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

Stem cell Developmental pathway

Hemocyto- Promegakaryocyte blast Platelets

Figure 17.12

Fast series of reactions for stoppage of bleeding 1. Vascular spasm 2. plug formation 3. Coagulation ( 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)