Alveolar osteotis Health Dictionary

Formerly known as adult respiratory distress syndrome. A form of acute respiratory failure in which a variety of di?erent disorders give rise to lung injury by what is thought to be a common pathway. The condition has a high mortality rate (about 70 per cent); it is a complex clinical problem in which a disproportionate immunological response plays a major role. (See IMMUNITY.)

The exact trigger is unknown, but it is thought that, whatever the stimulus, chemical mediators produced by cells of the immune system or elsewhere in the body spread and sustain an in?ammatory reaction. Cascade mechanisms with multiple interactions are provoked. CYTOTOXIC substances (which damage or kill cells) such as oxygen-free radicals and PROTEASE damage the alveolar capillary membranes (see ALVEOLUS). Once this happens, protein-rich ?uid leaks into the alveoli and interstitial spaces. SURFACTANT is also lost. This impairs the exchange of oxygen and carbon dioxide in the lungs and gives rise to the clinical and pathological picture of acute respiratory failure.

The typical patient with ARDS has rapidly worsening hypoxaemia (lack of oxygen in the blood), often requiring mechanical ventilation. There are all the signs of respiratory failure (see TACHYPNOEA; TACHYCARDIA; CYANOSIS), although the chest may be clear apart from a few crackles. Radiographs show bilateral, patchy, peripheral shadowing. Blood gases will show a low PaO2 (concentration of oxygen in arterial blood) and usually a high PaCO2 (concentration of carbon dioxide in arterial blood). The lungs are ‘sti?’ – they are less e?ective because of the loss of surfactant and the PULMONARY OEDEMA.

Causes The causes of ARDS may be broadly divided into the following:... acute respiratory distress syndrome (ards)

A pulmonary condition with loss of elasticity in the alveoli and the interalveolar septa...the meat-foam and their interleaving sheaths that you fill up when you breathe. If a septum gets too stretched over time, several of the little sacs will coalesce together, decreasing the surface area for oxygen and carbon dioxide exchange. If enough of these sacs lose their separateness, like small soap bubbles joining to make a few larger ones, breathing gets harder because each breath accomplishes less interchange of gases, resulting in emphysema Caused by years of bad asthma, tobacco smoking, chemical damage, and other chronic lung disorders, it can be halted but not reversed. The first breath you take as a newborn defines forever the number of the alveolar bubbles...they cannot be regenerated if they coalesce together.... emphysema

Positioned in the chest, the lungs serve primarily as respiratory organs (see RESPIRATION), also acting as a ?lter for the blood.

Form and position Each lung is a sponge-like cone, pink in children and grey in adults. Its apex projects into the neck, with the base resting on the DIAPHRAGM. Each lung is enveloped by a closed cavity, the pleural cavity, consisting of two layers of pleural membrane separated by a thin layer of ?uid. In healthy states this allows expansion and retraction as breathing occurs.

Heart/lung connections The HEART lies in contact with the two lungs, so that changes in lung volume inevitably affect the pumping action of the heart. Furthermore, both lungs are connected by blood vessels to the heart. The pulmonary artery passes from the right ventricle and divides into two branches, one of which runs straight outwards to each lung, entering its substance along with the bronchial tube at the hilum or root of the lung. From this point also emerge the pulmonary veins, which carry the blood oxygenated in the lungs back to the left atrium.

Fine structure of lungs Each main bronchial tube, entering the lung at the root, divides into branches. These subdivide again and again, to be distributed all through the substance of the lung until the ?nest tubes, known as respiratory bronchioles, have a width of only 0·25 mm (1/100 inch). All these tubes consist of a mucous membrane surrounded by a ?brous sheath. The surface of the mucous membrane comprises columnar cells provided with cilia (hair-like structures) which sweep mucus and unwanted matter such as bacteria to the exterior.

The smallest divisions of the bronchial tubes, or bronchioles, divide into a number of tortuous tubes known as alveolar ducts terminating eventually in minute sacs, known as alveoli, of which there are around 300 million.

