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 (skin)
Non-keratinising – nuclei are visible in the surface cells
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
Non-Keratinising Stratified Squamous – oesophagus
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?
Keratinising and Non-keratinising stratified squamous
What is Epidermolysis bullosa an example of?
Disorder of cytokeratin and desmosomes
what are pseudostratified cells?
they look multilayered but actually, all the surface cells are in contact with the basal lamina
what are basal infolding for?
they are closely associated with mitochondria to provide energy for active transport of molecules in transporting epithelium
what is the histology of the intestinal villi?
- they have crypts and goblet cells and enterocytes
what is exocrine secretion?
apical secretion to the duct / lumen (vesicles at the top )
what is endocrine secretion
this is secretion into the bloodstream (vesicles at the bottom)
