5.2 Adaptation and injury Flashcards
What are the two types of adaptation to injury?
- Physiological adaptation-cellular response to normal stimulation
- Hormones
- Endogenous chemicals
- Pathological adaptation-cellular response to stimulation secondary to underlying disease/ to avoid injury
What happens in hypertrophy?
- Increased work load (physiological and pathological stimuli)
- Increased size of cells resulting in increased size of organ
- No new cells, just larger cells
- Non-dividing cells increase in size (myocytes, skeletal muscle)
What are two examples of things which lead to hypertrophy?
What is hyperplasia?
- Increase in number of cells in an organ or tissue
- Only in cell populations capable of dividing
- Physiological and pathological response
What are examples of physiological and pathological cause of hyperplasia?
- Physiological
- Hormonal (puberty)
- Compensatory (liver resection)
- Increased demand (Low atmospheric O2 leads to increased erythrocytes)
- Pathological
- Hormonal (endometriosis)
- Viral infection (skin warts)
- Chronic stress (callous)
What is atrophy?
- Reduced size of organ resulting from decrease in cell size and number.
- Physiological atrophy is common during normal development (embryonic structures, uterus following pregnancy)
- Pathologic atrophy depends of the underlying cause.
What can cause atrophy?
- Decreased work load
- Immobilization
- Loss of innervation
- Loss of blood supply
- Inadequate nutrition
- Loss of endocrine stimulation
- Pressure
- Aging
What is metaplasia?
- Replacement of one differentiated cell type with another
- Cells sensitive to stress replaced by a cell type better able to withstand stress
- Stem cell reprogramming
- For example cigaratte smoking turns ciliated columnar to stratified squamous.
- Chronic gastric reflux turns stratified squamous to gastric columnar epithelial
What is the difference between adaptation and reversible and irreversible injury?
- Adaptation: A response to stress or increased demand that maintains the steady state of the cell without compromising cellular function.
- Reversible/ sublethal injury: A response to stress/ stimuli that compromises cellular function.
- Irreversible injury: A response to stress/ stimuli that compromises cellular function to the point that it cannot recover
What happens in reversible injury?
- Cell function compromised
- Recovery if injury is removed
- May compromise organ function
- Eg. Reversibly injured myocytes (transient ischemia) may be transiently non- contractile which will affect function of the heart
What happens in irreversible injury and cell death?
- When the cell cannot recover and it dies
- Two types of cell death which differ in morphology, cause and roles in disease
- Necrosis
- Apoptosis
- May have occurred before morphological changes become apparent
When does injury cause irreversible damage? What cell and injury factors
How is sequential development of changes seen in cell injury?
- Cells may be non- functional but viable
- Cells may undergo biochemical changes and be non-viable (dead) before the appearance of ultrastructural, microscopic and macroscopic changes are apparent.
What is the haemotoxylin stain?
- It is used to stain acidic (or basophilic) structures a purplish blue.
- Stains nucleic acids (DNA in nucleus, RNA in ribosomes and RER)
What is the eosin stain?
- It stains basic (or acidophilic) structures red or pink (also sometimes termed ‘eosinophilic’)
- Most proteins
What morpholigcal features of injury can be seen with a light microscope?
What morphological features of reversible injury can be seen in the ultrastructure?
When does irreversible injury occur?
- Occurs when mitochondrial dysfunction can’t be reversed and when membranes lose their structural integrity
What membrane changes are seen in irreversible injury?
- Lysosomal membranes
- Contents leak into cell
- Nuclear and cytoplasmic components degraded
- Plasma membrane
- Loss of osmotic balance
- Cellular contents leak into extracellular space (inflammation)
- Mitochondrial membrane
What are the six mechanisms of cell injury?
How does a loss of ATP bring about other changes for cell injury?
How does damage to mitochondria bring about other cellular changes for cell injury?
What cellular changes does an influx of calcium cause during cell injury?
What are free radicals?
- Chemical species with unpaired electron in outer orbital
- Unstable and reactive
- Attack nucleic acid, protein and lipids
What are reactive oxygen species?
- Oxygen derived free radical
- Byproduct of respiration
- Produced by phagocytic leukocytes
- Removed by scavengers
Increase in reactive oxygen species or decrease in scavengers causes oxidative stress
What leads to membrane damage during cell injury?
How does hypoxia affect respiration?
How does hypoxia affect ATP dependent transport?
How does hypoxia affect the synthesis of macromolecules?
What are the effects of cell membrane damage due to hypoxia?
What changes in morphology are seen when there is hypoxia of the heart?
- Increased staining with eosin
- Proteins now denatured so bind to eosin more strongly (eosinophilia)
- Loss of basophilic RNA
- Reduced nuclei (less haematoxylin staining)
- Edema
- Inflammatory cells
What happens to proteins in hypoxia of the heart?
- Intracellular proteins leak through damaged cell membrane
- Cardiac specific enzymes
- Cardiac isoform of creatine kinase
- Contractile protein troponin
- Serum levels reflect tissue injury
- Myocardial infarction (irreversible injury, plasma membrane integrity lost)
- Angina (reversible injury, plasma membrane intact)
