole causing a split within the retina; the inner part of the retina becomes detached from the outer part, the latter remaining in contact with the choroid. Detached retina loses its ability to detect light, with consequent impairment of vision. Retinal detachments are more common in the short-sighted, in the elderly or following cataract extraction. Symptoms include spots before the eyes (?oaters), ?ashing lights and a shadow over the eye with progressive loss of vision. Treatment by laser is very e?ective if caught early, at the stage when a hole has developed in the retina but before the retina has become detached. The edges of the hole can be ‘spot welded’ to the underlying choroid. Once a detachment has occurred, laser therapy cannot be used; the retina has to be repositioned. This is usually done by indenting the wall of the eye from the outside to meet the retina, then making the retina stick to the wall of the eye by inducing in?ammation in the wall (by freezing it). The outcome of surgery depends largely on the extent of the detachment and its duration. Complicated forms of detachment can occur due to diabetic eye disease, injury or tumour. Each requires a specialised form of treatment.
Scleritis In?ammation of the sclera (see EYE). This can be localised or di?use, can affect the anterior or the posterior sclera, and can affect one or both eyes. The affected eye is usually red and painful. Scleritis can lead to thinning and even perforation of the sclera, sometimes with little sign of in?ammation. Posterior scleritis in particular may cause impaired vision and require emergency treatment. There is often no apparent cause, but there are some associated conditions – for example, RHEUMATOID ARTHRITIS, GOUT, and an autoimmune disease affecting the nasal passages and lungs called Wegener’s granulomatosis. Treatment depends on severity but may involve NON-STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS), topical CORTICOSTEROIDS or systemic immunosuppressive drugs.
Stye Infection of a lash follicle. This presents as a painful small red lump at the lid margin. It often resolves spontaneously but may require antibiotic treatment if it persists or recurs.
Sub-conjunctival haemorrhage Haemorrhage between the conjunctiva and the underlying episclera. It is painless. There is usually no apparent cause and it resolves spontaneously.
Trichiasis Inward misdirection of the lashes. Trichiasis occurs due to in?ammation of or trauma to the lid margin. Treatment involves removal of the patient’s lashes. Regrowth may be prevented by electrolysis, by CRYOTHERAPY to the lid margin, or by surgery.
For the subject of arti?cial eyes, see under PROSTHESIS; also GLAUCOMA, SQUINT and UVEITIS.... eye, disorders of
The human backbone is about 70 cm (28
inches) in length, and varies little in full-grown people; di?erences in height depend mainly upon the length of the lower limbs. The number of vertebrae is 33 in children, although in adult life ?ve of these fuse together to form the sacrum, and the lowest four unite in the coccyx, so that the number of separate bones is reduced to 26. Of these there are seven in the neck, known as cervical vertebrae; 12 with ribs attached, in the region of the thorax known as thoracic or dorsal vertebrae; ?ve in the loins, called lumbar vertebrae; ?ve fused to form the sacrum; and four joined in the coccyx. These numbers are expressed in a formula thus: C7, D12, L5, S5, Coc4=33.
Although the vertebrae in each of these regions have distinguishing features, all the vertebrae are constructed on the same general plan. Each has a thick, rounded, bony part in front, known as the body, and these bodies form the main thickness of the column. Behind the body of each is a ring of bone, the neural ring, these rings placed one above another forming the bony canal which lodges the spinal cord. From each side of the ring a short process of bone known as the transverse process stands out, and from the back of the ring a larger process, the spinous process, projects. These processes give attachment to the strong ligaments and muscles which unite, support, and bend the column. The spines can be seen or felt beneath the skin of the back lying in the centre of a groove between the muscular masses of the two sides, and they give to the column its name of the spinal column. One of these spines, that of the seventh cervical vertebra, is especially large and forms a distinct bony prominence, where the neck joins the back. Between the bodies of the vertebrae lies a series of thick discs of ?brocartilage known as intervertebral discs. Each disc consists of an outer portion, known as the annulus ?brosus, and an inner core, known as the nucleus pulposus. These 23 discs provide the upper part of the spine with pliability and resilience.