The branches of the pulmonary artery accompany the bronchial tubes to the furthest recesses of the lung, dividing like the latter into ?ner and ?ner branches, and ending in a dense network of capillaries. The air in the air-vesicles is separated therefore from the blood only by two delicate membranes: the wall of the air-vesicle, and the capillary wall, through which exchange of gases (oxygen and carbon dioxide) readily takes place. The essential oxygenated blood from the capillaries is collected by the pulmonary veins, which also accompany the bronchi to the root of the lung.

The lungs also contain an important system of lymph vessels, which start in spaces situated between the air-vesicles and eventually leave the lung along with the blood vessels, and are connected with a chain of bronchial glands lying near the end of the TRACHEA.... lungs

Broadly, any discharge of pus, but usually referring to periodontitis or Pyorrhea alveolaris, with inflammatory and degenerative conditions in the gums, jaw bone and cementum. There may be alveolar bone resorption, teeth loss and receding gums...and hefty dental and oral surgery bills. These costs may be valid, but there is some thought in some radical dental circles that there is overdiagnosis of the condition.... pyorrhea

Oil secreting glands, mostly clustered around hair follicles. The oil, sebum, is released into the oil glands from the disintegrated cytoplasm of shedding holocrine cells that line the alveolar surfaces. The nature of the secretion is a direct reflection of the state of the body’s lipid metabolism.... sebaceous gland

Hard organs developed from the mucous membranes of the mouth and embedded in the jawbones, used to bite and grind food and to aid clarity of speech.

Structure Each tooth is composed of enamel, dentine, cement, pulp and periodontal membrane. ENAMEL is the almost translucent material which covers the crown of a tooth. It is the most highly calci?ed material in the body, 96–97 per cent being composed of calci?ed salts. It is arranged from millions of long, six-sided prisms set on end on the dentine (see below), and is thickest over the biting surface of the tooth. With increasing age or the ingestion of abrasive foods the teeth may be worn away on the surface, so that the dentine becomes visible. The outer sides of some teeth may be worn away by bad tooth-brushing technique. DENTINE is a dense yellowish-white material from which the bulk and the basic shape of a tooth are formed. It is like ivory and is harder than bone but softer than enamel. The crown of the tooth is covered by the hard protective enamel and the root is covered by a bone-like substance called cement. Decay can erode dentine faster than enamel (see TEETH, DISORDERS OF – Caries of the teeth). CEMENT or cementum is a thin bone-like material which covers the roots of teeth and helps hold them in the bone. Fibres of the periodontal membrane (see below) are embedded in the cement and the bone. When the gums recede, part of the cement may be exposed and the cells die. Once this has happened, the periodontal membrane can no longer be attached to the tooth and, if su?cient cement is destroyed, the tooth-support will be so weakened that the tooth will become loose. PULP This is the inner core of the tooth and is

composed of a highly vascular, delicate ?brous tissue with many ?ne nerve-?bres. The pulp is very sensitive to temperature variation and to touch. If the pulp becomes exposed it will become infected and usually cannot overcome this. Root-canal treatment or extraction of the tooth may be necessary. PERIODONTAL MEMBRANE This is a layer of ?brous tissue arranged in groups of ?bres which surround and support the root of a tooth in a bone socket. The ?bres are interspersed with blood vessels and nerves. Loss of the membrane leads to loss of the tooth. The membrane can release and re-attach the ?bres to allow the tooth to move when it erupts, or (to correct dental deformities) is being moved by orthodontic springs.

Arrangement and form Teeth are present in most mammals and nearly all have two sets: a temporary or milk set, followed by a permanent or adult set. In some animals, like the toothed whale, all the teeth are similar; but in humans there are four di?erent shapes: incisors, canines (eye-teeth), premolars (bicuspids), and molars. The incisors are chisel-shaped and the canine is pointed. Premolars have two cusps on the crown (one medial to the other) and molars have at least four cusps. They are arranged together in an arch in each jaw and the

cusps of opposing teeth interdigitate. Some herbivores have no upper anterior teeth but use a pad of gum instead. As each arch is symmetrical, the teeth in an upper and lower quadrant can be used to identify the animal. In humans, the quadrants are the same: in other words, in the child there are two incisors, one canine and two molars (total teeth 20); in the adult there are two incisors, one canine, two premolars and three molars (total 32). This mixture of tooth-form suggests that humans are omnivorous. Anatomically the crown of the tooth has mesial and distal surfaces which touch the tooth next to it. The mesial surface is the one nearer to the centre line and the distal is the further away. The biting surface is called the incisal edge for the anterior teeth and the occlusal surface for the posteriors.

