Pathology Concepts 1 – Types of Cell Injury Flashcards
A cell/tissue has been stressed, but overcomes this stress and resumes normal physiologic function
Reversible cell injury
No notable long-term morphologic or physiologic changes
A cell/tissue has become damaged and will eventually die due to the severity of the damage
Irreversible cell injury
there is a change in cellular/tissue structure or function that is almost always due to long term stresses
Adaptation
These changes are usually somewhat reversible
examples of Adaptation
Examples: hypertrophy, hyperplasia, atrophy, metaplasia
what are the types of cell injury?
- reversible cell injury
- irreversible cell injury
- adaptation
types of insults to tissues or cells
types of cellular response that happen:
* Hypoxia and ischemia
* Infection, inflammation, and immune-mediated
disorders
* Toxins/chemical agents
* Trauma, compression, thermal injuries
* Deficiencies in nutrients or growth factors
The cellular response to injury depends on:
- type of injury
- duration of the injury
- the severity of the injury
- The adaptability and the metabolism/phenotype of the cell
Big difference between cardiac cells and skeletal muscle cells re: vulnerability to ischemia
a state in which oxygen is not available in sufficient amounts at the tissue level to maintain adequate homeostasis
hypoxia
a condition in which blood flow (and thus oxygen) is restricted or reduced in a part of the body
ischemia
what types of pathophysiological consequences of the insult are clearly visible under the microscope?
- cellular swelling
- non-specific nuclear changes
- Ribosomal detachment, membrane abnormalities due to cytoskeletal disassembly, accumulation of lipids
pathophysiological consequences that are more difficult to observe:
Damage to proteins (including misfolding), DNA, subtle changes in organelle function and size due to damaged membranes
Reversible injury that you can’t see under a light microscope
▪ Changes in calcium concentrations
▪ Unfolded proteins
▪ Damage to DNA or cytoskeletal elements
▪ Loss of membrane potentials or abnormal distribution of molecules across cell membranes
▪ ATP depletion
what is the pathophysiological consequences of loss of mRNA to the cell? Is this visible under a microscope?
a more eosinophilic cytoplasm. This is visible under a microscope
what are small “blebs”? Are they visible under a microscope?
bubble-like outpouchings in the membrane. These are visible under a microscope
what types of irreversible cellular injury would be visible under the microscope?
- Serious loss of integrity – plasma membrane, lysosomal membranes, mitochondrial membranes, ER membranes
- Destruction of cytoskeletal elements
- DNA and nuclear “disruption”
- Karyolysis
- Pyknosis
- Karyorrhexis
Describe karyolysis, an irreversible cellular injury that would be visible under the microscope.
– chromatin fades
Describe Pyknosis, an irreversible cellular injury that would be visible under the microscope.
chromatin condenses, more basophilic (purple), the nucleus shrinks
Describe Karyorrhexis, an irreversible cellular injury that would be visible under the microscope.
visibility of nucleus fragments
what are the two major categories of cell death?
necrosis and programmed cell death
The agents that have injured the physiology/biochemistry of
the cell → immediate loss of cellular viability
necrosis
in necrosis, is cell signalling involved?
If cellular signalling is involved in this process, it is disorganized and unregulated
Cell death is delayed and requires protein synthesis. This can be due to long-term, irreparable cellular damage or
loss of cell use
programmed cell death
is cell signalling involved in programmed cell death?
Cellular signalling is always involved and the cell proceeds through an orderly series of steps → death
what are the best examples of programmed cell death?
apoptosis and necroptosis
Necrosis – mechanisms of injury
▪ Depletion of ATP
▪ Mitochondrial damage
▪ Calcium accumulation
▪ Oxidative stress / free radicals
▪ Membrane damage
▪ Denatured proteins
▪ DNA damage
can occur in isolation or simultaneously
- one may lead to another
what does the reduction (5 – 10% of
normal) in ATP levels results in:
- Na+/K+ pump dysfunction
and swelling (Eventually leads to membrane damage) - Anaerobic metabolism decreases pH (lactic acid, inorganic phosphate)
- Increased production of free radicals
- Failure of calcium pumps
- Reduction in protein synthesis, detachment of ribosomes, misfolding of proteins
what do high overall levels of cytosolic calcium do?
▪ Activate a variety of destructive enzymes
▪ Directly activate caspases
▪ Cause calcium release from mitochondria - would decrease ATP
what is the extracellular concentration of calcium (in mmol)
1– 2 mmol
what is the intracellular concentration of calcium (in mmol) at rest?
0.0001 mmol
Phospholipids are both _____________ and not synthesized during ischemic injury. This causes cytoskeleton damage which increases physical stresses on the membrane.
broken down.
Lipid breakdown (in the membrane) results in:
▪ Leaky membranes
▪ Lipid breakdown products that can have a detergent effect on cellular membranes
why is calcium considered a “special” ion?
Only ion that is a ubiquitous second messenger
- Interacts with a number of intracellular proteins (i.e. calmodulin) that can activate or inactivate intracellular processes
calcium can also activate enzymes that are particularly relevant to necrosis. These include:
- Proteases
- Phospholipases
- Endonucleases (DNA, chromatin fragmentation)
what will the loss of cytosolic calcium (within cell) lead to?
▪ Loss of regulation → nonspecific overall activation of the enzymes specified above
▪ ATP deficiency disrupts appropriate calcium sequestration
▪ Cytosolic calcium accumulation opens the mitochondrial permeability transition pore (MPTP)
Mitochondrial membranes can be damaged by ____________
free radical attack
what does MPTP stand for
mitochondrial permeability transition pore
what are detergent-like effects:
- unesterified free fatty acids
- acylcarnitine
- lysophospholipids
Activation of proteases by increased cytosolic calcium may cause damage to elements of the cytoskeleton. What does this lead to?
Lose the “anchoring” and stabilizing effect of the cytoskeleton on cell membranes
what are two causes of cytoskeleton absnormaltieis
- Activation of proteases by increased cytosolic calcium may cause damage to elements of the cytoskeleton
- cell swelling which causes detachment of the membrane from the cytoskeleton
what does cell swelling causing detachment of the membrane from the cytoskeleton lead to?
membrane susceptible to stretching
and rupture
A “broken” cytoskeleton compounds this process
Injury to lysosomal membranes results in:
- Direct enzymatic damage to cellular components
- activation of enzymes by lysosomal enzymes
what are lysosomal enzymes?
Enzymes include RNases, DNases, proteases,
phosphatases, glucosidases and cathepsins
What needs to happen to the intracellular mileiu before lysosomal enzymes can be activated?
Unregeulated enzymatic degradation of cell
components leads to loss of ______ which causes death by ________
Unregeulated enzymatic degradation of cell
components → loss of DNA, RNA, glycogen,
cytoskeletal proteins → death by necrosis