Cell Injury Flashcards
How does stress affect cells?
Cell attempts to adapt
Failure to adapt can lead to cell death
What is hyperplasia?
Increase in cell number in response to external stimulus
Can be physiological or pathological
Reversed on withdrawal of stimulus
- Exception: Cancer keeps growing on absence of stimulus
- Hyperplastic tissue = risk site for development of cancer
Physiological and Pathological hyperplasia:
Physiological: E.g. breast tissue in puberty
Pathological: Hormonally induced e.g. excess oestrogen
What is Hypertrophy, when does it occur, and what can it cause?
Increase in cell size
Often occurs:
- In conjunction with hyperplasia
- In isolation in non-dividing cells (e.g. skeletal muscle)
- In response to mechanical stress
Becomes pathological when heart/muscle can no longer function leading to heart failure.
What is hypoxia and how is it caused?
Interferes with aerobic oxidative respiration
Caused by
•Ischaemia (restricted blood flow)
•Reduction in oxygen carrying capacity of the blood
•Inadequate blood oxygenation
What is hypoxic injury and what can it cause?
Reduction in intracellular generation of ATP:
- Reduces sodium pump activity causing sodium to accumulate in cell resulting in gain of water causing cellular swelling
- Depletion of glycolysis stores due to increase in anaerobic glycolysis
What is atrophy?
Reduction in cell size
Can be physiological or pathological:
- Physiological (e.g. embryological structures)
- Pathological (e.g. blocked blood supply)
5 types of necrosis:
COAGULATIVE NECROSIS
•Tissue with connective tissue, basic arrangement preserved
COLLIQUATIVE NECROSIS
•Tissue with minimal connective tissue ‘liquifies’
CASEOUS NECROSIS
•‘Cheese’-like necrotic debris
GRANGRENOUS NECROSIS
•DRY – sterile coagulative necrosis e.g. distal limb
•WET – coagulative necrosis with superimposed infection
FAT NECROSIS
•Focal necrosis in fat due to action of lipases (also trauma)
Autolysis
‘Rotting’ of tissue
Lysis of tissue by their own enzymes following death
Physiological importance of apoptosis:
Embryogenesis
Menstrual cycle
Immune system:
•Death of post-inflammatory neutrophils
•Removal of self-reactive lymphocytes
•Death of virally infected cells
Primary and secondary healing
Primary healing:
•Restitution with no – or minimal – residual defect
Secondary healing:
•Organisation and repair where there is tissue loss
Metaplasia
Reversible change in which one adult cell type is replaced by another adult cell type
How does ionising radiation damage cells?
Damages DNA
3 types of cell regeneration:
Labile : good capacity to regenerate (eg surface epithelial cells)
Stable : divide at a slow rate, but can regenerate if needed (eg hepatocytes in liver)
Permanent: eg nerve cells, striated muscle cells – no means of effective regeneration
What can happen if hypoxic injury persists?
Cytoskeleton can break down
Cell death