Development The ?rst stage in the formation of the teeth is the appearance of a down-growth of EPITHELIUM into the underlying mesoderm. This is the dental lamina, and from it ten smaller swellings in each jaw appear. These become bell-shaped and enclose a part of the mesoderm, the cells of which become specialised and are called the dental papillae. The epithelial cells produce enamel and the dental papilla forms the dentine, cement and pulp. At a ?xed time the teeth start to erupt and a root is formed. Before the deciduous teeth erupt, the permanent teeth form, medial to them. In due course the deciduous roots resorb and the permanent teeth are then able to push the crowns out and erupt themselves. If this process is disturbed, the permanent teeth may be displaced and appear in an abnormal position or be impacted.

Eruption of teeth is in a de?nite order and at a ?xed time, although there may be a few months’ leeway in either direction which is of no signi?cance. Excessive delay is found in some congenital disorders such as CRETINISM. It may also be associated with local abnormalities of the jaws such as cysts, malformed teeth and supernumerary teeth.

The usual order of eruption of deciduous teeth is:

Middle incisors 6–8 months Lateral incisors 8–10 months First molars 12–16 months Canines (eye-teeth) 16–20 months Second molars 20–30 months

The usual order of eruption of permanent teeth is:

First molars 6–7 years Middle incisors 6–8 years Lateral incisors 7–9 years Canines 9–12 years First and second premolars 10–12 years Second molars 11–13 years Third molars (wisdom teeth) 17–21 years

The permanent teeth of the upper (top) and lower (bottom) jaws.

Teeth, Disorders of

Teething, or the process of eruption of the teeth in infants, may be accompanied by irritability, salivation and loss of sleep. The child will tend to rub or touch the painful area. Relief may be obtained in the child by allowing it to chew on a hard object such as a toy or rusk. Mild ANALGESICS may be given if the child is restless and wakens in the night. A serious pitfall is to assume that an infant’s symptoms of ill-health are due to teething, as the cause may be more serious. Fever and ?ts (see SEIZURE) are not due to teething.

Toothache is the pain felt when there is in?ammation of the pulp or periodontal membrane of a tooth (see TEETH – Structure). It can vary in intensity and may be recurring. The commonest cause is caries (see below) when the cavity is close to the pulp. Once the pulp has become infected, this is likely to spread from the apex of the tooth into the bone to form an abscess (gumboil – see below). A lesser but more long-lasting pain is felt when the dentine is unprotected. This can occur when the enamel is lost due to decay or trauma or because the gums have receded. This pain is often associated with temperature-change or sweet foods. Expert dental advice should be sought early, before the decay is extensive. If a large cavity is accessible, temporary relief may be obtained by inserting a small piece of cotton wool soaked, for example, in oil of cloves.

Alveolar abscess, dental abscess or gumboil This is an ABSCESS caused by an infected tooth. It may be present as a large swelling or cause trismus (inability to open the mouth). Treatment is drainage of the PUS, extraction of the tooth and/or ANTIBIOTICS.

Caries of the teeth or dental decay is very common in the more a?uent countries and is most common in children and young adults. Increasing awareness of the causes has resulted in a considerable improvement in dental health, particularly in recent years; this has coincided with a rise in general health. Now more than half of ?ve-year-old children are caries-free and of the others, 10 per cent have half of the remaining carious cavities. Since the start of the National Health Service, the emphasis has been on preventive dentistry, and now edentulous patients are mainly found among the elderly who had their teeth removed before 1948.

The cause of caries is probably acid produced by oral bacteria from dietary carbohydrates, particularly re?ned sugar, and this dissolves part of the enamel; the dentine is eroded more quickly as it is softer (see TEETH – Structure). The exposed smooth surfaces are usually protected as they are easily cleaned during normal eating and by brushing. Irregular and overcrowded teeth are more at risk from decay as they are di?cult to clean. Primitive people who chew coarse foods rarely get caries. Fluoride in the drinking water at about one part per million is associated with a reduction in the caries rate.

