The exocrine glands are classified as they perform its secreting functions, such that: holocrine, apocrine, merocrine.
The majority of exocrine glands are merocrine, hence its secreting functions occur without harming the cells.
The secretions of holocrine exocrine glands are contained in cytoplasm, hence, they need to release the entire cell into duct.
The secretions of apocrine exocrine glands are contained in the apical zone, hence, they need to separate this zone of the cell and release it in the duct.
Exocrine glands are involved in many functions such that: protection of ear through cerumen secretion, eye lubrication through secretion of tears, regulation of body temperature through secretion of sweat, protection against bacterial infection through secretion of protective enzymatic films.