Lecture 10: Necrosis, Apoptosis, Autophagy

what are the 3 D’s of pathology

disease, destruction, death

what is disease

changes from normal body anatomy and physiology → clinical signs, lesions, death

what is destruction

process of how body tissues are damaged by disease

• due to factors of a causative agent

• due to body response to tissue damage

what is death

loss of cells, tissues, organs, systems, whole organisms, multiple organisms

what is degeneration

reversible damage to cells/tissues, if inciting cause is removed, will go back to normal

what is necrosis

• irreverisble damage to cells/tissues

• past the “point of no return”

• dead tissue must be removed, walled off (fibrosis), or replaced

what are the types of necrosis

• ischemic/coagulation necrosis

• liqueficative necrosis

• caseation necrosis

• gangrenous necrosis

• fat necrosis

what is ischemic/coagulation necrosis

• acute necrosis

• cells die from loss of blood supply; tissue architecture preserved

• acutely tissue is swollen, paler than normal, and has “red rim of reaction RRR), blood trying to get blood flow in

• over time, dead tissue is removed (shrunken/depressed), replaced by fibrosis (firmer), paler than surrounding tissue

• problem starts due to vascular problems:

  • occlusion (blockage), vasospasm, disruption

what is liquefactive necrosis

• tissues dissolve due to factors released by agents or inflammatory cells; tissue architecture lost

• neutrophils can cause “explosion”, supprative inflammation

what is caseation necrosis

inflammatory cells that normally liquefy instead undergo coagulation necrosis, frozen in time; “cheese-like”

what is gangrenous necrosis

• tissue death and anaerobic bacterial growth in dead tissue → produce gas and distorts or liquefies architecture

• can result in sloughing or loss of large portions of dead tissues

what is fat necrosis (saponification)

calcium release in dying adipocytes (fat cells) complexes with lipids turning them into “soap”

what is apoptosis

programmed (physiological) cell death

what triggers apoptosis

can be triggered internally (intrinsic) by mitochondrial signals or externally (extrinsic) by Fas receptor/ligand by cytotoxic T-cells

process of apoptosis

• cell breakdown internally without disruption of membrane

• small portions of cellular/nuclear fragments are released in membrane bound vesicles called apoptotic bodies

• neighboring cells or macrophages internalize apoptotic bodies and digest to component parts

what is autophagy

cells break down own internal components (damaged organelles, etc), intracellular “recycling”

normal and abnormal autophagy

can be normal physiologic process or pathway can bring about death of a cell under certain conditions

“autolysis”

• after death experience

• self digestion (decomposition) of body cells that occurs after death of the whole animal or removal of tissue from the body