1. Blood Vessels

2. Pathway of Blood Leaving the Heart  Aorta  Arteries  Arterioles  Capillaries  oxygen and nutrients given to the cells of your body and exchanged for waste  Venules  Veins  Superior and Inferior Vena Cava

3. Walls of the Blood Vessels  Three Layers:  Tunica interna: inner layer  Made up of squamous epithelial cells over a thin layer of connective tissue that allows blood to easily pass through  Tunica media: middle layer  Made up of smooth muscle and elastic and collagen tissue that can expand and contract to control the diameter of the vessel  Tunica externa: outer layer  Made of fibrous tissue and provides support and protection for the blood vessel

4. Arteries vs. Veins  Arteries = thicker walls  Contain elastic laminae – extra layer of elastic tissue to help deal with increased pressure  Veins  Contain valves to prevent backflow that may be caused by the low pressure  Surrounded by skeletal muscle that can contract to push blood toward the heart

5. Capillaries  Only made up of tunica interna so the walls are only one cell thick  Allows for oxygen, nutrients, and wastes to easily pass through to the tissue cells  Come together to form a web of vessels called a capillary med

6. Capillary Beds  Made up of:  Vascular Shunt: main road connecting the arteriole to the venule  True Capillaries: vessels that make up the actual exchanges with the tissues  Precapillary Sphincters: smooth muscle that dictate if blood can flow through or not

7. How Clotting Works:  Step 1: Damage occurs to the blood vessel  Step 2: Platelets attach  Step 3: Platelets send out signals for more platelets to come and a platelet plug is created  Step 4: Platelets release serotonin which stops blood flow to the area  Step 5: Coagulation - fibrin causing a netlike patch and snags more blood cells and platelets  Step 6: Clot forms  Step 7: Clot begins to retract pulling the damaged edges of the blood vessel together, which allows epithelial tissue to regenerate over time  Step 8: Clot is dissolved