Cell Division: From 2 Different Sources
The processes by which cells multiply. Mitosis is the most common form of cell division, giving rise to
daughter cells identical to the parent cells.Meiosis produces egg (see ovum) and sperm cells that differ from their parent cells in that they have only half the normal number of chromosomes.
reproduction of cells by division first of the chromosomes (karyokinesis) and then of the cytoplasm (cytokinesis). Cell division to produce more body (somatic) cells is by *mitosis; cell division during the formation of gametes is by *meiosis.
A generally slow growing malignant epithelial tumour, which has potential to invade and metastasise, especially if untreated.... basal cell carcinoma
The smallest unit of living material that can function independently.... cell
Those embryonic cells with the potential to develop into ova (see OVUM) or spermatozoa (see SPERMATOZOON).... germ cell
See HYPERNEPHROMA.... renal cell carcinoma
Malignant tumour of squamous epithelium of skin, which generally spreads and metastasises.... squamous cell carcinoma
See: ARTERITIS. ... giant cell arteritis
This is the basic cell from which all types of blood cells originate. Its appearance is believed to be similar to that of a LYMPHOCYTE.... haemopoietic stem cell
See NEURON(E).... nerve cell
A type of cell found in one highly malignant form of lung cancer. The cell is small and either oval or round. The nucleus stains darkly and the cytoplasm is sparse and di?cult to identify. Oat-cell, or small-cell, carcinoma of the bronchus is usually caused by smoking, and comprises around 30 per cent of all bronchial cancers. It responds to radiotherapy and chemotherapy but, because the growth has usually spread widely by the time it is diagnosed, the prognosis is poor. Results of surgery are unsatisfactory.... oat cell
That fraction of the blood’s total volume made up of red cells. The packed cell volume is found by centrifuging blood in a tube and measuring the depth of the column of red cells as a fraction of the whole column of blood. (See also HAEMATOCRIT.)... packed cell volume
See ERYTHROCYTES; BLOOD.... red blood cell
See MEIOSIS.... reduction division
See OAT CELL.... small-cell carcinoma
A specialised white cell (lymphocyte) responsible for cell-mediated immunity. See also T-lymphocyte.... t-cell
See LEUCOCYTES.... white blood cell
See lymphocyte.... b-cell
A growth comprised of immature sperm cells in the male testis or of immature ova in the female ovary. A seminoma is one type of germ cell tumour (see testis, cancer of).... germ cell tumour
A type of white blood cell that circulates through the body and is able to detect the presence of the foreign agents. Once exposed to an antigen on the agent, these cells differentiate into plasma cells to produce antibody.... b-lymphocyte (or b-cell)
See TRANSFUSION.... cell salvage transfusion
A defence mechanism involving the coordinated activity of two subpopulations of TLymphocytes, helper T-Cells and killer T-Cells. Helper T-Cells produce a variety of substances that stimulate and regulate other participants in the immune response. Killer T-Lymphocytes destroy cells in the body that bear foreign antigens (e.g. cells that are infected with viruses or other microorganisms).... cell-mediated immunity
A method of autologous blood TRANSFUSION – using a patient’s own blood, salvaged during a surgical operation – instead of conventional blood-bank transfusion.... perioperative cell salvage
These have almost completely replaced BONE MARROW TRANSPLANT, used to treat malignancies such as LEUKAEMIA and LYMPHOMA for the past 20 years. The high doses of CHEMOTHERAPY or RADIOTHERAPY used to treat these diseases destroy the bone marrow which contains stem cells from which all the blood cells derive. In 1989 stem cells were found in the blood during recovery from chemotherapy. By giving growth factors (cytokines), the number of stem cells in the blood increased for about three to four days. In a peripheral-blood stem-cell transplant, these cells can be separated from the peripheral blood, without a general anaesthetic. The cells taken by either method are then frozen and returned intravenously after the chemotherapy or radiotherapy is completed. Once transplanted, the stem cells usually take less than three weeks to repopulate the blood, compared to a month or more for a bone marrow transplant. This means that there is less risk of infection or bleeding during the recovery from the transplant. The whole procedure has a mortality risk of less than 5 per cent – half the risk of a bone marrow transplant.... peripheral-blood stem-cell transplants
