Anatomy and Physiology
Epithelial Tissue in Glands
- Epithelial tissue performs important secretory functions in glands. This epithelial tissue in glands is called glandular epithelium.
- Glands are divided into two basic categories: endocrine glands and exocrine glands. Endocrine glands secrete hormones. Exocrine glands primarily secrete enzymes.
- Exocrine glands have ducts, while endocrine glands do not. Therefore, exocrine glands are called ducted glands; endocrine glands are known as ductless glands.
- Exocrine glands are subdivided according to the number of cells they have. Some exocrine glands, such as goblet cells, consist of one only cell. These glands are called unicellular glands. Multicellular glands contain many cells.
- Exocrine glands are also subdivided as merocrine or holocrine glands. The cells of merocrine glands (ex: sweat glands and salivary glands) remain intact during secretion. The cells of holocrine glands rupture during secretion. The sebaceous glands of the skin are an example of a holocrine gland.