D cells Health Dictionary

Also called Leydig cells, these cells are scattered between the SEMINIFEROUS TUBULES of the testis (see TESTICLE). LUTEINISING HORMONE from the anterior PITUITARY GLAND stimulates the interstitial cells to produce androgens, or male hormones.... interstitial cells

Star-shaped cells present in the blood-sinuses of the LIVER. They form part of the RETICULOENDOTHELIAL SYSTEM and are to a large extent responsible for the breakdown of HAEMOGLOBIN into the BILE pigments.... kupffer cells

These are a group of cells that line the capillaries of tissues that come in contact with the outside, like skin, sinuses, and lung mucosa. They, like their first cousin basophils, are produced in the red bone marrow and migrate to the appropriate tissues, where they stay. They bind IgE, supply the histamine and heparin response that gives you a healing inflammation, and cause allergies.... mast cells

These are cells that produce ANTIBODIES and occur in bone-forming tissue as well as the lining of the gastrointestinal tract and the lungs. The cells develop in LYMPH NODES, SPLEEN and BONE MARROW when T-lymphocytes (see IMMUNITY) are stimulated by antigens (see ANTIGEN) to produce the precursor cells from which plasma cells originate.... plasma cells

Large specialised nerve cells occurring in great numbers in the cortex (super?cial layer of grey matter) of the cerebellum of the BRAIN. They have a ?ask-shaped body, an AXON and branching tree-like extensions called dendrites, which extend towards the surface of the brain (see NEURON(E)).... purkinje cells

The basic structural unit of body tissues. There are around 10 billion cells in the human body and they are structurally and functionally linked to carry out the body’s many complex activities.

Every cell consists essentially of a cell-body of soft albuminous material called cytoplasm, in which lies a kernel or nucleus which seems to direct all the activities of the cell. Within the nucleus may be seen a minute body, the nucleolus; and there may or may not be a cell-envelope around all. (See also MITOCHONDRIA.) Each cell nucleus carries a set of identical CHROMOSOMES, the body’s genetic instructions.

Cells vary much in size, ranging in the human body from 0·0025 mm to about 0·025 mm.

All animals and plants consist at ?rst of a single cell (the egg-cell, or ovum), which begins to develop when fertilised by the sperm-cell derived from the opposite sex. Development begins by a division into two new cells, then into four, and so on till a large mass is formed. These cells – among them stem cells (see STEM CELL) which have the potential to develop into a variety of specialised cells – then arrange themselves into layers, and form various tubes, rods, and masses which represent in the embryo the organs of the fully developed animal. (See FETUS.)

When the individual organs have been laid down on a sca?olding of cells, these gradually change in shape and in chemical composition. The cells in the nervous system send out long processes to form the nerves; those in the muscles become long and striped in appearance; and those which form fat become ?lled with fat droplets which distend the cells. Further, they begin to produce, between one another, the substances which give the various tissues their special character. Thus, in the future bones, some cells deposit lime salts and others form cartilage, while in tendons they produce long white ?bres of a gelatinous substance. In some organs the cells change little: thus the liver consists of columns of large cells packed together, while many cells, like the white blood corpuscles, retain their primitive characters almost entire.

Thus cells are the active agents in forming the body, and they have a similar function in repairing its wear and tear. Tumours, and especially malignant tumours, have a highly cellular structure, the cells being of an embryonic type, or, at best, forming poor imitations of the tissues in which they grow (see TUMOUR).... cells

Literally, those derived from embryonic mesoderm; practically, those in a tissue that give it structure and form. The opposite of parenchymal.... mesenchymal cells

A type of lymphocyte which assists the B-Lymphocytes in producing antibodies.... t-helper cells

White blood cells that have matured in the thymus gland. There are at least two kinds of T-lymphocytes - helpers and suppressors. In AIDS, the number of helper cells is decreased.... t-lymphocytes (or t-cells)

