Topic 5 - Tissue Organisation Flashcards
What holds cells together?
- fibres inside and outside cell in communication with each other through signalling
Name the 5 lateral cell adhesion systems?
- tight junctions
- adhesion junctions
- desmosome (adhesion plaque)
- gap junctions
- cell adhesion molecules
What are the 5 basal cell adherence systems?
- hemi desmosomes
- focal adhesions
- integrins
- proteoglycans
- cell adhesion molecules
What is the role of a tight junction?
- to prevent movement of large molecules through the lumen into the deeper tissue layers of the organ (in the gut though it can transiently open to allow small molecules to cross - paracellular transport)
Where are adhesion junctions found?
- intercellular space (between cells)
What is the strongest of all the cell to cell adhesions?
- desmosome
In which type of cell are desmosomes the only cell to cell adhesion?
- epidermal cells (skin cells)
What is the function of a gap junction?
- to quickly communicate changes in intercellular molecular composition e.g. electrolyte and energy changes
Where are hemi desmosomes found?
- on a layer of extracellular matrix (NOT on cell)
Which cell to cell adhesion operates as an alpha, beta dimer pair?
- Integrins
Which ion is key to all cell to cell adhesions?
- calcium 2+
What is a mucosal membrane?
- lines all moist, hollow organs
- continuous with skin at various openings
- secretes mucus
What are rugae?
- folds of gastric mucosa forming longitudinal ridges in stomach
What are the 3 main functions of mucosa?
- absorb substances from the lumen
- prevent ingress of pathogens
- move contents and expel waste
What are transitional epithelium in the ureter called?
- urothelium
Why are there lots of fat cells in the bladder wall?
- provides shock absorption for expanding bladder
Why might it be advantageous to have bladder epithelial cells produce mucus?
- protects bladder from damage by acidic urine
What are the two sections of the respiratory tract known as?
- conducting portion
- respiratory portion
The trachea, primary, secondary and tertiary bronchi are missing what?
- outer layer of smooth muscle
Explain the mucociliary elevator.
In the trachea and bronchi, these things are produced:
- mucins and water (forms mucus)
- serum proteins (lubrication)
- lysozyme (destroys bacteria)
Cilia wave moves material to the oral cavity where it can be expelled or swallowed.
What is the role of elastin fibres in the alveolus?
- elastic recoil of the lungs
Explain the differences between mucous and serous membranes.
- mucous membranes line internal tubes that are open to the outside (e.g. GI tract) whereas serous line closed body cavities and envelop the viscera (e.g. pericardial sac that envelops the heart)
- mucous membranes are 3 layered (epithelium, lamina propria, muscularis mucosae (smooth muscle layer) whereas serous are formed of 2 layers (simple squamous epithelium, thin connective tissue)
Explain, using an analogy, how serous membranes envelop body cavities.
- organ invaginates into a cavity like a fist pressing into a balloon giving an inner (visceral) and outer (parietal) membrane with a surrounding serous cavity.
What are epithelia?
- sheets of neighbouring cells that cover the external surface of the body and line internal surfaces, including blood vessels.
