 The function of the circulatory system is to transport substances such as gases (O 2, CO 2 ), nutrients/wastes, hormones, immune system. It is also used to regulate body temperature.

 Blood Vessels  Blood  Heart

 There are 3 paths that blood travels:  Systemic circuit: to the body and back  Pulmonary circuit: to the lungs and back  Cardiac circuit: to the heart and back

 There are three types of blood vessels:  Arteries  Capillaries  Veins

 thick muscular walls, carry blood away from heart, propelled by blood pressure (heart)

 Very thin walls, only one cell thick, site of nutrient/gas exchange

 Thinner walls, carry blood towards the heart, blood propelled by muscle contractions, have valves to control flow of blood

 1.aorta  2.pulmonary artery  3.pulmonary vein  4.left atrium  5.AV (mitral) valve  6.left ventricle  7.semi-lunar (aortic) valve  8.right ventricle  9.AV (tricuspid) valve  10. right atrium  11. vena cava

  The heart is a muscular organ consisting of 4 chambers. The atria receive blood and the ventricles pump blood.

 The right side of the heart receives blood from body and pumps it to lungs. The left side of the heart receives blood from lungs and pumps it to the body.

 The blood in the right side of the heart is de- oxygenated (does not have oxygen) while the blood in the left side of the heart is oxygenated (has oxygen).

 Different valves stop blood from flowing in the wrong direction.

 Atrio-ventricular (AV) valves prevent blood from flowing from the ventricle to the atrium.  The tricuspid valve is on the right side while the bicuspid (mitral) valve is on the left.

 The semi-lunar valves prevent blood from flowing from the arteries to the ventricles.  They are also known as the pulmonary and aortic valves.

 55% of blood is plasma which is mostly water and dissolved proteins, gases, glucose, hormones and ions.  Platelets are involved in blood clotting.

 The remaining 45% is mostly red blood cells with a few white blood cells.  Red blood cells have no nuclei.  They contain the protein hemoglobin which is used to carry oxygen.

 White blood cells are part of the immune system.  They protect the body from infections by engulfing foreign bacteria and producing antibodies.

 Atherosclerosis: hardening of the arteries  Heart disease: cardiac vessels are blocked, weakening heart  Stroke: blood vessels in the brain burst causing brain damage  Hemophilia: blood does not clot properly  Sickle-cell anemia: Reduced number of red blood cells due to abnormal hemoglobin