Glands: exocrine vs endocrine, secretion types !
- Tissue
Glands are epithelial cells that make and release products, either into a duct (exocrine) or into the blood (endocrine).
Updated 2026-11-01
See it in 3D: Parotid gland · Submandibular gland
What it is
Glands form when epithelium grows down into the connective tissue during development. Exocrine glands keep a duct that opens onto a surface; endocrine glands lose the duct and release hormones into capillaries. Exocrine glands are classified by their shape, by the kind of product (serous or mucous) and by how the cell releases it (merocrine, apocrine or holocrine).
Key facts
- Exocrine: has ducts (salivary glands, sweat glands, exocrine pancreas).
- Endocrine: ductless, richly vascular (thyroid, adrenal, islets).
- The goblet cell is a unicellular exocrine gland that secretes mucus.
- Shape: simple (one unbranched duct) or compound (branched duct); secretory units are tubular, acinar (alveolar) or tubuloacinar.
- Mixed glands such as the submandibular gland contain both serous and mucous cells.
Structure
- Serous acini: pyramidal cells with round basal nuclei, a basophilic base (rough ER) and pink apical zymogen granules; small central lumen.
- Mucous acini: pale, foamy-looking cytoplasm with flattened nuclei pushed against the base.
- Serous demilunes: serous cells forming a crescent cap on a mucous acinus (classic in the submandibular gland; partly a fixation artefact).
- Myoepithelial cells wrap acini and small ducts and contract to squeeze out the secretion.
How exocrine cells release their product
| Mode | What happens | Example |
|---|---|---|
| Merocrine (eccrine) | Vesicles fuse with the apical membrane (exocytosis); the cell stays intact | Salivary glands, eccrine sweat glands, exocrine pancreas |
| Apocrine | The apical cytoplasm pinches off with the product | Apocrine sweat glands of the axilla and groin; lipid in the mammary gland |
| Holocrine | The whole cell fills with product, dies and becomes the secretion | Sebaceous glands |
Clinical notes
- Cystic fibrosis thickens the secretions of exocrine glands (pancreas, airway, sweat glands); a high sweat chloride is the classic test.
- Acne involves the sebaceous (holocrine) gland and its hair follicle.
- Pleomorphic adenoma, the most common salivary gland tumour, usually arises in the parotid.
Test yourself
Think of the answer, then tap the question to see it.
What is the defining difference between an exocrine and an endocrine gland?
An exocrine gland releases its product through a duct onto a surface; an endocrine gland has no duct and releases hormones into the blood.
Which secretion mode does a sebaceous gland use?
Holocrine: the whole cell fills with lipid, breaks down and becomes the secretion; new cells replace it from the base.
How do serous acini look on H&E compared with mucous acini?
Serous cells are darker, with round basal nuclei and pink apical granules; mucous cells are pale and foamy with flattened nuclei pressed to the base.
Which salivary gland is almost purely serous?
The parotid gland.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Epithelium: classification (the table to know)
- Salivary glands: serous and mucous acini
- Hair follicles, sebaceous and sweat glands, nails
- Pancreas: acini and islets
- Organelles: nucleus, ER, Golgi, mitochondria, lysosomes, peroxisomes
Related conditions
Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.
Sources: 4.2 Epithelial Tissue (OpenStax, 2022); Epithelial Tissue (National Cancer Institute, SEER Training Modules, 2024).
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Representative model, for educational purposes only.