Epithelial Tissues Flashcards
(34 cards)
What is epithelia ?
cells that line or cover internal and external body surfaces. Form secretory gland or ducts.
Function of epithelia
Protection- epidermis
Absorption- intestinal lining
Secretion- salivary gland
Lamina propria
CT underneath epithelium
How does epithelial cells derive nutrition?
Epithelial cells are avascular (lack blood vessels).
Derive nutritions and O2 from vessels in the lamina propria (connective tissue)
Epithelium is classified by ?
Shape and arrangement.
What are the shapes of epithelial cells?
Squamous- flat cells, wider than they are tall.
Cuboidal- equal in height and width
Columnar- taller than they are wide.
What are the arrangements of epithelial cells?
Simple- single layer of cells
Stratified- multiple layers of cells.
Specialized- pseudostratified and transitional epithelium.
Simple Squamous
-Single layer of flattened cells
tends to have scanty cytoplasm and flatter nuclei.
- cells specialized for easy diffusion across their cytoplasm.
Don’t need to know location
appear in air sacs of lungs, lining of blood vessels (endothelium), and structures in kidney
Simple cuboidal
appear square. round nuclei.
line collecting tubules of kidneys that participates in water reabsorption.
Simple columnar and location
Taller than they are wide.
rounded nuclei.
found in bronchial tubes of the lungs, uterine tubes, and lining of stomach and intestinal tract.
Stratified epithelium?
How is it classified?
-epithelia composed of more that one layer of cells.
-only bottom layer touches the basement membrane.
-nuclei in each layer are basically aligned with each other.
classified based on shape of the TOP layer into:
stratified squamous, stratified cuboidal, and stratified columnar.
What are the rare types of stratified epithelium found in larger gland and male urethra?
Stratified cuboidal and stratified columnar epithelium.
Stratified cuboidal line ducts of sweat gland.
Stratified columnar in the male urethra protect tissue from urine by secreting mucus.
Stratified Squamous
-Piles of flattened cells with many layers.
- most common type of stratified epithelium.
- in places that undergo friction.
- can undergo keratinization; cells synthesize keratin filament to enhance cell toughness.
- Found in the vocal folds, esophagus, epidermis of the skin, vagina.
What is the most common type of stratified epithelium ?
Stratified squamous cells
Keratinized stratified squamous cells
Cells synthesized keratin filament to enhance cell toughness.
found in high friction area.
Cells in the upper layers may eject cellular organelles including nucleic. In histological section , cells closest to the lumen lack nuclei.
Pseudostratified epithelium
Cells of different shapes and sizes.
May appear as if cells are in layers, however all cells touch the basement membrane.
Eg. epithelium of respiratory system contains columnar cells, basal cells, and globules.
Cilia often associated with pseudo stratified but not always.
Non keratinized stratified squamous
in esophagus and vagina.
Apical Domain
Facing the lumen.
Contains specialized structures that add functionality such as receptors.
three important apical specializations:
- microvilli
-cilia
-stereocilia
Microvili
what are they?
what side of the cell?
where are they present ?
how do they appear in TEM?
what are they made off ?
-Short, finger-like projections of UNIFORM length. Enclosed by plasma membrane
- on the apical surface.
- appear as individual structures in a TEM
Increases surface area.
- compromised of actin microfilaments that inserted into network cytoskeletal protein referred to as the terminal web
- bc it can’t be seen clearly in LM, it’s referred to as brush border
Cilia
what is the protein?
can it bee seen in LM ?
-Longer, hair-like apical specializations
-Not uniformed in length
-individual strands can be seen in light microscope.
-Microtubules in 9+2 arrangement.
- Motility; attached to outer microtubules are dyne motor proteins
In respiratory tract; cilia beats to move fluid and harmful surfaces.
Primary Cilia Dyskinesia
why does this happen?
Recessive genetic disorder where ciliary microtubules lack dyne arms and are therefore nonmotile.
In respiratory system, cilia can’t clear mucus resting in chronic sinusitis and bronchitis.
All cilia in the body is affected since this is a genetic disorder.
Stereocilia
what kind of filaments?
Motility ?
length? branching ?
Related to microvilli
Core of actin filament that attache to terminal web
Longer, can branch.
Rare; found in the epididymis(male parts) and inner ear.
Not motile.
Basal domain
faces the basement membrane.
Includes important structures:
- Basement membrane
- hemidesmosomes: junctions that attach the cell to BM
- basal infolding (striations): plasma membrane of the cell folds around the cell.
Basement membrane
Cellular/aceelular?
function?
mutation cause what?
Acellular sheet of macromolecules that function as:
- structural support of epithelium and attachment site to lamina propria
- semipermeable filter; mutation in BM results in kidney disease where filtration is compromised
divides into basal lamina and reticular lamina.
