1. Glandular Epithelium
Made of cells that secrete substances into ducts or body fluids
Almost always columnar and cuboidal epithelia
Exocrine vs Endocrine
Exocrine Glands: secrete their products into ducts that open onto surfaces (ex: skin, lining of digestive tract)
Endocrine Glands: secrete their products into tissue fluid or blood
Exocrine Glands can be subdivided into three types based on the way in which they secrete their products
Merocrine Glands
Apocrine Glands
Holocrine Glands

2. Merocrine Exocrine Glands
Release watery, protein-rich fluid by exocytosis (product leaves the cell)
Examples:
Salivary glands
Pancreatic glands
Sweat glands of the skin (eccrine)
Most abundant type of exocrine gland among the three types

3. Apocrine Exocrine Glands
Lose small portions of the
glandular cell body during
secretion
Examples:
Mammary glands
Ceruminous glands lining
the external ear canal
Apocrine sweat glands
(axillary-stinky sweat)

4. Holocrine Exocrine Glands
The entire cell lyses (splits open) during secretion; the cell disintegrates
Found in the sebaceous glands of the skin (sebum producing cells surrounding hair follicles)
Special sebaceous glands in the eyelids called meibomian glands keep the tear film from evaporating