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Epithelia (S+T)

QuestionAnswer
What causes breast cancer? Abnormal proliferation of the epithelial cells (1 in 8 women).
What causes cystic fibrosis? Defective epithelial chloride transport ion transport (1 in 2500 live births).
What causes cholera? Enhanced activation of epithelial chloride ion transport in gastrointestinal tract.
What causes atherosclerosis? Superficial injury to the epithelial lining of blood vessels causes cardiovascular disease (40% of the UK population will die due to associated complications with atherosclerosis).
What are epithelia? Cells that cover or line all the body surfaces, tubes and cavities. Cells that form interfaces between different physiological fluid compartments.
What connects epithelia? Cells are in intimate contact with each other and may be connected by tight junctions.
What separates the epithelial cells from underlying tissues? The basement membrane.
How is the epithelial layer maintained? Cells undergo rapid division to replace those continually lost from the surface.
What are the three shapes of epithelial cells Columnar, Cuboidal and Squamous.
What is the structure of a columnar cell? Apex- of the cell-next to the lumen. Base-basal part of the cell-next to the BM.
What is the shape of squamous cells? Sheets of flattened cells.
What is the structure of simple epithelia? One layer of cells. All cells in direct contact with the lumen and BM. They are found in sites in the body where there is: diffusion, absorption or secretion.
What is the structure of stratified epithelia? Multiple layers of cells. Cells in contact with BM= basal. Cells in contact with lumen= apical. They are found in sites in the body where there is need for protection.
Why are stratified epithelia used for protection? The thicker the epithelium the greater the protection from abrasion, infection or caustic content.
Why are simple epithelium thin? The thinner the epithelium, the quicker diffusion or absorption can occur.
What type of epithelium do blood vessels have? Simple squamous.
What type of epithelium does the kidney tubule have? Simple cuboidal.
What type of epithelium does the GI tract have? Simple columnar.
What type of epithelium does the skin have? Stratified squamous.
What type of epithelium does the reproductive system have? Stratified cuboidal.
What type of epithelium does the respiratory system have? Pseudostratified columnar.
What type of epithelium does the bladder have? Transitional.
Describe the structure of an exchange surface. One cell layer. Squamous cells. Pores between cells permit easy passage of molecules.
Describe the structure of a transport surface. One cell layer. Cuboidal or columnar cells. Tight junctions limit movement between cells.
Describe the structure of a ciliated surface. One cell layer. Cuboidal or columnar cells. Cilia move fluid across the surface.
Describe the structure of a protective surface. Many cell layers. Squamous on the surface: polygonal in deeper layers. Cells tightly connected by many desmosomes (an area of contact between two cells).
Describe the structure of a secretory surface. One up to many cell layers. Columnar or polygonal cells. Extensive RER (proteins) or SER (steroids).
What are the features of a simple squamous epithelium? Single layer of flattened cells. Individual cells are very thin with a central nucleus. Irregular shape. Close proximity to each other.
What is a mesothelium? The single layer of cells that lines serous membranes.
What is a serous membrane? A smooth transparent membrane, consisting of mesothelium and underlying elastic fibrous connective tissue.
What is the function of simple columnar epithelium? Lining of the small intestine: 1. to increase surface area for absorption. 2. mucus secretion to lubricate gut contents.
What forms the brush border of a simple columnar epithelium? Apical surface of each cell is covered by several hundred microvilli forming the brush border mucus adheres to.
What is the function of Goblet cells in the simple columnar epithelium? Release intensely staining mucus to lubricate gut contents.
What is the function of the basement membrane in the simple columnar epithelium? Separates the epithelial cells from the underlying tissues.
What does the pseudostratified ciliated columnar epithelium consist of? Columnar cells, Goblet cells and Basal cells.
What is the structure of the stratified squamous epithelium? Flattened cells that are worn off and shed from the surface- desquamation. Basal cells on the BM divide and move upwards to the surface.
What is the function of the stratified squamous epithelium? It protects underlying tissues from abrasion.
Where would you find a stratified squamous epithelium? Mouth, vagina and anal canal.
Define desquamation. The process in which the outer layer of the epidermis of the skin is removed by scaling.
Where is the apical membrane? Bordering the lumen.
Where is the basolateral membrane> In between epithelium cells.
Where is the basal membrane? Bordering the BM.
What membrane proteins are in a tight junction? Claudin and occludin.
Which cytoskeleton fibre is in a tight junction? Actin.
What is paracellular movement? Secretion and absorption in adjacent tight junctions.
What are the roles of tight junctions? Barriers, fences and gates.
How does a tight junction act as a barrier? Separates one compartment from another.
How does a tight junction act as a fence? Maintain the asymmetric distribution of lipids and proteins in the apical and basal membrane.
How does a tight junction act as a gate? Allow some molecules to flow more easily than others.
What does a tight junction create? Apical and basal membrane domains.
How does epithelial transport enable compartments with different compositions? Differential distribution of transport systems enables trans-epithelial vectorial transport. Trans-epithelial vectorial transport creates compartments with different compositions.
In summary, tight junctions... 1. create a barrier between different compartments. 2. allow the processes of absorption and/or secretion to create compartments with different molecular compositions.
Created by: robertspedding