Flashcards in BL - Integrating Cells Deck (35):
How long can packed red cells be stored at 6 degrees C for?
What is found between adjacent epithelial cells?
What is the function of a cell junction?
They ensure that cells are tightly adhered to one another.
What are the three types of cell junction?
Tight junctions, desmosomes and gap junctions
How do tight junctions attach cells together?
They fuse the plasmalemma.
What is the function of a tight junction?
They form an impenetrable barrier so molecules cannot pass between the two cells (and must pass through the cell instead). This allows them to act as a "security guard".
Give an example of where tight junctions can be found.
In the epithelial lining of the intestine.
True or false - desmosomes are often found very close to tight junctions?
Where are desmosomes often found?
Between epithelial cells that often undergo abrasion, eg in the skin.
Which type of cell junction involves proteins that interlock between epithelial cells?
What is the function of a gap junction?
They allow cells to communicate with each other.
What are connexons?
Small channels (proteins) that allows ions and small molecules to pass between cells so they can communicate.
What is the basement membrane?
The structural site and point of attachment for overlying cells and underlying connective tissue.
In what two ways can cells attach to the basement membrane?
Hemidesmosomes or focal adhesions
What is the difference between a hemidesmosome and a desmosome?
Hemidesmosomes attach cells to the basement membrane, desmosomes attach cells to cells.
What is the function of a focal adhesion?
They anchor intracellular actin filaments to the basement membrane, and aid cell movement.
What are the two main functions of integrins?
Attachment of the cell to the extracellular matrix and signal transduction from the ECM to the cell.
What is used to separate cells from tissues?
Collagenase or microdissection
Give some disadvantages of cultured cells as a research tool.
They behave and look differently to cells in tissues, they demonstrate contact inhibition, they have a limited life span ("senescence").
In direct contact communication, which cells are contacted by the original cell?
The ones connected to it via connexons.
In autocrine communication, which cells are contacted by the original cell?
The same cell (it is contacting itself).
What is the difference between paracrine and endocrine communication?
Paracrine is to nearby cells via local regulator in the extracellular fluid while endocrine is to cells further away via hormone in the bloodstream.
What is neurocrine communication?
Electrical signal moves along neuron, signal then travels through blood to the target cell. Eg anterior pituitary, posterior pituitary and adrenal medulla.
What is the difference between necrosis and apoptosis?
Necrosis is unplanned and caused by physical disruption to the cell, while all cells are programmed for apoptosis.
Explain how necrosis takes place.
1) The cell is damaged, eg. by bacteria
2) The cell loses functional control, osmotic pressure causes swelling in organelles
3) Chromatin clumps
4) Cell bursts
5) cytotoxic components spill out and cause tissue damage and inflammation
What does the Bcl-2 protein on the outer mitochondrial membrane play a major role in?
Inhibiting apoptosis - if it is deactivated, apoptosis begins.
How is the cell re-packaged for safe removal during apoptosis?
The chromatin condenses, the cell shrinks and it fragments into small apoptotic bodies.
What happens to the compacted cell after it has split into apoptotic bodies?
It is phagocytised by adjoining cells.
What's the difference between endocytosis and exocytosis?
Endocytosis allows things to enter the cell, exocytosis allows things to exit the cell.
Give some examples of cells that are static and do not require replacing.
Central nervous system, cardiac and skeletal muscle cells.
Give some examples of stable cells that do not require frequent replacement.
Fibroblasts, endothelium, smooth muscle cells.
Give some examples of cells that require constant replacing.
Blood, skin epithelium, gut epithelium.
Most epithelial cells have a free surface and exhibit polarity. What are the three domains?
Apical, lateral and basal.
Give an example of an epithelioid cell.
Leydig cells in testis, lutein cells of ovary, islets of langerhans in pancreas, parenchyma of adrenal gland.