Prolonged severe disease in infancy is associated with poor calci?cation of the teeth, making them more vulnerable to decay. As the teeth are formed and partly calci?ed by the time of birth, the diet and health of the mother are also important to the teeth of the child. Pregnant mothers and children should have a good balanced diet with su?cient calcium and vitamin

D. A ?brous diet will also aid cleansing of the teeth and stimulate the circulation in the teeth and jaws. The caries rate can be reduced by regular brushing with a ?uoride toothpaste two or three times per day and certainly before going to sleep. The provision of sweet or sugary juices in an infant’s bottle should be avoided.

Irregularity of the permanent teeth may be due to an abnormality in the growth of the jaws or to the early or late loss of the deciduous set (see TEETH – Development). Most frequently it is due to an imbalance in the size of the teeth and the length of the jaws. Some improvement may take place with age, but many will require the help of an orthodontist (specialist dentist) who can correct many malocclusions by removing a few teeth to allow the others to be moved into a good position by means of springs and elastics on various appliances which are worn in the mouth.

Loosening of the teeth may be due to an accident or in?ammation of the GUM. Teeth loosened by trauma may be replaced and splinted in the socket, even if knocked right out. If the loosening is due to periodontal disease, the prognosis is less favourable.

Discoloration of the teeth may be intrinsic or extrinsic: in other words, the stain may be in the calci?ed structure or stuck on to it. Intrinsic staining may be due to JAUNDICE or the antibiotic tetracycline. Extrinsic stain may be due to tea, co?ee, tobacco, pan (a mixture of chuna and betel nuts wrapped in a leaf), iron-containing medicines or excess ?uoride.

Gingivitis or in?ammation of the gum may occur as an acute or chronic condition. In the acute form it is often part of a general infection of the mouth, and principally occurs in children or young adults – resolving after 10–14 days. The chronic form occurs later in life and tends to be progressive. Various microorganisms may be found on the lesions, including anaerobes. Antiseptic mouthwashes may help, and once the painful stage is past, the gums should be thoroughly cleaned and any calculus removed. In severe conditions an antibiotic may be required.

Periodontal disease is the spread of gingivitis (see above) to involve the periodontal membrane of the tooth; in its ?orid form it used to be called pyorrhoea. In this, the membrane becomes damaged by the in?ammatory process and a space or pocket is formed into which a probe can be easily passed. As the pocket becomes more extensive, the tooth loosens. The loss of the periodontal membrane also leads to the loss of supporting bone. Chronic in?ammation soon occurs and is di?cult to eradicate. Pain is not a feature of the disease but there is often an unpleasant odour (halitosis). The gums bleed easily and there may be DYSPEPSIA. Treatment is largely aimed at stabilising the condition rather than curing it.

Dental abscess is an infection that arises in or around a tooth and spreads to involve the bone. It may occur many years after a blow has killed the pulp of the tooth, or more quickly after caries has reached the pulp. At ?rst the pain may be mild and intermittent but eventually it will become severe and a swelling will develop in the gum over the apex of the tooth. A radiograph of the tooth will show a round clear area at the apex of the tooth. Treatment may be by painting the gum with a mild counter-irritant such as a tincture of aconite and iodine in the early stages, but later root-canal therapy or apicectomy may be required. If a swelling is present, it may need to be drained or the o?ending teeth extracted and antibiotics given.

Injuries to teeth are common. The more minor injuries include crazing and the loss of small chips of enamel, and the major ones include a broken root and avulsion of the entire tooth. A specialist dental opinion should be sought as soon as possible. A tooth that has been knocked out can be re-implanted if it is clean and replaced within a few hours. It will then require splinting in place for 4–6 weeks.

