SSN Session
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Transcript of SSN Session
SSN Session
Epithelial TissueJennifer Chang (jtc2109)
Bram Welch-Horan (tbw5)October 11, 2005
Epithelium
What is epithelium?
• Covers exterior surfaces• Lines internal closed cavities and body tubes• Forms secretory portions of ducts and glands• Avascular tissue• High regeneration capacity
Polarized Cells
Apical: • faces the lumen or outside world• separated from the basolateral side by tight junctions
Basolateral:• Lateral:
• side that faces neighboring cell• forms functional continuum with basal side
• Basal: • adheres to extracellular connective tissue – basement membrane
Apical
Lateral
Lumen
Basal
The Apical RegionEpithelial Specializations:
Microvilli Stereocilia Cilia
small intestines epididymis fallopian tube
• Cytoplasmic processes that extend from cell surfaces
• Made of actin skeleton above intermediate filaments
• Increase area for absorption as in small intestine
• Insert into terminal web
Microvilli
terminal web
microvillus border
Small intestines
Stereocilia• Long microvilli (NOT CILIA!)• Non-motile
Epididymis
• Motile processes of microtubules that move synchronously
• Insert into basal bodies (1 cilium per 1 body)
• 9+2 microtubule arrangement
Cilia
cilia Basal bodies
Trachea
Fallopian tube
The Lateral RegionJunctional Complex (aka Terminal Bar) : site of specialized attachment of adjoining epithelial cells
terminal bar
terminal bar
microvillus border
terminal web
Bodian silver stain
3 Components (apical -> basal):
1. Zonula Occludens=Tight Junction•most apical•located around entire perimeter•diffusion barrier
2. Zonula Adherens •around entire perimeter•add to integrity of epithelial surface
3. Macula Adherens=Desmosome•occur at small discrete sites
Gap junctions•at small discrete sites•metabolic and electrical coupling
The Junctional Complex
Electron micrographs of the junctional complex
The Basal RegionBasement membrane1. Basal Lamina
• Secreted by epithelial cells• Barrier between epithelium and connective tissue• Collagen type IV, proteogylcans & glycoproteins (PAS +)
2. Reticular Lamina• Connective tissue below epithelium• Collagen type III
HemidesmosomesJunctions that anchors epithelial cells to basal lamina
basal lamina
PAS stain
Question 1. This structure is typically found in the
a) tracheab) kidneyc) epididymisd) small intestines
Question 2.Which of the following is FALSE regarding the structure at the pointer?
a) its permeability determines whether the epithelia is “tight or “leaky”b) it occurs at small discrete sitesc) it separates the apical surface from the basolateral surfaced) it is a component of the junctional complex
Question 3What type of collagen is found in the tissue at the pointer?
a) type IIb) type IIIc) type IVd) type VII
Types of Epithelial Cells
Epithelial Cell Types - Nomenclature
• Simple – 1 cell layer thick
• Stratified – 2 or more cell layers thick
• Squamous – cell width > height (i.e., flat)
• Cuboidal – width/depth/height ~same
• Columnar – cell height >> width
Simple Squamous Epithelium
• 1 cell layer thick
• function: exchange
• absorption, secretion, diffusion
• e.g. – blood vessels
• barrier function in CNS
Simple Cuboidal
• cuboidal shape (or pyramidal)• round, central nucleus• absorption / secretion, conduit• e.g. – small ducts of exocrine glands (pancreas), kidney tubules
Simple Columnar
• elongated cells w/ elongated nuclei
• height > width
• absorptive (e.g. small intestine) or secretory (e.g. gastric glands)
• other examples: -lining of colon, stomach, gall bladder
Stratified Epithelium
• 2 or more layers thick
• classified based on surface cells (can be squamous, cuboidal, or columnar)
• functions include: protection, barrier, resist abrasion
• Examples: epidermis, esophagus, larger exocrine ducts
What type of stratified epithelium is seen above?
Stratified Epithelium
What type of stratified epithelium is seen above?
Stratified Squamous Epithelium
• 2 or more layers thick
• classified based on surface cells (can be squamous, cuboidal, or columnar)
• functions include: protection, barrier, resist abrasion
• Examples: epidermis, esophagus, larger exocrine ducts
Pseudostratified Epithelium
All cells rest on basement membrane, but not all reach apical surface
-function: secretion, absorption, conduit-e.g., trachea, epididymis
Transitional Epithelium
Transitional Epithelium – “Urothelium"
• special stratified epithelium
• apical surface may appear “domed”
(empty) and flattened full)
• function: distensibility
• lines lower urinary tract
• i.e., ureters, bladder, proximal urethra
Question 4
What kind of epithelium lines the secretory alveoli of this exocrine gland?
a. Simple Columnar
b. Simple Cuboidal
c. Squamous
d. Transitional
Questions 5, 6
• 5. Select the one correct statement regarding the surface epithelium.• 6. The tissue or tissues that are specialized to provide a barrier to
luminal absorption are shown in:
Figure A Figure B
Lab 3, Slide 35 Lab 3, Slide 25
Question 7
This epithelial cell type is found in:
a. Bladder
b. Kidney tubules
c. Intestinal epithelium
d. Epidermis
Question 8
What type of epithelium is this?
a. Pseudostratified
b. Stratified Columnar
c. Stratified Squamous
d. Stratified Cuboidal