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Eclipse - Oral Physiology Biology Dictionary
Category: Health and Medicine > Oral Physiology
Date & country: 18/09/2007, UK
Words: 391


Acetyl choline
Aneurotransmitter substance found at all cholinergic synapses including those of motoneurones at the neuromuscular junction.

Acini
the secreting units of a gland. Each acinus is a sack-like structure, lined by secreting cells. The sack opens out into a tubule.

Adapt
to modify in response to change. When used in regard to evolution, it means that some structure or behaviour of an organism may over time, appear to change in response toa new threat or opportunity in the environment. The bacterium which causes tuberculosis has developed certain strains which have adapted to the antibiotics used to treat the disease which is now becoming more difficult to treat.

Adductors
muscle bringing a limb or the jaw towards the body.

Adhesion
to form a chemical bond of attachment between two surfaces (see Ligand and lectin).

Adrenalin
see epinephrine.

Aerobic respiration
a type of respiration which requires oxygen and in which glucose is broken down to release energy in a series of steps. The end products are carbon dioxide and water. Step 1;glucose is broken down to pyruvic acid in the cell cytoplasm with the release of 4 hydrogen atoms. Step 2; pyruvic acid is oxidised to acetylcoenzyme A (acetyl CoA), with the release of 4 further hydrogen atoms. Step 3; In the KREB cycle, 16 atoms of hydrogen are released. At all stages the hydrogen atoms are used to form the high energy molecule adenosine triphospate (ATP) via the electron transport system . See also Anaerobic respiration .

Affected dentine
dentine which has been demineralised by acids in advance of invading caries bacteria. A distinction is made between affected dentine and infected dentine, because affected dentine is able to remineralise and should not be removed during cavity preparation.

Aggregate
clumps or collections of small particles or bacteria .

Alkaline phosphatase
an enzyme which removes phosphate groups from organic compounds at an alkaline pH. It is found in high concentrations in matrix vesicles which are about to form new bone mineral. Alkaline phosphatase activity is a good indicator of bone formation.

Alveolar bone
bone which develops around the roots of the teeth to hold them firmly in place. See gomphosis. If the teeth are extracted, the alveolar bone resorbs away. Alveolar bone consists of both trabecula and cortical types of bone.

Ameloblasts
cells which differentiate from ectoderm and secrete enamel during tooth development.

Amino acids
building blocks of proteins containing a carboxyl group (COOH) and an amino group(NH2) both attached to the same carbon atom . The difference between the 20 common amino acids lies in the nature of a side chain the 'R' group. Each amino acid, has a code of three adjacent nucleotides on the DNA molecule. Amino acids are joined together by peptide bonds to form polypeptides and proteins.

Amorphous calcium phosphate
a non crystalline form of apatite which may form as much as30% of bone mineral.

Amygdala
part of the limbic system, which seems to provide the emotional assessment of a new sensation with the memory of a similar sensation.

Anaerobic respiration
the first step in the production of ATP is to break down glucose. This process of glycolysis is a 10 step series of reactions leading finally to the smaller molecule pyruvate. The energy derived from this process is a hydrogen ion and an electron, which are both placed onto the carrier molecule as nicotinamide adenine dinucleotide (NADH+). As the pyruvate and NAD H+ are produced they could move into the mitochondria, for the nextstage of aerobic respiration, provided oxygen is available. If there is no oxygen, NAD H H+ is used in a process of substrate phosphorylation to form ATP. But the pyruvate builds up. It is then converted to lactic acid and removed to the liver. If lactic acid is not removed fast enough it causes muscle weakness and pain. Anaerobic glycolysis does not produce a high yield of energy. There are still high energy bonds remaining in the pyruvate and there is no benefit from the large yield of ATP made possible by the electron transport system in the mitochondria

Angiogenesis
the development of blood vessels - a key event in embryology and healing.

Ankylosis
bony fusion of the two surfaces of a joint to each other, which prevents movement. Ankylosis of the tooth root to its bony socket may causes root resorption.

Antibacterial
inhibiting the growth of bacteria.

Antibodies
-are proteins called immunoglobulins which circulate in the blood and body fluids. They bind specifically to antigens that have induced them. Antibodies are able to inactivate bacterial toxins, viruses and help phagocytes to engulf whole bacteria. They ha

Antigens
proteins, usually foreign, which cause the bodies defense system to produce an antibody. Antigens may be food proteins, bacteria ,viruses or protozoa or cells from another individual(transplant).

Antrum
a hollow cave or SINUS, inside the maxillary bone which is lined by respiratory epithelium.

Apatites
a family of calcium phosphate salts which are found in hard tissues like bone, teeth and shells.

Apoptosis
death of a cell which is programmed by a set of specific genes. Apoptosis of chondrocytes allows osteoblasts to attach to their calcified matrix, and the epithelial cells forming webs between the fingers to die.

