Humans have a double circulatory system where deoxygenated blood is pumped from the heart to the lungs, becomes oxygenated, and then returns to the heart to be pumped to the organs
The benefit of the double circulatory system is that the blood passes through the heart twice, allowing it to travel rapidly to the body cells and deliver the oxygen they need
Heart
Organ consisting mainly of muscle tissue
Job is to pump blood around the body
Chambers of the heart
Left atrium
Right atrium
Left ventricle
Right ventricle
The atria are separated from the ventricles by valves
Main blood vessels entering and leaving the heart
Vena cava (brings in oxygenated blood from the body)
Pulmonary artery (blood passes from heart to lungs)
Pulmonary vein (oxygenated blood passes from lungs to heart)
Aorta (blood is pumped from heart to body)
Pattern of blood flow through the heart
1. Blood enters left and right atria
2. Atria contract, forcing blood into ventricles
3. Ventricles contract, forcing blood out of heart
4. Valves prevent backflow into atria
Left ventricle
Has thicker muscular wall than right ventricle
Pumps blood around entire body, so needs greater force
Right ventricle
Only pumps blood to the lungs
Coronary arteries
Branch out of the aorta and spread into the heart muscle
Purpose is to supply oxygen to the muscle cells of the heart
Pacemaker
Group of cells found in the right atrium that control the natural resting heart rate
