1. Chapter 4.1: Tissues

2. Epithelial Tissue  Epithelia—layers of cells that cover internal or external surfaces  Glands—secreting cells of epithelia  Characteristics  Cells very close together  Apical surface—exposed to outside/environment  Basement membrane—attaches epithelia to connective tissue  Avascular—no blood vessels  Continually replaced

3. Figure 4.3a

4. Functions of Epithelia  Protection from abrasion and dehydration  Controls permeability  Sensation (especially touch)  Secretions  Exocrine—secrete onto surface  Endocrine—secrete into blood  Ex: Hormones—regulate and coordinate

5. Intracellular Connections  Cell Adhesion Molecules (CAMS)  Hold together epithelial cells  Cell Junction—where 2 cells meet  Tight Junction—tightly bound  No passage of water/solutes  Ex: Stomach—prevent HCl acid from harming body  Gap Junction—forms channel between cells  Allows small molecules and ions to pass  Ex: Cardiac and Smooth muscles  Desmosome—bendable connection  Ex: Skin

6. Figure 4.2

7. Figure 4.2c

8. Figure 4.2d

9. Epithelial Surface  Microvilli  Increase surface area by 20x  Cilia  Beat together to move substances forward

10. Figure 4.3b

11. Epithelial Renewal and Repair  Stem cells—unspecialized cells  Found near basement membrane

12. Cell Layers  Simple Epithelium—one layer of cells  Thin and fragile  Line internal compartments  Good for secretion and absorption  Stratified Epithelium—2 or more layers of cells  Surface of skin