Adaptation & Injury Flashcards
What is hypertrophy?
The enlargement of an organ or tissue from the increase in size of its cells. No new cells, just larger cells, non-dividing cells eg. myocytes, skeletal muscle.
What is atrophy?
Decreased amount of structural proteins and organelles due to decreased protein synthesis and increased protein degradation. Results in decreased cell size/number and therefore decreased organ size.
What is hyperplasia?
The enlargement of an organ or tissue caused by growth factor driven proliferation of mature cells and stem cells.
What is metaplasia?
Replacement of one differentiated cell type (epithelial or mesenchymal) with another. Cells sensitive to stress replaced by a cell type better able to withstand stress.
Difference between a physiological and pathological adaptation to stress:
While adaptation can be physiological to aid the body, may also be disease related, or pathological, and is a very important indicator of disease.
Provide an example of epithelial metaplasia:
Smoking. Change from ciliated columnar type cells to stratified squamous type cells in the respiratory tract in response to chronic irritation.
Why is metaplasia eg. in lungs, not a good outcome?
The disadvantage of this is the intended effect of the original cell type is now lost. For example, in the respiratory epithelium, the columnar cells which usually produce mucus and protect from infection via cilia are now absent, and it is easer for the lung to become infected.
Define adaptation:
A response to stress or increased demand that maintains the steady state of the cell without compromising cellular function.
What is the difference between reversible and irreversible injury?
Both are a response to stress stimuli that compromises cellular function, however in irreversible injury cellular function is compromised to the point that it cannot recover. It occurs when mitochondrial dysfunction cannot be reversed and when membranes lose their structural integrity.
What is the difference between haematoxylin staining and eosin staining?
Haematoxylin is a basic dye that is used to stain acidic/basophilic structures a purple/blue. It stains nucleic acids (DNA in nucleus, RNA in ribosomes and RER).
Eosin is an acidic dye which stains basic/acidophilic structures a red/pink. It stains most proteins.
List the mechanisms of cell injury:
- Decreased ATP
- Damage to mitochondria
- Influx of calcium
- Accumulation of ROS
- Membrane damage
- DNA and protein damage
How does mitochondrial damage, a mechanism of cell injury, occur?
Increased cytosolic Ca2+, ROS and lipid peroxidation lead to mitochondrial injury or dysfunction.
What is the difference between mitochondrial necrosis and mitochondrial apoptosis?
Mitochondrial necrosis occurs when there is a mitochondrial permeability transition which leads to loss of membrane potential and inability to generate ATP.
Mitochondrial apoptosis occurs when cytochrome C (which is involved in electron transport and ATP formation-survival) becomes pro-apoptotic death.
How do intracellular calcium ions assist cell injury?
Influx of calcium ions activates cytosolic enzymes such as proteases, phospholipases, endonucleases, ATPases which enhance mitochondrial permeability.
What are the pathological effects of ROS?
ROS reacts with lipids, proteins and DNA, which leads to damage of DNA and proteins and leads to apoptosis. ROS must be removed by scavengers or will lead to oxidative stress.
