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Bio 163 Forsyth tech
Chapter 4 (Epithelia)
| Term | Definition |
|---|---|
| Epithelial Tissue | tissue that covers a body surface of lines a body cavity forms parts of most glands |
| Epithelia 1 | layers of cells that cover both external or internal body surfaces, it also lines internal cavities and passageways. |
| Epithelia 2 | • Cells are bound closely together • Attached to underlying connective tissue by a basement membrane • Continual replacement or regeneration of damaged or lost epithelial cells |
| Glands | are secretory structures derived from epithelia. |
| Avascular | the absence of blood vessels. Epithelial are avascular. |
| 1Functions of Epithelia (Protection, control Permeability Provide Sensation and to Produce Secretions) | 1 • Protection- epithelia protects exposed and internal surfaces from abrasion, dehydration, and destruction by chemical biological agents. |
| 2Functions of Epithelia (control permeability) | 2 • Control permeability- any substance that enters the body must cross an epithelium, some are impermeable and other are easily crossed by large compounds like protein |
| 3Functions of Epithelia(provide sensation) | 3 • Sensation- specialized epithelial cells can detect changes in the environment and relay the information about the changes to the nervous system Ex: touch receptors, sensory nerves |
| 4Functions of Epithelia (produce secretions) | 4• Secretions- epithelial cells that produce secretions are called gland cells. Gland cells are typically scattered among other cell types in an epithelium |
| Exocrine | secretion is released onto the body surfaces |
| Endocrine | Endocrine: secretions known as hormones, are released into the surrounding tissue fluid and blood. Endocrine secretions are produced in the: pancreas, thyroid glands, and pituitary glands. |
| Cell Junctions | specialized attachment sites that attach a cell to another cell or extracellular materials. |
| Cell adhesion molecules (CAMs)- | these proteins bind to each other and extracellular materials by a thin layer of proteoglycans |
| Tight Junctions 1 | tight conjunctions prevent the passage of water and solutes between cells by interlocking membrane proteins |
| Tight Junctions 2 | • A tight junction is formed by the fusion of the outer layers of two plasma membranes • These junctions are common between epithelial cells exposed to harsh chemicals or powerful enzymes. • Ex. in stomach, intestines, bladder. |
| Gap Junctions | two cells that are held together by embedded membrane proteins called connexons. • Connexons form a narrow passageway that lets small molecules and ions pass from cell to cell. |
| Desmosomes | the plasma membranes of two cells are locked together by CAM’s and proteoglycans between the opposite dense areas of each cell. • A spot desmosome ties adjacent cells together • Ex. in cardiac muscle |
| Hemidesmosomes | attach a cell to extracellular structure such as protein fibers in the basement membrane (half of a desmosome ) |
| Base Membrane | is between the epithelium and underlying connective tissue |
| Stem Cells (germinative cells) | a division that continually replaces the short- lived epithelial cells. |
| Simple Epithelium | a single layer of cells covering the basement membrane |
| Stratified Epithelium | found above the basement membrane consists of several layers this creates a greater protection |
| Squamous Epithelium | the nucleus fills the thickest portion of the cell, the cells are thin and flat |
| Cuboidal | cells appear like little boxes hexagonal shape (6) six sides |
| Columnar | cells are taller and slender hexagonal shapes |
| Simple Squamous Epithelium | found in a slippery area reducing friction or in an area of absorption takes place. |
| Simple Squamous Epithelium (examples) | inner surfaces of heart, the gas exchange surfaces of the lungs, the linings of pericardial, pleural, peritoneal cavities, blood vessels, and portions of kidney tubules. |
| Simple Cuboidal Epithelia | found in areas of absorption or secretion and provides little protection. Examples are found in pancreas, salivary glands, and portions of kidney tubules. |
| Simple Columnar Epithelia | offers some protection and is found in areas of absorption or secretion such as lining of the stomach, the intestinal tract, and excretory ducts. |
| Stratified Squamous Epithelia | typically found in areas of mechanical stresses are harsh or in areas of constant use such as the linings of mouth, tongue, esophagus and anus. |
| Stratified Cuboidal Epithelia | Relatively rare. occurs along the ducts of sweat glands and in the larger ducts of the mammary glands. |
| Stratified Columnar Epithelia | (also rare) Found along portions of the pharynx, epiglottis, anus, urethra and a few large excretory ducts. (If more than two layers are present, only the superficial cells are columnar.) |
| Pseudostratified Epithelia | Columnar epithelium that includes a mixture of cell type |
| Transitional Epithelia | A stratified epithelium that tolerates repeated cycles of stretching and recoiling. |
| Glandular Epithelia | A layer of cells with a secretory function, the secreted products entering the spaced lined by the epithelium. |
| Merocrine Secretion | The product is released from secretory vesicles by exocytosis (most common method of exocrine secretion). |
| Apocrine Secretion | Involves the loss of both cytoplasm and the secretory product. |
| Holocrine Secretion | -Does not leave a cell intact. Instead the entire cell becomes packed with secretory vesicles and then bursts releasing the secretion but destroying the cell. |
| Mucus | An effective lubricant, a protective barrier, and a sticky trap for foreign particles and microorganisms. |
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ccarterreid1
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