chapter 4.1: tissues. epithelial tissue epithelia—layers of cells that cover internal or external...
TRANSCRIPT
Chapter 4.1: Tissues
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
Figure 4.3a
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
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
Figure 4.2
Figure 4.2c
Figure 4.2d
Epithelial Surface Microvilli Increase surface area by 20x Cilia Beat together to move substances forward
Figure 4.3b
Epithelial Renewal and Repair Stem cells—unspecialized cells Found near basement membrane
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