Prevention of dental disease As with other disorders, prevention is better than cure. Children should be taught at an early age to keep their teeth and gums clean and to avoid re?ned sugars between meals. It is better to ?nish a meal with a drink of water rather than a sweetened drink. Fluoride in some of its forms is useful in the reduction of dental caries; in some parts of the UK natural water contains ?uoride, and in some areas where ?uoride content is low, arti?cial ?uoridation of the water supply is carried out. Overcrowding of the teeth, obvious maldevelopment of the jaw and persistent thumbsucking into the teens are all indications for seeking the advice of an orthodontist. Generally, adults have less trouble with decay but more with periodontal disease and, as its onset is insidious, regular dental inspections are desirable.... teeth

a rare inherited disorder associated with lung and liver diseases. It is caused by a deficiency of ?1-antitrypsin, a plasma globulin whose role is to inhibit the action of various protease enzymes (including trypsin), which protect the lungs against the action of the enzyme neutrophil elastase. This results in degradation of the *elastin of alveolar walls as well as structural proteins in other tissues, including the liver. Although many patients present in childhood, the disorder can occur in adults as well.... alpha-1 antitrypsin deficiency

This is a term encompassing chronic BRONCHITIS, EMPHYSEMA, and chronic ASTHMA where the air?ow into the lungs is obstructed.

Chronic bronchitis is typi?ed by chronic productive cough for at least three months in two successive years (provided other causes such as TUBERCULOSIS, lung cancer and chronic heart failure have been excluded). The characteristics of emphysema are abnormal and permanent enlargement of the airspaces (alveoli) at the furthermost parts of the lung tissue. Rupture of alveoli occurs, resulting in the creation of air spaces with a gradual breakdown in the lung’s ability to oxygenate the blood and remove carbon dioxide from it (see LUNGS). Asthma results in in?ammation of the airways with the lining of the BRONCHIOLES becoming hypersensitive, causing them to constrict. The obstruction may spontaneously improve or do so in response to bronchodilator drugs. If an asthmatic patient’s airway-obstruction is characterised by incomplete reversibility, he or she is deemed to have a form of COPD called asthmatic bronchitis; sufferers from this disorder cannot always be readily distinguished from those people who have chronic bronchitis and/ or emphysema. Symptoms and signs of emphysema, chronic bronchitis and asthmatic bronchitis overlap, making it di?cult sometimes to make a precise diagnosis. Patients with completely reversible air?ow obstruction without the features of chronic bronchitis or emphysema, however, are considered to be suffering from asthma but not from COPD.

The incidence of COPD has been increasing, as has the death rate. In the UK around 30,000 people with COPD die annually and the disorder makes up 10 per cent of all admissions to hospital medical wards, making it a serious cause of illness and disability. The prevalence, incidence and mortality rates increase with age, and more men than women have the disorder, which is also more common in those who are socially disadvantaged.

Causes The most important cause of COPD is cigarette smoking, though only 15 per cent of smokers are likely to develop clinically signi?cant symptoms of the disorder. Smoking is believed to cause persistent airway in?ammation and upset the normal metabolic activity in the lung. Exposure to chemical impurities and dust in the atmosphere may also cause COPD.

Signs and symptoms Most patients develop in?ammation of the airways, excessive growth of mucus-secreting glands in the airways, and changes to other cells in the airways. The result is that mucus is transported less e?ectively along the airways to eventual evacuation as sputum. Small airways become obstructed and the alveoli lose their elasticity. COPD usually starts with repeated attacks of productive cough, commonly following winter colds; these attacks progressively worsen and eventually the patient develops a permanent cough. Recurrent respiratory infections, breathlessness on exertion, wheezing and tightness of the chest follow. Bloodstained and/or infected sputum are also indicative of established disease. Among the symptoms and signs of patients with advanced obstruction of air?ow in the lungs are:

RHONCHI (abnormal musical sounds heard through a STETHOSCOPE when the patient breathes out).

marked indrawing of the muscles between the ribs and development of a barrel-shaped chest.

loss of weight.

CYANOSIS in which the skin develops a blue tinge because of reduced oxygenation of blood in the blood vessels in the skin.

bounding pulse with changes in heart rhythm.

OEDEMA of the legs and arms.

decreasing mobility.

Some patients with COPD have increased ventilation of the alveoli in their lungs, but the levels of oxygen and carbon dioxide are normal so their skin colour is normal. They are, however, breathless so are dubbed ‘pink pu?ers’. Other patients have reduced alveolar ventilation which lowers their oxygen levels causing cyanosis; they also develop COR PULMONALE, a form of heart failure, and become oedematous, so are called ‘blue bloaters’.

