A naevus is a congenital growth or pigmented blemish on the skin, such as a birthmark or mole.
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In humans the nails are flattened, horny, protective coverings on the upper surface of the outer segments of the fingers and toes comprised of dead cells containing the fibrous protein keratin. Each nail consists of a root concealed within a fold of the skin; an exposed body attached to the surface of the skin; and a free anterior extremity called the edge. The skin below the root and body of the nail is termed the matrix. The matrix is thick and covered with highly vascular papillae, and its colour is seen through the transparent horny tissue. Near the root the papillae are smaller and less vascular making this portion of the nail appear whiter. From its crescent form this portion is termed the lunula or moon. The nail advances forward by the successive growth of new cells at the root and under the body of the nail. Homologous structures in other animals include the hooves of horses and the claws of birds.
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A narcotic is a brain dulling and analgesic drug, not a sleep inducing drug as many believe (though narcotics can be used to induce sleep in large enough doses), there is a notable difference between a state of sleep and a state of a dulled brain. Sleep inducing substances are known as hypnotics. Most narcotics are stimulating when given in moderate doses; in larger doses they produce sleep; and in poisonous doses they bring on stupor, coma, convulsions, and even death. Opium, hemlock, henbane, belladonna, aconite, camphor, digitalis, tobacco, alcohol, leopard's-bane, and a variety of other substances, are narcotics.
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The nares (nostrils) serve as the opening for the nasal fossae, the two cavities in the middle of the face. The anterior nares open at the front of the face and the posterior
nares open into the nasopharynx. The posterior nares are somewhat smaller because they are narrowed by the mucous membrane that helps filter the air.
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Nasal is a classification of human skull shape found primarily in Negroes.
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The nasal bone forms the roof of the nasal cavity and the bridge of the nose. The nasal bone is supported by the ethmoid bone and is joined to the frontal process of the maxillary bone and to the frontal bone just below the glabella.
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The nasal cavity is in the middle of the face and is formed by a number of bones. The nasal bone forms the roof, while the sides are formed by the ethmoid bone and maxillary bones. Within the
nasal cavity is a vertical plate, or septum which divides the cavity into two halves. The top and front of the septum is made of the vertical plate of the ethmoid bone, while the bottom and back of the septum is formed by the vomer. Each side of the nasal cavity features three curved ledges, called turbinates or conchae. The superior and middle turbinates are protrusions from the ethmoid bone, while the inferior turbinate is attached to the maxillary bone. The back of the
nasal cavity opens just behind the palatine bone.
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The nasal septum is the tissue that separates the right and left nasal cavities. It is made of cartilage at the front and bone (vomer) towards the back of the nasal cavity. Mucous membrane lines the cavities and covers the septum. Two narrow cavities, called olfactory clefts, lie on each side of the nasal septum at the very top of the nose. The olfactory membranes lie in the olfactory clefts.
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The nasalis muscle consists of two parts: the alar and the transverse. The alar is used when the nostrils are flared and runs along the side of the nose. The transverse runs diagonally and is used to wrinkle the nose. The nasalis is composed of three small muscles: the compressor nasi, the dilator naris posterior, and the depressor septi nasi. The compressor nasi is a small, thin muscle with a triangular shape. It runs along the bridge of the nose and depresses the cartilage and compresses the alae together. The depressor nasi is a short muscle that lies between the musclular structure and the mucous membrane of the lip. It arises from the upper lip and extends to be inserted into the septum of the nose. It constricts the nares (nostrils) of the nose, the opposite action of the compressor nasi muscle. The dilator nares posterior is a small muscle that originates from the edge of the nasal notch and is inserted into the skin near the edge of the nostril. This muscle works with the dilator naris anterior, which is located in front of it,
to dilate the opening of the nares. All muscles of the nose are supplied by the facial nerve.
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The nasopharynx is the part of the pharynx situated above and behind the soft palate.
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Naturopathy is a method of treating disorders, involving the use of herbs and other naturally grown foods, sunlight, fresh air, etc.