The ?rst and second cervical vertebrae are specially modi?ed. The ?rst vertebra, known as the atlas, is devoid of a body, but has a specially large and strong ring with two hollows upon which the skull rests, thus allowing forward and backward movements (nodding). The second vertebra, known as the axis, has a pivot on its body which ?ts into the ?rst vertebra and thus allows free rotation of the head from side to side. The spinal column has four natural curves (see diagram) which help to cushion the shocks of walking and running.
The neural rings of the vertebrae form a canal, which is wide in the neck, smaller and almost round in the dorsal region, and wide again in the lumbar vertebrae. Down the canal runs the spinal cord, and the nerves leaving the cord do so through openings between the vertebrae which are produced by notches on the upper and lower margins of each ring. The intervertebral foramina formed by these notches are so large in comparison with the nerves passing through them that there is no chance of pressure upon the latter, except in very serious injuries which dislocate and fracture the spine.... spinal column
– an early graded return to activity gives the best long-term results, but doing too much too soon runs the risk of exacerbating the original injury.
Chronic (overuse) injuries affecting the bones (see BONE), tendons (see TENDON) or BURSAE of the JOINTS are common in many sports. Examples include chronic INFLAMMATION of the common extensor tendon where it
attaches to the later EPICONDYLE of the humerus – common in throwers and racquet sportspeople – and stress fractures of the TIBIA or METATARSAL BONES of the foot in runners. After an initial period of rest, management often involves coaching that enables the athlete to perform the repetitive movement in a less injury-susceptible manner.
Exercise physiology is the science of measuring athletic performance and physical ?tness for exercise. This knowledge is applied to devising and supervising training regimens based on scienti?c principles. Physical ?tness depends upon the rate at which the body can deliver oxygen to the muscles, known as the VO2max, which is technically di?cult to measure. The PULSE rate during and after a bout of exercise serves as a good proxy of this measurement.
Regulation of sport Sports medicine’s role is to minimise hazards for participants by, for example, framing rule-changes which forbid collapsing the scrum, which has reduced the risk of neck injury in rugby; and in the detection of the use of drugs taken to enhance athletic performance. Such attempts to gain an edge in competition undermine the sporting ideal and are banned by leading sports regulatory bodies. The Olympic Movement Anti-Doping Code lists prohibited substances and methods that could be used to enhance performance. These include some prohibited in certain circumstances as well as those completely banned. The latter include:
stimulants such as AMPHETAMINES, bromantan, ca?eine, carphedon, COCAINE, EPHEDRINE and certain beta-2 agonists.
NARCOTICS such as DIAMORPHINE (heroin), MORPHINE, METHADONE HYDROCHLORIDE and PETHIDINE HYDROCHLORIDE.
ANABOLIC STEROIDS such as methandione, NANDROLONE, stanazol, TESTOSTERONE, clenbuterol, androstenedone and certain beta-2 agonists.
peptide HORMONES, mimetics and analogues such as GROWTH HORMONE, CORTICOTROPHIN, CHORIONIC GONADOTROPHIC HORMONE, pituitary and synthetic GONADOTROPHINS, ERYTHROPOIETIN and INSULIN. (The list produced above is not comprehen
sive: full details are available from the governing bodies of relevant sports.) Among banned methods are blood doping (pre-competition administration of an athlete’s own previously provided and stored blood), administration of arti?cial oxygen carriers or plasma expanders. Also forbidden is any pharmacological, chemical or physical manipulation to affect the results of authorised testing.
Drug use can be detected by analysis of the URINE, but testing only at the time of competition is unlikely to detect drug use designed to enhance early-season training; hence random testing of competitive athletes is also used.
