The human heart and circulatory system

The human heart is the most efficient pump-better than any man made pump. It works ceaselessly to supply blood to all the cells of the body.

On an average it beats about 100.000 times per day and nearly 34 million times in a year.

Just try to figure out how many times it beats in a life span of 60 yrs and your head starts reeling.

The heart keeps working round the clock. The heart rate varies depending on age and also on the state of the body. When the body is at rest heart rate comes down and when we are working it goes up to meet the increased demand for oxygen.

On an average it pumps about 5-6 liters of blood per minute in an adult and 7200 liters per day and more than 2.4 million liters per year.

The heart is situated in the center of the chest behind the breast bone with its tip pointing to the left. It weights about 300 grams.

The heart is a four chambered organ. The two upper chambers are called atria-left and right (singular is atrium). The two lower ones are called ventricles –left and right. The 2 atria are completely separated by a structure called inter-atrial septum.

Similarly the ventricles are separated by the inter-ventricular septum. Thus blood in the left side of the heart is completely separated from the blood in the right side (fetal circulation is different).

The opening between the right atrium and the right ventricle is guarded by a valve called the tricuspid valve. That between the left atrium and the left ventricle is guarded by mitral valve.

These valves allow blood to flow from the atria to ventricles but close when the ventricles are about to contract and pump blood into the corresponding blood vessels-left ventricle to aorta and right ventricle to pulmonary trunk- and prevent blood from going to the atria. If the valves do not function properly there will be regurgitation of blood into the atrium during ventricular contraction.

There is a valve between the left ventricle and the entry to aorta (aortic valve). Similarly another valve is situated between the right ventricle and the pulmonary trunk opening (pulmonary valve). These valves prevent blood from coming back to the ventricles after they pump blood into these main vessels. Malfunction of these valves leads to regurgitation blood into the corresponding ventricle.

The closure of these valves gives rise to heart sounds. Closure of atrio-ventricular valves (tricuspid and mitral) causes the first heart sound while the closure of the pulmonary and aortic valves causes the second heart sound.

The left ventricle pumps blood into the biggest artery in the body called aorta, which has a diameter of about 3 centimeters. It arches backwards and to the left over the root of the left lung and descends in the thorax and then through the diaphragm into the abdominal cavity. The diaphragm is a muscular dome shaped structure which separates the thorax and the abdomen. The lungs and heart rest on it.

On its way it gives off branches to supply blood to every organ. The branches go on dividing and subdividing into smaller branches. The smallest blood vessels are called capillaries.

They are so small that they cannot be seen by the unaided eye but can only be seen under a microscope. The red blood cells have to move in a single file inside the capillaries. The total length of blood vessels in human body is estimated to be about 60,000 miles (SIXTY THOUSAND MILES). This is more than twice the distance around the earth.

After supplying oxygen and nutrients to all the cells blood has to return to heart to be pumped into the lungs (human respiratory system) so that it gives up carbon dioxide and takes up oxygen again.

Blood drains into slightly different type of blood vessels called veins. Veins have thinner walls compared to arteries. Smaller veins join progressively bigger veins. Blood from the lower limbs and abdomen enter a big vein called inferior vena cava.

Blood from head, thorax and upper limbs enter into another big vein called superior vena cava. These two big veins empty blood into the right atrium from where the blood enters the right ventricle which then pumps it into a big blood vessel called the pulmonary trunk.

The pulmonary trunk divides into right and left pulmonary arteries one for each lung. They go on dividing and subdividing into smaller tubes till they reach the alveoli where the blood takes up oxygen. The oxygenated blood then drains into progressively bigger blood vessels.

All the blood from the lungs is collected by four blood vessels called pulmonary veins, which empty blood into the left atrium. From the left atrium the blood flows into the left ventricle. The entire cycle goes on and on till the end of life.

Take care of your heart: Your heart does so much for you. You should know how to take care of it. Heart attack is a leading cause of mortality and morbidity. Today it is seen at a much younger age than a decade ago. Unbalanced diet and unhealthy life style are contributing to this.

Daily exercise is very important for the health of the heart. Aerobic exercises like running and swimming strengthen the muscles of the heart and maintain the elasticity of the blood vessels.

Beware of what you eat (diet and health). Do not consume too much of fat. Eat plenty of fresh fruits and vegetables.

Negative emotions like anger, jealousy and greed have an adverse effect on heart. Cultivating a spiritual attitude goes a long way in overcoming these negative emotions (spiritual development).

Cigarette smoking increases the risk of heart disease. Obesity is another risk factor.

Though many people say that moderate alcohol drinking is good for heart and blood vessels excessive drinking of alcohol definitely causes damage to heart muscle-a condition called alcoholic cardiomyopathy.

Return from human heart to human body