Autophagy
Self-eating membrane extension, fusion with lysosomes
Survival mechanism in deprivation and starvation
Degenerative CNS disease and cancer
Necrosis
Un-programmed cell death
Cell changes include:
– Karyolysis: Nuclear dissolution and chromatin lysis
– Pyknosis: Clumping of the nucleus
– Karyorrhexis: Fragmentation of the nucleus
Types of necrosis:
1. Liquefaction necrosis
– Tissue transforms into a liquid viscous mass due to release
of hydrolytic enzymes
o Common in brain, liver and lungs
o Due to bacterial infection
2. Coagulative necrosis
– Denaturation of structural proteins (coagulation) including
lysosomal enzymes
– Like an egg on a hot pan
3. Fat necrosis
– Tissue broken down into fatty acids by action of lipases
o Liver, breast, pancreas and other abdominal organs
o Common in liver. Lipases break down hepatocytes into fatty acids
4. Caseous necrosis
– Combination of coagulative and liquefactive necrosis
– Thick, yellowish “cheesy” substance
o Tuberculosis pulmonary infection
5. Infarction
– Area of dead tissues as a result of oxygen deprivation
– E.g Myocardial infarction
6. Gangrene
– Area of dead tissues due to severe and persistent hypoxic injury
o Dry gangrene (arterial occlusion; feet and toes; DM)
o Wet gangrene (venous occlusion; most tissues/organs
strangulated hernia)
o Gas gangrene: hypoxia + gas production (Clostridium perfringens)
Aging
Humans have normal life span and life expectancy
Aging vs disease
– Aging is a physiological process (not a disease). Atrophy, decline in number and size of cells, low blood supply, poor healing, poor skin elasticity…etc
Cellular aging
– Atrophy, decreased function/renewal, and organelle damage
Tissue and systemic aging
– Progressive stiffness and rigidity
– Sarcopenia (muscle loss; decreased body mass with aging)
Frailty
– Complex clinical syndrome, common in elderly
– Affects: mobility, balance, muscle strength, motor activity, cognition, nutrition, endurance and bone density
– Person vulnerable to falls, fractures, functional decline
Somatic Death
Death of the entire person
Manifestations:
Post-mortem change is diffuse and does not involve the inflammatory response
– Cessations of respiration and circulation
– Pupil dilation
– Gradual lowering of body temp
– Loss of elasticity and transparency of skin
– Muscle stiffening (rigor mortis)
– Skin discoloration
Types of post-mortem changes:
– Algor mortis
o Reduction in body temp
– Livor mortis
o Purplish red discoloration of the skin
– Rigor mortis
o Stiffness of body parts, visible within 2-4 hours, fully developed 6-12 hours after death
– Post-mortem decomposition
o Autolysis
o Putrefaction: obvious around 24-48 hours after death. Rotting or decaying of the body.
o Maceration: aseptic autolysis of dead fetus in utero within amniotic fluid.
End of Module