L
labia (lips) labia majora two large lip-like folds of skin extending from the mons veneris to form the vulva. labia minora two smaller folds lying within the labia majora.
labial (buccal) adjacent to the lips or cheeks.
labioglossolaryngeal relating to the lips, tongue and larynx.
labyrinth the cavities of the internal ear including the cochlea and semicircular canals. bony labyrinth that part which is directly hollowed out of the temporal bone. membranous labyrinth the membrane lining the bony labyrinth.
labyrinthectomy surgical removal of part or the whole of the membra-nous labyrinth of the internal ear. Sometimes carried out for M°ni°re’s disease.
labyrinthitis inflammation of the internal ear.
laceration a wound with torn and ragged edges.
lacrimal, (lachrymal, lacrymal) associated with tears.
lacrimal bone a tiny bone at the inner side of the orbital cavity.
lacrimal duct connects lacrimal gland to upper conjunctival sac.
lacrimal gland situated above the upper, outer canthus of the eye.
lacrimonasal associated with the lacrimal and nasal bones and ducts.
lactacid (lactic) anaerobic system a series of chemical reactions occurring within the cells where a very small amount of adenosine triphosphate (ATP) for energy use is produced from glucose, without oxygen. The end product being lactic acid.
lactacid oxygen debt component the amount of oxygen required to remove lactic acid from muscle tissue and blood during the process of recovery from intense exercise.
lactase (β-galactosidase) digestive enzyme present in the small intestine mucosa. It catalyses the hydrolysis of lactose to glucose and galactose.
lactation secretion of milk, the period during which an infant receives nourishment from breast milk.
lacteals the commencing lymphatic ducts in the intestinal villi; they absorb digested fats and convey them to the cisterna chyli.
lactiferous conveying or secreting milk.
lactose deficiency the management depends on severity and may involve the exclusion or restriction of lactose-containing foods.
lacuna a space between cells; usually used in the description of bone.
lamella a thin plate-like scale or partition. A ring of bone round a haversian system. A gelatine-coated disc containing a drug; it is inserted under the eyelid.
lamina a thin plate or layer, usually of bone.
lamina dura a layer of bone forming the outer layer of the socket in which a tooth lies.
lamination layering, soft iron sheets with insulation between each sheet found in a transformer core to reduce eddy currents.
laminectomy removal of vertebral laminae – to expose the spinal cord nerve roots and meninges. Most often performed in the lumbar region, for removal of degenerated intervertebral disc.
LAN (Local Area Network) a number of computers connected together, for example in a hospital.
laparoscopic cholecystectomy removal of the gallbladder using minimally invasive surgical techniques. See also laparoscopy.
laparoscopy (peritoneoscopy) endoscopic examination of the internal organs by the transperitoneal route. A laparoscope is introduced through the abdominal wall after induction of a pneumoperitoneum. A variety of surgical procedures are performed in this way, including biopsy, cyst aspiration, division of adhesions, tubal ligation, assisted conception techniques, appendicectomy and cholecystectomy.
laparotomy incision of the abdominal wall. Usually reserved for exploratory operation.
Larmor equation (ω γBo) the proportional relationship between the precessional angular frequency of a nuclear magnetic moment (ω in Hertz) and the main magnetic field (Bo in Tesla). The gyromagnetic constant (γ) is a proportionality constant and is fixed for the nucleus, for example, 42.6 MHz/Tesla for hydrogen.
Larsen syndrome multiple joint dislocations.
laryngeal associated with the larynx.
laryngeal mask airway with inflatable cuff placed via the mouth into the oropharynx to maintain the airway during general anaesthesia.
laryngeal mirror mirror for inspecting the oral cavity and larynx.
laryngectomy surgical removal of the larynx.
laryngitis inflammation of the larynx.
laryngopharynx the lower portion of the pharynx.
laryngoscope instrument for visualization of the larynx, for diagnostic or therapeutic purposes or to facilitate the insertion of an endotracheal tube into the larynx under direct vision.
laryngoscopy direct or indirect visual examination of the interior of the larynx.