Articular
one of the bones which together with the quadrate bones and the dentary, made/make up a reptile's jaw. In mammals the quadrate bone is incorporated into the middle ear as the malleus.

Artificial mouth
- a laboratory device for keeping bacteria growing in a controlled environment It allows for observing bacteria and their growth under different experimental conditions.

Ascorbic acid
or Vitamin C is a dietary requirement for the proper formation of collagen. Deficiency causes scurvy.

ATP - adenosine triphosphate
ATP is a convenient packet of energy used by both animals and plant cells. The energy in ATP is stored in its three negatively charged phosphate groups which are held close together, in spite of their repulsion for each other. This energy, multiplied many hundreds of thousand of times, for each cell is able to move our muscles, transport molecules across membranes and power all the cells other energy requirements. Once the energy has been used the ATP molecule now only has two phosphate groups. It needs energy now from either aerobic or anaerobic respiration to charge it up again, a process known as phosphorylation. Large stores of ATP are not kept as it is highly reactive. The long term storage of energy in animals is in carbon rich molecules, such as glycogen or fatty acids. In plants energy is stored as starch.

Attachment
, see epithelial-attachment

Autocrine
;cell messengers which areproduced by the cell itself and regulate the expression of genes .

Autonomic nervous system
controls routine body functions such as gut activity, respiration, blood pressure and heart rate. There are two main divisions the sympathetic nervous system and the parasympathetic system.

Axon
the extension of a nerve cell, as a thin tube which may be as long a metre or a few short microns in length. The axon, like the cell body is able to depolarise and carry impulses along its length. The impulses from one axon to another nerve cell are transmitted at a synapse. Axons may be myelinated or unmeyelinated, and they may vary in diameter. Thicker, myelinated axons transmit impulses faster than thins unmeyelinated axons.

Basal lamina
a term used to describe the different layers which make up the basement membrane. These different layers of the basement membrane, the lamina lucida and lamina densa are only visible with electron microscopy. Into the lamina dense collagen fibres of the lamina propria are anchored. And on the epithelial side are anchored bundles of tonofilaments from the hemi-desmosomes which anchor the basal epithelial cells to the basement membrane.

Basement membrane
a thin sheet of proteins held together by type IV collagen. On this sheet epithelial cells attach with hemi-desmosomes. All epithelia, whether simple cuboidal cells such as found in the salivary glands, or endothelial cells lining capillaries or thick stratified squamous epithelia of the skin, are all anchored to a basement membrane.

Benign
not harmful. In the sense of tumours, not malignant. When referring to parasites, quite harmless.

Biofilm
- a layer of microorganisms on a surface which is kept constantly wet. Dental plaque is an oral biofilm

Biosurfactants
products of bacteria which increase the hydrophilic nature of a surface so as to allow for better adhesion.

Blood clotting
one of three key processes in haemostasis, the prevention of blood loss. After three minutes of rupture of a small blood vessel, the entire cut is filled with a blood clot. After an hour, the clot has retracted inside the vessel making the plug even more effective. Within a few more hours, fibroblasts have moved into the clot, followed by capillary -forming endothelial cells. Within 10 days the clot is replaced by fibrous scar tissue. Clotting takes place in three steps. 1. In response to damage to the blood vessel prothrombin activator is formed. 2 this activator converts prothrombin into thrombin. 3.The thrombin acts as an enzyme converting fibrinogen into fibrin threads which adhere to the damaged walls of the blood vessel, trap platelets, blood cells and plasma to form a clot.

Blood groups
blood cells from different people do not always have the same cell surface antigens. A transfusions of blood whose antigens do not match the recipient evokes an immune response and the donor cells are broken down. Two of the common blood groups are the A,B,O group and the Rh group. The blood group antigens are glycoproteins or glycolipids.

Bolus
a piece of food which is being chewed to break it down into small pieces.

Bone membrane
a theoretical membrane separating the fluid surrounding bone crystals from the fluid of the surrounding connective tissue. The membrane would be formed by the endosteum.

Bone morphogenic proteins (BMP)
part of the cytokine family of transforming growth factors. BMP have a powerful ability to cause differentiation of stem cells into osteoblasts and to initiate bone formation.

Bradykinin
one of several substances, all known as kinins, which cause vasodilation and increased capillary permeability, both events associated with inflammation.

Buffers
chemical which are able to keep the pH of a solution within a normal range, neither acid nor alkali. Salivary buffers are important in reducing the progress of caries by neutralising plaque acids.

Buttress
an arch shaped support, used by builders of bridges and churches in the days before steel.

Calcium-binding proteins
- proteins which have the ability to store calcium ions and to bind onto calcium in the hydroxyapatite of the enamel surface.

