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 have a vital role to play in the bodies immune response to foreign proteins.

    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.