laryngostenosis narrowing of the glottic aperture.
laryngotomy surgical opening in the larynx.
laryngotracheal associated with the larynx and trachea.
larynx the organ of voice situated below and in front of the pharynx and at the upper end of the trachea.
laser (Light Amplification by Stimulated Emission of Radiation) a tube in which stimulated emission takes place and the light produced oscillates in a regular pattern to produce a high-energy, coherent, parallel beam of light. Energy is transmitted as heat which can coagulate tissue. Used in the production of modern radiographic images by exposing a film to laser light. Has many therapeutic uses that include: endometrial ablation, detached retina, skin lesions and cancer. Precautions must be taken by those using lasers as eye damage can occur.
laser back pointer mounted in the counterbalance of the gantry of radiotherapy equipment and projects a sheet of light in the direction of the axis of rotation of the gantry and the axis of rotation of the diaphragm system indicating the entry and exit point of the radiation beam.
laser printer characters or images are built up by the image being scanned by a laser and then toner is fused onto the paper to produce the final print.
laser printing film a single-sided emulsion used with imaging plates.
latent image the image produced on a film after exposure but prior to development.
latent period the time between the exposure to a carcinogenic agent and the clinical appearance of disease.
lateral at or belonging to the side; away from the median line.
lateral decubitus radiograph the patient lies on their side and the central ray passes from the anterior to the posterior aspect of the body. The projection is named after the side of the body that is uppermost.
lateral radiograph the patient is either erect or lying with the side of their body nearest the film. The projection is named after the side of the body nearest the film.
lateral resolution in ultrasound, the ability to see small structures that lie along the beam, this is equal to the effective beam width and is best at the focus and reduces the further away from the focus the object is.
latex allergy an allergic reaction to natural latex or one of the components used in production of latex equipment such as medical gloves and catheters. Latex allergy is becoming increasingly common in healthcare workers due to the increased use of gloves following the rise in the incidence of blood-borne viruses.
latissimus dorsi muscle of the back.
latitude the range of useful exposures a film will tolerate. See also useful exposure range.
latitude emulsions a film with a reduced average gradient of 2.2 to enable a large range of densities to be recorded.
laughing gas nitrous oxide (N2O).
lavage irrigation of or washing out a body cavity.
law of conservation of energy energy can neither be created nor destroyed but can be changed from one form to another. The amount of energy in a system is therefore constant.
law of conservation of matter matter is neither created nor destroyed, but it may change its chemical form as a result of chemical reaction.
law of conservation of momentum the total linear or rotational momentum in a given system is constant.
laxatives (aperients) drugs used to prevent or treat constipation. Administered orally, or rectally as suppositories or by enema. They may be: bulking agents that retain water and form a large, soft stool; faecal softeners that lubricate or soften the faeces; osmotic laxatives that increase fluid in the bowel lumen; stimulants that increase peristalsis, and combined softeners and stimulants.
lead equivalence a method of comparing protection barriers by calculating the thickness of lead required to have the same absorption to an exposure to radiation.
lead poisoning caused by excessive intake of lead, radiographically, dense transverse lines appear at the shafts of long bones.
lead shielding shielding blocks of lead placed on a tray below the radiotherapy tube to shape the radiation beam so that it accurately covers the treatment area and/or shields organs at risk. Alternative products may be used, usually alloys of bismuth or cadmium. See also MCP block.
lead strip a contouring device formed by placing a lead strip round the patient and the skin markings are transferred to the lead using marker pen, the markings are then copied onto papers giving the patient contour.
leakage radiation unwanted radiation that is emitted from an X-ray tube in directions other than the useful beam, it is reduced by the addition of lead round the X-ray tube.
lecithins a group of phospholipids found in animal tissues, mainly in cell membranes. They are present in surfactant. lecithin-sphingomyelin ratio a test which assesses fetal lung maturity. Below 2.0 is indicative of a higher risk of neonatal respiratory distress syndrome.