The cells that produce the MYELIN sheath of the AXON of a medullated NERVE. They are wrapped around a segment of the axon, forming concentric layers.... schwann cell
See LYMPHOMA.... t-cell lymphoma
CEREBRUM This forms nearly 70 per cent of the brain and consists of two cerebral hemispheres which occupy the entire vault of the cranium and are incompletely separated from one another by a deep mid-line cleft, the longitudinal cerebral ?ssure. At the bottom of this cleft the two hemispheres are united by a thick band of some 200 million crossing nerve ?bres
– the corpus callosum. Other clefts or ?ssures (sulci) make deep impressions, dividing the cerebrum into lobes. The lobes of the cerebrum are the frontal lobe in the forehead region, the parietal lobe on the side and upper part of the brain, the occipital lobe to the back, and the temporal lobe lying just above the region of the ear. The outer 3 mm of the cerebrum is called the cortex, which consists of grey matter with the nerve cells arranged in six layers. This region is concerned with conscious thought, sensation and movement, operating in a similar manner to the more primitive areas of the brain except that incoming information is subject to much greater analysis.
Numbers of shallower infoldings of the surface, called furrows or sulci, separate raised areas called convolutions or gyri. In the deeper part, the white matter consists of nerve ?bres connecting di?erent parts of the surface and passing down to the lower parts of the brain. Among the white matter lie several rounded masses of grey matter, the lentiform and caudate nuclei. In the centre of each cerebral hemisphere is an irregular cavity, the lateral ventricle, each of which communicates with that on the other side and behind with the third ventricle through a small opening, the inter-ventricular foramen, or foramen of Monro.
BASAL NUCLEI Two large masses of grey matter embedded in the base of the cerebral hemispheres in humans, but forming the chief part of the brain in many animals. Between these masses lies the third ventricle, from which the infundibulum, a funnel-shaped process, projects downwards into the pituitary body, and above lies the PINEAL GLAND. This region includes the important HYPOTHALAMUS.
MID-BRAIN or mesencephalon: a stalk about 20 mm long connecting the cerebrum with the hind-brain. Down its centre lies a tube, the cerebral aqueduct, or aqueduct of Sylvius, connecting the third and fourth ventricles. Above this aqueduct lie the corpora quadrigemina, and beneath it are the crura cerebri, strong bands of white matter in which important nerve ?bres pass downwards from the cerebrum. The pineal gland is sited on the upper part of the midbrain.
PONS A mass of nerve ?bres, some of which run crosswise and others are the continuation of the crura cerebri downwards.
CEREBELLUM This lies towards the back, underneath the occipital lobes of the cerebrum.
MEDULLA OBLONGATA The lowest part of the brain, in structure resembling the spinal cord, with white matter on the surface and grey matter in its interior. This is continuous through the large opening in the skull, the foramen magnum, with the spinal cord. Between the medulla, pons, and cerebellum lies the fourth ventricle of the brain.
Structure The grey matter consists mainly of billions of neurones (see NEURON(E)) in which all the activities of the brain begin. These cells vary considerably in size and shape in di?erent parts of the brain, though all give o? a number of processes, some of which form nerve ?bres. The cells in the cortex of the cerebral hemispheres, for example, are very numerous, being set in layers ?ve or six deep. In shape these cells are pyramidal, giving o? processes from the apex, from the centre of the base, and from various projections elsewhere on the cell. The grey matter is everywhere penetrated by a rich supply of blood vessels, and the nerve cells and blood vessels are supported in a ?ne network of ?bres known as neuroglia.
The white matter consists of nerve ?bres, each of which is attached, at one end, to a cell in the grey matter, while at the other end it splits up into a tree-like structure around another cell in another part of the grey matter in the brain or spinal cord. The ?bres have insulating sheaths of a fatty material which, in the mass, gives the white matter its colour; they convey messages from one part of the brain to the other (association ?bres), or, grouped into bundles, leave the brain as nerves, or pass down into the spinal cord where they end near, and exert a control upon, cells from which in turn spring the nerves to the body.
