Epithelia Flashcards
Sheets of cells that cover external surfaces and line internal surfaces of the body
Surface Epithelium
Secretory cells of glands
Glandular Epithelium
Where is epithelium present?
Present on surface of skin as well as organs who have communication with external environment
Single layer of flattened, scale-, or plate-like cells - nuclei often flattened or ovoid
Simple Squamous Epi. - the large body cavities such as heart, blood vessels, and lymph vessels typically have this
Simple cuboidal epi
cells appear cuboidal in sections perpendicular to surface - from surface look like small polygons -Occurs in small excretory ducts of many glands, follicles of thyroid glands, tubules of kidney and on surface of ovaries
Cells that are taller than wide - single layer
Simple Columnar Epi: - nuclei of cells within epi are usually located at the same height within cells - often close to base of the cells - internal surface of large and small intestine
What type of epithelium layer is this?
Stratified squamous Epi:
- named from the cells at the surface
- appear like flat scales - same as simple squamous but more layered now
- most apical layer lose nucleus = dead, make up a tough layer called keratin instead
- specialized in mammalian skin
What type of epi layer is this?
Transitional Epi:
- is unique and found exclusively in the excretory urinary passage
- in a relaxed state: appear cubidal or columnar in shape
- in a distended state: resemble a stratified squamous epi
What type of epi layer is this?
Pseudostratified columnar epithelium:
- all cells are in contact with basement membrane - BUT - not all reach the surface of the epi.
- the nuclei of cells that do not reach the surface are often located in different heights within the epithelium and give it a stratified appearance but it is NOT
- found in the excretory ducts of many glands
Name the 3 difference surfaces of a cell:
top: apical (free) surface
middle: lateral (or contact) surfaces - neighbourning epithelial cells
bottom: basal surface
- rests on basement membrane
What is the basement membrane?
membrane that the basal surface of cells is connected to.
- made up of an extracellular supporting layer = function is support
- basement membrane also acts as a selectively permeable filter between epithelium and connective tissue
What are microvilli and stereocilia?
- non-motile finger- or thread-shaped extensions of epithelial cells
- main function: increase surace area of cells active in absorption
- micro are much shorter than stereo
What are motile strucutres that beat in a synchronous manner to move material across epi surfaces?
Cilia
Name an Occuluding type junctional complex
- Tight junctions: connects adjacent cells; close to apical surface
- form very tight connection with neighbouring cells
- stop all movement to basement membrane
What are teh 2 adhering type junctional complexes?
- Desmosomes/zonulae adherens: anchor cells to each other; connected to cytoskeleton
- Hemidesmosomes: connect cells to basement membrane
- not combining with another cell - but binding into place
- both are found in lateral surfaces