Tissues


 * Almost all organs are essentially made up of three types of tissues: epithelial, basement membrane, and connective tissue
 * Epithelia
 * Epithelial layer covers all surfaces, tubes, and cavities of the body
 * Avascular (no blood vessels)
 * No significant amount of ECM, 100% cells
 * Basement Membrane
 * Acellular, avascular, continuous layer of ECM
 * Separates the epithelial layer and the connective tissue
 * No cells, 100% matrix, no blood vessels
 * No collagen, mostly laminin
 * Connective Tissue
 * Cellular, contains ECM, heavily vascularized, and provides a reservoir for nutrient uptake to and waste removal from the basement membrane and epithelia
 * Cells, matrix, and blood vessels
 * Thicker than 200 um