Epithelia Flashcards
What are epithelial cells?
Cells that cover or lone all the body surfaces, tubes and cavitiesCells that form the interfaces between different physiological fluid compartments
What do all epithelial cells stand on?
The basement membrane
What are tumours called if they develop from epithelial cells?
Carcinomas
What connects epithelial cells that are in intimate contact?
Tight junctions
Why do epithelial cells have to undergo rapid division?
Cells are being constantly lost from the surface
What are the three shapes of epithelial cells?
Columnar
Cuboidal
Squamous
What is the columnar shape split into?
Apex- next to the lumen
Base-basal part of the cell
What is unique about squamous epithelial cells?
They have the appearance of a flattened sheet
How can epithelial cells also be structured?
By stratified, more than one layer
What are the benefits of a single layer of epithelial cells?
All cells in direct contact with the lumen and BM
Quicker diffusion or absorption
What are the benefits of a stratified layering?
Greater protection from abrasion, infection or caustic content
What are epithelial cells called if they are in contact with the BM in a stratified system?
Basal
What are epithelial cells called if they are in contact with the lumen in a stratified system?
Apical
How can stratified cells also be arranged?
With a mixture of columns, cuboidal and squamous
Where will you find a simple squamous structure?
Blood vessels
Where will you find a simple cuboidal structure?
Kidney tubules
Where will you find a simple columnar structure?
Gastro-intestinal tract
Where will you find a stratified squamous structure?
Skin
Where will you find a stratified cuboidal structure?
Reproductive system
Where will you find a pseudostratified columnar structure?
Respiratory
Where will you find a transitional structure?
Bladder
What is a simple squamous epithelium structure?
Single layer flattened cells
Pavement-like appearance
No gaps Lines of body cavities (serous membranes)
What is a simple columnar epithelium structure?
Increase in surface area for absorption
Mucus secretion to lubricate gut contentsLarge folds visible to the naked eye
Microscopic villi covered
Microvilli modifications of the apical surface of the epithelial cells
What are goblet cells?
Cells that intensely staining mucus released to lubricate gut contents
What is a pseudostratified ciliated columnar epithelium structure?
Found in bronchus inclusive of columnar cells, goblet cells, basal cells
What is a stratified squamous epithelium structure?
Lining of oesophagus
Flattened cells that are worn off and shed from the surface, desquamation
Basal cells on the BM divide, move upwards to the surface
Protects underlying tissues from abrasion
What is a stratified squamous keratinised epithelium structure?
Includes; epithelium, connective tissue, hair follicle, hyopdermis adipose tissue, apocrine sweat gland, melanocyte
Resists water loss
What is a melanocyte cell?
A mature melanin forming cell
What is a transitional epithelium bladder structure?
Found in bladder
Stratified epithelium- many layers thick
Basal cells lying on basement membrane
Connective tissue
What additional feature prevents leakage of urine in a transitional eputhelium bladder cell?
Lots of tight junctions
What allows epithelial cells to know what direction they are in space?
The basement membrane
What are the membrane proteins of tight junctions?
Claudin and occludin
What is the cytoskeleton fibre made out of in tight junctions?
Actin
What movements do tight junctions allow?
Trans-cellular and paracellular movement
What is trans-cellular movement?
Secretion
What is paracellular movement?
When the tight junctions have leakage and allow molecules into the cell
What counteracts paracellular movement?
Sealing strands (doubling up on tight strands
What are the roles of tight junctions?
Barries- separate one compartment from another
Fences- maintain asymmetric distribution of lipids and proteins in he membranes
Gates
