Epithelial Flashcards
What is epithelia?
Cells that cover or lines all body surfaces, tubes and cavities
Describe some of the characteristics of epithelium
The cells are in direct contact with each other joined by junctions. Undergo rapid cells division to replace cells that are continuously lost (due to infection or damage)
What separates epithelia cells from underlying tissue
The basement membrane (BM)
Tumour cells developed from epithelium are called?
Carcinomas
What are the two ways in which epithelia cells are classified?
1 - shape of cells
2 - number of layers
What are the three shapes of epithelium cells?
Squamous
Cuboidal
Columnar
what is the lumen?
The gap between epithelium
Describe the features of simple epithelia
All epithelia cells will be are in contact with the lumen and basement membrane. They are found at sites where diffusion, secretion and absorption take place. Thinner epithelium then the faster the diffusion and absorption
Describe the features of stratified epithelium
Found at sites where the body needs protection. The thicker epithelium provides greater protection for abrasion, infection or caustic content.
What is caustic content?
substances able to burn or corrode organic tissue by chemical action
Where does simple squamous line?
Blood vessels, alveoli and capillaries, allows for rapid diffusion.
Where does simple cubiodal line?
Lines kidney tubules and liver, allows for secretion and absorption.
Where does simple columnar line?
Lines the GI tract (small intestine), allows for secretion and absorption
Where does pseudostratified line?
(apparently two layers) Lines the conduction part of their airway
Where does stratified squamous line?
oesophagus and epidermis
Where does stratified cuboidal line?
Reproductive system
Where does stratified columnar
Male urethra
Where does transitional
Bladder
What are the features of exchange epithelium cells?
One cell layer,
Flattened cell shape,
Pores between cells allowing easy passage of molecules,
Located in lungs and blood vessels
What are the features of transporting epithelium?
One cell layer,
Columnar or cuboidal shape,
Tight junctions will limit movement between cells,
Located in intestine and kidney tubules
What are the features of ciliated epithelium?
Once cell layer,
Cuboidal and columnar shape,
cilia move fluid fluid across surfaces,
located in the trachea and female reproductive tract
What are the features of protective epithelia
It has many cell layers, flattened on surface, the cells are connected by desmosomes and they are found in skin and mouth
What are the features of secretory epithelia
Has one or many layers, is columnar or polygonal in shape. They have an extensive rough ER for proteins and a smooth ER for steroids. They are found in the exocrine and endocrine systems.
Where does mesothelium line?
Body cavities (makes serous membranes)
What three methods increase surface area for absorption?
Large folds, Microscopic villi and microvilli
What does mucus allow for?
The prevention of pathogen binding to the epithelium
Define desquamation
The process where flattened cells are worn off and shed from the surface
Name and describe the movements of molecules across epithelial cells
Trans-cellular = through the cells
Paracellular Movement = movement in opposite directions passing through intracellular space between cells
What are sealing strands? And what are the proteins that make them up?
Major tight junctions. Proteins that make up tight junctions are Claudin and Occludin
What determines how leaky/tight a cell is and give examples of where both can be founf
The number of sealing sealing strands present in the tight junction. In the kidney there are fewer sealing strands making them more leaky. Whereas in the bladder there are more sealing strands giving an example of tight epithelium.
Name the three roles of tight junctions?
Barriers - Separate one compartment from another
Fences - Maintain the asymemetric distribution of lipids and proteins in the apical and basal membranes
Gates - Allows for some molecules to flow more easily than others