Both grey and white matter are bound together by a network of cells called GLIA which make up 60 per cent of the brain’s weight. These have traditionally been seen as simple structures whose main function was to glue the constituents of the brain together. Recent research, however, suggests that glia are vital for growing synapses between the neurons as they trigger these cells to communicate with each other. So they probably participate in the task of laying down memories, for which synapses are an essential key. The research points to the likelihood that glial cells are as complex as neurons, functioning biochemically in a similar way. Glial cells also absorb potassium pumped out by active neurons and prevent levels of GLUTAMATE – the most common chemical messenger in the brain – from becoming too high.
The general arrangement of ?bres can be best understood by describing the course of a motor nerve-?bre. Arising in a cell on the surface in front of the central sulcus, such a ?bre passes inwards towards the centre of the cerebral hemisphere, the collected mass of ?bres as they lie between the lentiform nucleus and optic thalamus being known as the internal capsule. Hence the ?bre passes down through the crus cerebri, giving o? various small connecting ?bres as it passes downwards. After passing through the pons it reaches the medulla, and at this point crosses to the opposite side (decussation of the pyramids). Entering the spinal cord, it passes downwards to end ?nally in a series of branches (arborisation) which meet and touch (synapse) similar branches from one or more of the cells in the grey matter of the cord (see SPINAL CORD).
BLOOD VESSELS Four vessels carry blood to the brain: two internal carotid arteries in front, and two vertebral arteries behind. These communicate to form a circle (circle of Willis) inside the skull, so that if one is blocked, the others, by dilating, take its place. The chief branch of the internal carotid artery on each side is the middle cerebral, and this gives o? a small but very important branch which pierces the base of the brain and supplies the region of the internal capsule with blood. The chief importance of this vessel lies in the fact that the blood in it is under especially high pressure, owing to its close connection with the carotid artery, so that haemorrhage from it is liable to occur and thus give rise to stroke. Two veins, the internal cerebral veins, bring the blood away from the interior of the brain, but most of the small veins come to the surface and open into large venous sinuses, which run in grooves in the skull, and ?nally pass their blood into the internal jugular vein that accompanies the carotid artery on each side of the neck.
MEMBRANES The brain is separated from the skull by three membranes: the dura mater, a thick ?brous membrane; the arachnoid mater, a more delicate structure; and the pia mater, adhering to the surface of the brain and containing the blood vessels which nourish it. Between each pair is a space containing ?uid on which the brain ?oats as on a water-bed. The ?uid beneath the arachnoid membrane mixes with that inside the ventricles through a small opening in the fourth ventricle, called the median aperture, or foramen of Magendie.
These ?uid arrangements have a great in?uence in preserving the brain from injury.... divisions
A form of anaemia growing into an acute social problem, affecting people of African, Asian, and Mediterranean origin. Thalassaemias are caused by defects of a gene that produces the globin part of haemoglobin. Such defects in the DNA can now be detected in the womb before birth. The name derives from sickle-shaped cells instead of circular red blood cells. Few sufferers survive beyond their 40th year.
Symptoms. Unhealthy pallor, listlessness, sore tongue, dizziness, vague aches and pains, rapid pulse and breathing, tinnitus, palpitation. The skull may be disproportionately large, resistance to infection feeble, chances of survival poor. This form of anaemia is linked with defective colour vision. Impaired liver function. Stunted growth, great pain. Sufferers have a higher risk of infection.
Malaria. Sufferers are less likely to die of malaria because their red cells do not support the growth of malaria parasites very well.
Carriers: Carriers of the sickle-cell gene can now be identified by a simple blood test.
