The heart is made up of cardiac muscle and divided into four chambers.
Atria (upper two chambers)
The upper two chambers of the heart are called the right and left atrium. Both chambers receive blood via the veins.
Ventricles (lower two chambers)
The bottom two chambers of the heart are the right and left ventricles. Both these chambers pump blood into the arteries.
The chamber of the heart that pumps deoxygenated blood to the lungs via the pulmonary artery.
The heart chamber that has the most muscular wall as it must pump blood around the entire body, via the Aorta.
The aorta delivers oxygenated blood from the left ventricle to the body tissues. The strongest artery with the thickest wall, as it must withstand high blood pressure.
Circulation of blood
The Systemic Circulatory System
The blood flow between the heart and the body tissues. Consisting of the: Left ventricle, right atrium, aorta and vena cava.
The Pulmonary Circulatory System
The blood flow between the heart and the lungs. Consisting of the: Left atrium, right ventricle, the pulmonary artery and the pulmonary vein.
The heart has valves to prevent the back flow of blood. The artria valves are called the atrioventricular valves which prevent the back flow of blood from ventricles to atria. Or put another way they ensure the one way flow of blood from atria to ventricles.
The heart also has semilunar valves which prevent the back flow of blood from the pulmonary artery and aorta into the ventricles.
Inside the wall of the right atrium is the hearts own pacemaker, the sinoatrial node (SAN). The SAN is controlled by the autonomic nervous system and responsible for the contraction of the heart.