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Transitional Epithelium
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Classification
by shape, no. layers and surface
- Shapes:
- Cuboidal, columnar, squamous
- Layers:
- Simple, stratified, pseudostratified
- Surface:
- Special class: Transitional epithelium (urothelium)
Features:
- Basement membrane
- All attached in simple and pseudostratified
- Only bottom layer attached in stratified
- Apical and basolateral domains
- Separated by junctional complex
- Tight junctions have varying degrees of permeability to solutes,
water, etc.
- Tight junctions fix proteins in one or other domain of plasma membrane
- Brush Border
- May or may not be present.
- Extends apical surface area
- Composed of microvilli
- Glycocalyx
- Glycosylated protein extends from apical end
- Protects from attack by digestive enzymes, etc.
- Used in targeting
5.1
EPITHELIAL TISSUES
[Currently: 1 lecture + 1 ´ 2h class in histology
(1st term), plus 1 lecture in renal physiology (3rd term)]
5.1.1
Structure [Hist]
| Cell shape and organization: simple (squamous, cuboidal,
columnar, pseudostratified), stratified, transitional. |
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| Cell types: differentiated cells and stem cell
populations. |
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| Polarity: apical and basolateral surfaces. |
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| Functions: transport, synthesis and secretion;
protection; generation of movement over the apical surface (ciliated
epithelia). |
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| Junctions: junctional complexes, gap junctions,
desmosomes, other. |
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| Basement membranes: composition, structure and functions. |
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| Epithelial morphogenesis in the embryo (e.g. neurulation),
and later (e.g. mammary gland). |
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5.1.2 Fundamentals of Epithelial Transport [Phys]
Currently: 1 lecture in renal physiology course (moved here from Renal
Physiology section)
| Absorptive and secretory epithelia: transepithelial
solute and water transport driven by active Na and secondary active Cl
transport, respectively. Koefoed-Johnson and Ussing model of active Na
transport in absorptive epithelia; channel-mediated versus
carrier-mediated apical Na entry mechanisms in tight and leaky epithelia. |
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