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test-1 epithelium
| Question | Answer |
|---|---|
| Epithelium: | Consists of cells arranged in continuous sheets, in either single or multiple layers. Because the cells are closely packed and are held tightly together by many cell junctions, there is little intercellular space between adjacent plasma membranes. |
| Function of Epithelial tissue: | Forms coverings and linings throughout the body. It is never covered by another tissue, so it always has a free surface. |
| Major function of Epithelium: | Form selective barriers that limit or aid the transfer of substances into and out of the body. |
| Major function of Epithelium: | Form secretory surfaces that release products produced by the cells onto their free surfaces. |
| Major function of Epithelium: | Form protective surfaces that resist the abrasive influences of the environment. |
| Apical surface of an epithelial cell: | Faces the body surface, a body cavity, the lumen (interior space) of an internal organ, or a tubular duct that receives cell secretions. |
| Lateral surface of an epithelial cell: | Faces the adjacent cells on either side, may contain tight junctions, adherens junctions, desmosomes, and/or gap junctions. |
| Basal surface of an epithelial cell: | opposite the apical surface. The basal surfaces of the deepest layer of epithelial cells adhere to extracellular materials such as the basement membrane. |
| Apical layer: | Top-most layer of cells in a multi layer epithelium. |
| Basal layer: | Basement layer of cells in a multi layer epithelium. |
| Basement membrane: | Thin, extracellular layer between epithelium and connective tissue consisting of a basal lamina and a reticular lamina. |
| Basal lamina: | Situated closer to—and secreted by—the epithelial cells. It contains proteins such as laminin and collagen, as well as glycoproteins and proteoglycans. |
| Laminin: | Proteins in the in the basal lamina, which adhere to integrins in hemidesmosomes and thus attach epithelial cells to the basement membrane. |
| Reticular lamina: | Lower basement membrane layer, it is situated closer to the underlying connective tissue and contains proteins such as collagen produced by connective tissue cells called fibroblasts. |
| Other functions of basement membranes: | Form a surface along which epithelial cells migrate during growth or wound healing, restrict passage of larger molecules between epithelium and connective tissue, and participate in filtration of blood in the kidneys. |
| Nerve and blood supply of epithelium: | Epithelial tissue has its own nerve supply, but it is avascular (no blood vessels). |
| Exchange of materials between epithelium and connective tissue: | Exchange of substances between epithelium and connective tissue occurs by diffusion. |
| Growth of epithelium: | A high rate of cell division allows epithelial tissue to constantly renew and repair itself by sloughing off dead or injured cells and replacing them with new ones. |
| Simple (unilaminar) epithelium: | A single layer of cells that functions in diffusion, osmosis, filtration, secretion, or absorption. Example: lining of small intestine. |
| Pseudo-stratified epithelium: | Appears to have multiple layers of cells because the cell nuclei lie at different levels and not all cells reach the apical surface, it is actually a simple epithelium because all its cells rest on the basement membrane. Example: linings of the airway |
| Function of pseudo-stratified epithelium: | Cells that do extend to the apical surface may contain cilia; others (goblet cells) secrete mucus. |
| Stratified (multilaminar) epithelium: | consists of two or more layers of cells that protect underlying tissues in locations where there is considerable wear and tear. Example: skin. |
| Squamous epithelial cells: | Arranged like floor tiles and are thin, which allows for the rapid passage of substances. |
| Cuboidal epithelial cells: | As tall as they are wide and are shaped like cubes or hexagons. They may have microvilli at their apical surface and function in either secretion or absorption. |
| Columnar epithelial cells: | Much taller than they are wide, like columns, and protect underlying tissues. Their apical surfaces may have cilia or microvilli, and they often are specialized for secretion and absorption. |
| Transitional epithelial cells: | Change shape, from flat to cuboidal and back, as organs such as the urinary bladder stretch (distend) to a larger size and then collapse to a smaller size. |
| Types of simple epithelium: | Simple squamous, Simple cuboidal, Simple columnar, Pseudostratified columnar. |