Treatment. No specifics exist but supportive herbal treatment has been known to increase output of red cells and raise haemoglobin levels:– Red Clover flowers, Yellow Dock, Echinacea, Burdock, Wild Indigo, Gentian, Nettles, Birch leaves, Sage, Walnut leaves, Centaury, Gota Kola (Indian Pennywort). Alternatives:– Tea. Mix equal parts: Iceland Moss, Nettles, Red Clover flowers. 2 teaspoons to each cup boiling water; infuse 15 minutes; 1 cup morning and evening.
Decoction. Mix equal parts; Echinacea, Walnut leaves, Balm of Gilead buds; 1 teaspoon to each cup water gently simmered for 20 minutes. Half-1 cup, cold, 3 times daily, before meals.
Tablets/capsules. Sarsaparilla. Ginseng. Iceland Moss. Red Clover. Echinacea. Gentian.
Powders. Formula: Echinacea 1; Fringe Tree half; Ginseng half; White Poplar bark 1. Dose: 500mg (two 00 capsules or one-third teaspoon) thrice daily before meals.
Liquid extracts. Formula. Echinacea 2; Dandelion 1; Oat Husk (avena sativa) 1. Mix. Dose, 1-2 teaspoons before meals, in water or one of the above teas or decoctions.
Tinctures. Same combination. Dose: 2-3 teaspoons.
Dong quai. See entry.
Pollen. Claimed to be of value.
Diet. Dandelion coffee. Molasses. Desiccated liver. Calf liver, fresh. Green leafy vegetables contain chlorophyll, iron and folic acid. Cider vinegar. Dried beans, apricots and shellfish. Dandelion leaves in salads. Milk, eggs, meats, Soya. Carrot juice to increase red cells.
Supplements. Daily. Vitamin B12. Vitamin C, 1g; Folic acid 400mcg, Floradix. Of particular value: Vitamin E 400iu. Zinc.
Note: Those at risk should submit themselves for screening. The disease cannot be cured but can be controlled largely by orthodox measures and sometimes by natural medicine. ... anaemia: sickle cell
A growth composed of cells that produce various hormones. These cells, amine precursor uptake and decarboxylation (APUD) cells, occur in different parts of the body. Some tumours of the thyroid gland, pancreas, and lungs are cell tumours, as are a carcinoid tumour (see carcinoid syndrome) and phaeochromocytoma (a type of adrenal tumour).... apud cell tumour
(APC) a cell, such as a *dendritic cell or a *macrophage, that processes antigen for presentation to a T lymphocytes (see helper T cell).... antigen-presenting cell
(blood corpuscle) any of the cells that are present in the blood in health or disease. The cells may be subclassified into three major categories, namely red cells (*erythrocytes); white cells (*leucocytes), which include granulocytes, lymphocytes, and monocytes; and *platelets (see illustration). The blood cells account for approximately 40% of the total volume of the blood in health; red cells comprise the vast majority.... blood cell
An inherited blood disease in which the red blood cells contain haemoglobin S, an abnormal type of haemoglobin. This crystallizes in the capillaries, making red cells sickle-shaped and fragile, and leading to haemolytic anaemia. The abnormal cells are unable to pass easily through tiny blood vessels. The blood supply to organs is blocked intermittently, causing sickle cell crises. The disease affects mainly black people.Symptoms usually appear after age 6 months, often beginning with painful swelling of the hands and feet. Chronic haemolytic anaemia causes fatigue, headaches, shortness of breath on exertion, pallor, and jaundice. Sickle cell crises start suddenly; they are sometimes brought on by an infection, cold weather, or dehydration, but may also occur for no apparent reason. The sufferer may experience pains (especially in the bones), blood in the urine (from kidney damage) or damage to the lungs or intestines. If the brain is affected, seizures, a stroke, or unconsciousness may result.
In some affected children, the spleen enlarges and traps red cells at a particularly high rate, causing a life-threatening form of anaemia. After adolescence, the spleen usually stops functioning, increasing the risk of infection in those affected.
Diagnosis is made from examination of a blood smear and electrophoresis.
Supportive treatment may include folic acid supplements, and penicillin and immunization to protect against infection.
Life-threatening crises are treated with intravenous infusions of fluids, antibiotics, oxygen therapy, and analgesic drugs.