Leeds test objects a number of different test objects produced by the University of Leeds, used for quality control in radiology, to test, for example, film-screen combinations, television systems and CT scanners, etc.
left anterior oblique a radiographic projection with the patient either erect or semi prone at 45° to the film with the left side of the body closest to the film and the right side away from the film.
left colic (splenic) flexure is situated at the junction of the transverse and descending parts of the colon. It lies at a higher level than the right (hepatic) flexure.
left posterior oblique a radiographic projection with the patient either erect or semi supine at 45° to the film with the left side of the body closest to the film and the right side away from the film (see figure on p. 232).
left ventricular assist device (LVAD) mechanical pump used to increase the output of blood from the left ventricle of the heart. May be used in the short term to support critically ill patients, those waiting for a heart transplant, or to give the heart time to recover from disease.
Legionella a type of small Gram-negative bacillus associated with infected water supplies.
legionnaires’ disease a severe and often fatal pneumonia caused by Legionella pneumophila; there is pneumonia, dry cough, and often non-pulmonary involvement such as gastrointestinal symptoms, renal impairment and confusion. A cause of both community- and hospital-acquired pneumonia, it is associated with an infected water supply in public buildings such as hospitals and hotels. There is no person-to-person spread.
leg length discrepancy a difference of up to 1 cm in true length is considered to be within a normal variation. The effects of discrepancy may either cause a compensatory pelvic tilt and secondary spinal scoliosis, or will force the person to walk on their toes in order to lengthen the leg. The latter will, in time, result in shortening of the Achilles tendon.
leimyoma a benign tumour of smooth muscle.
leiomyosarcoma a sarcoma which contains large spindle cells of unstriated muscle.
Leksell unit a stereotactic radiotherapy unit containing a hemispherical array of 201 collimated, cobalt sources. It is usually used for the delivery of single fractions of radiation to intracranial targets.
lens the small biconvex crystalline body which is supported by the suspensory ligament immediately behind the iris of the eye. On account of its elasticity, the lens can alter in shape, enabling light rays to focus exactly on the retina. A glass or plastic used to correct refractive errors (spectacles or contact lens) or in optical instruments.
Lenz’s law the direction of the induced current in a conductor caused by a changing magnetic flux is such that its own magnetic field opposes the changing magnetic flux. The law only applies in closed circuits.
leptomeningeal disease a vascular abnormality of the skin described as resembling a port wine stain. Inflammation of the pia mater and arachnoid membranes of the brain and spinal cord.
lesion pathological change in a bodily tissue.
lesser omentum a smaller fold, passing between the transverse fissure of the liver and the lesser curvature of the stomach.
leucocytes generic name for white blood cells. They are nucleated, mobile and are all involved with body defences, e.g. some are phagocytic and others produce antibodies. There are two main groups: (a) polymorphonuclear cells or granulocytes (neutrophils, basophils and eosinophils) – these have a many-lobed nucleus and granules in their cytoplasm; (b) monocytes and lymphocytes – these generally have no granules, but some lymphocytes are granular.
leucocytolysis destruction and disintegration of white blood cells.
leucocytosis increased number of leucocytes in the blood. Often a response to infection.
leucopenia decreased number of white blood cells in the blood.
leucopoiesis formation of white blood cells from stem cells.
leukaemia a progressive, malignant disease of the blood-forming organs, with, most commonly, abnormal proliferation of white cells (leucocytes). Uncontrolled proliferation of the leukaemic cells causes secondary suppression of other blood components, and anaemia and a reduction in the number of platelets in the blood (thrombocytopenia) result. The lack of mature white cells increases the risk of infection, thrombocytopenia increases the risk of bleeding, and anaemia is also characteristic. Causes include ionizing radiation, previous chemotherapy, retroviruses, chemicals, genetic anomalies (e.g. Down’s syndrome). The classification is according to cell type – lymphocytic or myelocytic, and the course acute or chronic. The chronic leukaemias may enter a ‘blast crisis’ or acute phase. Therapeutic options include chemotherapy, radiotherapy, interferon alpha, monoclonal antibodies and bone marrow transplantation, either using the patient’s bone marrow (autologous) or that of a donor (allograft). See also myelopro-liferative disorders.
leukoplakia chronic inflammation characterized by white, thickened patches on the mucous membranes, particularly on the tongue, gums and inside the cheeks. Usually patchy and often premalignant. See also kraurosis vulvae.
leukotrienes regulatory lipids derived from arachidonic acid (fatty acid). They function as signalling molecules in the inflammatory response and in some allergic responses.
levator a muscle which acts by raising a part. An instrument for lifting a depressed part.
