0.1 Cellular Response to Injury Flashcards
According to Claude Bernard, all living systems are homeostatic. How does injury impact this state?
Injury = moves away from homeostatic position
Response = method to achieve new homeostatic position
Response failure = death
Cell / Tissue injury can be reversible or irreversible. What does this mean in terms of healing ability?
Reversible = can return to health after adaptation
Irreversible = inability to adapt causes cell dysfunction and death (can STILL heal, but harder + not fully)
How is necrosis different from apoptosis?
Necrosis = Passive, aciidental cell death from inflammation
Apoptosis = Active, programmed cell dismantling, not inflammatory
Reversible cell injury takes shape in 7 different ways. What are they?
- Hydropic change (cellular swelling)
- Fatty change (accumulation of lipids)
- Hypertrophy (increased size)
- Atrophy (decreased size/number)
- Hyperplasia (increased number/proliferation)
- Metaplasia (change in state)
- Anaplasia (cancerous transformation)
Atrophy can take two different forms, what are they?
Apoptosis = reduction in NUMBER of cells
Autophagy (self-eating) = reduction in SIZE of cells
What are some pathological characteristics of hydropic change?
Swelling of ER, vacuoles, and mitochondria
Plasma membrane blebs
Loss of microvilli (fingerlike membrane protrusions)
What are the pathological changes of fatty change?
Cells unable to metabolise lipids = accumulates in cytoplasm
Most apparent in tissues with high lipid metabolism eg liver
COPD and Sialosis (persistent enlargement of major salivary glands) are examples of what type of reversible cellular injury?
Hypertrophy = swelling
Chronic bacterial sialdenitis (salivary gland infection) is an example of what type of reversible cellular injury?
Atrophy = decreased size / number of cells
What is the process behind autophagy?
- Primary lysome unable to complete phagocytosis (lacking nutrients) becomes autophagic vacuole
- Residual body of vacuole unable to undergo exocytosis like a normal phagolysome
- Lipofuscion pigment granule lingers as brown/black granules in tissue
In what situation is autophagy commonly found?
In muscles that have been worked too hard
Traumatic keratosis is the proliferation of epithelial cells to form superficial swelling. What type of reversible injury is this an example of?
Hyperplasia = change in tissue by cell proliferation
Metaplasia is more complex than hyperplasia. Why is that?
Metaplasia is the change in form from one to another
Hyperplasia is simply a change in size
What is a common occurrence of metaplasia and why does it appear as a protective reaction?
Squamous metaplasia of respiratory epithelium in smokers
Makes the epithelium tougher and more resistant to smoke
What is dysplasia?
Disordered growth = alteration in size, shape, and oragnisation
Necessary stage in cancerous transformation
What is anaplasia?
Cancerous growth via loss of cell differentiation
What is the key difference between metaplasia and dysplasia?
Metaplasia = REPLACEMENT of one cell by another
Dysplasia = gradual CONVERSION of one cell into another
All froms of necrosis lead to cellular leakage and inflammation. What are these 4 types of necrosis?
- Coagulative
- Liquefactive
- Caseous
- Fat necrosis
Coagulative necrosis involves the modification of the nucleus. What are the 3 key examples of this?
- Pyknosis (dense)
- Karyorrhexis (blebbing)
- Karyolysis (destroyed)
What is fat necrosis specific to?
Adipocytes
Often found in pancreas and breasts
What physiological processes normally involve apoptosis?
Fusion of palate
Lumen formation in glands
Involution of breast (post-lactational or lobular/ageing)
What are 5 commmon pathological examples of apoptosis?
- Removal of excess cells in healing
- Excessive apoptosis in diabetic healing
- Endothelial injury in athersclerosis
- Autoimmune destruction of cells
- Response to some injuries eg radiation, radicals, viral infection
What is the progression of necrosis?
- Normal cell
- Reversible injury occurs leading to swelling of ER and mitochondria + membrane blebbing
- If no recovery, it beocmes a progressive injury
- Breakdown of plasma membrane, organelles, and nucleus as well as leakage of contents causing inflammation
What are the 5 key differences in cell structure between necrotic and apoptotic cells?
- Size (necrotic = enlarged, apoptotic = reduced)
- Nucleus (necrotic = modified, apoptotic = fragmented)
- Plasma membrane (necrotic = disrupted, apoptotic = intact, but altered)
- Cellular contents (necrotic = enzymatic digestion + leakage, apoptotic = intact)
- Inflammation (necrotic = frequent, apoptotic = never)
What are the 4 pathways towards morphology of cellular injury?
- ATP depletion
- Loss of membrane integrity / membrane damage
- Increased Ca2+
- Reactive oxygen species (ROS)
