Expansion
Classified by duct branching, secretory unit shape and mode of secretion
Expansion
By mode of secretion
- Merocrine (eccrine): exocytosis with no loss of cell material. Most glands, including eccrine sweat and salivary glands
- Apocrine: apical cytoplasm is pinched off with the secretion. Apocrine sweat glands of axilla and groin, and the lactating breast
- Holocrine: the entire cell disintegrates to become the secretion. Sebaceous glands
By shape of the secretory unit: tubular, acinar (alveolar), or tubuloacinar.
By duct branching: simple (unbranched duct) or compound (branched).
By secretion type
- Serous: watery, protein rich, with basophilic cytoplasm and round central nuclei. Parotid gland
- Mucous: viscous, with pale foamy cytoplasm and flattened basal nuclei. Sublingual gland
- Mixed: submandibular gland, with serous demilunes capping mucous acini
Endocrine glands by contrast are ductless, secreting into blood, and are typically arranged in cords or follicles with a rich capillary network.