Epithelial tissues Flashcards
Describe the differences between squamous, cuboidal and columnar cells.
Squamous are wider than they are tall (plate shaped)
Cuboidal are as wide as they are long Columnar are taller than they are wide
What are the two types of layering you find in epithelia?
Simple – one layer Stratified – several layers
What is the difference between keratinising and non-keratinising squamous epithelia?
Keratinising – nuclei are not visible in the surface cells and the layer is dry because the cells have hardened and died
Non-keratinising – nuclei are visible in the surface cells and the layer is wet
Give one example of where you would find: simple squamous, simple cuboidal, simple columnar, stratified squamous (keratinising and non-keratinising) and pseudostratified columnar epithelia.
Simple Squamous – endothelial cells, lung alveolar
Simple cuboidal – kidney collecting duct Simple columnar – enterocytes Keratinising Stratified Squamous – skin/epidermis
Non-Keratinising Stratified Squamous – oesophagus/lining of the mouth
Pseudostratified columnar – upper airways
What is the key player in establishing epithelial polarity?
Tight Junctions
How do they establish epithelial polarity?
They block the paracellular pathways so molecules that want to pass across the epithelia must pass through the cells
Why is it necessary for epithelial cells to have polarity?
Many processes (e.g. secretion, absorption) are unidirectional
Describe cell division in the villus
There are intestinal stem cells in the crypt. New cells are shunted up the villus as other new cells form. Cells are lost from the tip.
What type of epithelia usually constitutes protective epithelia?
Stratified squamous epithelia.
Keratinising and Non-keratinising stratified squamous
What is Epidermolysis bullosa an example of?
Disorder of cytokeratin and desmosomes
What is responsible for the polarity of cells?
It is the polarity of the plasma membrane which allows the functions to take place. The junctions are also important in allowing the cells to maintain polarity.
Absorptive and transporting epithelial. What happens at the apical membrane
Apical membrane has passive channels allowing Na+ and water to be drawn.
What happens at the basal membrane and describe the structure?
Basal membrane has several folds- bigger SA. Na+ is pumped out at basal side using ATP
What happens if you inhibit ATP production
SWELLING of the apical because the passive transport is not matched with the active transport at the basal membrane.
What do desmosomes do
Link cells to each other and the ECM
