STRUCTURE AND FUNCTION: TISSUES AND ORGANS Study Questions 1. Why are cells so small? Due to the surface area to volume ratio. If the volume gets too large for the cell’s surface area, then the cell will explode. Diffusion is a good reason (cells have to communicate with other cells and receive gases like O2 and get rid of things like CO2) If they are too big they are going to take too long to react and diffuse. 2. Distinguish (by structure and function) between epithelial cells, connective tissue cells, muscle cells, and cells of the nervous system. Inc Epithelial cells cover the body surfaces (skin) and line hollow internal body organs (bladder, gut, blood vessels, etc); Connective tissue cells specialize in the connecting, anchoring, cushioning, and support of other tissues (tendons, ligaments, bones, cartilage, blood); Muscle cells are elongated and specialized for contraction and generation of forces to cause movements of internal body organs and body limbs; Nervous system cells do the generation, conduction, and processing of electrical impulses, sense various characteristics of internal and external environments. 3. What is meant by epithelial polarity? Give an example of polarity. Epithelial polarity means differentiation between “top” and “bottom” ends of an organism or structure. For instance, the apical surface faces the lumen or the environment (often ciliated) while the basolateral surfaces face the blood.