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Nausea is the feeling of wanting to vomit.
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The navicular bone is one of the eight carpal bones which constitute each wrist (and is also found in the foot) . This bone is so named because its shape resembles that of a sailboat. This bone is sometimes referred to as the scaphoid bone.
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Nebulaphobia is the fear of fog.
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The neck is the part of the body which connects the head with the shoulders. In a human, the neck is based around seven cervical vertebrae encased by a complex system of muscles which both move the vertebrae and hold them in position. The human stereoscopic vision relies upon a supple neck to allow the head to be rotated, but other than for this purpose humans have less need and reliance upon their neck than most other animals, since humans make primary use of their hands rather than their mouth.
When a human foetus is forming, gills are present in the neck, a throw-back to man's earlier evolutionary period as an aquatic mammal. By the time of birth the gills have disappeared, but rarely a gill remains either as a cyst or as an opening at the side of the neck. These anomalies are usually corrected with surgery.
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In physiology, necrobiosis is the normal degeneration and death of cells.
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Necrophobia is the fear of death or dead bodies.
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Necrosis is the death or decay of tissue in a particular part of the body, usually due to bacterial poisoning or loss of local blood supply.
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Necrotizing enterocolitis is condition in which part of the tissue in the intestines is destroyed. It occurs mainly in under-weight newborn babies. A temporary ileostomy may be necessary.
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Necrotizing fasciitis is an extremely rare fatal bacterial infection caused by Streptococcus pyogenes. Toxins and enzymes produced by the bacteria rapidly digest human tissue. There were 15 cases in Britain in the first half of 1994. In the USA there are up to 500 cases annually.
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Necrotomy is the surgical excision of dead tissue from a living organism.
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In psychology, negative reinforcement is the reinforcing of a response by giving an aversive stimulus when the response is not made and omitting the aversive stimulus when the response is made.
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Negrophobia is the fear of Black people and things.
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Nelophobia is the fear of glass.
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Neoarsphenamine is a derivative of arsenic used in treating syphilis.
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Neomycin is an antibiotic obtained from the bacterium Streptomyces fradiae. It is administered locally in the treatment of skin and eye infections or orally for bowel infections.
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Neonatal hepatitis is an irritation of the liver with no known cause. It occurs in newborn babies and the symptoms include jaundice and liver cell changes.
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Neonatology is the branch of medicine concerned with the development and disorders of newborn babies.
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Neopharmaphobia is the fear of new drugs.
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Neophobia is the fear of novelty.
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In pathology, a neoplasm is any abnormal new growth of tissue or a tumour.
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Neoplastic disease forms one of the main groups of disorder requiring surgical treatment. It arises at any age, in any site of the body. Both innocent (benign) growths and those which are malignant (non-benign or cancer) can arise from most tissues and their cell structure resembles that of the tissue of origin. An innocent growth causes disease by its size; it grows slowly and may remain stationary in size for many years. It may be brought to the patient's notice by the appearance of a visible lump or by symptoms from pressure on some other organ or tissue. It does not eat its way into other tissues by 'invasion'. It does not recur if it is removed, and it does not spread by a process of seeding. A malignant growth on the other hand, increases at a variable rate but relentlessly. It erodes and invades surrounding tissue, forming ulcers, craters, abscesses and, in bone, fractures. Malignant disease by its attack on blood vessels frequently presents as severe haemorrhage. It spreads to neighbouring lymph glands; by the blood stream it is
seeded to other parts of the body. It affects the whole patient, produces debility, anaemia and ultimately death. Innocent tumours may change their nature and become malignant after many years of lying dormant. This risk is a good reason for the removal of apparently harmless tumours. Neoplasms are parasites. They live at the expense of their host and serve no purpose. Certain tumours produce cells which can function like their parent cell, as for instance in producing hormones. A tumour of the pituitary or pancreas may so alter the patient's metabolism that the endocrine change is the first feature to arouse suspicion that a neoplasm is present.
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Neoplasty is the surgical formation of new tissue structures or the repair of damaged structures.
