GENERAL HISTOLOGY

Detailed explanation-1: -Types of fixation Fixation of tissues can be achieved by chemical or physical means. Physical methods include heating, micro-waving and cryo-preservation (freeze drying). Heat fixation is rarely used on tissue specimens, its application being confined to smears of micro organisms.

Detailed explanation-2: -Mechanism of Fixation The two main mechanisms of chemical fixation are cross-linking and coagulation. Cross-linking involves covalent bond formation both within proteins and between them, which causes tissue to stiffen and therefore resist degradation.

Detailed explanation-3: -Fixation is considered as physiochemical process where cells or tissues are fixed chem-ically. Fixatives perform various functions such as prevention of autolysis and tissue putrefaction. Various fixative agents include formaldehyde, glutaraldehyde, osmium tetroxide, glyoxal, picric acid, and so on.

Detailed explanation-4: -Acetic acid is a fixative. It will partially hydrolyze proteins in the specimen. Bouins solution consists of picric acid, acetic acid and formaldehyde in an aqueous solution. It is a fixative for gastrointestinal tract biopsies, animal embryos and endocrine gland tissue.