Epithelial Tissue Lecture Notes PDF

EPITHELIAL TISSUE PART 1 OF 2 PAULYN V. ILARINA-ZONITA, MD, DPSP OUTLINE CHARACTERISTIC FEATURES OF EPITHELIAL CELLS SPECIALIZATIONS OF THE APICAL CELL SURFACE MEDICAL APPLICATION FOUR BASIC TISSUE TYPES EPITHELIAL CONNECTIVE MUSCULAR NERVOUS  cells producing...

EPITHELIAL TISSUE PART 1 OF 2 PAULYN V. ILARINA-ZONITA, MD, DPSP OUTLINE CHARACTERISTIC FEATURES OF EPITHELIAL CELLS SPECIALIZATIONS OF THE APICAL CELL SURFACE MEDICAL APPLICATION FOUR BASIC TISSUE TYPES EPITHELIAL CONNECTIVE MUSCULAR NERVOUS  cells producing elongated cells cellsnspecialized very abundant specialized for to receive, ECM contraction and generate, and movement transmit nerve impulses Connective Muscular Nervous tissue tissue tissue MOST ORGANS ARE DIVIDED INTO: Parenchyma responsible for the organ’s specialized functions Stroma supporting role *Except in the brain and spinal cord, the stroma is always connective tissue. Epithelial Tissue Greek word epi: “upon”, thele: “nipple” composed of closely aggregated polyhedral cells adhering strongly to one another lines all external and internal surfaces of the body Principal Functions of Epithelial Tissues Covering, lining, and protecting surfaces Absorption Secretion CERTAIN EPITHELIA, contractile sensory CHARACTERISTIC FEATURES OF EPITHELIAL CELLS Tall Cuboidal Squamous columnar cells cells cells spherical flattened elliptical nuclei nuclei (oval) nuclei Stroma Lamina propria connective tissue that underlies the epithelia lining the organs of the digestive, respiratory, and urinary systems Papillae small evaginations, projecting into the epithelium  Epithelial cells generally show polarity –basal pole –apical pole Lateral surface Basement Membranes thin extracellular, felt-like sheet of macromolecules semipermeable filter can be stained and visualized with the LM Two parts of th BM, seen under EM: – basal lamina – reticular lamina Intercellular Adhesion & Other Junctions provide adhesion and communication between cells present in the lateral surfaces of epithelial cells and have different functions  Tight or occluding Adherent or Gap junctions junctions anchoring junctions form a seal sites of strong cell channels for between adjacent adhesion communication cells between adjacent cells TIGHT JUNCTIONS also called zonulae occludens most apical of the junctions ensures that molecules crossing an epithelium in either direction do so by going through the cells (a transcellular path) rather than between them (the paracellular pathway)  other function: restricting movements of membrane lipids and proteins ADHERENS JUNCTION also called zonula adherens immediately below the tight junction firmly anchoring a cell to its neighbors DESMOSOME also called macula adherens disc-shaped structures at the surface of one cell that are matched with identical structures at an adjacent cell surface provide firm cellular adhesion and strength throughout the epithelium GAP JUNCTIONS mediate intercellular communication (rather than adhesion or occlusion between cells) HEMIDESMOSOMES basal epithelial surface adhesive structures resemble a half-desmosome ultrastructurally FOCAL ADHESION also called focal contact found in cells that are moving during epithelial repair or reorganization smaller, more numerous than hemidesmosomes also important in migrating nonepithelial cells such as fibroblasts SPECIALIZATIONS OF THE APICAL CELL SURFACE MICROVILLI STEREOCILIA STE CILIA Functions: increase the apical surface area move substances along the epithelial surface MICROVILLI especially seen in epithelia specialized for absorption example in the small intestine, densely packed microvilli are visible as a brush or striated border projecting into the lumen contains membrane-bound proteins and enzymes for digestion STEREOCILIA seen on the absorptive epithelial cells lining the male reproductive system motion-detecting function: inner ear sensory cells much longer and less motile than microvilli, and may show branching distally CILIA long, highly motile apical structures, larger than microvilli abundant on cuboidal or columnar cells of many epithelia Primary cilium: seen in other cell types; short projection which is not motile but is enriched with receptors and signal transduction complexes for detection of light, odors, motion, and flow of liquid past the cells MEDICAL APPLICATION  Clostridium perfringens Helicobacter pylori  Pemphigus vulgaris  Celiac disease  Kartagener syndrome (immotile cilia syndrome) THANK YOU