Certain cells of the body in addition to carrying out some metabolic processes necessary for their own existence, also manufacture specific substance not for their own use, but to be extruded, from the cells and used elsewhere in the body – secretion(e.g. gastric juice) or discarded – excretion (e.g. urine). Such cells are known as gland cells or glandular epithelium cells are usually grouped into small units, enclosed and supported by a connective tissue framework.
A gland may consist of a single cell, as for example, the goblet cell or the unicellular glands of invertebrates. Most glands of the body are composed of more than one cell (multicellular gland).
