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chapter 11: cardiovascular system: blood: 11-7 (blood disorders (types of…
chapter 11: cardiovascular system: blood: 11-7
hemostasis = the stoppage of bleeding from the blood vessel
3 steps involved
vascular phase ( cell walls constrict)
vasospam ( endothelium contracts)
reduced blood flow for 20 minutes
platelet phase
platelets become more sticky and adhere to one another ( platelet plug)
platelets also release the hormone serotonin, which causes further vasoconstriction of the vessel
coagulation phase= formation of blood clot
complex cascade of events ( positive feedback mechanism)
requires calcium ions, and vitamin k so liver can make 4 clotting factors
2 possible starting pathways
extrinsic clotting mechanism
starts when damaged tissue or tissue outside of blood vessel ( hence, extrinsic) tissue factor (TF)
TF + factor VII + Ca2 = common pathway factor x
intrinsic clotting mechanism ( all factors normally found in blood )
starts when proenzymes ( in blood) collects collagen fibers
platelet factor released by platelets
Ca2+ + multiple clotting factors = common pathway factor x
common pathway factor x makes prothrombinase
prothrombinase causes prothrombin to convert to thrombin
thrombin catalyzes the polymerization of fibrogen to fibrin
fibrin threads make up meshwork of clot
fate of blood clots and prevention of coagulation ( fibrolynolytic system)
fibronolytic system provides checks and balances so that blood clotting does not go away
platelets contract, called clot reaction
fibroblasts, smooth muscle cells, and endothelial cells make repairs
fibrinolysis : dissolving the clot
plasminogen and t-PA ( tissue plasma activator ) make plasmin
thrombus = platelets sticking to a vessel wall
embolus = floating clot ( air bubbles, fat globules, abnormal mass)
embolism = when embolus gets lodged into a small vessel obstructing blood flow
fibrinolytic substances include
tissue plasminogen activator ( t-PA)
naturally produced
also injected quickly after MI to dissolve coronary thrombus
heparin is an anticoagulant
naturally produced by basophils and mast cells
also used as a pharmacologic agent extracted from lung tissues of animals
used during open-heart surgery and hemodialysis
warfarin ( coumadin) is another anticoagulant
given to patients prone to thrombosis
slower acting than heparin
blood disorders
sickle cell disease
hemochromatosis
chronic granulomatous disease
King George III and porphyria
types of anemias
hemorraghic anemia
aplastic anemia
iron deficiency anemia
pernicious anemia
leukemia
edema
DIC, disseminated intravascular clotting
atherosclerosis
thrombocytopenia
hemophilia