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Epithelial Tissue

Epithelial Tissue. Tissue Lecture 2. Basic Structure. Consists of cells arranged in continuous sheets, in either single or multiple layers Cells are closely packed and are held together by many cell junctions allowing for little intercellular space between cells.

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Epithelial Tissue

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  1. Epithelial Tissue Tissue Lecture 2

  2. Basic Structure • Consists of cells arranged in continuous sheets, in either single or multiple layers • Cells are closely packed and are held together by many cell junctions allowing for little intercellular space between cells. • Epithelial cells have three surfaces - • Apical surface: faces the body surface, a body cavity, the internal space (lumen) of an internal organ, or a tubular duct that receives cell secretions

  3. Lateral surfaces: face the adjacent cells on either side • Basal surface: opposite the apical surface and attached to another layer of cells if the tissue has multiple layers or is attached to basement membrane is only one layer thick

  4. Nerves, Nutrients, and Gas Exchange • Epithelial tissue has its own nerve supply. • It is avascular and does NOT have blood vessels for nutrients and gas exchange. • Blood vessels in the adjacent connective tissue provide nutrients and gas exchange as well as remove wastes through diffusion.

  5. Function • Epithelial cells are under a lot of stress. • A high rate of cell division allows epithelial tissue to constantly renew and repair itself by sloughing off dead or injured cells and replacing them with new ones. • Epithelial tissue functions include protection, filtration, secretion, absorption, and excretion. • Epithelial tissue combines with nervous tissue to form the sensory organs for smell, hearing, vision, and touch.

  6. Types of Epithelial Tissue • Covering and lining epithelium forms the outer covering of the skin and some internal organs. • It also lines blood vessels, ducts, and body cavities as wells as the interior of the respiratory, digestive, urinary, and reproductive systems. • Glandular epithelium makes up the secreting portion of glands such as the thyroid gland, adrenal glands, and sweat glands. • A gland may consist of a single cell or a group of cells that secrete substances into ducts, onto a surface, or into the blood.

  7. Endocrine glands diffuse directly into the bloodstream without going through a duct. Their secretions are hormones. • Exocrine glands secrete their products into ducts that empty onto the surface of an organ or into the lumen of an organ.

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