Epithelia Flashcards
What is epithelia
Comprise cohesive sheet of cells, with one or more layers, resting on a basement membrane
Think -lining
Define simple epithelia
Single layer of cells on a basement membrane
Define stratified (compound) epithelia
Two or more layers of cells on a basement membrane
Define simple squamous epithelium
Single layer of flattened plate-like cells on a basement membrane
Often the nucleus will look like it stands proud
Parallel oval nuclei (1 per cell)
What does simple squamous epithelium line
Blood vessels (endothelium)
Outside the lungs (mesothelium)
Abdominal organs (peritoneum)
Lung alveoli
Define simple cuboidal epithelium
Single layer of cells with similar height and width on a basement membrane
Central spherical nuclei (1 per cell)
What do simple cuboidal epithelium line
Kidney tubules
Small ducts e.g. salivary glands
Define simple columnar epithelium
Single layer of cells taller than they are wide, on a basement membrane
What do simple columnar epithelium line
Stomach
Intestines
Uterus
May or may not have cilia or microvilli
Define microvilli
Microscopic projections on luminal surface of absorptive cells
Increase surface area
Intestinal brush border
Where would you find microvilli and cilia
Columnar epithelium
Give examples of where you would find cilia
Respiratory tract
Reproductive tract
Trachea
Fallopian tubes
Define cilia
Microscopic projections on luminal surface of cells
Define stratified epithelia
More than one layer of cells resting on the basement membrane
Protective function
Where would you find stratified epithelia
Areas which are being continually worn down, worn away cells replaced from below
Found at sites subject to abrasive forces
e.g. skin, mouth (action of speaking, eating), oesophagus, vagina, cervix
In stratified epithelia where do cells start
Resting on basement membrane - quite immature
As develop pushed up by new cells forming underneath them
Define stratified squamous epithelium
Multiple layers of cells on basement membrane
Mature surface layers are plate like-squames
Where would you find stratified squamous epithelium
Mouth
Oropharynx
Oesophagus
Vagina
What are the two types of stratified squamous epithelium
Keratinised - skin
Non-keratinised
What is the role of keratin
Waterproof epithelium
Wet sites of the body will not find keratin production
Define pseudostratified epithelium
Single layer of cells of variable height
Mimicking multiple layers on basement membrane
All cells in contact with basement membrane
Where would you find pseudostratified epithelium
Lines the conducting airways
What is another name for pseudostratified ciliated epithelium
Respiratory epithelium
Define urothelium
Specialised stratified epithelium
Breaks the rules -
Surface layer of umbrella cells
Cells between umbrella cells appear 3-7 layers thick and this layer is pseudostratified
What is another name for urothelium
Transitional epithelium
Where is urothelium found
Lines collecting part of the urinary tract
- Bladder
- Ureter
- Renal pelvis
What is the significance of the basement membrane
Always present
Infer presence between difference in epithelium and underling tissue
What stain would you use if you wanted to see the basement membrane
PAS - stains basement membrane magenta
What is the basement membrane
Composed of several extra-cellular proteins including collagen IV and fibronectin
Essential for the proper functioning and survival of the epithelium
What is important for the proper functioning of the epithelium
Basement membrane and epithelial junctions
What are epithelial junctions
Occluding (tight) junctions
Band-like fusions between cells that are impervious to most molecules
Prevent diffusion between cells
What is the role of desmosomes in epithelial junctions
Anchoring/Adherent junctions
Plaques that form physical joins between cells and connect the cytoskeletons of adjacent cells
Spread forces across several cells
Prominent in the skin - places where abrasive
What is the role of gap junctions
e.g. communicating junctions
Electrical junctions that permit the transfer of small molecules
Electrically couple adjacent cells
Where are microvilli found
Absorptive epithelial cells e.g. gut and kidney tubules
How many cilia are there per epithelial cell
300
What do all epithelial have
Basement membrane