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Nepenthe was a drug which was fabled by the ancient poets to banish the memory of grief and to cheer the soul. It is thought by many to have been what is now called opium.
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Nephophobia is the fear of clouds.
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Nephrectomy is the surgical term for the removal of a kidney.
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Nephrology is the branch of medicine concerned with diseases of the kidney.
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The nephron is the functional unit of the kidney, responsible for the actual purification and filtration of the blood. About one million nephrons are in the cortex of each kidney, and each one consists of a renal corpuscle and a renal tubule which carry out the functions of the nephron. The renal tubule consists of the convoluted tubule and the loop of Heinle.
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A nephroscope is a tubular medical instrument inserted through an incision in the skin to enable examination of a kidney.
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Nephrosis is any noninflammatory degenerative kidney disease.
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A nephrotomy is a surgical incision into a kidney.
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The nerves are a part of the body which generate and transmit electrical impulses.
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The nerve-muscle junction features a connection, or synapse, between an axon terminal and a group of muscle fibres. A space between the neural and muscular tissue is called the synaptic space. When a nerve impulse is transmitted to the axon terminal, it causes a neurotransmitter to be released from small sacs, called synaptic vesicles, within the terminal, or knob. The neurotransmitter causes sodium ions to be transferred to the muscle fibres which, in turn, contract. The neurons are covered by an insulating, lipid-based coating, called the myelin sheath, which prevents stray neural signals from passing to other neurons or to other tissues.
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The nervous system of the human anatomy is responsible for sending, receiving, and processing nerve impulses. All of the body's muscles and organs rely upon these nerve impulses to function. Three systems work together to carry out the mission of the nervous system: the central, the peripheral, and the autonomic nervous systems. The nervous system may be basically classified as comprised of the central nervous system and the peripheral nervous system. The central nervous system is responsible for issuing nerve impulses and analyzing sensory data, and includes the brain and spinal cord. The peripheral nervous system is responsible for carrying nerve impulses to and from the body's many structures, and includes the many craniospinal nerves which branch off of the brain and spinal cord. The autonomic nervous system is composed of the sympathetic and parasympathetic systems and is responsible for regulating and coordinating the functions of vital structures in the body. Of all of these components, the brain is the primary component of the nervous system, occupying the cranial cavity and comprising 97% of the nervous system. The brain is connected to the
upper end of the spinal cord and is responsible for issuing nerve impulses, processing nerve impulse data, and engaging in the higher order thought processes.
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The neural tube is the structure in mammalian embryos that develops into the brain and spinal cord. Incomplete development results in neural-tube defects, such as spina bifida, in a newborn baby.
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Neuralgia is a severe spasmodic pain caused by damage to or malfunctioning of a nerve and often following the course of the nerve.
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The neurapophyses or neural arches is the name applied to the upper or superior arches which spring from the body of the typical vertebra, or segment of the vertebrate spine, and which by their union form a canal - - the 'neural canal' - inclosing the spinal marrow.
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Neurasthenia is an obsolete technical term for a neurosis characterised by extreme lassitude and the inability to cope with any but the most trivial tasks.
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A neurectomy is the surgical removal of a nerve segment.
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A neurinoma is a tumor that arises from the cells of the thin sheath that covers a nerve.
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Neuritis is a form of fibrositis of the nerves due to inflammation of the surrounding connective tissue. It is often accompanied by pain and the loss of function in the affected part.
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Neuroanatomy is the study of the structure of the nervous system.
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An neuroblast is an embryonic nerve cell.
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In embryology, the neurocoele is a cavity in the embryonic brain and spinal cord that develops into the ventricles and central canal respectively.
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Neuroendocrinology is the study of neuroendocrine systems and neurohormones.
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The neurofibrils are delicate threads within the body of a nerve cell that extend into the axon and dendrites.
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A neurohormone is a hormone, such as noradrenaline, oxytocin, or vasopressin, that is produced by specialized nervous tissue rather than by endocrine glands.
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The neurohypophysis is the posterior lobe of the pituitary gland.
