Basic pathology
Necrosis
- Cells can be damaged by damaged by various processes including
- Reduced oxygen supply
- Physical agents
- Chemical agents
- Toxins
- Viruses
- Abnormal immunological reactions
- Necrosis results from cell death
- Results in disintegration of nucleus, cytoplasmic organelles and the
plasma membrane
- Intracellular enzymes are released
- Necrosis is associated with visible changes
- Coagulative necrosis
- Colliquative necrosis
- In coagulative necrosis
- Nucleus fades and dissolves (karyolysis)
- Nucleus becomes more dense (pyknosis)
- Nucleus fragments (karyorrhexis)
Apoptosis
- Apoptosis is programmed cell death
- A physiological process
- Affects single cells in populations of healthy cells
- Mechanism of of removing effete and abnormal cells
- Normal cells divide to replace lost cells
- No evidence of inflammation
- Provides a balance between cell proliferation and elimination
- It is associated with:
- Maintenance of organ size in adults
- Organ development in the embryo
- Physiological atrophy and involution
Atrophy
- Decrease in organ size
- Due to a reduction in cell size or number
- Causes include:
- Gradual diminution in blood supply
- Reduced functional activity
- Interrupted nerve supply
- Endocrine deficiency
- Pressure
Calcification
- Abnormal deposits of calcium salts occur in two circumstances
Dystrophic calcification
- Local deposits of calcium may occur when
- Necrotic tissue is not absorbed
- Tissues undergo slow degeneration
Metastatic calcification
- Occurs when serum calcium is elevated for a long period of time
- Associated with:
- Increased calcium absorption due to high vitamin D levels
- Resorption of bone
- Mobilisation of calcium due to PTH excess
- Chronic renal failure
- Calcium is deposited in:
- Arterial walls
- Kidneys
- Lungs
- Stomach wall
Amyloid
- Abnormal protein is deposited in extra-cellular tissue
- Occurs around basement membrane and capillaries
- Resistant to degradation
- Two types are recognised
- Primary amyloidosis due to unknown causes
- Secondary amyloidosis secondary to:
- Tuberculosis
- Pyogenic infection
- Rheumatoid arthritis
- Myeloma
- Hodgkin's disease
- Affects several organs including
- Heart
- Intestinal tract
- Kidneys
- Results in atrophy due to pressure
- Transudation of proteins due to increased permeability and vessel
narrowing
- Pathologically can be detected by Lugol's iodine and Congo red dye
- With Congo red tissues show apple green fluorescence in polarised
light
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