BIO 211 Lecture 3: Unit C: Tissues and Membranes
Document Summary
Unit c: tissues and membranes: histology, tissues. Groups of similar cells and extracellular material. Four types of tissue with varied structure and function. Nervous: epithelial tissue, epithelium in general. Composed of one or more layers of closely packed cells. Forms majority of glands: epithelium specific traits. Exposed to external environment or internal body space. All composed of collagen, glycoproteins, and proteoglycans. Continual replacement of lost cells by division of stem cells: cell-cell connections. Regulate movement of water and solutes between epithelial layers. Allow for direct chemical communication between adjacent cellular cytoplasm through diffusion without contact with extracellular fluid. Two adjacent connexons interact complete gap junction channel. Ex: uniform contraction of heart muscle, signal transfers in brain. Each cell has a plaque in it. First cell sends out fibers, attaches to plate in second cell. Second cell sends out fibers, attaches to plate in first cell. Ties cell to other cells/ec matrix: epithelium functions.
