Cell Injury Flashcards
What can cause cell injury?
Hypoxia. Toxins. Physical agents: trauma, temp, pressure, electricity. Radiation. Microorganisms. Immune. Deficiencies.
What is the difference between hypoxia and ischemia?
Hypoxia = decreased oxygen.
Ischemia = decreased blood supply
Outline the 4 types of hypoxia
Hypoxaemia hypoxia = O2 arterial content low.
Anaemic hypoxia = decreased Hb ability to carry O2.
Ischaemic hypoxia = interrupted blood supply.
Histiocytic hypoxia = inability to utilise O2 due to disabled oxidative phosphorylation enzymes
Explain how the immune system can damage body cells?
Hypersensitivity = secondary injury to vigorous immune reaction.
Autoimmune reaction = fail to distinguish self
Which cell components are most susceptible to injury?
Cell membranes nucleus,
proteins,
mitochondria
What happens at a molecular level during hypoxia
Lower O2 = lower oxidative phosphorylation = lower ATP
1) failure of Na K ATPase pump = ion gradient lost = ions pour in = cell swelling.
2) raised glycolysis = lower pH.
3) lower protein synthesis = lipid deposition
Outline what occurs in prolonged hypoxia
Irreversible = massive influx of Ca2+ = activation of phospholipase, proteases, endonucleases
Explain what free radicals are and how they cause damage
Single unpaired electron in an outer orbit = unstable configuration that will react with other molecules
mutagenic = carcinogenic, lipid peroxidation, autocatalytic chain reaction
Name the 3 free radicals that are of particular biological significance in cells
OH (hydroxyl),
O2- (superoxide),
H2O2 (hydrogen peroxide)
How are radicals produced?
Oxidative phosphorylation, inflam, radiation, contact with unbound metals, drugs/chemicals
How does the body control free radicals
A, C, E vits donate electrons, metal carrier/storage proteins sequester iron/copper, enzymes neutralise
What are heat shock proteins?
Aim to mend mis-folded proteins
Describe the 3 ways injured/dying cells look like under a microscope
Pyknosis = irreversible condensation of nucleus chromatin
karyorrhexis = fragmentation of nucleus with chromatin distributed irregularly throughout cytoplasm.
karyolysis = dissolution of a cell nucleus
Describe what injured/dying cells look like under an electron microscope
Can now visualise organelles: irreversible =
myelin figures (damaged cell membrane collection of fat), lysis of ER, mitochondrial swelling, rupture of lysosomes, nucleus pyknosis, karyolysis or karyorrhexis
How can we diagnose cell death?
Testing cell function with uptake of dye, if alive = no dye due to impermeable cell membrane
Define apoptosis, necrosis and oncosis
Apoptosis = controlled cell death non-random DNA cleavage.
Necrosis = morphologic changes that occur after a cell has been dead for a period of time.
Oncosis = cell death with swelling, DNA cleaved in random lengths
What are the types of necrosis?
Coagulative: solid organs, protein denaturation.
Liquefactive: loose tissue, enzyme release = liquefaction of tissue.
Caseous: infections, structureless debris (cheese look).
fat necrosis: action upon fat by digestive enzymes, appear as white chalky deposits
Define gangrene
Necrosis visible to the naked eye
Define infarction
Necrosis caused by reduction in arterial blood flow
Define infarct
Area of necrotic tissue as a result of low arterial blood supply
What is the difference between wet and dry necrosis?
Dry = necrosis modified by exposure to air (coagulative necrosis).
Wet = necrosis by infection (liquefactive necrosis) (can be wet gas gangrene: presence of anaerobic bacteria that prod gas)
What are the causes of an infraction?
Thrombosis, embolism, blood supply twisting: sigmoid colon or spermatic cord
What is the difference between a thrombus and an embolism?
Thrombus: formation of a solid mass of blood within the circulatory system
Embolism: blockage of a blood vessel by solid, liquid or gas at a site distant from its origin
How and why does infarcted tissue look different?
Can be white = occlusion of end artery in solid tissue.
Red = dual blood supply in loose tissue.