A type of T-lymphocyte that stops antibody production when the invading antigen has been inactivated.... t-suppressor cells

cells that share the metabolic property of amine-precursor uptake and decarboxylation. They have a wide distribution, especially in the mucosa of the gastrointestinal tract and pancreas, and their function is to synthesize and release polypeptides that serve as regulator peptides and neurotransmitters. They are often known as the diffuse neuroendocrine system.... apud cells

cells that stain readily with silver salts. Such cells occur, for example, in the crypts of Lieberkühn in the intestine.... argentaffin cells

see Hürthle cell tumour.... askanazy cells

see islets of Langerhans.... beta cells

parafollicular cells of the thyroid gland, which are derived from neural crest tissue. They produce *calcitonin. *Medullary carcinoma of the thyroid has its origin in the C cells.... c cells

Cells, also called blood corpuscles, present in blood for most or part of their lifespan. They include red blood cells, which make up about 45 per cent by volume of normal blood, white blood cells, and platelets. Blood cells are made in the bone marrow by a series of divisions from stem cells.

Red blood cells (also known as RBCs, red blood corpuscles, or erythrocytes) transport oxygen from the lungs to the tissues (see respiration). Each is packed with haemoglobin, enzymes, minerals, and sugars. Abnormalities can occur in the rate at which RBCs are either produced or destroyed, in their numbers, and in their shape, size, and haemoglobin content, causing forms of

anaemia and polycythaemia (see blood, disorders of).

White blood cells (also called WBCs, white blood corpuscles, or leukocytes) protect the body against infection and fight infection when it occurs. The 3 main types of are granulocytes (also called polymorphonuclear leukocytes), monocytes, and lymphocytes. Granulocytes are further classified as neutrophils, eosinophils, or basophils, and each type of granulocyte has a role in either fighting infection or in inflammatory or allergic reactions. Monocytes and lymphocytes also play an important part in the immune system. Lymphocytes are usually formed in the lymph nodes. One type, a T-lymphocyte, is responsible for the delayed hypersensitivity reactions

White (see allergy) and Red blood blood cell is also involved in cell (neutrophil) protection against cancer. T-lymphocytes manufacture chemicals, known as lymphokines, which affect the function of other cells. In addition, the T-cells moderate the activity of B-lymphocytes, which form the antibodies that can prevent a second attack of certain infectious diseases. Platelets (also known as thrombocytes), are the smallest blood cells and are important in blood clotting.

The numbers, shapes, and appearance of the various types of blood cell are of great value in the diagnosis of disease (see blood count; blood film).... blood cells

types of *neurons (nerve cells) within the central nervous system. Golgi type I neurons have very long axons that connect different parts of the system; Golgi type II neurons, also known as microneurons, have only short axons or sometimes none.... golgi cells

see interstitial cells. [F. von Leydig (1821–1908), German anatomist]... leydig cells

see juxtaglomerular apparatus.... mesangial cells

see parietal cells.... oxyntic cells

(oxyntic cells) cells of the *gastric glands that secrete hydrochloric acid in the fundic region of the stomach.... parietal cells

rows of supporting cells between the sensory hair cells of the organ of Corti (see cochlea).... phalangeal cells

cells with cytoplasmic processes that form intercellular bridges. The germinative layer of the *epidermis is sometimes called the prickle cell layer.... prickle cells

the cells that lay down the *myelin sheath around the axon of a medullated nerve fibre. Each cell is responsible for one length of axon, around which it twists as it grows, so that concentric layers of membrane envelop the axon. The gap between adjacent Schwann cells forms a *node of Ranvier. [T. Schwann (1810–82), German anatomist and physiologist]... schwann cells

cells found in the walls of the seminiferous tubules of the *testis. Compared with the germ cells they appear large and pale. They anchor and probably nourish the developing germ cells, especially the *spermatids, which become partly embedded within them. A Sertoli-cell tumour is a rare testicular tumour causing *feminization. [E. Sertoli (1842–1910), Italian histologist]... sertoli cells

haemopoietic *stem cells collected from umbilical cord blood donated at birth, which can be stored indefinitely and used if a sibling or any other blood-compatible baby develops an illness (such as leukaemia) that could only be treated by cord-blood stem-cell transplantation. This facility is now available in the UK and the USA.... umbilical cord blood banked stem cells