Lhermitte’s sign an electric shock-like symptom radiating down the spine and into the limbs.
Lhermitte’s syndrome flexion of the neck. A syndrome characterized by lymphoblastic infiltrations of the peripheral nervous system – associated with paresis.
lienculus a small accessory spleen.
lienorenal associated with the spleen and kidney. See also splenorenal.
Li-Fraumeni syndrome familial breast cancer affecting young women and associated with soft-tissue sarcomas and other cancers in close relatives.
ligament a band of fibrous tissue binding joints together and connecting the articular surfaces to allow movement. A layer of serous membrane extending from one organ to another, for example, the peritoneum.
ligate to tie off blood vessels, etc., at operation.
ligation tying off; usually reserved for ligation of the uterine (fallopian) tubes, a method of sterilization.
ligature the material used for tying vessels or stitching the tissues. See also suture.
light adaptation adjustments made by the eye in bright light. The pupils constrict, rhodopsin breakdown reduces retinal sensitivity and cone activity increases. See also dark adaptation.
light beam diaphragm a light source, incorporated in the tube housing to visually indicate the area covered by the radiation emitted from the X-ray tube.
light pen a device, shaped like a pen, which interfaces with a computer screen and enables the computer to know which part of the screen is being pointed to.
Likert scale a scale used in questionnaire surveys. Participants are asked to specify their degree of agreement with a particular statement, i.e. strongly agree, agree, unsure, disagree and strongly disagree.
liminal of a stimulus, of the lowest intensity that can be perceived by human sense organs. See also subliminal.
line defects edge dislocation when an extra plane of atoms extends into the crystal lattice.
linea alba the white line visible after removal of the skin in the centre of the abdomen, stretching from the ensiform cartilage to the pubis, its position on the surface being indicated by a slight depression.
lineae albicantes white lines which appear on the abdomen after reduction of tension as after childbirth, tapping of the abdomen, etc. See also striae.
linea nigra pigmented line from umbilicus to pubis which appears in pregnancy.
linear accelerator radiotherapy equipment where electrons produced by an electron gun pass through a waveguide and are accelerated and fed into a treatment head to produce high-energy X-rays or an electron beam used in the treatment of various cancers.
linear array in ultrasound, a set of elements mounted in line and pulsed electronically in sequence to produce a rectangular field of view.
linear attenuation coefficient (μ) measures the probability of photon interaction along the path of an X-ray beam, that is the fraction of X-rays removed from a beam per unit thickness of the attenuating medium. Differences in the linear attenuation coefficient are responsible for radiographic image contrast and it is a series of these measurements which are used to produce the image in CT. It is dependent upon the beam energy, and the structure and density of the material traversed.
linear energy transfer the energy that a particle dissipates, per unit length of its path, as it travels through absorbing medium.
linear expansivity is a measure of thermal expansion and is defined as the change in unit length per unit change in temperature in degrees Kelvin.
linear measurement the measurement of a straight line between two points.
linear scanner in radionuclide imaging the crystal moves backwards and forwards across an organ, the images are then recorded as a photoscan or a dot diagram. The equipment has been superseded by gamma cameras.
linear sources several collinear tubes mounted in an applicator and used in intercavitary therapy to treat line sources, for example the uterine canal.
linitis plastica a form of gastric cancer which infiltrates throughout the gastric wall. This leads to diffuse thickening and failure to inflate at endoscopy and barium examinations.
lipase any fat-splitting enzyme, such as pancreatic lipase. They convert fats into fatty acids and glycerol.
