Rob Pike; Week 11 MED1011; Biochemistry
Platelets are from megakaryocytes, live 1-4 days, accumulate at sites of trauma/damaged sub-endothelium, adhere, clump and aggregate. They secrete procoagulants, vasoconstrictors to cause spasm, form a plug to stop bleeding and can clump inappropriately. Thrombocytopaenia can cause immediate, continued bleeding from trauma or bleeding into skin and mouth with no trauma. Haemostasis is good in small vessels, varies in large vessels. Normal endothelium prevents clotting. Extrinsic pathway is from sources other than the blood itself. Factor released is tissue factor or thromboplastin, and is a potent activator of clotting. Intrinsic pathway is from blood itself.
Thrombin converts fibrinogen to fibrin to form mesh. Within 30 minutes there is clot retraction, clot must be removed to allow healing to occur once trauma is resolved, occurs through fibrinolysis. Plasmin cleaves fibrin strands to form fibrin degradation products. Plasmin is from plasminogen. Tissue plasminogen activator activates plasmin. DVT is thrombosis of deep venous system of lower limbs. Increased risk with immobility, stasis, surgery, hormone therapy. Can cause pulmonary embolism if it breaks off.
phlebo- pertaining to veins. varico- twisted, swollen.