Your Circulatory System The circulatory system is the body’s transportation system. It allows the body to transport, or move, materials from one place to another. These materials are carried in the blood: Dissolved oxygen (inside red blood cells) Dissolved food particles (nourishment) White blood cells (help fight off infections) Hormones (cause cells to grow or change in some way)

The Work Of The Heart The heart is a very strong muscle. It has four chambers, each of which plays a different role in the circulation of blood. The left atrium receives oxygen-rich blood returning from the lungs. The left ventricle pumps this oxygen-rich blood to body tissues. Oxygen-poor blood returns to and enters the heart through the right atrium. Then the right ventricle pumps this oxygen-poor blood to the lungs, and the whole process repeats.

The Work Of Blood Vessels Arteries carry oxygen-rich blood away from the heart. Veins carry oxygen-poor blood back to the heart. The branches of arteries and veins become smaller as they go away from the heart. Capillaries are very tiny branches of arteries and veins. They connect the smallest arteries with the smallest veins. Capillaries provide blood directly to cells.

Blood Pressure Blood pressure is the force of blood pushing against the walls of the arteries. Blood pressure is greatest when the heart contracts, or pushes out blood. Blood pressure is lowest between beats, or when the heart relaxes. “Average” blood pressure is 120/80, “high” blood pressure is 140/95 or above.

Parts Of The Blood Blood contains both liquid and solid parts. Plasma is the liquid portion of blood, making up about half its volume. 92% of plasma is water. Plasma’s job is to transport dissolved food and blood cells. Red blood cells carry oxygen to all the other cells of the body and carry away some waste products. White blood cells help destroy pathogens (disease-carrying germs) that enter the body. Platelets help your blood clot, so you don’t bleed to death when you get a cut.

Blood Types There are four main blood types: “A”, “B”, “AB” & “O”. Blood also contains an Rh factor. Blood is either Rh+ or Rh-. People with Rh+ blood can receive a transfusion from people with either Rh+ or Rh- blood. People with Rh- blood can only receive blood from a Rh- type. When receiving a blood transfusion, care must be exercised to ensure that the person doesn’t receive the wrong blood type.

Keeping Your Circulatory System Healthy Here are some ways to help protect your circulatory system: Eat a balanced diet. Avoid stress. Exercise regularly. Try to maintain your ideal weight. Don’t smoke.