Investigations include various tests of lung function, including the patient’s response to bronchodilator drugs. Exercise tests may help, but radiological assessment is not usually of great diagnostic value in the early stages of the disorder.

Treatment depends on how far COPD has progressed. Smoking must be stopped – also an essential preventive step in healthy individuals. Early stages are treated with bronchodilator drugs to relieve breathing symptoms. The next stage is to introduce steroids (given by inhalation). If symptoms worsen, physiotherapy – breathing exercises and postural drainage – is valuable and annual vaccination against INFLUENZA is strongly advised. If the patient develops breathlessness on mild exertion, has cyanosis, wheezing and permanent cough and tends to HYPERVENTILATION, then oxygen therapy should be considered. Antibiotic treatment is necessary if overt infection of the lungs develops.

Complications Sometimes rupture of the pulmonary bullae (thin-walled airspaces produced by the breakdown of the walls of the alveoli) may cause PNEUMOTHORAX and also exert pressure on functioning lung tissue. Respiratory failure and failure of the right side of the heart (which controls blood supply to the lungs), known as cor pulmonale, are late complications in patients whose primary problem is emphysema.

Prognosis This is related to age and to the extent of the patient’s response to bronchodilator drugs. Patients with COPD who develop raised pressure in the heart/lung circulation and subsequent heart failure (cor pulmonale) have a bad prognosis.... chronic obstructive pulmonary disease (copd)

A method for treating babies who suffer from alveolar collapse in the lung as a result of HYALINE MEMBRANE DISEASE (see also RESPIRATORY DISTRESS SYNDROME).... continuous positive airways pressure

CONNECTIVE TISSUE which contains a profusion of yellow elastic ?bres. Long, slender and branching, these ?bres (made up of elastin, an albumin-like PROTEIN) ensure that the elastic tissue is ?exible and stretchable. The dermis layer of the skin, arterial walls and the alveolar walls in the LUNGS all contain elastic tissue.... elastic tissue

n. a dental X-ray film that provides a view of the crowns of the teeth together with the alveolar bone in part of both upper and lower jaws. This view is used in the diagnosis of caries and periodontal disease (where alveolar bone does not appear on the bite-wing this indicates loss of bony support).... bite-wing

n. 1. a splitting open, as of a surgical wound. 2. (in dentistry) loss of alveolar bone from the facial aspect of a tooth that leaves a root-exposing defect, typically oval in shape, extending from the *cemento-enamel junction towards the apex.... dehiscence

There is no reason why lung weakness of childhood should not, in later life, resolve into vigorous respiration. However, some cases present a life-long hazard, arresting full development and reducing the body’s ability to defend itself. To strengthen alveolar tissue, allay infection and enhance respiratory function a good pectoral may ensure against future disorders of lungs, trachea, bronchi and bronchioles.

Tablets/capsules. Iceland Moss.

Decoction. Irish Moss.

Tea. Combine equal parts, Comfrey, White Horehound, Liquorice. 1 heaped teaspoon to each cup water simmered gently 1 minute. Dose: half-1 cup morning and evening. Pinch Cayenne improves.

Potential benefits of Comfrey for this condition outweigh risk. ... lung weakness

n. (pl. alveoli) 1. (in the *lung) a blind-ended air sac of microscopic size. About 30 alveoli open out of each alveolar duct, which leads from a respiratory *bronchiole. The alveolar walls, which separate alveoli, contain capillaries. The alveoli are lined by a single layer of *pneumocytes, which thus form a very thin layer between air and blood so that exchange of oxygen and carbon dioxide is normally rapid and complete. Children are born with about 20 million alveoli. The adult number of about 300 million is reached around the age of eight. 2. the part of the upper or lower jawbone that supports the roots of the teeth (see also mandible; maxilla). After tooth extraction it is largely absorbed. 3. the sac of a *racemose gland (see also acinus). 4. any other small cavity, depression, or sac. —alveolar adj.... alveolus

n. failure of part of the lung to expand. This occurs when the cells lining the air sacs (alveoli) are too immature, as in premature babies, and unable to produce the wetting agent (surfactant) with which the surface tension between the alveolar walls is overcome. It also occurs when the larger bronchial tubes are blocked from within by retained secretions, inhaled foreign bodies, or bronchial cancers, or from without by enlarged lymph nodes, such as are found in patients with tuberculosis and lung cancers. The lung can usually be helped to expand by physiotherapy and removal of the internal block (if present) via a *bronchoscope, but prolonged atelectasis becomes irreversible.... atelectasis

