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General Histology lecture three : Glandular Epithelium Ahmed Abdul-Aziz Mohamed. PhD 1 Reference : Anthony L. MESCHER, Jonquiere's Basic Histology TEXT & ATLAS  Glands def...

General Histology lecture three : Glandular Epithelium Ahmed Abdul-Aziz Mohamed. PhD 1 Reference : Anthony L. MESCHER, Jonquiere's Basic Histology TEXT & ATLAS  Glands definition Glandular epithelia are tissues formed by cells specialized to produce secretion. Glandular epithelial cells may synthesize, store, and secrete: Proteins (e.g; pancreas), Lipids (e.g; adrenal, sebaceous glands), Complexes of carb & proteins (e.g; salivary glands). The mammary glands secrete all 3 substances.  Development of glands Formation of glands from covering epithelia. Epithelial cells proliferate and penetrate connective tissue followed by further differentiation. They may–or may not– maintain contact with the surface. When contact is maintained, exocrine glands are formed; Without contact, endocrine glands are formed. General histological structure of gland Externally a gland is surrounded by a dense layer of connective tissue which forms capsule of the gland. From the capsule connective tissue septa extend into the gland, thereby dividing its substance into a number of lobes. Thinner septa subdivide each lobe into smaller lobules. The functional part of a gland, formed by its secretory cells, is known as parenchyma of the gland. The supporting elements of the gland, which consists mainly of connective tissue, are referred to as stroma of the gland. General histological structure of gland  Classification of Glands (General) Exocrine Glands Endocrine Glands Mixed Glands Release their products Release their products ( Some glands possess onto an epithelial hormones) into the both exocrine and surface, either directly or blood stream, e.g; endocrine function. e.g; through a duct e.g; the thyroid gland, pancreas, liver cells. salivary glands, sweat parathyroid glands, and glands, mammary glands. pituitary gland.  EXOCRINE GLANDS Histological classification according to secretory mechanisms: A- MEROCRINE: the secretory B- APOCRINE SECRETION C- HOLOCRINE SECRETION : product is released by : the apical part of breakdown and discharge of exocytosis = secretory cytoplasm of the cells is the entire secretory cell and granules leave the cell lost together with the its product; (e.g. sebaceous without any further loss of secretory product; (e.g. glands of the skin) cell substance; (e.g. pancreas, female mammary gland) salivary glands)  Histological classification according to duct system A. Simple (the ducts are not branched); B. Compound (with a branching duct system) according to secretory portion: A. Tubular (shaped like a tube); e.g. glands of intestine, stomach B. Acinar or alveolar (flask-shaped with narrow centrally placed lumen); e.g. pancreas, parotid salivary gland C. Tubuloacinar (combination of the tube ends with a sac- like dilatation); e.g. submandibular and sublingual salivary glands Simple and compound glands Simple tubular Simple alveolar Compound tubulo- alveolar  Histological classification according to nature of the secretions : 1. Mucous glands: these glands produce a viscid, slimy, carbohydrate-rich secretion which is called mucus, e.g; Pyloric glands of stomach 2. Serous glands: these glands produce a thin, watery, protein-rich secretions, often high in enzymatic activity e.g; Exocrine pancreas, the parotid salivary gland. 3. Mixed glands: these glands produce both mucous and serous secretions e.g; the sublingual and submandibular salivary glands. Serous glands Mucous glands Mixed glands