The increasing professionalism and competitiveness (among amateurs and juveniles as well as professionals) in sports sometimes results in pressures on participants to get ?t quickly after injury or illness. This can lead to
players returning to their activity before they are properly ?t – sometimes by using physical or pharmaceutical aids. This practice can adversely affect their long-term physical capabilities and perhaps their general health.... sports medicine
A distinction may be made between clinical audit, which refers to total care (involving doctors, nurses, paramedical staff, etc.), and medical audit, which refers to medical care specifically performed by doctors, although in practice the two terms are often used interchangeably.... clinical audit
Adult kidneys have a smooth exterior, enveloped by a tough ?brous coat that is bound to the kidney only by loose ?brous tissue and by a few blood vessels that pass between it and the kidney. The outer margin of the kidney is convex; the inner is concave with a deep depression, known as the hilum, where the vessels enter. The URETER, which conveys URINE to the URINARY BLADDER, is also joined at this point. The ureter is spread out into an expanded, funnel-like end, known as the pelvis, which further divides up into little funnels known as the calyces. A vertical section through a kidney (see diagram) shows two distinct layers: an outer one, about 4 mm thick, known as the cortex; and an inner one, the medulla, lying closer to the hilum. The medulla consists of around a dozen pyramids arranged side by side, with their base on the cortex and their apex projecting into the calyces of the ureter. The apex of each pyramid is studded with tiny holes, which are the openings of the microscopic uriniferous tubes.
In e?ect, each pyramid, taken together with the portion of cortex lying along its base, is an independent mini-kidney. About 20 small tubes are on the surface of each pyramid; these, if traced up into its substance, repeatedly subdivide so as to form bundles of convoluted tubules, known as medullary rays, passing up towards the cortex. One of these may be traced further back, ending, after a tortuous course, in a small rounded body: the Malpighian corpuscle or glomerulus (see diagram). Each glomerulus and its convoluted tubule is known as a nephron, which constitutes the functional unit of the kidney. Each kidney contains around a million nephrons.
After entering the kidney, the renal artery divides into branches, forming arches where the cortex and medulla join. Small vessels come o? these arches and run up through the cortex, giving o? small branches in each direction. These end in a tuft of capillaries, enclosed in Bowman’s capsule, which forms the end of the uriniferous tubules just described; capillaries with capsule constitute a glomerulus.
After circulating in the glomerulus, the blood leaves by a small vein, which again divides into capillaries on the walls of the uriniferous tubules. From these it is ?nally collected into the renal veins and then leaves the kidney. This double circulation (?rst through the glomerulus and then around the tubule) allows a large volume of ?uid to be removed from the blood in the glomerulus, the concentrated blood passing on to the uriniferous tubule for removal of parts of its solid contents. Other arteries come straight from the arches and supply the medulla direct; the blood from these passes through another set of capillaries and ?nally into the renal veins. This circulation is con?ned purely to the kidney, although small connections by both arteries and veins exist which pass through the capsule and, joining the lumbar vessels, communicate directly with the aorta.
Function The kidneys work to separate ?uid and certain solids from the blood. The glomeruli ?lter from the blood the non-protein portion of the plasma – around 150–200 litres in 24 hours, 99 per cent of which is reabsorbed on passing through the convoluted tubules.
Three main groups of substances are classi?ed according to their extent of uptake by the tubules:
(1) SUBSTANCES ACTIVELY REABSORBED These include amino acids, glucose, sodium, potassium, calcium, magnesium and chlorine (for more information, see under separate entries).
(2) SUBSTANCES DIFFUSING THROUGH THE TUBULAR EPITHELIUM when their concentration in the ?ltrate exceeds that in the PLASMA, such as UREA, URIC ACID and phosphates.
(3) SUBSTANCES NOT RETURNED TO THE BLOOD from the tubular ?uid, such as CREATINE, accumulate in kidney failure, resulting in general ‘poisoning’ known as URAEMIA.... structure each kidney is about 10 cm long,
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