Types of Necrosis: unprogrammed cell death Flashcards
What is necrosis?
Accidental, unprogrammed cell death in response to irreversible cell injury
What cellular components are damaged and so trigger necrosis?
Membranes
What 2 responses are triggered by damage to cell membranes in necrosis?
Lysosomal digestion, cell leakage triggers inflammatory response
Are there different types of causes for necrosis?
Cause is always pathological
Give 4 examples of pathological causes that trigger necrosis?
Ischaemia, toxins, trauma, infections
How do calcium ions cause mitochondrial damage which leads to necrosis?
Calcium ions enter cell which stimulates Mitochondrial Permeability Transition Pores (MPTP) to open in inner membrane, so ATP is depleted
How does calcium cause DNA damage which leads to necrosis?
Calcium activates enzymes that cause DNA damage, as well as nuclear and membrane damage
How does free radical damage occur, that leads to necrosis?
Free radicals are highly reactive unpaired electrons that modify adjacent molecules eg. proteins, nucleic acids, lipids
How do free radicals affect interacting molecules in auto-catalytic reactions?
Converts interacting molecules into free radicals
What are the 2 ways in which antioxidants protect against free radical damage, preventing necrosis?
Block free radical formation, inactivate free radicals
What 3 vitamins are antioxidants that protect against free radical damage, preventing necrosis?
Vitamins A,C,E
What substance is an antioxidant that protects against free radical damage, preventing necrosis?
Glutathione
Which 2 immune cells produce ROS free radicals in large amounts?
Neutrophils, macrophages
What is coagulative necrosis caused by?
Ischaemia
What are the 2 microscopic features of coagulative necrosis?
Cells have lost their nuclei, eosinophilia (hyper-pink H&E stained cytoplasm)
What is the macroscopic feature of coagulative necrosis?
Necrotic area is paler than healthy tissues
What causes coagulative necrosis in the kidney, and what does this lead to?
Thromboembolism, which causes coagulative necrosis leading to renal infarct
What is a thromboembolism?
Thrombus breaks off and travels through bloodstream, blocking off vessel in which it gets stuck
What 2 conditions cause liquefactive necrosis?
Bacterial infection, stroke
What is the macroscopic feature of liquefactive necrosis?
Viscous liquid mass formed as dead tissue is digested
What causes ischaemial stroke that leads to liquefactive necrosis in brain?
Thromboembolus blocking cerebral artery
How does ischaemial stroke affect brain’s structural strength?
Surface collapses
What causes gangrenous necrosis?
Severe ischaemia
What causes dry gangrene?
Lack of blood supply to tissues, so it is a form of coagulative necrosis that occurs in different tissue planes
What causes wet gangrene?
Dry gangrene exposed to bacterial infection, also a form of liquefactive necrosis
Where in the body does gangrenous necrosis generally occur?
Extremities
What are the 2 macroscopic features of gangrenous necrosis?
Blackened skin, putrefaction (rotting)
What are the 2 microscopic features of liquefactive necrosis?
Macrophages, neutrophils
How are the microscopic features of wet and dry gangrene different?
Wet is similar to liquefactive necrosis features, dry is similar to coagulative necrosis features
What causes caseous necrosis?
Foreign noxious stimulus eg. tuberculosis can’t be destroyed by immune system, so is contained
What stain is used to confirm a diagnosis of tuberculosis, and what colour does it stain the bacteria?
Ziehl-Neelsen stain, can see red acid-fast bacilli
What is the most common cause of caseous necrosis?
Tuberculosis, usually in lungs
What structure is formed by caseous necrosis?
Caseating granuloma that contains necrotic tissue and a border of fibroblasts and macrophages
What is the macroscopic feature of caseous necrosis?
Cheese-like yellow sphere with border
What are the 2 microscopic features of caseous necrosis?
Large multinucleated cells, macrophages
What condition causes fat necrosis?
Acute pancreatitis
What enzymes are released from the inflamed pancreas in acute pancreatitis, that causes fat necrosis?
Pancreatic lipase
What is the macroscopic feature of fat necrosis?
Swollen hemorrhagic pancreas
What are the 3 microscopic features of fat necrosis?
Infiltrate of macrophages, anucleated adipocytes, unclear borders between adipocytes
