Epithelia and Glands Flashcards
2 main characteristics of epithelial cells
- closely apposed and adhere to one another via cell-cell adhesion junctions
- Have polarity
Describe the polarity of epithelial cells
- apical domain (free surface)
- lateral domain (surfaces that face neighboring epithelial cells)
- basal domain (attached to basal lamina
Location/catergories of epithelium
- covering the surface of the body (skin)
- Exocrine and endocrine glands
- Lines peritoneal, pleural, and pericardial cavities (mesothelium)
- likes blood and lymphatic vessels (endothelium)
functions of epithelium
Covering
Sensory
Myoepithelium
- protection (skin)
- secretion (glands)
- absorption (small/large intestine)
- gas exchange/Resperatory (lung alveoli)
- transport between blood and tissues (vascular endothelium)
Simple vs. Stratified epithelium
simple = one layer stratified = multiple layers
shape of epithelium
DEPENDS ON MOST APICAL SURFACE OF CELLS
squamous, cuboidal, columnar
Simple squamous
single layer and adhere closely to one another via edges
EX:
meothelium (line cavities) and endothelium (vessel)
Renal Tubules:? outer bowman capsule
Pulmonary alveoli
THINK: allow for diffusion
Simple Cuboidal
single row of square/low rectangular cells where the height and width of the cells are nearly the same
EX:
small ducts of exocrine glands;
Renal tubules: collecting ducts in kidney`?
Thyroid gland follicles
Simple Columnar
defined rectangular outlines where the cells are taller than they are wide
- nuclei are about the same level and end to be elongated
EX:
Small and large intestines
Stomach
Gallbladder and bile ducts
uterine mucosa- endometrium snd inner epithelium of uterine cervix
stratified squamous
- thick, many layers of cells with nuclei sort of aligned
- deep cells (near basal laminar) are more cuboidal, surface cells are squamous
- either keratinized or non-keratinized
Keratinized stratified squamous
-thickened plasma membrane and bundles of tonofilaments (keratin intermediate filaments) in cytoplasm.
-NO NUCLEUS in keratin portion
-on open (free surfaces).. exposed to world/abrasion
-provide thickness for increased protection
EX: epidermis of skin, palm of hand/feet
tonofilaments
type of keratin intermediate filament found in keratin stratified squamous cells
Non-keratinized stratified squamous
-found on inner/moist surfaces EX: esophagus oral cavity, pharynx, oesophagus nasal vestibule, vocal cords larynx anal canal (transitions into weakly K) vagina
stratified cuboidal
- deep layers = irregular polyhedral cells that do not reach free surface
- superficial (apical) cells = cuboidal
- EX: ducts of sweat glands
stratified columnar
- deep layers = irregular polyhedral cells that do not reach free surface
- superficial (apical) cells = columnar (taller than wide)
- EX: LARGEST ducts of exocrine glands
TRANSITIONAL ZONES: anorectal junction (into non k stratified ep) uterine cervix (into non k stratified ep)
pseudostratified columnar
- SIMPLE EPITHELIUM BU ALL OF THE CELLS DO NOT REACH THE FREE SURFACE
- nuclei NOT aligned (stratified)
- EX: goblet cell (ciliated) in respiratory system = respiratory epithelium
Transitional epithelium
- shape of superficial (apical) cells can change depending on relaxed (contracted) or distended (stretched)
- In relaxed (contracted): basal cells = cuboidal/columnar, apical cells = dome shaped
- in distended (stretched): cells look squamous because the bladder is filling
- EX ** urinary system: ureter, bladder
Apical domain location
free surface of epithelial cells; directed towards the lumen of an enclosed cavity of tube or the external environment (PART OF THE CELL THAT INTERACTS WITH THE ENVIRONMENT)
apical domain function
secretion, absorption, protection, transport of materials along the surface/into the epithelium, transduction of external stimuli via receptors
list the apical domain modifications
cilia, microvilli, sterocilia
lateral domain of epithelial cells: Location
- facing neighboring epithelial cells
- sometimes form interdigitations to increase surface area for cell-cell interactions
lateral domain of epithelial cell: function
adhesion of neighboring epithelial cells, cell-cell communication, creation of osmotic/ionic gradient
Basal domain of epithelial cell: location
- above the ECM
- associated with basal lamina and ECM adhesion junctions
Basal domain of epithelial cell: function
attach epithelium to the underlying CT (loose connective tissue)
Cilia function
move fluid and particles along the epithelial surface
cilia structure
- axoneme (9+ 2 microtubules, 2 microtubules in center)
- Basal body (MTOC: 9+ 3 microtubules) anchors cilium to apical region of the epithelial cell cytoplasm
how is the beating movement of cilia produced?
movement of doublet microtubules (in axoneme) in relation to each other via dynein
dynein
protein that allows microtubule doublets to move in relation to eachother
structure of axoneme vs. cilia basal body vs. centrosome
axoneme: 9 + 2 microtubules (with dyenin on them) with 2 microtubules in center
cilia basal body: 9 + 3 microtubules
centrosome: 9 + 3 microtubules
where are ciliated epithelia found?
trachea, bronchi, and oviducts
common disorders due to immotile (dysfunctional) cilia
- chronic respiratory problems
- Kartagener’s syndrome (absence of dynein causes male sterility due to immotile flagella)
- Young’s syndrome: malformation of radial spokes and dynein arms
Microvilli general/function/examples
cytoplasmic projections on the apical surface of epithelial cells
- NOT involved in movement of particles
- Involved in INCREASED ABSORPTION (by increasing the surface area of PM
- EX: intestinal absorptive cells (small intestine) = striated border, kidney tubule = brush border
Microvilli structure
- bundle of actin filaments attached at the membrane ti and extended down into the cytoplasmic terminal web
- core of actin filaments joined by actin-crosslining proteins (villlin and fimbrin)
- actin linked to membrane via myosin I and calmodulin
- terminal web
- glycocalyx (integral membrane glycoproteins)
terminal web of microvilli
contains actin, IM filaments, linking molecules; anchor into the junctional complex
glycocalyx of microvilli
- made of integral membrane glycoproteins that interact with the external environment
- aid in trapping or slowing external molecules close to the cell surface
- in intestines, it contains digestive enzymes
Steroecilia (what, what made of, where found)
- long, slender, immotile structure
- ACTIN core (similar to microvilli)
- found in epididymus and ductus deferns; sensory hair of inner ear
Stereocilia structure
- cytoplasm = actin bundles anchored to terminal web
- arise from apical protrusions at base
- thin stereocilia are sometimes linked via cytoplasmic bridges
- at finger-like region, actin are crosslinked by fimbrin and anchored to PM via ezrin
- in aprical protrusions & terminal web, actin crosslinked by alpha actinin
cilia vs. microvilli vs. stereocilia filament composition + mobile?
Cilia: microtubules; motile
Microvilli: actin; motile
Sterocilia: actin; immotile
Junctional Complex
- epthelial cell-cell adhesion junction
- aka “terminal bar” in LM
- 3 zones: zonula occludens, zonula adherens, macula adherens