L4: Epithelial Tissues Flashcards
What are the main functions of epithelial tissues?
For barrier or lining:
- Protection;
- Absorption;
- Diffusion;
- Secretion.
(PADS)
What are the two major types of epithelial tissues?
- Surface;
2. Glandular.
What do surface epithelial tissues do?
Cover or line all body surfaces, tubes and cavities to create boundaries between environments
What do glandular epithelial tissues do?
Primarily for secretion, endo and exocrine
How are epithelial tissues classified?
3 main criteria:
- Number of layers;
- Shape;
- Adaptations.
How can epithelial tissues be layered?
- Simple, 1 layer (for DAS);
- Stratified, 2 or more layers (for P);
- Pseudostratified, 1 layer but looks like more.
Why do pseudostratified epithelium, look stratified?
- Nuclei at different heights;
- Different height of apical surface.
Why are stratified epithelium good for areas exposed to more stress?
Quick turnover of cells - cells mature from the basal layer by continuous division of stem cells
What shapes can epithelial cells be?
- Squamous;
- Cuboidal;
- Columnar;
- Transitional.
What adaptations can epithelial cells have and what does this contribute to their function?
- Microvilli - projections, increase SA, good for greater absorption;
- Cilia - long, motile projections that beat rhythmically;
- Keratin - increases mechanical strength of the layer and is good for protection.
Where do you find simple squamous epithelial? Provide an example
Line surfaces involved in passive diffusion, e.g. lungs, capillaries.
Where do you find simple cuboidal epithelial? Provide an example
Line small ducts and tubules, e.g. collecting tubules in the kidneys, small ducts of salivary glands.
Where do you find simple columnar epithelial? Provide an example
Line absorption surfaces, e.g. small intestine (with microvilli).
What are goblet cells?
Modified columnar epithelial cells, they synthesise and secrete mucus and are scattered throughout simple columnar epithelium.
Where do you find ciliated simple columnar epithelial? Provide an example
Ciliary action facilitates transport of the ovum, ovary to the uterus. E.g. female reproductive tract.
Where do you find ciliated pseudostratified columnar epithelial? Provide an example
Cilia propel the mucus at the surface containing trapped particles, e.g. airways of the respiratory system.
Where do you find stratified squamous epithelial? Provide an example
Line surfaces of the oral cavity, provide protection against sharpness, hot/ cold, mechanical work.
Non-keratinised: soft mucosal tissues and pharynx.
Keratinised*: gingival tissues.
- epidermis (top layer of skin) too.
Where do you find stratified cuboidal epithelial? Provide an example
Ideal for secretory surfaces e.g. secretory ducts of exocrine glands, such as salivary.
Where do you find stratified columnar epithelial? Provide an example
E.g. Male urethra and lining of some glands.
Where do you find transitional epithelial? Provide an example
Allows for expansion, e.g. the bladder.
What differentiates, regarding the structure, non and keratinised epithelium?
Keratinisation is based on the layer at the apical surface of an epithelium
What does keratinisation provide?
Enhanced resistance to stress by forming a tough, non-living layer at the surface (epithelial cells accumulate keratin as they mature).
At what surface of an epithelium do you find ‘free’ cells?
The apical surface
At what surface of an epithelium do you find the basement membrane?
The basal surface
How are carcinomas classified?
Based on cells or origin, e.g. squamous cell carcinoma resembles a stratified squamous epithelium.
What does the term ‘dysplastic epithelial cells’ mean?
Cells proliferating in an uncontrolled manner, can destroy and invade adjacent cells.
