Bio lec. 11 pt 1

• We use iron in our blood to enable circulation and diffusion in multicellular organisms, but not in single-celled or small organisms
• Hemorrhage


  Loss of blood from the circulatory system
• Hemorrhage is a problem for most multicellular organisms
• Circulatory system


  • Open vs. closed (we have a closed system)
• Insects


  Have a shorter distance between cells and substances in the body, reducing the need for a circulatory system
• Cardiovascular system


  Heart-blood vessels pass blood over a respiratory system to exchange gases, then back into the body
• Heart


  • 4-chambered, with 2 atria that prime the two ventricles, which pump blood
• Right ventricle


  Pumps blood to the lungs
• Left ventricle


  Pumps blood to the body
• Arteries


  • Muscular, carry oxygenated blood from the heart to the organs, have smooth muscle to adjust blood flow and pressure
• Arterioles


  Interface between arteries and capillaries
• Veins


  • Carry deoxygenated blood towards the heart from the organs, contain valves to prevent backflow
• Capillaries


  Narrow, numerous and leaky, allow movement of fluid, nutrients and gases in and out of cells
• Circulation


  Double-loop, with a pulmonary circuit from heart to lungs and back, and a systemic circuit from heart to tissues and back
• Cardiac function


  • Systole (heart contracting), diastole (heart relaxing and filling with blood), valves at input and output sites to prevent backflow
• Cardiac cycle


  Atrial systole, ventricular systole, atrial and ventricular diastole
• The "lub-dub" sound of the heartbeat is caused by the closing of the atrioventricular and semilunar valves