Flashcards in Cells, tissues & organs Deck (32):
Give examples of cells that exist independently.
What is tissue?
Collection of cells woven together.
What are the 4 basic types of tissue?
What are the 6 types of specialised connective tissue?
What are organs and how many do we have in total?
- Association of at least 2 types of tissue.
What are systems and how many do we have?
- A group of tissues and organs working together to complete a task.
Name the 11 body systems.
How can we separate cells from tissues/organs?
Cells are then cultured in Petri dishes/flasks and grown in an incubator.
Why is it difficult to culture individual cells?
- provide nutrients
- control pH, temperature and oxygen
- prevent bacterial contamination
What are the cons of cultured cells (despite being a valuable research tool)?
1. Behave and look different to the same cells in tissues.
2. Demonstrate contact inhibition.
3. Have a limited lifespan (senescence).
What are the 4 main types of junctions mediating cell-cell adhesion (lateral domain)?
1. Tight junctions
3. Gap junctions
4. Adherens junctions
What are tight junctions and what is their function?
- Fusion of plasmalemma of neighbouring cells.
~ Seal: prevents movement of molecules between 2 cells.
~ Selective barrier for products
- Location: intestinal epithelium
What are desmosomes and what is their function/location?
- Proteins that connect intermediate filaments of neighbouring cells.
- Function: firmly adhere and strengthen the bond between cells.
- Location: between epithelial cells that need to withstand physical stress (e.g. Skin). Found just under/next to tight junctions.
What are adherens junctions?
Proteins that connect actin filament bundles in neighbouring cells.
What are gap junctions and what is their function?
- Connexon proteins form small channels that allow ions and small molecules to migrate between cells.
- Functions: cell-cell communication and coordination (allow passage of small water-soluble molecules).
What is cell attachment to the basement membrane mediated by?
2. Focal adhesions
What are hemidesmosomes and where are they found?
- Anchor intermediate filaments in cells to the basement membrane.
- Found in tissues subject to abrasion, e.g. Skin, oral cavity.
What are focal adhesions and in what process are they important ?
- Anchor intracellular actin filaments to the basement membrane.
- Play a prominent tole in cell movement such as migration of epithelial cells in wound repair.
What are the 2 main functions of integrins?
Transmembrane proteins that?
1. Attach the cell cytoskeleton to the ECM (sense whether adhesion has occurred).
2. Signal transduction from the ECM to the cell.
Also involved in a wide range of other biological activities, inc. immune patrolling and cell migration.
What causes necrosis?
Physical disruption to the cell through injury, bacterial toxins or nutritional deprivation.
Describe 3 characteristics of cell death by necrosis.
Cell loses functional control:
~ osmotic pressure causes organelle swelling
~ chromatin clumps
~ cell bursts
What is the outcome of necrosis?
Cytotoxic cellular components spill out from the membrane - tissue damage and inflammation.
What causes apoptosis?
Most eukaryotic cells are genetically programmed for cell death - molecular signals continually inhibit or promote this process.
- Process initiated through a chain of enzymatic reactions leading to bcl-2 deactivation.
Which protein plays an important role in apoptosis inhibition?
Bcl-2 on the outer mitochondrial membrane
Describe the process of apoptosis.
Catabolic processes being throughout the cell.
- Enzymes digest cytosolic components and fragment the nuclear DNA.
- Caspases (specialised cysteine proteases) target proteins in the nuclear lamina and cytoskeleton.
What is the outcome of apoptosis?
The cell is 're-packaged' for safe removal.
- Chromatin condenses, cell shrinks and fragments into small membrane-bound apoptotic bodies.
- Compacted cell is phagocytosed by adjoining cells.
Which cell types are static (do not renew)?
Which cells display stable renewal rates?
Smooth muscle cells
Which cell types display high renewal rates?
Is there a relationship between cell renewal rate and propensity to develop cancer?
- Renewing cell lineages are at high risk for accumulating mutations.
- 90% of adult-onset cancers arise as carcinomas in epithelial tissues (skin and intestine - renew throughout life).
- Rare childhood cancers concentrate in tissues that undergo cell division early in life followed by relative cellular quiescence.
What are the different domains of epithelial cells?