If the crisis still does not respond, an exchange blood transfusion may be performed.
This may be done regularly for people who suffer frequent severe crises.... sickle cell anaemia
(echinocyte) a red blood cell (erythrocyte) with abnormal small thorny projections. See crenation.... burr cell
(perikaryon) the enlarged portion of a *neuron (nerve cell), containing the nucleus. It is concerned more with the nutrition of the cell than with propagation of nerve impulses.... cell body
a machine that aspirates blood lost during surgery and immediately spins, washes, and filters it for retransfusion back into the patient’s body (see autotransfusion). The process, called intraoperative cell salvage, is used in surgery that has significant blood loss, such as orthopaedic and vascular surgery and Caesarean section, and avoids the costs and risks of *allogeneic transfusion.... cell saver
molecules on the surface of cell membranes that are responsible for most cellular functions directly related to their immediate environment. Many have very precise functions of adhesion (see adhesion molecules), metabolic exchange, hormone reception, respiration, and immune reactions. Cell-to-cell exchanges involve specialized surface structures (junctions), which form a communicating nexus.... cell-surface molecules
(clear-cell adenocarcinoma) a variant of *adenocarcinoma that tends to arise from the kidneys or the female genital tract. In the latter case it is linked to intrauterine exposure to *diethylstilbestrol during the 1950s and 1960s and takes the form of a vaginal cancer, which can be treated by radical surgery followed by radiotherapy.... clear-cell carcinoma
a group of lymphomas in which abnormal T *lymphocytes are concentrated in the skin. The most common form is *mycosis fungoides.... cutaneous t-cell lymphoma
a type of T *lymphocyte that destroys cancerous cells, virus-infected cells, and *allografts. Cytotoxic T cells recognize peptide antigens attached to proteins that are encoded by the *HLA system.... cytotoxic t cell
a type of haemopoietic cell with specialized antigen-presenting functions. The head and neck are common sites for dendritic cell pathology. See antigen-presenting cell.... dendritic cell
n. 1. the separation of an organ or tissue into parts by surgery. 2. see cell division.... division
n. any of the gastrin-secreting cells of the stomach lining located predominantly in the gastric *antrum. Gastrin stimulates the production of gastric acid by parietal cells in the stomach. Increased G-cell activity is associated with the formation of duodenal ulcers and the *Zollinger-Ellison syndrome.... g-cell
any large cell, such as a *megakaryocyte. Giant cells may have one or many nuclei.... giant cell
an abnormal white blood cell that has the appearance of an immature lymphocyte with fine hairlike cytoplasmic projections around the perimeter of the cell. It is found in a rare form of leukaemia (hairy-cell leukaemia) most commonly occurring in young men.... hairy cell
a type of T *lymphocyte that plays a key role in cell-mediated immunity by recognizing foreign antigen on the surface of *antigen-presenting cells when this is associated with the individual’s *MHC antigens, having been processed by antigen-presenting cells. Helper T cells stimulate the production of *cytotoxic T cells, which destroy the target cells.... helper t cell
an androgen-producing tumour of the ovary found in older women and often resulting in *virilization. Such tumours are so called as they tend to occur around the area of the ovary where the blood vessels enter (the hilum). They are usually small and are treated by surgical removal, with resolution of most of the symptoms.... hilar cell tumour
a malignant tumour of the thyroid gland that arises from Hürthle (or Askanazy) cells, altered follicular cells of the gland that have large nuclei and stain deeply with eosin (these cells are also found in benign nodules and Hashimoto’s disease). Hürthle cell carcinoma is not as common as papillary, follicular, or anaplastic thyroid carcinomas (see thyroid cancer). [K. W. Hürthle (1860–1945), German histologist]... hürthle cell tumour
see luteinizing hormone.... interstitial-cell-stimulating hormone
a group of autoantibodies directed against components of the insulin-secreting beta cells of the pancreas. They are usually detectable in the blood of people presenting with type 1 diabetes. Antibodies against *glutamic acid decarboxylase (GAD) in the beta cells have become a more specific test for islet cell antibodies, to help confirm a diagnosis of type 1 diabetes.... islet cell antibodies