lipogenesis a metabolic process where amino acids and glucose are converted to triglycerides (triacylglycerols) prior to storage in adipose tissue. It is stimulated by insulin.
lipoma a benign tumour of fatty tissue, which develops in connective tissue.
lipoprotein lipids combined with a protein that transport triglycerides (triacylglycerols) and cholesterol around the body in the blood. They are classified as: high-density lipoproteins (HDLs), low-density lipoproteins (LDLs) or very-low-density lipoproteins (VLDLs). A high level of LDL in the blood is associated with arterial disease whereas HDLs are considered to be protective. A high HDL:LDL is associated with a decreased risk of arterial disease.
liposarcoma a malignant tumour of the fat cells.
liquid crystal display a form of flat screen imaging monitor using liquid crystals and a back light to produce the image. In colour monitors each pixel is subdivided into three colours, red, blue and green by the use of filters, each of which can be activated independently to produce the colour image.
liquid scintillation process a method of detecting radionuclides which decay solely by beta decay. The solution used contains a solvent, a scintillation solute and a secondary solute in which is dissolved a radionuclide.
liquor a solution. liquor amnii fluid surrounding the fetus.
Lisfranc injury dislocation of the third, fourth and fifth metatarsals with a fracture through the base of the second metatarsal.
LISP (LISt Processor language) a high-level computer language.
literature review a methodical and wide-ranging examination of the papers relevant to a topic. Research methods and results are analysed and presented critically. The literature review includes how the search was carried out, e.g. bibliographical databases such as Medline.
lithiasis any condition in which there are calculi.
litholapaxy (lithopaxy) crushing a stone within the urinary bladder and removing the fragments by irrigation.
lithotripsy destruction of calculi by crushing using high-powered ultrasound.
lithotriptor a machine which sends shock waves through renal calculi, causing them to fragment and be passed naturally in the urine.
lithotrite an instrument for crushing a stone in the urinary bladder.
litmus a vegetable pigment used as an indicator of alkalinity (blue) or acidity (red). Often stored as paper strips: red litmus paper turns blue when exposed to an alkali; blue litmus paper turns red with an acid.
liver the largest gland in the body, the weight in adults is within the range 1.2–1.5 kg. The liver is situated in the right upper part of the abdominal cavity. It is vital to homeostasis and its functions include: breakdown of red blood cells with the production of bile, detoxification of drugs and hormones, nutrient metabolism, protein synthesis and storage of glycogen, vitamins and minerals. The liver is the site of considerable heat generation.
liver function tests blood tests used to assess liver function including: alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, coagulation tests, gamma-glutamyltransferase, serum bilirubin and serum proteins.
liver transplant liver failure may be treated by surgical transplantation of a liver from a suitable donor.
lobe a rounded section of an organ, separated from neighbouring sections by a fissure or septum, etc.
lobectomy removal of a lobe, for example lung or liver.
lobule a small lobe or a subdivision of a lobe.
local anaesthetic a drug used to render a specific area of the body insensitive to pain.
localization the method of delineating the exact clinical target volume in a patient prior to radiotherapy treatment.
localize to limit the spread. To determine the site of a lesion.
local rules rules outlining safe working practices of employees working with or coming into contact with radiation.
locomotor can be applied to any tissue or system used in movement. Most usually refers to nerves and muscles. Sometimes includes the skeletal system.
locomotor ataxia the disordered gait and loss of sense of position (proprioception) in the lower limbs, which occurs in tabes dorsalis.
locoregional referring to a specific part of the body.
loculated divided into numerous cavities.
loculation the presence of many small spaces or cavities.
logarithm the logarithm of a number to a given base, is the power by which the base must be raised to give the number. For example the logarithm of 100 to the base 10 is 2 as 102 = 100.
log It curve see characteristic curve.
loin that part of the back between the lower ribs and the iliac crest; the area immediately above the buttocks.
long bones these have a shaft of compact bone with a central medullary cavity, the ends are expanded, for example, the femur, the radius.
