Business
Due in Lab PreLab #8 Priority registration is Thursday 2/28/13 Midterm 2 is Monday 3/4/13 Study Guide posted
Cardiovascular System
BLOOD CLOTTING Platelets
Stem cell Developmental pathway
Hemocyto- Promegakaryocyte blast Megakaryoblast Megakaryocyte Platelets
Figure 17.12 Hemostasis
Fast series of reactions for stoppage of bleeding 1. Vascular spasm 2. Platelet plug formation 3. Coagulation (blood clotting) Vascular Spasm
Vasoconstriction of damaged blood vessel Triggered by Direct injury Chemicals released by endothelial cells and platelets
Platelet Plug
Platelets attracted to injured vessel wall Collagen and glycoprotein Actin and myosin Step 1 Vascular spasm • Smooth muscle contracts, causing vasoconstriction.
Step 2 Platelet plug formation • Injury to lining of vessel
Collagen exposes collagen fibers; fibers platelets adhere. • Platelets release chemicals that make nearby platelets sticky; platelet plug forms. Platelets Step 3 Coagulation • Fibrin forms a mesh that traps red blood cells and platelets, forming the clot. Fibrin
Figure 17.13 Coagulation
Blood is transformed from a liquid to a gel Reinforces platelet plug Coagulation
Damaged cells release Thromboplastin
Prothrombin Thrombin
Fibrinogen Fibrin Figure 17.15 Clinical Considerations
Bleeding disorders Prevent normal clot formation Thromboembolic disorders Undesirable clot formation Bleeding Disorders
Hemophilia Several similar hereditary bleeding disorders Symptoms Prolonged bleeding Treated Plasma transfusions Injection of missing factors
Bleeding Disorders
Thrombocytopenia Deficiency of circulating platelets Causes Bone marrow disease Symptoms Spontaneous bleeding petechiae Treatment Transfusion of concentrated platelets
Thromboembolytic Conditions
Thrombus: clot that develops and persists in an unbroken blood vessel May block circulation, leading to tissue death Embolus: a thrombus freely floating in the blood stream Pulmonary emboli Cerebral emboli Thromboembolytic Conditions
Atherosclerosis, inflammation, sedentary states Prevention Aspirin Heparin Warfarin (Coumadin)