Cell turnover Flashcards
What is graves disease?
Hyperplasia of the thyroid gland, which causes increased production of thyroxine (thyrotoxicosis).
What causes graves disease?
The production of thyroid stimulating auto-antibodies
(immunoglobulins) which act on same receptors as thyroid stimulating hormone
Not susceptible to normal negative feedback mechanism
What is hypoplasia?
NOT THE OPPOSITE OF HYPERPLASIA.
Failure of a tissue or organ to reach normal size during development
What are some causes of hypoplasia?
1) Genetic defect
2) Intrauterine infection
3) Toxic insults (EG: thalidomide)
What is atrophy?
Decrease in size of tissue or organ after initial development.
May be due to a decrease in cell size or number (i.e. opposite of hyperplasia and hypertrophy)
What can cause pathological atrophy?
1) Loss of hormonal stimulation (e.g. atrophy of endocrine organs secondary to pituitary disease)
2) Reduction in blood supply
3) Decreased workload (e.g. disuse atrophy of muscle)
4) Loss of innervation
What is ballooning degeneration?
Where cells grow in size before they die
What factors are involved in early (reversible) cell injury?
1) Entry of sodium and water into a cell
2) Mitochondrial swelling
3) Dilation of ER
What is hydropic change?
One of the early signs of cellular degeneration in response to injury.
It refers to the accumulation of water in the cell.
What are the nuclear changes in late (irreversible) cell injury? (i.e necrosis)
1) Shrinkage (pyknosis)
2) Fragmentation (karyorrhexis)
3) Disappearance (karyolysis)
What are the cytoplasmic changes in late (irreversible) cell injury? (i.e necrosis)
1) Denaturation of proteins
Increased cytoplasmic eosinophilia (Coagulative necrosis) –> Typically occurs in hypoxic/ischaemic injury e.g. myocardial infarction
2) Enzymatic digestion of cell
Disappearance of cells (Lytic necrosis) –> More common with cytokine-mediated injury e.g. acute viral hepatitis
What is metaplasia?
Replacement (potentially reversible) of one differentiated cell type by another differentiated cell type.
It usually occurs as response to unfavourable environment for the original cell type.
What are the consequences of metaplasia?
1) Loss of normal cell function
- -> EG: squamous metaplasia in bronchi, which means loss of cilia so less mucus clearing. This increases risk of bacterial infection so more chest infections.
2) Increased risk of malignancy (NOT malignancy itself)
What is dysplasia?
Disordered development.
Not yet invasive (i.e. not passed the basal membrane).
Changes resemble those seen in neoplastic cells.
