BSCI201: Anatomy &Physiology Chapter 4 (Tissues) Notes- Part 1 by Mehrnaz Ighani .Individual body cells are specialized which means each type performs specific functions that maintain homeostasis . Tissues: groups of similar cells that perform common and related function . Histology: study of tissues . 4 basic tissue types: (Fig. 4.1) 1. Connective: supports and binds other tissues together 2. Muscular: movement 3. Nervous: internal communication 4. Epithelial: forms boundaries between different environments . Epithelial tissue: a sheet of cell that covers body surfaces or cavities ­ 2 main types: 1. Covering and lining epithelia: an external/internal surface Ex. Skin 2. Glandular epithelia: secretory tissue in glands Ex. Salivary glands ­ Main functions: protection, secretion, absorption, filtration, excretion, and sensory reception . Epithelial tissue has 5 characteristics: 1. Polarity 2. Avascular but innervated 3. Specialized contacts 4. Supported by connective tissue 5. Regeneration ­ Polarity:  Cells have polarity (top and bottom)  Apical surface: upper free side that’s exposed to surface or cavity . Some apical surfaces have microvilli  Basal surface: lower attached side, faces inwards toward body . Attaches to basal lamina, an adhesive sheet that holds basal surface of cells to underlying cells  Both surfaces differ in structure and function ­ Specialized contacts: 