Clotting and Thrombosis Flashcards
What is an embolus
An object travelled from other parts of the body
May cause partial/total blockage of an affected area
Common types of embolus
-Thrombus/blood clots (very common)
-Air
-Atheroma
-Foreign bodies
Where can an embolus travel to
Brain
Heart
Lungs
Define ischaemia
Inadequate blood supply to an organ or part of the body
Depriving affected tissue of vital nutrients, especially oxygen.
What is infarction
death of tissue as a result of ischaemia
Factors which make ischaemia reversible
-duration of ischamic period
-metabolic demands of the tissue (cardiac myocytes and cerebral neurons are most vulnerable)
What does failure of the membrane pump lead to
-Osmoregulation loss - Na and H2O influx
-Increased cytosolic Ca++
-Damaging membranes, cytoskeleton and proteins
-Initiate cell death
What does lysosomal breakdown lead to
-Release of lysosomal contents - proteases, DNases etc degrading
intracellular components
-Reactive oxygen species leakage damaging intracellular organelles:
membranes, pumps, mitochondria and DNA
Thrombus formation steps
1) loss of endothelial cells and exposure of collagen
2) platelet adherance and activation
3) thrombus formed of alternating layers of platelet, fibrin, RBCs
Define haemostasis
Physiological process to prevent excessive blood loss after vascular injury (clot formation)
interaction of:
vessels
platelets
coagulation (clotting) factors
Stages of haemostasis
Damaged blood vessel
Restrict/slow blood flow form temporary plug
development of clot
What do vascular endothelial cells secrete
vasodilators :
Prostoglandin I2/Nitric oxide to inhibit clot formation
What occurs upon vascular injury
vasoconstriction - slow blood flow increases physical contact between platelets, exposed injured tissues and clotting factors
platelet activating factor released by damaged vessel wall
Damage vessel exposure - basement membrane (collagen/subendothelial tissue factor)
