Epithelia Flashcards
What are Epithelia (give both dry and wet)?
Epithelia are cells that cover or line all the body surfaces, tubes and cavities (dry epithelium)
Epithelia are cells that form the interfaces between different physiological fluid compartments;
- Blood and tissues (blood vessel wall)
- Gut and tissues (gut wall)
- Air and blood (lungs, alveoli)
What are the 4 functions of epithelia?
Epithelia;
- Can be diffusion controlling molecules (moving molecules via transcellular movements)
- Be the skin protecting the inside structures
- Secret water and ions as well as absorbing them
- Can communicate between one another and recruit immune cells when an issue is present
What are characteristics of epithelia?
- Epithelia are in intimate contact with each other and may be connected by tight junctions]
- Epithelial cells are separated from underlying tissues by the basement membrane - which anchors cells to the underlying tissue via the hemi-desmosomes
- Epithelila cells undergo rapid division to replace those that are constantly lost from the surface
What are tumours that develop from epithelial cells called?
Carcinomas
What are the 3 different shapes of epithelia?
Columnar, cuboidal and squamous
What are the 2 types of layers found in epithelium. and their features?
Simple - 1 layer of epithelial cells
- All cells are in direct contact with the lumen and basement membrane
- They are found at sites in the body where there is diffusion, absorption or secretion
Stratified - Multiple layers of epithelial cells
- Cells in contact with the basal membrane are basal cells
- Cells in contact with the lumen are apical cells
- They are found at sites of the body where protection is needed
What are the features of simple squamous epithelium?
- Single layer flattened cells
- Individual cells which are very thin with a central nucleus close to the basement membrane
- Irregular pavement like appearance
- Close proximity to each other (no gaps)
They line the skin, pleura, pericardium
What are the features of simple columnar epithelium and what do they line?
Simple columnar epithelium;
- increase the surface area for absorption
- Mucus secretion to lubricate gut contents
Simple columnar epithelium lines the small intestine
What type of epithelium lines the body cavities?
Mesothelium
What type of epithelium lines blood vessels?
Endothelium
What is caused if the endothelium is damaged?
Atherosclerosis - plaque building up in arteries
What are the 3 levels of folding in simple columnar epithelium in the small intestine that increases the surface area?
1) . Large folds - visible to the eye
2) . Microscopic villi - covered by a simple columnar epithelium
3) . Microvilli modifications of the apical surface of the epithelial cells, visible only at the electron microscope level.
Where is cuboidal epithelium found?
Small collecting ducts of the kidney, pancreas and salivary gland
What are the features of Pseudostratified ciliated columnar epithelium?
Pseudostratified Ciliated columnar epithelium is a type of respiratory epithelium.
They contain 3 cell types;
- Columnar cells
- Goblet cells
- Basal cells
It has cilia that sweep away mucus
What are the features of stratified squamous epithelium and what do they line?
Stratified squamous epithelium;
- Flattened cells that are worn off and shed from surface desquamation (getting rid off cells)
- Basal cells on the basement membrane divide and move upwards to the surface
- Protects underlying tissue. from abrasion
Stratified squamous epithelium is a characteristic of wet epithelia that is subject to abrasion but not dehydration
e.g - Mouth, Vagina, Anal canal
