Epithelia Flashcards
What is epithelia?
Epithelia are continuous sheet of cells (one or more layers thick) that create a frictionless surface between two epithelial surfaces. This helps prevent pain which can be caused when organs or tissues rub together.
What does a simple epithelium create?
Basement membrane- The thickness of the basement membrane depends on its function.
Specialised apical surface- This is what comes into contact with the material passing through the lumen
What is the difference between stratified and simple epithelia?
Stratified- multiple layers thick
Simple- one layer thick
Epithelium is avascular. What does this mean?
Nutrients must reach epithelial cells by diffusion (from blood vessels in tissues below the basement membrane) or from absorption (from the external environment)
Epithelial tissue has a high degree of cellularity. What does this mean?
It has many cells that are joined together, minimizing any extracellular material.
What is lamina proparia?
This is a bed of connective tissue found in the digestive, respiratory and urinary systems which often contains glands and blood vessels. It also holds epithelial cells together.
What is mucosa?
The combined epithelium, basement membrane and lamina propria.
What does squamous epithelium look like?
Cells are flat and scalelike in appearance. Nuclei conforms to the shape of the cell (in a flat cell they are disc shaped and centrally located)
How is stratified epithelium named?
They are named based on the shape of the apical cells. For example, if apical cells are flat then this epithelia would be called stratified squamous epithelium.
Are basal or apical epithelial cells dead or metabolically active?
Basal cells are metabolically active as they are closer to the basement membrane and blood supply. Thus means they receive more nutrients through diffusion. Epithelial cells on the apical surface are dead and atrophied as they are further from the blood supply.
In Cuboidal epithelial cells, which areas tend to be simple and which stratified?
Simple= areas that secrete or transport (e.g. kidney tubules)
Cuboidal= areas that require physical protection and strength (e.g
Where is the nucleus found in squamous and cuboidal cells?
Centrally.
What shape is the nucleus in squamous, cuboidal and columnar epithelial cells?
Squamous= disc-shaped
Cuboidal= Spherical
Columnar= conform to the shape of the cell (often elongated)
Where are pseudostratified columnar epithelial cells found? What cells do they contain within them?
In respiratory tract. They have the function of secretion and protection. Here, they are lined with cilia to waft away mucus.
Goblet cells. They secrete mucus and are typically larger than adjacent epithelial cells are stain a lighter pink.
What are pseudostratified epithelial cells?
This is epithelium where cells do not appear to be in contact with the basement membrane (look layered) however they actually are.
This is a specialised adapted as it reduces the transport pathway between a lumen and basement membrane. The nuclei sit wherever there is space.
