Cell injury and apoptosis II Flashcards
What is the sequence of events in cell injury
- Reversible
- Irreversible
- Cell death (necrosis)
What are the early FUNCTIONAL changes in cell injury?
- Decreased generation of ATP
- Loss of cell membrane integrity
- Defects in protein synthesis
- Cytoskeletal damage and DNA damage
What are the Morphological changes of reversible injury?
- Cellular swelling (under light microscopy)
- Ultrastructural changes:
-Plasma membrane alterations: blebbing, blunting and distortion of microvilli
- Mitochondrial swelling
- Dilation of the endoplasmic reticulum
- Nuclear alterations, with disaggregation of granular and fibrillar elements
What happens to the in irreversible injury, cell death (necrosis)?
- Extensive damage to all cellular membranes
- Swelling of lysosomes and vacuolization of mitochondria
- Extracellular calcium enters the cell
- Intracellular calcium (from stores) is released
- Activation of enzymes - catabolize membranes, proteins, ATP and nucleic acids
- Continued loss of proteins, coenzymes, RNA from the hyperpermeable plasma membrane
-Nuclear Changes: pyknosis (shrink), karyorrhexis (fragmentation) and karyolysis (disintegration)
What is Necrosis?
-Pathological cellular or tissue death in a living organism, irrespective of cause
-Refers to a spectrum of MORPHOLOGIC CHANGES that follow cell death, largely resulting from the progressive DEGRADATIVE ACTION OF ENZYMES on the lethally injured cells
What are the different types of necrosis seen in different tissues?
- Coagulative necrosis
- Liquefactive necrosis
- Caseous necrosis
- Fat necrosis
What is Coagulative necrosis?
- Most common form of necrosis
- Characteristic of hypoxic death of cells in all tissues except the brain
- Cell maintains its architecture having lost its nucleus
- Cytoplasm looks coagulated and stains pink with eosin
What is Liquefactive/colliquative necrosis?
- Characteristic of FOCAL BACTERIAL INFECTIONS (the accumulation of inflammatory cells)
- Hypoxic death of cells in CENTRAL NERVOUS SYSTEM
- Complete digestion of the dead cells results in the transformation of the tissue into a liquid viscous mass
- The material is frequently creamy yellow because of the presence of dead white cells and is called pus
What is Caseous necrosis?
- Most often in foci of tuberculous infection
- Cheesy white gross appearance
- The tissue architecture is completely obliterated
What is Fat necrosis?
- It is a descriptive of focal areas of fat destruction, typically occurring in acute pancreatitis as a result of the release of activated pancreatic lipases into the substance of the pancreas and the peritoneal cavity
What is Apoptosis
Programmed cell death
What happens in Apoptosis?
- Individual cell deletion in physiological growth control and in disease
- Activated or prevented by a variety of stimuli
-Reduced apoptosis contributes to cell accumulation e.g. neoplasia - Increased apoptosis results in excessive cell loss e.g. atrophy
What regulates apoptosis and what does it do to the cells DNA and proteins?
- Tightly regulated by INTRACELLULAR PROGRAM in which pro-apoptotic cells activate enzymes that degrade the cells’ own DNA and proteins
What happens in normal situations of Apoptosis?
- In normal situations, it serves to eliminate unwanted or potentially harmful cells
What happens in pathological events of Apoptosis?
- In pathological events (radiation, viral infection), to eliminate irreversibly damaged cells especially when the damage affects the cell’s DNA