Calculus
a hard deposit of calcified plaque which is found around the neck of the tooth. When it is above the free gingival margin (supra-gingival) it is white and chalky. When it is below (sub-gingival) it is dark and hard.

Candidiasis
an infection caused by Candida albicans, a normal commensal of the mouth; also called 'thrush';

Capsule
a fibrous casing surrounding an organ or gland; also a coating for some bacteria which protects them, from the bodies immune system. It is only the variety of Pneumococcus sp. which has a capsule which is able to pass the immune barrier and cause pneumonia

Caries
the demineralisation, and breakdown of tooth structure by plaque acids.

Cariogenic
likely to cause caries. Sugar is cariogenic because it supports the growth of plaque

Carious plaque
types of plaque which are associated with caries .

Carnivorous
an animal whose diet consists of animal tissue.

CEJ
see cemento-enamel junction.

Cell junctions
sites on the cell membrane where cells attach to neighbouring cells. There are three main types. 1. adhering junctions, which anchor cells to each other to resist separation. They may form a belt of adhesions between cells (as between muscle cells) or spot attachments like desmosomes which hold epithelial cells together. 2. tight junctions have no space between the membranes and allow no leakage between cells. They are found between cells of a secreting glands and between endothelial cells of blood vessels to prevent fluid leaking out. 3. gap junctions are channels which allow transfer of small molecules like ions, sugars and amino acids, between cells.

Cemento-enamel junction
the junction between the enamel covering the crown of the tooth and the cementum covering its root. Often referred to as the CEJ.

Cementoblasts
cells of mesenchyme origin, induced by proteins from cells of ectodermal origin, to form a layer of cementum around the roots of teeth.

Cementum
a thin layer of bone-like material covering the roots of teeth and sometimes the enamel surface, containing both extrinsic and intrinsic fibres.

Central nervous system
the brain and spinal cord. The nerves which leave the spinal cord and brain comprise the peripheral nervous system.

Chemotaxis
the movement of cells in response to chemical messengers. The movement of neutrophils and macrophages into damaged tissues is brought about by signals released by damaged tissues, and bacterial products.. The term applies to the movement of any organism attracted by a specific chemical, which may be a suitable nutrient.

Cholinergice
- cell receptors specific for the neurotransmitter acetyl choline. Cholinergic receptors are found at neuromuscular junctions of muscle fibres and at all the synaptic junctions of the parasympathetic nervous system. They are also found at the pre- ganglionic synapse of the sympathetic nervous system.

Chondroitin sulphate
- the major glycosaminoglycan of cartilage , the other being keratan sulphate.

Chromosomes
structures in the nucleus of a cell which appear visible during cell division. Each chromosome (humans have 24) is a tightly coiled string of DNA wound round a protein.

Clearance
the removal by swallowing, of substance in the mouth. Clearance is dependent on the completeness of swallowing and the rate of flow of saliva.

Clones
a family of cells, or organisms, which are all identical to a single parent. They are produced by asexual reproduction. When a B lymphocytes has recognised a foreign antigen, it provides millions of identical daughter cells in order to produce the specific antibodies in large quantities.

Clotting
see blood clotting

Code
the code of nucleotides is written in 'words' of three letters using an'alphabet' of four 'letters'. These four components of the code are adenine, thymine, cytosine, and guanine.

Collagen
the most common protein found in the body. It has a fibrous structure and makes up the main organic component of bone and dentine, and the fibres of tendons and ligaments.

Collagenase
an enzyme produced by fibroblasts which breaks down collagen fibres. The fibroblast recycles the component amino acids, and secretes new collagen fibres. This process of remodelling occurs throughout life. Osteoclasts also secrete collagenases in order to remove bone matrix. Several bacteria are able to secrete collagenases and are thus able to break down and penetrate through collagen fibres in the periodontal ligament.

Colonies
communities of organisms which have taken up residence in a habitat .

Competency
the ability of a cell to respond to messengers which could cause it to differentiate into a more specialised cell. Some cells, like pericytes remain competent throughout life, whereas others, such as the oral epithelium, are only able to form an tooth bud during the 12th to 16th week of foetal development.

Composite
a material made from two or more different types of material which contribute different properties. For example bone is a combination of a resilient fibres of collagen in a brittle matrix (hydroxyapatite).

Compressive strength
ability to withstand a crushing force.

Condylar process
the vertical extension of the mandible which ends in the condyle head, the moveable part of the temporomandibular joint.

Connective tissue
- one of the four main types of collections of cells (tissues) which consists of cells in a matrix of ground substance and fibres. Some connective tissues support structures like blood vessels and glands. Others are more structural, like bone, tendons and cartilage.

Contralateral
the opposite side as distinct from ipsilateral. Often used to refer to the teeth, joint or muscles on the opposite side from the chewing side.