longitudinal magnetization (Mz) part of the macroscopic magnetization vector, parallel to the main magnetic field (Bo). Following radio frequency excitation it returns to its equilibrium value (Mo) due to the characteristic time constant (T1) of the tissues that have been excited.
longitudinal relaxation time (T1, spin-lattice relaxation time, T1 relaxation time) in magnetic resonance imaging, the time taken for the spins to give the energy obtained from the initial radio frequency impulse, back to the surrounding environment and return to equilibrium. It represents the time required for the longitudinal magnetization (Mz) to go from 0 to 63% of its final maximum value.
longitudinal study research study where data are collected on more than one occasion, such as the study of a group of people over time. See also cohort study.
loopography the radiographic investigation of an ileal conduit, a Foley catheter is inserted and dilated to block the conduit and contrast agent is injected under fluoroscopic control and plain films are taken.
Looser’s zones pseudo (or false) fractures.
LOP (left occipitoposterior) used to describe the position of the fetus in the uterus.
lordoscoliosis lordosis complicated by the presence of scoliosis.
lordosis an exaggerated forward, convex curve of the lumbar spine.
lordotic radiograph a chest projection where the patient is positioned for a routine PA chest and leans backwards, towards the X-ray tube by approximately 30–40°, taken to demonstrate a right middle lobe collapse or an interlobular pleural effusion.
low back pain the commonest cause seems to be posteriolateral prolapse of the intervertebral disc, putting pressure on the dura and cauda equina and causing the localized pain of lumbago. It can progress to trap the spinal nerve root, causing the nerve distribution pain of sciatica.
low birthweight term used to indicate a weight of 2.5 kg or less at birth, whether or not gestation was below 37 weeks. See also small for gestational age.
low-density lipoprotein (LDL) see lipoprotein.
low energy X-ray beam radiotherapy beam in the order of 50–160 kV, very low energy beam 8–50 kV.
lower motor neuron a specialist nerve cell where the cell is in the anterior horn of the spinal cord and the axon passes to skeletal muscle.
lower respiratory tract infection (LRTI) pneumonia.
low spatial frequency algorithm in CT scanning an algorithm used to provide high contrast resolution. Frequently used in soft-tissue studies to demonstrate inherently low contrast tissues in close proximity.
low temperature chemistry radiographic processing chemicals with a higher concentration of hydroquinone, a different restrainer and a higher concentration of preservative which have a working temperature range of 26–33°C and a pH of about 10.00.
LSI (Large Scale Integration) a means of packing large numbers of electronic circuits into small chips.
LSP (Local Service Provider) a company that supplies computer net-working, for example, NHS PACS has five LSPs to deliver the system countrywide.
lubb-dupp words descriptive of the heart sounds as heard on auscultation.
lubricants faecal softeners that also lubricate and facilitate easy and painless defecation. See also laxatives.
lumbago incapacitating pain low down in the back.
lumbar associated with the loin for example lumbar nerve, lumbar vertebrae.
lumbar puncture (LP) the withdrawal of cerebrospinal fluid (CSF) through a hollow needle inserted into the subarachnoid space in the lumbar region of the spine. The CSF obtained is examined for its chemical (e.g. glucose) and cellular (e.g. white blood cells) constituents and for the presence of microorganisms; CSF pressure can be measured by the attachment of a manometer. Contrast agent can be introduced to demonstrate the subarachnoid space, spinal cord, nerve roots, ligaments, and associated structures.
lumbocostal associated with the loin and ribs.
lumbosacral associated with the loin or lumbar vertebrae and the sacrum.
lumen the space inside a tubular structure.
luminescence is caused when a material absorbs short wave length radiation and therefore lower energy photons are released, usually in the visible or near visible spectrum.
luminosity the measure of the amount of light emitted from an object.
lumpectomy the surgical excision of a tumour with removal of minimal surrounding tissue. Increasingly used, with radiotherapy and chemotherapy, for treatment of breast cancer.
lunate one of the eight carpal bones found in the wrist.