a new technique still under evaluation for curing type 1 *diabetes mellitus, which involves the injection of donated cells from the pancreatic *islets of Langerhans into the liver, where it is hoped they will seed and survive. The transplanted cells then take over insulin production from the recipient’s diseased pancreas.... islet cell transplantation
any tumour arising in a cell of the pancreatic *islets of Langerhans. These tumours, which include *insulinomas, *glucagonomas, and *somatostatinomas, form one of the two major subclasses of gastrointestinal neuroendocrine tumours, the other being the *carcinoid tumours.... islet cell tumour
overgrowth of cells of the *reticuloendothelial system. This includes disorders previously called histiocytosis X, including eosinophilic granuloma, Hand–Schüller–Christian disease, and Letterer–Siwe disease. [P. Langerhans (1847–88), German physician and anatomist]... langerhans cell histiocytosis
a long-lived lymphocyte that is formed following primary infection. It enables a faster and more robust immune response following a second exposure to the antigen.... memory cell
(NK cell) a type of *lymphocyte that is able to kill virus-infected cells and cancerous cells and mediates rejection of bone-marrow grafts. NK cells are a part of natural (or innate) *immunity. Their function is regulated by a balance between activating receptors, which recognize proteins on cancerous or virus-infected cells, and inhibitory receptors specific for certain molecules encoded by the *HLA system.... natural killer cell
(NSCLC) any type of lung cancer other than *small-cell lung cancer. Such cancers include *adenocarcinoma of the lung, large-cell carcinomas, and squamous-cell carcinoma of the lung.... non-small-cell lung cancer
a posterior ethmoidal sinus air cell (see paranasal sinuses). They are surgically important because of their proximity to the optic nerve and internal carotid artery. [A. Onodi (1857–1919), Hungarian rhinolaryngologist]... onodi cell
a type of neuron found in the *cerebral cortex, with a pyramid-shaped cell body, a branched dendrite extending from the apex towards the brain surface, several dendrites extending horizontally from the base, and an axon running in the white matter of the hemisphere.... pyramidal cell
a large binucleate cell that is characteristic of *Hodgkin’s disease. [D. Reed Mendenhall (1874–1964), US pathologist; C. Sternberg (1872–1935), Austrian pathologist]... reed–sternberg cell
(Treg cell) a type of T *lymphocyte that suppresses immune responses.... regulatory t cell
a cell that is not undergoing division. See interphase.... resting cell
progressive renal disease developing in 5–8% of patients with *sickle-cell disease. Infarcts in the cortex can occur with sickle-cell crises and present with pain and haematuria. Acute or more insidious damage to the medulla will lead to a urinary concentrating defect and later to papillary necrosis and/or fibrosis. Occlusion of vessels within the glomerular capillary tuft leads to a secondary form of *focal segmental glomerulosclerosis and can present with the *nephrotic syndrome.... sickle-cell nephropathy
(SCLC) a type of bronchial carcinoma characterized by small cells (or oat cells), small round or oval cells with darkly staining nuclei and scanty indistinct cytoplasm. Small-cell carcinoma is usually related to smoking and accounts for about one-quarter of bronchial carcinomas; it carries a poor prognosis due to early distant spread, typically to bones, liver, and brain. Treatment is primarily with chemotherapy and radiotherapy and paraneoplastic symptoms (see paraneoplastic syndrome) from *ectopic hormone production are common. Compare non-small-cell lung cancer.... small-cell lung cancer
see Reed–Sternberg cell.... sternberg–reed cell
a type of T *lymphocyte that prevents an immune response by B cells or other T cells to an antigen.... suppressor t cell
a form of cancer that affects the urothelium, which lines the urinary collecting system of the kidney, ureters, bladder, and the proximal part of the urethra. It is the most common type of bladder cancer.... transitional cell carcinoma
see regulatory T cell.... treg cell
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