ANAT 101 Chapter Notes - Chapter 4: Epithelium, Tight Junction, Gap Junction

• School: Queen's University
• Department: Anatomy and Cell Biology
• Course: ANAT 101
• Professor: Richard Oko

Document Summary

4-2 epithelial tissue covers body surfaces, lines cavities and tubular structures, and serves essential functions. Epithelia are layers of cells that cover internal or external surfaces. Glands are composed of secreting cells derived from epithelia. Epithelia have the following important characteristics: cells that are bound closely together. Because of this avascular condition, epithelial cells must obtain nutrients across their attached surface from deeper tissues or across their exposed surfaces: continual replacement or regeneration of epithelial cells that are damaged or lost at the exposed surface. Cover both external and internal body surfaces. Lines internal cavities and passageways which prevent friction, regulate the fluid composition of internal cavities, and restrict communication between the blood and tissue fluids. Epithelia perform four essential functions: provide physical protection, control permeability, provide sensation, produce specialized secretions. In a glandular epithelium most or all of the cells actively produce secretions. These secretions are classified according to where they are discharged.