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The neurolemma or neurilemma is the thin membrane that forms a sheath around nerve fibres.
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A neuroleptic drug is a major tranquillizer used in the treatment of psychosis. It works by reducing the intensity of the nerve functions.
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Neurology is the study of the anatomy, physiology, and diseases of the nervous system.
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A neuroma is a tumour composed of nerve tissue.
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A neuron or neurone (nerve cell) is a cell specialized to conduct nerve impulses and is one type of cell found in the nervous system. A neuron consists primarily of a cell body, axon, and dendrites, and different neurons may be different shapes.
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A neuropath is a person suffering from or predisposed to a disorder of the nervous system.
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Neuropathology is the study of diseases of the nervous system.
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Neuropathy is a disease of the nervous system. Many people who have had diabetes for a while have nerve damage. The three major forms of nerve damage are: peripheral neuropathy, autonomic neuropathy, and mononeuropathy. The most common form is peripheral neuropathy, which mainly affects the feet and legs.
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A neuropeptide is a peptide produced by neural tissue. The term is especially applied to a peptide with hormonal activity.
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Neurophysiology is the study of the functions of the nervous system.
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The neuropil is a dense network of neurons and glia in the central nervous system.
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Neuropsychiatry is the branch of medicine concerned with neurological and mental disorders.
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Neuropsychology is the study of the effects of brain damage on behaviour and the mind.
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Neuroscience is the study of the anatomy, physiology, and biochemistry of the nervous system.
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Neurosis is a mild mental condition of emotional disorders.
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Neurosurgery is the branch of surgery concerned with the nervous system.
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Neuroticism is a personality trait characterised by instability, anxiety, and aggression.
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A neurotomy is the surgical cutting of a nerve, usually to relieve intractable pain.
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A neurotoxin is a substance that interfere with the electrical activities of nerves, thus preventing them from functioning.
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A neurotransmitter is a chemical by which a nerve cell communicates with another nerve cell or with a muscle.
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A neutralizing antibody is an antibody that keeps a virus from infecting a cell, usually by blocking receptors on the cells or the virus.
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Neutropenia is an abnormal reduction in the number of neutrophils in the blood, as seen in certain anaemias and leukaemias.
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A neutrophil or neutrophile (also called a polymorph) is a leucocyte having a lobed nucleus and a fine granular cytoplasm, which stains with neutral dyes.
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Nifedipine is a calcium-channel blocker, anti-arrhythmic and anti-anginal drug used to prevent angina attacks, treat Reynaud's disease, treat high blood pressure and treat spasm of the oesophagus.
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The nipples contain the outlets of the milk ducts (lactiferous tubules). Each nipple is situated in the center of the mammary gland. It generally has a conical shape and is a light rosy colour that deepens during pregnancy. Nipples vary in size and shape and may be smooth, protruding, or inverted. The nipples enlarge during pregnancy, followed by enlargement of the entire mammary gland. The
nipples usually point upward and somewhat to the sides, a position that is believed to have evolved because it is most convenient for the sucking infant. The nipple and areola contain smooth muscle fibres that can contract in response to cold, to sexual stimulation, or to the baby's suckling, causing the areola to shrink and the nipple to become erect. The involuntary action squeezes the ducts and, during breast-feeding, helps release milk.
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Nissen fundoplication is an operation to sew the top of the stomach (the fundus) around the esophagus. It is used to stop stomach contents from flowing back into the esophagus (reflux) and to repair a hiatal hernia.
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Nitrazepam is a hypnotic drug given by mouth to treat insomnia.
