Lecture 8 - Epithelial Cells & Surface Specialisations Flashcards
What are mucous membranes + what do they line?
What are serous membrane + what do they line?
- Mucous membranes line internal tubes that open to the exterior - e.g.: respiratory, GI and urinary tract.
- Serous membrane line certain closed body cavities that dont open to the exterior - e.g.: the peritoneum (surrounds abdominal organs), the pleural sacs, pericardial sac.
What are the two parts of a serous membrane?
1) Visceral serosa - closest to organs in the cavity
2) Parietal serosa - lines the outer edge of the cavity
Define “epithelia”.
Give examples of 3 main surfaces they line
Epithelia are sheets of continuous cells of embryonic origin (derived from all 3 germ layers) that covers external surfaces (e..g: skin), internal surfaces that open to the exterior (e.g.: GI tract) and internal surfaces that dont open to the exterior (e.g.: blood vessels).
What are the 2 main types of epithelial cell types and the subdivisions of each?
1) Simple - i.e.: 1 cell layer
2) Stratified - e.g.: 2 or more cell layers
All of these can be squamous, cuboidal, & columnar
NB: also get psuedostratified + transitional which are special types.
Define squamous, cuboidal and columnar in terms of epithelial cells.
Sqaumous = flat & flaky Cuboidal = Height + Width same size Columnar = Height longer than width
Describe the function of simple squamous epithelium + why they’re suited to this function.
Where are simple squamous epithelium often found?
Rapid material exchanger (as theyre very thin and flat) & fluid barriers (due to presence of tight junctions).
- Bowmans capsule
- Serosa of heart, lungs and viscera
- In the lymphatic system
Describe the function and list locations of simple cuboidal epithelium.
- Absorption + secretion (in exocrine glands and kidney tubules)
- Barrier/covering (in ovary)
- Hormone synthesis, secretion & storage (in thyroid gland)
Describe the function and list the locations of simple columnar epithelium.
Simple columnar epithelium line the crypts of intestinal glands + have microvilli
- Absorption (SI, colon + gall bladder)
- Secretion (stomach lining, gastric glands, SI + colon)
- Lubrication (SI & colon)
What is psuedostratified epithelia?
Where is it found + what are its functions?
- All cells make contract with basement membrane but not all reach the apical membrane, giving impression of multiple cell layers and nuclei lying at different levels throughout
- They have motile cilia and goblet cells in URT
- Secretion (respiratory tract)
- Mucus production (respiratory tract)
- Particle trapping and removal (respiratory + nasal cavity)
What is stratified squamous epithelium?
Where is stratified squamous non-keratinised epithelium usually found - give examples.
- Epithelium made from variety of different layers, the outermost of which is thin/flat squamous epithelium.
- Stratified squamous non-keratinised epithelium are in areas that are moist and prone to abrasion - e.g.: oral cavity, oesophagus, vagina, anus, cornea etc to protect against it.
How does stratified squamous non-keratinised epithelium in the vagina maintain a suitably low pH for destroying non-native bacteria and viruses?
They contains large amount of glycogen, which is a substrate for lactobacilli. This produces lactic acid which keeps pH low.
What is stratified squamous keratinised epithelium?
What are its functions + where is it most commonly found?
Multiple cell layers with an outermost layer that have lost their nuclei and become cornified - this layer:
- Greatly reduces water loss
- Stops ingress of toxins
- Protects against abrasion
- Stops microbial colonisation (as there is no water)
Most commonly found on epidermis of skin (particularly on foot).
What is transitional epithelium?
Where is its main location + what are its functions?
Epithelium that vary in shape/size from cuboidal/columnar to flattened depending on if they’re stretched or relaxed.
- In the urinary tract
- Dispensability in micturition and protection of underlying tissues from toxic chemicals in urine.
Name 6 surface specialisations of epithelial cells and describe the functions of each.
Keratin = prevents water loss and protects against abrasion.
Cilia - controls movement of luminal contents
Goblet cells - secrete mucus, moistens + lubricates
Club cells - protects bronchioles and acts as stem cells for respiratory epithelium
Microfold cells = allows rapid sampling of gut microflora
Stereo-cilia = Converts pressure to electrical signals in auditory system
