MOD Flashcards
Five causes of cell death
Hypoxia, toxins, immune mechanisms, microorganisms, dietary insufficiency, genetic, heat, cold, trauma.
Definition of disease
Consequence of failed homeostasis, with consequent morphological and functional disturbances.
4 targets of cell injury
Cell membrane, nucleus, proteins (e.g. Structural proteins), mitochondria.
Describe Reversible hypoxic injury
Reduced ATP synthesis, Na+/K+ pump works less well. NA+ and water enters the cell resulting in oncosis. Ca2+ also enters, causing loss of microvilli, blebs and ER swelling. Anaerobic respiration takes place, causing increase in lactate, and decreased pH. This causes ribosomes to detach from ER and fat to accumulate.
Describe Irreversible hypoxic injury.
Most cells die due to oncosis. Increased permeability of membrane causing influx of ca2+ which activates enzymes, such as ATPase and Phospholipase. Lysosomes membrane is also damaged, so enzymes leak into the cell. Intracellular substances also leak out.
Why is returning blood flow to a previously ischaemic area harmful?
Increased production of ROS, increased neutrophils and activation of complement pathway.
Defences against ROS include…?
SOD enzyme, Vit A,C & E.
Role of heat shock proteins,
Protection against cell injury. Recognise misfolded proteins and repair them. If not possible to repair, then destroy them. Maintains protein viability.
Appearance of injured cells via light microscopy.
Reduced pink staining. Clumped chromatin, then pyknosis (shrinkage), karyorhexis (fragmentation), and karyolysis (dissolution) of the nucleus.
Appearance of injured cells via electron microscopy
Swelling, cytoplasmic blebs, clumped chromatin, myelin figures, ER lysis and swollen mitochondria.
What is oncosis
Cell death with swelling. (Changes prior to death).
What is necrosis?
Morphological changes in living organisms after cell died some time ago.
What is apoptosis?
Cell death with shrinkage, induced by regulated Intracellular programme, where enzymes degrade its own DNA and proteins.
Non-random cleavage of DNA. Helps to sculpt during embryological development aswell as removes unwanted/virally infected cells.
Describe the 4 types of necrosis.
Coagulative: protein denaturation. Ghost outline of cells. Cell proteins less soluble. Appears white.
Liquefactive: enzyme digestion of tissues. Neutrophil infiltration. Tissue becomes viscous. Pus present.
Caseous: structureless debris. Associated with infection. E.g TB
Fat Necrosis: adipose destruction. Increased release of lipases. FA release, which reacts with Ca2+ to form deposits (calcium soaps).
What is gangrene?
Necrosis visible to the naked eye. Can be dry (exposure to air) or wet (infection with bacteria).
What is an infarction?
Obstruction to a tissues blood supply. Can cause necrosis.
Where would you find white infarcts?
In solid organs such as the spleen, heart and kidneys. Due to end artery occlusion.
Where would you find red infarcts?
Looser organs such as lungs and small intestines. Caused by extensive haemorrhage into dead tissue due to dual blood supply.
Appearance of cells post apoptosis.
Shrunken, condensed chromatin, cytoplasmic budding, fragmentation forming apoptic bodies that are phagocytosed.
Intrinsic apoptosis process
DNA damage activates P53. This increases permeability of the mitochondria. Cytochrome C protein leaks out and binds to APAF. This then associates with Procaspase 9, forming an apoptosome. Caspase becomes activated causing apoptosis to take place.
Extrinsic apoptosis process
External Ligands such as TRAIL bind to death receptors on the outer cell membrane. Procaspase 8 binds, leading to activation of caspase 8. This initiates apoptosis.
What is pathological calcification?
Abnormal calcium salt deposition in tissues.
The two types of pathological calcification?
DYSTROPHIC: Only in area of dying tissue. Causes nucleation of hydroxyapatite crystals. Causes organ dysfunction.
METASTATIC: Affects whole body. Due to calcium metabolism disturbance. Can be lethal. Caused by PTH over secretion.
Relevance of cellular ageing?
Cells cannot replicate indefinitely as telomeres shorten. (Except germ cells as they contain telomerase to maintain telomeres)
3 effects of chronic alcohol intake on the liver
1) Fatty change, causing steatosis. (Reversible)
2) Acute alcoholic hepatitis. Malory bodies form and neutrophils infiltrate.
3) cirrhosis. Leads to a hard, shrunken, knobbly liver. Irreversible and potentially fatal.
What is acute inflammation?
The response to injury of vascularised tissue. It is innate, immediate and has a short duration.
What are 5 causes of acute inflammation?
- foreign bodies
- infections and microbial toxins
- trauma
- immune reactions
- tissue necrosis
- physical and chemical agents
What are the 5 clinical signs of acute inflammation?
Rubor - redness Tumour - swelling Color - heat Dolor - pain Loss of function, enforcing rest
What causes the pain during acute inflammation?
Stimulation of nerve endings by mediators, especially bradykinin.
Describe the change in blood flow during acute inflammation.
Vasoconstriction then vasodilation of arterioles and capillaries, increasing blood flow.
Increased permeability of blood vessels allowing plasma to escape.
Slowing of circulation.
Histamine released from mast cells causing increased vascular permeability and vasodilation.
Explain exudation of fluid into tissues during acute inflammation.
Membranes become leaky, arterioles dilate and plasma proteins escape into tissue. Increasing the fluid flow out of vessels, leading to oedema (increased fluid in tissue spaces).
What is exudate oedema?
Fluid loss in inflammation. High protein content.
What is transudate?
Fluid loss due to hydrostatic pressure imbalance. Low protein content.
How is excess fluid drained during acute inflammation.
Via lymphatic system ,taking microorganisms and antigens too. These are then presented to the immune system in the lymph nodes.
What is the role of opsonins?
They coat foreign material for phagocytosis.
What does neutrophil presence indicate?
A bacterial/parasitic invasion.
What are the 6 stages of a neutrophil?
1) chemotaxis
2) activation
3) margination
4) diapedesis
5) recognition-attachment
6) phagocytosis
What is chemotaxis?
The directional movement towards a chemical attractant.
How are neutrophils activated?
Ca2+ and Na+ ions rush into the cell. The cell swells and reorganises its cytoskeleton. The cell then sends out pseudopodia (cell extensions)
How do leukocytes leave venules?
Diapedesis- they produce collagenase that digests the basement membrane, allowing them to move towards their target.
Explain the recognition-attachment stage of neutrophils
They recognise bacteria via opsonins/ microbial surface antigens, and phagocytose them.
What are the two types of phagocytosis?
- oxygen-dependent: uses oxygen derived free-radicals which are then released into the phagosome = oxygen bursts.
- oxygen-independent: uses enzymes e.g. Proteases, nucleases, lysozymes.
Name 3 types of chemical mediators
Proteases (e.g. Kinins, complement system)
Prostaglandins/leukotrienes
Cytokines/chemokines (made by WBCs)
Which two chemical mediators cause increased blood flow?
Histamine and prostaglandins
Which chemical mediators increase vascular permeability?
Histamine and leukotrienes
Which chemical mediators induce neutrophil chemotaxis?
C5a, bacterial peptides.
Which chemical mediators induce phagocytosis?
C3b