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Nitrogen mustard, in its pure form, occurs as a dark liquid with a faint fishy odour. It is fairly volatile and decomposes slowly on standing, forming the polymeric quaternary ammonium salt. It is very slightly soluble in water. Nitrogen mustard hydrochloride, which is the form produced commercially for sale, is composed of large white, hygroscopic crystals that are soluble in water and methanol. When heated to decomposition, nitrogen mustard emits very toxic fumes of hydrochloric acid and other chlorinated compounds as well as nitrogen oxides (NOx). As formulated for injection,
nitrogen mustard hydrochloride contains 100% +/- 10% active ingredient. Currently, the only known commercial use of nitrogen mustard is as a chemical intermediate in the production of its hydrochloride. Nitrogen mustard hydrochloride is used as an anti-neoplastic agent, either alone or in combination with other chemo-therapeutic agents, to treat neoplastic diseases, including Hodgkin' s disease, leukaemia, generalised lymphosarcoma, mycosis fungoides, and bronchogenic carcinoma. Also, it is used to control pleural, peritoneal, and pericardial effusions caused by metastatic tumours. Clinical investigations have been performed in the past to evaluate its usefulness in treatment of rheumatoid arthritis and a variety of other non-malignant diseases. Research has also been conducted to investigate its use as a chemosterilant and as a cross-linking agent for the manufacture of ion-exchange fibres. Formerly, the pure form of nitrogen mustard was produced for use as a vesicant in chemical warfare.
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Nitrous oxide (laughing gas) is an odourless, non-explosive, toxic analgesic gas. It causes exhilaration, insensibility, analgesia, delirium and loss of motor control (which makes its use in pregnancy labour rather questionable), elation and excitement. It has a quick action and is used for short operations, such as the removal of teeth.
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A NK cell (natural killer cell) is a non-specific lymphocyte. NK cells, like killer T cells, attack and kill cancer cells and cells infected by microorganisms. NK cells are 'natural' killers because they do not need to recognize a specific antigen in order to attack and kill.
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Nocardiosis is a disease affecting the skin, lungs and brain resulting in abscesses.
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Noctiphobia is the fear of the night.
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The nodes of Ranvier are the small constricted portions of the neuron's myelin sheath which separate the axons along the cell's length. These narrowings, or gaps, are more permeable to potassium and sodium ions than the rest of the axon body. Consequently, these nodes allow nerve impulses to be transmitted from the axons, where otherwise the impulses would be shielded by the insulating myelin sheath.
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Nomatophobia is the fear of names.
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Noninsulin-dependent diabetes mellitus (NIDDM) is the most common form of diabetes mellitus; about 90 to 95 percent of people who have diabetes have NIDDM. Unlike the insulin-dependent type of diabetes, in which the pancreas makes no insulin, people with noninsulin-dependent diabetes produce some insulin, sometimes even large amounts. However, either their bodies do not produce enough insulin or their body cells are resistant to the action of insulin. People with NIDDM can often control their condition by losing weight through diet and exercise. If not, they may need to combine insulin or a pill with diet and exercise. Generally, NIDDM occurs in people who are over age 40. Most of the people who have this type of diabetes are overweight. Noninsulin- dependent diabetes mellitus used to be called 'adult-onset diabetes,' 'maturity-onset diabetes,' ' ketosis- resistant diabetes,' and 'stable diabetes.' It is also called type II diabetes mellitus.
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Nonsteroidal anti-inflammatory rrugs (NSAIDs) are a group of medications, including aspirin, ibuprofen, and related drugs, used to reduce inflammation that causes joint pain, stiffness, and swelling.
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Nonulcer dyspepsia is a constant pain or discomfort in the upper gastro-intestinal tract. Symptoms include burning, nausea, and bloating, but no ulcer. It is possibly caused by muscle spasms.
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The nose is the organ in man and the higher animals exercising the olfactory sense, or that of smell, and concerned through its apertures or passages in the function of respiration and in the production of voice. The bones of the nose comprise the boundaries of the nasal fossa or cavities, which open in front in the nasal apertures, and behind into the pharynx or back part of the mouth. The front nostrils, or openings of the nose, are in the skeleton of an oval or heart shape, while the openings of the posterior nostrils are of a quadrilateral form.
The bones which enter into the entire structure of the nose number fourteen. In addition there are certain cartilaginous pieces which assist in forming the structure of tlie nose, lateral cartilages on either side, and a cartilaginous septum in the middle between the two nostrils. There is also a bony septum which unites with the cartilaginous septum to form the complete partition of the nose. Several special muscles give a certain mobility to the softer parts of the organ.
