Epithelia Flashcards
What are epithelial cells?
Cells that cover or line all the body surfaces
What do all epithelial cells sit on?
Basement membrane
What are tumours called that develop from epithelial cells?
Carcinomas
What are epithelial cells connected by?
Tight junctions
What are the three different shape of epithelial cells?
Columnar
Cuboidal
Squamous
What are epithelial cells called if they only have one layer?
Simple
What are epithelial cells called if they have more than one layer?
Stratified
What are the cells called that are in contact with the lumen and BM?
Apical
Basal
What is the effect of a thicker epithelium?
The greater the protection from abrasion, infection or caustic content
What epithelium is found in blood vessels?
Simple squamous
What epithelium is found in kidney tubules?
Simple cuboidal
What epithelium is found in the GI tract?
Simple columnar
What epithelium is found in the skin?
Stratified squamous
What epithelium is found in the reproductive system?
Stratified cuboidal
What epithelium is found in the respiratory system?
Pseudostratified columnar
What epithelium is found in the bladder?
Transitional
What does a single layer of flattened epithelium allow?
Exchange of gases, nutrients
What does a single layer of cuboidal or columnar epithelium allow?
Transport system and ciliated surfaces
What does multiple layers of a flattened epithelium allow?
A protective barrier
What does one or many layers of columnar epithelium allow?
Secretory function
Describe simple squamous epithelium
Single layer flattened cells
Individual cells are very thin with a central nucleus
Irregular shape
Close proximity to each other
Where is simple squamous epithelium found?
Lining of body cavities
Where is simple columnar epithelium found?
Lining of small intestines
What three levels of folding are there in the small intestines?
Large folds to the naked eye
Microscopic villi covered by a SCE
Microvilli modifications of the apical surface of the epithelial cells
What does simple columnar epithelium in the small intestine allow?
Increase in surface area for absorption
Mucus secretion to lubricate gut contents
What are the three surface modifications of simple columnar epithelium?
Mucus adheres to the brush border created by several hundred microvilli
Goblet cells release mucus to lubricate gut contents
BM stops epithelium joining to other tissues
Where is pseudostratified ciliated columnar epithelium found?
In the respiratory tract
Describe the structure of pseudostratified epithelium
All the cells adhere to the BM but because of the length and shape of the individual cells, it makes it seem like it has multiple layers
Where is stratified squamous epithelium found?
Oesophagus, vagina, anal canal
What is desquamation?
Flattened cells that are worn off and are shed from the surface
What effect does stratified squamous keratinised epithelium have?
Resists water loss
Where is stratified squamous keratinised epithelium found?
Skin
Where is transitional epithelium found?
The bladder
What feature allows transitional epithelium to stop leakage?
High numbers of tight junctions
What are the different points of adherence?
Tight junctions
Desmosomes
Hemidesmosomes
Gap junctions
What are the different membrane proteins associated with the tight junctions?
Claudin and occludin
What type of junctions are cell-cell?
Gap
Tight
Adhering
Desmosome
What type of junctions are cell-matrix?
Hemi-desmosome
Focal adhesion
What protein are associated with hemi-desmosome?
Membrane- integrin
Cytoskeleton- Keratin
Extracellular matrix- laminin
What are the different ways molecule can pass through the epithelium layer?
Trans cellular movement
Paracellular movement
Two examples of trans cellular movement?
Absorption
Secretion
Example of paracellular movement
Diffusion
What are sealing strands?
Multiple layers of claudin and occludin creating a better barrier
What increases with an increase of number of sealing strands?
Resistance
What are the different functions of tight junctions?
Barriers
Fences- maintain the asymmetric distribution if lipids and proteins in the apical and basal membranes
Gates- selective movement