Coronoid process
the vertical extension of the mandible anterior to the condyle to which the temporal muscle attaches.

Cortical-bone
the outer layer of bone which is dense and made up of lamellae.

Covalent bond
a strong bond between atoms formed by sharing outer electrons. When an atom has 8 outer electrons it is stable. Those which naturally have 8, like neon and argon gasses are quite unreactive. The carbon atom has 4 outer electrons and therefore needs 4 extra electrons to be stable. Four hydrogen atoms make a good partnership for carbon,(CH4, C2 H6 ... etc) hence hydrocarbons,(saturated with hydrogen atoms) are quite stable, insoluble and unreactive. One oxygen atom (outer shell has 6 electrons) and two hydrogen atoms (H2O) also makes a stable arrangement, although not as stable as the hydrocarbon, family as the water molecule is a little unbalanced, providing hydrogen bonds and other unusual properties of biological importance, such as its ability to hold other molecules in a solution.

Cusps
peaks or raised areas of a tooth which usually fit into a fossa on the opposing tooth.

Cytokines
-chemical messengers that allow neighbouring cells to communicate with each other. They are paracrine messages as distinct from endochrine or hormonal messengers. There are several main families of cytokines including growth factors , neurotransmitters, ,

Cytoplasm
the contents of the cell, not including thenucleus.

Cytoskeleton
a system of fine filaments which cross the cell in all directions, helping toand keep or change its shape. There are three main types of filaments; in order of decreasing size they are, microtubules, microfilaments and intermediate filaments.

Cytotoxins
products released by bacteria which are toxic to other living cells.

Darwinian medicine
an approach to the treatment of infective diseases which takes account of the co-evolution between the host and its parasite.

Deciduous
from the Latin 'falling' it applies both to trees which lose their leaves in winter and teeth which are lost to make way for the permanent set.

Demineralisation
reduction in amount of mineral in tissue. This reduction occurs when the crystals of apatite are dissolved, usually in an acid environment.

Dental abscess-
an abscess around the apex of a tooth due to spread of infection from the pulp .

Dental papilla
the condensation of dental mesenchyme which provides the stem cells from which ondontoblasts, cementoblasts and osteoblasts will form the pulp-dentine, cementum and alveolar bone of the tooth socket.

Dentary
one of several bone which together made up the lower jaw in early reptiles. During evolution the other bones, the articular and quadrate bones, became part of the inner ear, and the dentary became the single the mandible of mammals.

Dentine
a hard material like bone which forms the root and inner core of the crown of teeth. Unlike bone, dentine has fine tubules which contain the elongated process of odontoblasts, the dentine forming cells.

Dentine-pulp
a term used to describe the unity between dentine and pulp, and to view it as one integrated tissue.

Depolarisation
all cells have a slight difference in electrical potential between the inside and outside of the cell membrane. This difference is called a membrane potential and is due to a greater number of sodium ions (positively charged) outside the cell than inside. This imbalance is maintained by a membrane pump which pushes sodium ions out of the cell. Another pump also pushes potassium ions into the cell so there should be no difference in the balance of positive ions. But the potassium ions leak back out again, so there is always a potential difference across the membrane. Nerve cells have the ability to depolarise or reverse the membrane potential so that the inside is positive and outside negative. This reversal is short lived and is soon corrected, but it is long enough to influence the adjacent parts of the membrane and to be carried, like a wave, all the way along a nerve axon to the next nerve where it reaches a synapse The reversal is caused by a sudden opening of cell membrane gates which allow a flood of sodium ions into the cell. This flood causes the inside to become positive, but the gates are soon shut and potassium gates opened, which allows potassium ions to flood out and restore the membrane potential. This can all happen several times in one second, but after a while there is no flood, and the sodium pump has to get to work to build up enough pressure for the depolarisation to work again.

Dermatan sulphate
a glycosaminoglycan found in skin, tendon, blood vessel and heart valves.

Desmosomes
-one of the types of cell junctions by which cells join or communicate with each other. Desmosomes consist of a round plaque of protein, desmoplakin on the cell membrane. Into the plaque are attached fine filamanents which are part of the cell's cytoskele

Desquamation
- the detachment of cells from the surface of an epithelium.

Dextrans
- polysaccharides made by bacteria. They have a slimy consistency and contribute to the sticky nature of plaque.

Differentiate
change in the pattern of genes expressed by a cell resulting in altered function, from a more primitive parent cell to a more specialised group of daughter cells.

Diphyodont
only two sets of teeth, one deciduous and one permanent (from 'di' = two,'phyo+ = generation and 'dont' =teeth). See also polyphyodont

Displacement
of a tooth refers to its movement within the confines of the tooth socket. A tooth can be displaced more easily when forced in a lateral direction than when forced into the socket. Continual or frequent displacement of a tooth may lead to it repositioning itself in the socket.