专业术语—口腔生理学术语C4(英文详解)
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, , lymphokines and many others. The method of communication involves detection of the chemical message, a ligand , by receptor proteins (for example an integrin on the cell membrane of the receiving cell. The result of the message is a shift in the level of gene expression or the expression of new genes and altered cell behaviour. Cytokines are complex as they sometimes inhibit and/or facilitate the actions of each other.
Cylasm - 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.
