Classification of glands (Based on presence or absence of ducts):
Endocrine (ductless) glands
Exocrine (ducted) glands
1.  Hypothalamus
2.  Pituitary
3.  Pineal
4.  Thyroid
5.  Parathyroid
6.  Thymus
7.  Pancreas (Islets of Langerhans)
8.  Adrenal
9.  Gonads (Testes & Ovary)
E.g. Chalice cells (Goblet cells) in the epithelial lining of the small intestine.
1.  Non-coiled tubular:
E.g. crypts of Lieberkuhn
1. Tubular: E.g. Milk glands of egg-laying mammals, Brunner’s glands
2.  Coiled tubular: E.g. Sweat glands
2. Alveolar: E.g. Mammary glands
3.  Branched tubular: E.g. Gastric glands, Brunner’s glands, Sweat glands of arm pit
3. Tubule-alveolar: E.g. Salivary glands, pancreas
4.  Alveolar (Acinus): E.g. Mucus secreting glands in frog skin

5.  Branched alveolar (Branched acinus):
E.g. Sebaceous glands (oil glands)
Classification of glands (Based on modes of secretion):
Holocrine glands
The entire cells disintegrate to release secretions. E.g. Ceruminous glands, Sebaceous glands
Merocrine glands
Glands release secretions by simple diffusion (without the loss of cytoplasm). E.g. Sweat glands, Salivary glands
Apocrine glands
The contents and the free ends of glandular cells are pinched off during secretion. E.g. Mammary glands, certain sweat glands
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