Basic Cell Types Flashcards
What are the four basic tissues?
- epithelial tissue
- supporting tissue
- muscular tissue
- nervous tissue
What does the epithelial tissue cover?
- Covers and lines all body surfaces, cavities and tubes
What is epithelial tissue involved in?
- containment
- selective diffusion
- absorption
- secretion
- physical protection
How does epithelial tissue play a part in immunohistochemistry?
All epithelial tissue contain cytokeratin intermediate filaments
What are all epithelial supported by?
A basement membrane:
- separates the epithelium from the underlying supporting tissue
- avascular
- polarised, as one side faces the basement membrane (basal surface) and now towards the surface (apical surface)
If its avascular how does the tissue gain nutrients?
The epithelium is dependent on diffusion of nutrients and oxygen from connective tissue for survival
How are surface epithelia classified?
- number of cell layers
- shape of component cells
- presence of surface specialisations such as cilia/keratin
What are the types of cell layers?
- single layer is simple
- multilayered is stratified
What are the shape of component cells?
Based on the appearance at right angles to the epithelial surface
- squamous (flattened)
- cuboidal
- columnar
What are the types of simple epithelial cells?
- simple squamous epithelium
- simple cuboidal
- simple columnar
- pseudostratified columnar ciliated epithelium
Simple squamous epithelium?
- flattened irregular shaped cells forming a continuous surface called pavemented epithelium
- supported by an underlying basement membrane
- found in organs that take part in diffusion of gases or fluids, such as lungs or blood capillaries.
Simple cuboidal epithelium?
- intermediate between simple squamous and simple columnar
- nucleus is round and located in the centre of the cell
- lines small ducts and may have excretory, secretory or absorptive functions like collecting tubules of kidney
Simple columnar epithelium?
- taller than simple cuboidal
- nuclei are elongated and may be located towards the base, apex or centre of the cytoplasm – polarity of the nucleus
- founding adoptive surfaces like the small intestine, gall bladder or in secretory places like the stomach
Psuedostratified columnar ciliated epithelium?
- All cells rest on the basement membrane but nuclei are all at different levels giving the appearance of different cell layers
- found in airways so known as respiratory epithelium
- cilia propel mucus to the pharynx = mucociliary escalator
What do all SIMPLE epithelium have in common?
- All of the cells rest on the basement membrane
- one layer
What is stratified epithelia?
- defined as epithelia consisting of 2 or more layers
- mainly have a protective function
- poorly suited for absorption and secretion due to thickness of all the cell layers
- classification is based on surface cell shape and structure
What are stratified epithelia poorly suited for?
Absorption and secretion due to the thickness of all cell layers
What is classification based on in stratified epithelia?
Surface cell shape and structure
What are the types of stratified epithelia?
- Stratified squamous epithelia
- Stratified cuboidal epithelia
- Transitional epithelium (urothelium)
What is the structure of a stratified squamous epithelium?
- Flattened cells at the top (surface)
- Keratinising stratified squamous epithelium constitutes the epithelium of skin = epidermis
- Cuboidal cells at the base (basement membrane)
How is a stratified squamous epithelium adapted?
- Adapted to withstand constant abrasions and desiccation due to tough non-living surface layer composed of protein keratin wrapped in plasma membrane
- as the epithelium matures, nuclei are eventually lost
What is the structure of stratified cuboidal epithelium?
- It is thin stratified epithelium usually 2 or 3 layers of cuboidal cells only
- more robust than simple epithelium
How is the stratified cuboidal epithelium adapted?
- It is found in the lining of larger excretory ducts of exocrine glands such as salivary glands
- not involved in significant secretory or absorptive activity
What is the structure of transitional epithelium (urothelium)?
- the features are intermediate between stratified cuboidal and squamous epithelia
- when relaxed, surface cells are large and rounded umbrella cells
- when stretched, intermediate and surface layers are extremely flattened
Where are transitional epithelium (urothelium) found?
- only found in urinary tract in mammals and is highly specialised to accommodate stretch and the toxicity is urinecuboidal
What are the membrane specialisations of epithelia?
- Cilia
- Microvilli
- Goblet cells
What is the structure of cilia?
- motile structures that project from the luminal surface of epithelial cells, esp. in the female reproductive and respiratory tract
- may be 10 micrometers long
- easily seen on light microscope
- a cell may have up to 300 cilia