Flashcards in 2. Epithelial tissues Deck (73)
Epithelia are classified by
What shapes can Epithelia take?
Squamous (flattened plate-shape)
What are the types of layering in Epithelia?
Single layer = simple epithelium
Multi-layered = stratified epithelium
Where is simple squamous epithelium found?
Mesothelium (lining major body cavities)
Endothelium lining blood vessels and other blood spaces
Where is simple cuboidal epithelium found?
Lining kidney collecting duct
Many other ducts
Where is simple columnar epithelium found?
Enterocytes (intestinal absorptive)
Many other absorptive and secretory epithelia
Where is keratinising stratified squamous epithelium found?
(nuclei not visible in surface layer cells)
Where is non-keratinising stratified squamous epithelium found?
Linings of mouth, oesophagus, anus, cervix and vagina (nuclei are visible in surface layer cells)
Where is pseudostratified epithelia found?
Airway (trachea & bronchi)
Various ducts in the urinary and reproductive tracts
Epithelia functions require ...
Must be directional
Epithelial layer surfaces
Apical surface at lumens (open) surface
Basal surface in contact with ECM
Basal & Lateral membrane of Epithelia are usually grouped
What can segregate the epithelial plasma membrane into apical & basolateral domains?
2 Types of cell-cell junctions between Epithelial cells
• Zonulae (continuous belts)
• Maculae (discrete spots)
Usually, cell-cell junctions are arranged as an apical junctional complex containing a...
Tight Junction nearest the apex and an Adherens junction just below it
Where are desmosomes (spot adhering junctions) often found?
Scattered throughout lateral membrane
What do Gap Junctions do?
Act as regions of direct communication between adjacent cells
What do cell-cell junctions do?
Give epithelia mechanical integrity
Act to seal intercellular pathways of the layer
Tight junctions seal the paracellular pathway
Prevents things passing between membrane of adjacent cell
Passing/ situated beside/between cells
Passing through cells
Tight Junctions allow cells to establish and maintain apical- basolateral polarity by...
Preventing the mixing of proteins and lipids between different plasma membrane compartments
Zonula occludens are also known as
What is the consequence of paracellular pathways (between cells) being sealed by tight junctions?
Concentration differences across cell layers can be maintained
The more elaborate the network of contacts in a tight junction...
The tighter the seal
Which pathways do tight junctions seal?
What is the fence function of tight junctions?
TJ's segregate apical and basolateral membrane polarity
Describe the membrane in transporting epithelia e.g. distal convoluted tubules
Apical membrane contains many ion/ water channels
Basal membrane has many infoldings and mitochondria for active transport
What increases efficiency of absorption? How can this be achieved?
Increasing surface area
Make it longer
Fold the lining to form structures e.g. villi
Create tubular protrusions e.g. microvilli