Lecture 30 11/7/23 Flashcards
How does epithelia function in protection?
-covering external surfaces
-lining internal surfaces
What are the secretory functions of epithelia?
producing:
-mucus
-gastric and pancreatic juices
-saliva
-“sweat”
Where does epithelia have absorptive function?
-intestines
-renal tubules
Which epithelium has sensory function?
olfactory epithelium
What are the transport functions of epithelia?
-movement of water/ions through and around cells
-movement of substances across surfaces
What are the special functions of epithelia?
-gas exchange
-gliding between surfaces
What are the features of epithelia?
-polygonal
-polar
-relatively avascular
-almost wholly cellular (very little connective tissue/extra space)
-cell-to-cell junctions
-bound to basement membrane through hemidesmosomes
How does the epithelia get blood if it is primarily avascular?
diffusion from local vessels
What are the types of junctions between cells?
-tight junctions
-zonula adherens
-macula adherens/desmosomes
What is the shape of squamous cells?
flat
What is the shape of cuboidal cells?
cubed, same width as height
What is the shape of columnar cells?
taller than wide
What is simple epithelia?
epithelia in a single layer
What is stratified epithelia?
epithelia in more than one layer
How is stratified epithelia named when the cell types change throughout?
based on the shape of the surface layer cells
what is pseudo-stratified epithelia?
-single layer that looks like multiple
-typically columnar
Which types of epithelia have all cells touching the basement membrane?
-simple
-pseudostratified
What are the characteristics of microvilli?
-short
-non-motile
-increased surface area for absorption
What are the characteristics of cilia?
-long
-motile
-aid in clearance
Where are microvilli found?
simple or pseudo-stratified epithelium
Where are microvilli of importance?
-intestinal brush border
-proximal convoluted tubules of kidney
Where are cilia found?
simple or pseudo-stratified epithelium
What is respiratory epithelium?
pseudostratified ciliated columnar epithelium +/- goblet cells
What are the characteristics of stereocilia?
-long microvilli
-non-motile
Where are stereocilia found?
-hair cells of the ear
-male repro. tract
What are the characteristics of goblet cells?
-modified columnar cells
-produce mucus
Where will simple squamous epithelium be found?
-lining cardiovascular system
-lining body cavities
-lining posterior surface of cornea
-glomerulus of kidney
-alveoli of lungs
What does simple squamous epithelium look like?
single layer of flattened nuclei w/ little cytoplasm
What are the roles of simple squamous epithelium?
-allowing things to glide by
-allowing for movement through a barrier
What is the role of stratified squamous epithelium?
very tough, so found at high friction sites
Where is stratified squamous epithelium found?
-oral cav.
-pharynx
-esophagus
-anal canal
-uterine cervix
-vagina
-anterior cornea
What is keratinized stratified squamous epithelium?
-cells die and leave behind tough dead “skeletons” filled with keratin
-makes surface resistant to friction and drying out
Where is keratinized squamous epithelium found?
-skin/footpads
-oral cav.
-forestomachs of herbivores
How do orthokeratosis and parakeratosis differ?
-orthokeratosis has no cell nuclei in the keratin layer
-parakeratosis does have cell nuclei in keratin layer
What are the roles of simple cuboidal epithelium?
-tougher than simple squamous; found in duct linings
-transport/absorption at kidney tubules
-comprises apocrine gland
Where is stratified cuboidal epithelium seen?
excretory ducts (apocrine and salivary glands)
What are the roles of simple columnar epithelium?
-tougher than cuboidal
-protection
-absorption
-transport
-sensory
Where is simple columnar epithelium found?
-GI tract
-gall bladder
-repro. tract
-nose
What does simple columnar epithelium look like?
-tall rectangles
-nucleus near bottom of cell
Where is stratified columnar epithelium seen?
-conjunctiva
-salivary gland ducts
What are the characteristics of transitional epithelium?
-surface layers transition between squamous and cuboidal
-only found in urinary tract/called urothelium
-accommodates stretching of urinary bladder
-withstands “irritation” of urine
