GLANDULAR EPITHELIUM GLANDULAR EPITHELIUM Gland is composed of

GLANDULAR EPITHELIUM

GLANDULAR EPITHELIUM Gland is composed of epithelial cells specialized for synthesis & secretion of a specific product.

FORMATION OF GLANDS FROM EPITHELIA

CLASSIFICATION Based on site of secretion: Exocrine glands : secrets its products onto a surface through ducts. E. g. salivary glands v Endocrine glands : secrets its products into blood stream. E. g. thyroid gland v Paracrine glands : secrets its products into local extracellular space affecting the surrounding cells. e. g enteroendocrine cells of GIT v

Based on number of cells v Unicellularcomposed of a single cell. e. g goblet cell. v Multicellular – composed of many cells. All glands other than goblet cell.

Based on mode of secretion : v Merocrine : the secretory product is delivered in membrane bound vesicle to apical surface of cell extrude their content by exocytosis e. g. pancreatic acinar cell o

v Holocrine secretion : whole cell is excreted with secretion by apoptosis both secretory products & cell debris are discharged into the lumen of gland e. g sebaceous gland tarsal gland

v Apocrine secretion : apical cytoplasm is shaded out with secretion secretory product (large lipid droplet) is surrounded by a thin layer of cytoplasm released in apical portion of cell e. g lactating mammary gland

Based on nature of secretion : v Serous gland : secretes thin watery material rich in enzymes. E. g parotid salivary gland v Mucous gland : secretes thick viscous material for lubrication. E. g sublingual gland v Mixed gland : secretes both watery & viscous material. E. g submandibular gland

Serous acinus : thin watery secretion nature of secretory granules – zymogen granules nucleus – round & centrally placed lumen small e. g. parotid gland

Mucous acini : secretion is thick viscous nature of secretory granules – mucigen nucleus flat &peripherally placed lumen large e. g sublingual gland

Based 1. ü ü ü on cellular arrangement : Simple (having unbranched duct) – Tubular Alveolar Tubuloalveolar

Tubular – ü straight (glands of large gut) ü coiled (sweat gland) ü branched (mucous secreting glands of pylorus)

Alveolar – ü Simple (urethral gland) ü Branched (mucous secreting glands of cardiac end of stomach)

Tubulo alveolar – parotid gland

2. Compound (having branched duct) – ü tubular (brunners gland) ü alveolar ( excretory portion of pancreas) ü tubulo-alveolar (submandibular gland)

ARRANGEMENT OF CELLS OF ENDOCRINE GLANDS A. Cord like arrangement: cells are arranged as cords or clumps around capillaries, e. g; most of the endocrine glands – adenohypophysis, adrenal cortex B. Follicular arrangement: cells are into follicls and the secretions are accumulated in the lumen of the follicles, e. g; Thyroid gland

DIFFERENT TYPES OF EPITHELIAL CELLS A. Serous cells: - cells are polyhedral or pyramidal shaped - Nucleus- rounded and centrally placed - in the basal region abundant r. ER are present, thus providing the basophilia of the cells

B. Mucus-secreting cells: - cells are columner - nuclei are compressed towards the base - secretory granules fill the apical pole - well developed Golgi apparatus is located above the nucleus

Steroid secreting cells: - cells are polyhedral or rounded - nucleus – centrally placed - usually rich in lipid droplets - rich in s. ER - sperical or elongated mitochondria containing tubular cristae - cells are acidophilic

Ion-transporting cells: - Invagination of the basal plasmamembrane occurs - Numerous elongated mitochondria are present along the infoldings - Known as striated cells