GLANDS Dr. Safaa

Glandular Epithelium A gland is one or more cells that makes and secretes an aqueous fluid Both endocrine and exocrine glands are developmentally derived from epithelia, which form a down-growth into the underlying connective tissue.

Exocrine - Endocrine

Glandular Epithelium Two types of glands formed by the infolding (invagination) of epithelium: Endocrine: Ductless No contact with exterior of body Usually produce hormones (pituitary, thyroid, adrenals, pancreas) Secretions enter directly into blood vessels Exocrine: Open to exterior of body via ducts (sweat glands, pancreas , sebaceous glands, salivary glands)

glands Classification of Endocrine Two types of endocrine glands can be recognized based on the arrangement of their cells: Cords interspersed between dilated blood capillaries eg, adrenal gland, parathyroid, anterior lobe of the pituitary. Vesicles or Follicles filled with noncellular material eg, the thyroid gland.

Exocrine glands Exocrine glands have: A secretory portion, which contains the secretory cells responsible for the secretory process. Ducts, which transport the secretions.

Types or Classification of Exocrine Glands According to the number of cells: Unicellular: goblet cells Multicellular: e.g sweat gland, sebaceous glands salivary glands. According to the branching of the duct: Simple ‒ unbranched duct Compound ‒ branched duct According to the secretory part: Tubular cells organize as tubules Acinar or alveolar the cells organize as spherical or globular units

Multicellular Glands with an unbranched excretory duct are called simple: Simple tubular e.g intestine. Simple coiled tubular e.g sweat glands. Simple branched tubular e.g stomach. Simple acinar e.g urethra. Simple branched acinar e.g sebaceous glands.

Multicellular glands with branched excretory duct are called compound glands: Compound branched tubular e.g duodenum. Compound acinar e.g .pancreas. Compound tubuloacinar e.g . submandibular salivary gland.

Multicellular Exocrine Glands

According to how the secretory products leave the cell: Merocrine Apocrine Holocrine

Exocrine glands Classified by method of secretion: Merocrine Apocrine Holocrine

Merocrine Secrete products by exocytosis Cell membrane intact No loss of cell substance E.g Sweat gland, pancreas

Apocrine Secrete products with part of the cytoplasm and cell membrane lost. The continuity of the plasma membrane is restored by the fusion of the broken edges of the membrane. Mammary gland ,apocrine sweat glands, and the prostate

Holocrine Secrete products by rupture of cell membrane Breakdown and discharge of the entire secretory cell. Whole cell dies, replaced by new cell It is only seen in the sebaceous glands of the skin.

According to type of secretion Serous – watery secretion Mucous – viscous secretion Mucoserous – mixed secretion

THANK YOU