(alveolar osteitis) a painful dental condition in which the normal healing of a tooth socket has been disturbed. Instead of being filled with a blood clot the socket is empty as a result of a nonspecific event; treatment consists of flushing out the socket, placement of medicated dressings, pain relief, and self-care. The condition normally resolves within 14 days.... dry socket

n. a swelling on the gum or alveolar mucosa. There are three types: fibromatous (originating from the fibrous tissues in the mouth), ossifying (originating from fibrous and bony tissues), and acanthomatous (emerging from the periodontal ligament). A parulis is an epulis at the opening of a *sinus tract.... epulis

n. 1. (in dentistry) a ‘window’ of bone loss on the facial or lingual aspect of a tooth that places the exposed root surface directly in contact with the gum or the alveolar mucosa. 2. a surgical operation in which a new opening is formed in the bony *labyrinth of the inner ear as part of the treatment of deafness due to *otosclerosis. It is rarely performed today, having been superseded by *stapedectomy.... fenestration

n. (pl. gingivae) the gum: the layer of dense connective tissue and overlying mucous membrane that covers the alveolar bone and necks of the teeth. —gingival adj.... gingiva

n. the conversion of lung tissue, which normally holds air, into a solid liver-like mass during the course of acute lobar *pneumonia. In the early stages of lobar pneumonia, the lungs show red hepatization due to the presence of red and white blood cells in the alveolar spaces. As the disease progresses, the red cells are destroyed and phagocytosed, resulting in grey hepatization.... hepatization

n. a bladder-like cyst formed in various human tissues following the growth of the larval stage of an *Echinococcus tapeworm. E. granulosus produces a single large fluid-filled cyst, called unilocular hydatid, which gives rise internally to smaller daughter cysts. The entire hydatid is bound by a fibrous capsule. E. multilocularis forms aggregates of many smaller cysts with a jelly-like matrix, called an alveolar hydatid, and enlarges by budding off external daughter cysts. Alveolar hydatids are not delimited by fibrous capsules and produce malignant tumours, which invade and destroy human tissues. See also hydatid disease.... hydatid

n. breathing at an abnormally shallow and slow rate, which results in an increased concentration of carbon dioxide in the blood. Alveolar hypoventilation may be primary, which is very rare, or secondary, which can be due to destructive lesions of the brain or to an acquired blunting of respiratory drive arising from failure of the respiratory pump.... hypoventilation

(inferior alveolar nerve block) a type of injection to anaesthetize the inferior *dental nerve. Inferior dental block is routinely performed to allow dental procedures to be carried out on the lower teeth on one side of the mouth.... inferior dental block

n. the tissues that support and attach the teeth to the jaw: the gums (see gingiva), *periodontal membrane, alveolar bone, and *cementum.... periodontium

a disease of the tissues that support and attach the teeth – the gums, periodontal membrane, and alveolar bone. It is caused by the metabolism of bacterial *plaque on the surfaces of the teeth adjacent to these tissues. Periodontal disease includes *gingivitis and the more advanced stage of periodontitis, which results in the formation of spaces between the gums and the teeth (periodontal pockets), the loss of some fibres that attach the tooth to the jaw, and the loss of bone. The disease is widespread and is the most common cause of tooth loss in older people. Poor oral hygiene is a major contributory factor, but the resistance of the patient also has some influence; for example, the reduced resistance of patients with AIDS may predispose to periodontal disease.... periodontal disease

n. inflammation of the lung caused by bacteria, in which the air sacs (*alveoli) become filled with inflammatory cells and the lung becomes solid (see consolidation). The symptoms include those of any infection (fever, malaise, headaches, etc.), together with cough and chest pain. Pneumonias may be classified in different ways.