| Types of stratified epithelium: | Stratified squamous, Stratified cuboidal, Stratified columnar, Transitional epithelium. |
| Covering and lining epithelium: | Forms the outer covering of the skin and some internal organs. It also forms the inner lining of blood vessels, ducts, and body cavities, and the interior of the respiratory, digestive, urinary, and reproductive systems. |
| Glandular epithelium: | Makes up the secreting portion of glands such as the thyroid gland, adrenal glands, and sweat glands. |
| Simple squamous epithelium description: | Single layer of flat cells; centrally located nucleus. |
| Simple squamous epithelium location: | Lines heart, blood vessels, lymphatic vessels, air sacs of lungs, glomerular (Bowman's) capsule of kidneys, and inner surface of the tympanic membrane (eardrum); forms epithelial layer of serous membranes, such as the peritoneum, pericardium, and pleura. |
| Simple squamous epithelium function: | Filtration, diffusion, osmosis, and secretion in serous membranes. |
| Simple cuboidal epithelium description: | Single layer of cube-shaped cells; centrally located nucleus. |
| Simple cuboidal epithelium location: | Covers surface of ovary, lines kidney tubules and smaller ducts of many glands, and makes up the secreting portion of some glands such as the thyroid gland and the ducts of some glands such as the pancreas. |
| Simple cuboidal epithelium function: | Secretion and absorption. |
| Nonciliated simple columnar epithelium description: | Single layer of nonciliated column-like cells with nuclei near base of cells; contains goblet cells and cells with microvilli in some locations. |
| Nonciliated simple columnar epithelium location: | Lines the gastrointestinal tract (from the stomach to the anus), ducts of many glands, and gallbladder. |
| Nonciliated simple columnar epithelium function: | Secretion and absorption. |
| Ciliated simple columnar epithelium description: | Single layer of ciliated column-like cells with nuclei near base; contains goblet cells in some locations. |
| Ciliated simple columnar epithelium location: | Lines some bronchioles (small tubes) of respiratory tract, uterine (fallopian) tubes, uterus, some paranasal sinuses, central canal of spinal cord, and ventricles of the brain. |
| Ciliated simple columnar epithelium function: | Moves mucus and other substances by ciliary action. |
| Pseudostratified columnar epithelium description: | Not a true stratified tissue; nuclei of cells are at different levels; all cells are attached to basement membrane, but not all reach the apical surface. |
| Pseudostratified columnar epithelium location: | Pseudostratified ciliated columnar epithelium lines the airways of most of upper respiratory tract; pseudostratified nonciliated columnar epithelium lines larger ducts of many glands, epididymis, and part of male urethra. |
| Pseudostratified columnar epithelium function: | Secretion and movement of mucus by ciliary action. |
| Stratified squamous epithelium description: | Several layers of cells; cuboidal to columnar shape in deep layers; squamous cells form the apical layer and several layers deep to it; cells from the basal layer replace surface cells as they are lost. |
| Stratified squamous epithelium location: | Keratinized variety forms superficial layer of skin; nonkeratinized variety lines wet surfaces, such as lining of the mouth, esophagus, part of epiglottis, part of pharynx, and vagina, and covers the tongue. |
| Stratified squamous epithelium function: | Protection. |
| Stratified cuboidal epithelium description: | Two or more layers of cells in which the cells in the apical layer are cube-shaped. |
| Stratified cuboidal epithelium location: | Ducts of adult sweat glands and esophageal glands and part of male urethra. |
| Stratified cuboidal epithelium function: | Protection and limited secretion and absorption. |
| Stratified columnar epithelium description: | Several layers of irregularly shaped cells; only the apical layer has columnar cells. |
| Stratified columnar epithelium location: | Lines part of urethra, large excretory ducts of some glands, such as esophageal glands, small areas in anal mucous membrane, and part of the conjunctiva of the eye. |
| Stratified columnar epithelium function: | Protection and secretion. |
| Transitional epithelium description: | Appearance is variable (transitional); shape of cells in apical layer ranges from squamous (when stretched) to cuboidal (when relaxed). |
| Transitional epithelium location: | Lines urinary bladder and portions of ureters and urethra. |
| Transitional epithelium function: | Permits distension. |
Created by:
bwoods