Holocrine is a term used to classify the mode of secretion in exocrine gland

Exocrine gland

Exocrine glands are a type of ductal glands that secrete their products into ducts that lead directly into the external environment...

s in the study of histology

Histology

Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...

. Holocrine secretions are produced in the cytoplasm

Cytoplasm

The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...

 of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the lumen

Lumen (anatomy)

A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...

.

Holocrine secretion is the most damaging type of secretion, with merocrine

Merocrine

Merocrine is a term used to classify exocrine glands and their secretions in the study of histology. A cell is classified as merocrine if the secretions of that cell are excreted via exocytosis from secretory cells into an epithelial-walled duct or ducts and thence onto a bodily surface or into the...

 secretion being the least damaging and apocrine

Apocrine

Apocrine is a term used to classify exocrine glands in the study of histology. Cells which are classified as apocrine bud their secretions off through the plasma membrane producing membrane-bound vesicles in the lumen. This method is also called decapitation secretion...

 secretion falling in between.

Examples of holocrine glands include the sebaceous glands of the skin and the meibomian glands of the eyelid

Eyelid

An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily...

. The sebaceous gland is an example of a holocrine gland because its product of secretion (sebum) is released with remnants of dead cells.

External links

• Diagram at uwa.edu.au