(1) According to the X-ray appearance. Lobar pneumonia affects whole lobes and is usually caused by Streptococcus pneumoniae, while lobular pneumonia refers to multiple patchy shadows in a localized or segmental area. When these multiple shadows are widespread, the term bronchopneumonia is used. In bronchopneumonia, the infection starts in a number of small bronchi and spreads in a patchy manner into the alveoli. Interstitial pneumonia is the result of an inflammatory process centred within the alveolar walls rather than the alveolar airspaces. It may be due to a variety of factors, including certain infections, drugs, inhalation of fumes, and exposure to high concentrations of oxygen.

(2) According to the infecting organism. The most common organism is Streptococcus pneumoniae, but Haemophilus influenzae, Staphylococcus aureus, Legionella pneumophila, and Mycoplasma pneumoniae (among others) may all be responsible for the infection. See also atypical pneumonia; viral pneumonia.

(3) According to the clinical and environmental circumstances under which the pneumonia is acquired. These infections are divided into community-acquired pneumonia, hospital-acquired (nosocomial) pneumonia, and pneumonias occurring in immunocompromised subjects (including those with AIDS). The organisms responsible for community-acquired pneumonia are totally different from those in the other groups.

Appropriate antibiotic therapy, based on the clinical situation and on microbiological studies, will result in complete recovery in the majority of patients.... pneumonia

the artery that conveys blood from the heart to the lungs for oxygenation: the only artery in the body containing deoxygenated blood. It leaves the right ventricle and passes upwards for 5 cm before dividing into two, one branch going to each lung. Within the lungs each pulmonary artery divides into many fine branches, which end in capillaries in the alveolar walls. See also pulmonary circulation.... pulmonary artery

a system of blood vessels effecting transport of blood between the heart and lungs. Deoxygenated blood leaves the right ventricle by the pulmonary artery and is carried to the alveolar capillaries of the lungs. Gaseous exchange occurs, with carbon dioxide leaving the circulation and oxygen entering. The oxygenated blood then passes into small veins leading to the pulmonary veins, which leave the lungs and return blood to the left atrium of the heart. The oxygenated blood can then be pumped around the body via the *systemic circulation.... pulmonary circulation

n. a rare malignant tumour, usually of childhood, originating in, or showing the characteristics of, striated muscle. Pleomorphic rhabdomyosarcoma occurs in late middle age, in the muscles of the limbs. Embryonal rhabdomyosarcomas, affecting infants, children, and young adults, are classified as botryoid (in the vagina (see sarcoma botryoides), bladder, ear, etc.), embryonal (most common in the head and neck, particularly the orbit); and alveolar (at the base of the thumb). The pleomorphic and alveolar types respond poorly to treatment; botryoid tumours are treated with a combination of radiotherapy, surgery, and drugs. The embryonal type, if treated at an early stage, can often be cured with a combination of radiotherapy and drugs (including vincristine, dactinomycin, and cyclophosphamide).... rhabdomyosarcoma

n. 1. (in neurology) a bundle of nerve fibres at its emergence from the spinal cord. The 31 pairs of *spinal nerves have two roots on each side, an anterior root containing motor nerve fibres and a posterior root containing sensory fibres. The roots merge outside the cord to form mixed nerves. 2. (in dentistry) the part of a *tooth that is not covered by enamel and is normally attached to the alveolar bone by periodontal fibres. 3. the origin of any structure, i.e. the point at which it diverges from another structure. Anatomical name: radix.... root

n. (in anatomy) a hollow or depression into which another part fits, such as the cavity in the alveolar bone of the jaws into which the root of a tooth fits. See also dry socket.... socket

n. (pl. teeth) one of the hard structures in the mouth used for cutting and chewing food. Each tooth is embedded in a socket in part of the jawbone (mandible or maxilla) known as the alveolar bone (or alveolus), to which it is attached by the *periodontal membrane. The exposed part of the tooth (crown) is covered with *enamel and the part within the bone (root) is coated with *cementum; the bulk of the tooth consists of *dentine enclosing the *pulp (see illustration). The group of embryological cells that gives rise to a tooth is known as the tooth germ. There are four different types of tooth (see canine; incisor; premolar; molar). See also dentition.... tooth