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EPITHELIAL TISSUES (Simple
squamous
epithelium (L
kidneys, lungs,…
EPITHELIAL TISSUES
Simple
squamous
epithelium
-
-
S
- single layer, scale-like cells
- centrally located nuclei
- cells in direct contact with each other
F
- diffusion, osmosis, filtration
Simple
cuboidal
epithelium
-
-
-
S
- single layer, cube-like cells
- centrally located nuclei
Simple
columnar
epithelium
-
Ciliated simple columnar
S - have cilia
F - motility, more fluids/particles
L - uterine tubes, bronchioles, brain ventricles
-
S
- single layer columnar (rectangular) cells and goblet cells (secrete mucus)
-
-
-
-
Transitional
epithelium
F
- capable of stretching - distension of organs
-
S
- several layers of cells - variable shapes
L
- lines bladder, ureters, urethra, uterus
Function
Secretory surface
- releases molecules produced by cells into free surface
- secretion, excretion
Protective surface
- resist abrasive influence of environment
- movement, protection, reproduction
Selective barrier
- help transfer substances in/out of body
- diffusion, osmosis, filtration or absorption
Classified by
Cell
arrangement
Stratified
- two/more cell layers thick
Pseudostratified
- all cells contact basement membrane
- not all cells reach apical membrane
- nuclei located at multiple levels
-
Cell shape
-
-
-
Transitional
- shape varies - allows for stretching
-
Types
L
- epidermis of skin
- lining of blood vessels, ducts, respiratory, reproductive, urinary, GI tract
Glandular
L
- secreting portion of glands
- thyroid, adrenal, sweat glands
Basement
membrane
S
- basal lamina (made by epithelial cells and collagen)
- reticular lamina (secreted by connective tissue, composed of reticular fibres)
F
- guide for cell migration during development
- may become thickened (increased collagen and laminen production)
- something for epithelium to attach to
- covers body surfaces
- lines hollow organs, body cavities and ducts
- closely packed cells
- very little extracellular material
- always has a free surface - apical (upper free surface)
- many cell junctions
- cells sit on basement membrane
- basal - sits against basement membrane
- avasular
- good nerve supply
- rapid mitotic cell division
