Term
| What three functionally and morphologically distinct structures define the epithelia junctional complex? |
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Definition
1) Tight junction (zonula occludens)
2) Adherence junction (zonula adherens)
3) Desmosome (maculae adherentes) |
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Term
| Describe the basic structure of the basement membrane of an epithelial cell. |
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Definition
Basal Lamina (closest to cell)- clear zone/lamina lucida and electron dense zone/lamina densa (laminan, fibronectin, proteoglycan-rich)
Reticular lamina (furthest from cell)-produced by fibroblasts and contains fibrillar collagen |
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Term
True:False
Epithelial tissue is avascular and relies on diffusion of substances from capillary bed through basolateral surfaces. |
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Definition
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Term
What is the difference b/w carcinomas and adenocarcinomas?
What about b/w papillomas and adenomas? |
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Definition
1) Carcinoma- malignant tumor arising from surface epithelia
2) Adenocarcinoma- malignant tumor arising from glandular tissue
3) Papilloma- benign mass from surface epithelia
4) Adenoma- benign mass from glandular tissue |
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Term
| What are the major functions of the glycocalyx "sugar coat" in the apical surface of epithelial cells of the intestinal tract? |
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Definition
Glycoproteins, glycolipids and glycosaminoglycans coat apical surface.
1) Prevent edema through water uptake
2) Lubrication
3) Selective permeability due to negative charge (charge and size)
4) Signaling- heparin (binding epidermal growth factor and lipoprotein lipase) |
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Term
| These ridge-like folds are coated by a glycocalyx and probably functions as a cushion to protect the apical surface of epithelia from abrasion. |
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Definition
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Term
| These structures exist as extensions of the apical membrane of epithelial tissue in the enterocytes of the intestine and proximal tubules of nephrons to encourage absorption. |
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Definition
Microvilli
Actin-microfilaments anchored to terminal web containing spectrin, actin, intermediate filaments and myosin II. |
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Term
| These elongated, actin-based structures assist in fluid re-absorbtion from developing sperm delivered from seminiferous tubules and for sound perception in the inner ear. |
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Definition
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Term
| What is the difference b/w 9+2 and 9 + 0 organized microtubule-based cilia? |
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Definition
1 9+2 are Motile
Have a single doublet enclosed by 9 other doublets that are crosslinks with the (-) acting dynein, which causes whiplike motion through ATPase activity.
2. 9+0 are non-motile "primary cilia." They are involved in sensory perception |
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Term
1) What types of epithelia cells line the alveolar surface of the lung and the nephrons of the kidney?
2) What types of epithelia are found specifically in the trachea and epidydimus?
3) What types of epithelia are found in the epidermis and the esophagus? |
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Definition
1) Simple Epithelia
2) Pseudostratified epithelia
3) Stratified squamus epithelia |
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Term
| What are the two primary roles of tight junctions in epithelial cells? |
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Definition
1) Gate function- limits ion and water transport through paracellular space between adjacent cells (accomplished by claudins and gap junctions)
2) Fence function- limits protein and lipid flux in exofacial leaflet of apical and basolateral PM domains. |
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Term
| How does familial hypomagnesemia with hypercalciuria and nephrocacinosis arise? |
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Definition
Defects in claudin-16 ("paracellin")
Patients cannot absorb magnesium and calcium in the thick ascending loop of Henle in the kidney.
Remember, claudins are integral membrane proteins that are tethered to the actin cytoskeleton by ZO-1, -2 and -3 peripheral membrane proteins. |
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Term
| Which integral membrane proteins are found in adherence junctions and how do they regulate junction formation? |
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Definition
Cadherins form homophilic head-to-head interactions between adjacent cells.
They are calcium-binding proteins, making the formation of adherens junctions calcium-dependent. |
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Term
| Why does EDTA dissolve the entire junctional complex? |
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Definition
| ETDA will dissolve junctional complex because the complex requires the adherens junction and the adherens junction is calcium-dependent! |
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Term
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Definition
Autosomal recessive condition caused by plakaglobin (y-catenin) defects. It is a problem with adherens junctions and possibly desmosomes.
Affects heart, skin and hair follices.
Remember, cadherins association with p120, alpha, beta and gamma catenins at the adherens junction to link adjacent cells. |
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Term
| What major feature differentiated desmosomes from tight junctions and adherens junctions? |
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Definition
They form spot welds or plagues, instead of continuous belts
Desmosomes include cytoplasmic plaques which are composed of keratin that anchors and mechanically reinforces cell-cell attachments. |
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Term
| How do desmosomes link adjacent cells together. |
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Definition
| Desmologleins and desmocollins project into the intercellular space in a calcium-dependent manner and associate cytoplasmically with Plakoblobin, plakophilin and desmoplakin (latter two interact with keratin). |
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Term
| What is pemphigus vulgaris? |
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Definition
| Autoimmune response against desmoglein-3 that disrupts cell-cell adhesion in deep layers of skin and results in the formation of blisters. |
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Term
| How are connexon pores reversibly closed to prevent ions and small molecules from passing between cells? |
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Definition
low pH and high Ca lead to channel closure
high pH and low Ca open channels |
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Term
1) Why is a mutation in connexin-50 of clinical concern?
2) What about Connexin-32? |
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Definition
Gap junction issues!
1) Cataracts in the lens of the eye
2) Charcot-Marie-Tooth disease with motor and sensory nerve deficits |
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Term
| What types of molecules anchor the basal membrane to the basement membrane? How do they relate to hemidesmosomes? |
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Definition
Integrins (heterodynamic alpha-beta chains with ligand binding domains)
Hemidesmosomes are abundant in the epidermus and resemble half-desmosomes. They depend on alpha-beta integrin and appear as electron dense plaques o the cytoplasmic surface of the basal membrane, to which keratins attach |
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Term
| Why would defects in umbrella cell layers of the uroepithelium be of clinical importance? |
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Definition
| These transitional cells line the renal pelvis, ureter and bladder and allow stretching of the tissues when fluids move through them generating pressure. |
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Term
| What is the mucociliary escalator? |
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Definition
Ciliated epithelial monolayers that prevent particle accumulation in smaller airways.
Take particles from trachea to pharynx where they are swallowed |
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Term
| What are three immune surveillance systems present in epithelial cells? |
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Definition
1) Secreted defensin proteins that form pores in bacterial membranes
2) Imunoglobulin receptors that bind pathogen-specific immunoglobulins IgA and iGM and transcytose them across the cell to the apical surface to target pathogens.
3) M-cells that sample pathogens and transport them to dendritic cells and lymphocytes to trigger response. |
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Term
True:False
Taste buds are composed of stratified epithelium. Filiform papillae have mechanosensory functions while fungiform and circumvallate papillae have taste buds. |
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Definition
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Term
| What types of epithelium are found in the roof of the nasal cavity? What are they composed of? |
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Definition
Pseudo-stratified columnar epithelium.
Most important is CPOCs!
Composed of Ciliated Bipolar Olfactory Cells (project into extracellular environment), sustentacular support cells, microvillar cells and basal cells |
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Term
| What is the relevance of tip links that connect stereocilia? |
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Definition
Sound perception.
TIp links project into K-rich endolymph and attach to the tectorial membrane. When basilar membrane moves, the stereocilia bend, opening mechanogated ion channels and allowing K to flow in and depolarize the cell.
Different hair cells are tuned to different frequencies! |
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