lungs the two main organs of respiration which occupy the greater part of the thoracic cavity; they are separated from each other by the heart and other contents of the mediastinum. They are concerned with gas exchange – the oxygenation of blood and excretion of carbon dioxide. lung transplantation may be single, double, heart–lung transplants, or sometimes in the case of child recipients, live-related lobar transplants.
lung ventilation the passage of air in the lungs studied by the inhalation of a radioactive gas.
lunula the semilunar pale area at the root of the nail.
luteinizing hormone (LH) a gonadotrophin secreted by the anterior pituitary gland. In females high levels in mid menstrual cycle stimulate ovulation and formation of the corpus luteum. The same hormone in males is called interstitial-cell stimulating hormone (ICSH); it stimulates the production of testosterone by the testes.
lymph the fluid contained in the lymphatic vessels. It is formed from interstitial (tissue) fluid and is similar to plasma. Unlike blood, lymph contains only one type of cell, the lymphocyte. lymph circulation that of lymph collected from the tissue spaces; it then passes via capillaries, vessels, nodes and ducts to be returned to the blood. lymph nodes accumulations of lymphatic tissue at intervals along lymphatic vessels. They mainly act as filters. They provide a site for B and T lymphocyte/cell proliferation and the production of immunoglobulins.
lymphadenectomy excision of one or more lymph nodes.
lymphadenitis inflammation of a lymph node.
lymphadenopathy any disease of the lymph nodes.
lymphangiectasis dilation of the lymph vessels.
lymphangiography lymphography.
lymphangioma a simple tumour of lymph vessels frequently associated with similar formations of blood vessels.
lymphangioplasty any plastic surgery on lymph vessels, such as those used to improve drainage. See also lymphoedema.
lymphangitis inflammation of a lymph vessel.
lymphatic associated with, conveying or containing lymph.
lymphoblast an immature lymphocyte. Present in the blood and bone marrow in conditions such as acute lymphoblastic leukaemia (ALL).
lymphocyte one variety of white blood cell. The lymphocytic stem cells undergo transformation to T lymphocytes/cells (in the thymus), which provide cellular immunity involved in destroying cancer cells, virus-infected cells and transplanted cells (graft), or B lymphocytes/cells, which form immunoglobulins (antibodies) and provide humoral immunity. The transformation is usually complete a few months after birth.
lymphocytosis an increase in lymphocytes in the blood.
lymphoedema excess fluid in the tissues from abnormality or obstruction of lymph vessels that blocks or interrupts lymph drainage. There is swelling of (usually) a limb and increased risk of cellulitis. It may occur, for example, after lymph node resection and/or radiotherapy; most common in breast cancer. Treated by compression bandaging.
lymphoepithelioma rapidly growing malignant pharyngeal tumour. May involve the tonsil. Often has metastases in cervical lymph nodes.
lymphography the radiographic investigation of the lymphatic system following the direct injection of contrast agent into a lymphatic vessel of the foot. Generally replaced by CT scanning.
lymphoid associated with lymph. lymphoid tissue tissue similar to lymph nodes, situated in a variety of locations, bone marrow, gut, liver, spleen, thymus and tonsils.
lymphokines a term applied to cytokines produced by stimulated T lymphocytes. They function during the immune response as intercellular chemical mediators.
lymphoma a group of neoplastic diseases developing in lymphoid tissue. Lymphoma is characterized by lymph node enlargement, night sweats/swinging pyrexia, pain from splenic enlargement/infarction, hepatomegaly, weight loss, malaise or recurrent infection. Causes include viral infections but most are idiopathic. Classified according to histological appearances to either Hodgkin’s lymphoma or non-Hodgkin’s lymphoma (NHL). Staging depends on sites involved – location and number, as well as associated ‘secondary’ symptoms. Therapy may be radiotherapy alone for the earliest stages, and/or chemotherapy. Bone marrow transplantation may also be necessary. See also Burkitt’s lymphoma.
lymphosarcoma obsolete term for some types of lymphoma.
lysis the gradual decline of a disease, the destruction of cells.
lysozyme an antibacterial enzyme present in many body fluids such as tears and saliva.
lytic lesion disintegration or breakdown usually of bone cells.