The nostrils and nasal cavities are lined by the mucous membrane (pituitary membrane) richly furnished with arteries and veins and covered with a copious mucous secretion which keeps it in the moistened state favourable to the due exercise of the function of smell. The proper nerves of smell, the olfactory nerves, form the first pair of cerebral nerves or those which take origin from the cerebrum; while the nerves of common sensibility of the nose belong to the fifth pair of cerebral nerves. The olfactory nerves are distributed in the mucous membrane of either side in the form of a sort of thick brush of small nerve-fibres.
The study of the comparative anatomy of the nasal organs shows us that man possesses a sense of smell greatly inferior in many instances to that of the lower animals. The distribution of the olfactory nerves in man is of a very limited nature when compared with what obtains in such animals as the dog, sheep, etc. All Vertebrates above fishes generally resemble man in the essential type of their olfactory apparatus. In most fishes the nostrils are simply shut or closed sacs, and do not communicate posteriorly with the mouth. The proboscis of the elephant exemplifies a singular elongation of the nose, in which the organ becomes modified for tactile purposes. In the seals and other diving animals the nostrils can be closed at will by sphincter muscles or valvular processes. The most frequent diseases or abnormal conditions which affect the nose comprise congenital defects, and tumours or polypi.
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Nosemaphobia is the fear of illness.
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Nosocomephobia is the fear of hospitals.
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Nosology (from the Greek, nosos meaning disease) is the branch of medicine concerned with the classification of diseases, with names and definitions, according to the distinctive character of each class, order, genus, and species. Many systems of nosology have been proposed at different times, but that of Dr. William Farr has been very generally adopted as practically useful. By this system all diseases are classed under the heads of (1) Zymotic Diseases, including fevers and all diseases that may be attributed to the introduction of some ferment or poisonous matter into the system; (2) Constitutional Diseases, as gout, rheumatism, cancer, scrofula, consumption, etc; (3) Local Diseases, as diseases connected with the nerves, circulation, digestion, respiration, urinogenital system, skin, etc; and (4) Developmental Diseases, as malformations, special diseases of women, diseases connected with childhood or old age, &etc.
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Nosophobia is the fear of illness.
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Nostophobia is the fear of returning home.
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Novabritine is a brand name for Amoxicillin.
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Novamoxin is a brand name for Amoxicillin.
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Novenzymin is a brand name for Amoxicillin.
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Novercaphobia is the fear of step-mothers.
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Novocaine (procaine) was a synthetic drug invented in 1905 and formerly widely used as a local anaesthetic. It has replaced cocaine, being equally strong when injected-but only one-third as toxic and not habit-forming. It is, however, not nearly so effective when used as a surface anaesthetic. It was always used with adrenaline. It is now seldom used, having been replaced by agents such as lignocaine.
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Novosalmol is a brand name for albuterol.
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On the external surface of the occipital bone, visible in the posterior and inferior views of the skull, are two transverse crests. The upper crest is called the superior
nuchal line, while the lower is the inferior nuchal line. These lines cross over the median occipital crest which contains the external occipital protuberance.
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Nuclear medicine is the branch of medicine concerned with the use of radionuclides in the diagnosis and treatment of disease.
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Nucleomituphobia is the fear of nuclear weapons.
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Nucleoside is a component molecule of RNA and DNA.
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Nudophobia is the fear of nudity.
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Numerophobia is the fear of numbers.
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Nutcracker syndrome is abnormal muscle tightening in the esophagus.
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Nyctalopia is an ophthalmic disorder, sufferers from which can only see in darkness or in a faint light, being deprived of sight in daylight. The term has also been applied to hemeralopia or night-blindness, the exactly opposite defect of vision.
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Nyctophobia is the fear of night.
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Nystagmus is the rapid, rhythmic oscillation of the eyes; movements may be vertical, horizontal or rotary. It may occur with poor vision or it may be due to a disorder in the brain.
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