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The Heart's Anatomy

The heart is a fist sized power house which is hollow, cone-shaped and is located between the lungs and behind the breastbone. The heart is made up of three layers known as the endocardium, myocardium and pericardium. The inside lining is called the endocardium; the middle layer of heart muscle is called the myocardium and the heart muscle is surrounded by a fluid filled sac called the pericardium.

Heart Chambers: The heart has two sides namely the right and the left side and is divided into four chambers:

  • The right atrium: It receives oxygen-poor blood from the veins and pumps it to the right ventricle.
  • The right ventricle: This ventricle gets blood from the right atrium and pumps it into the lungs, where it is enriched with oxygen.
  • The left atrium: It receives oxygen-rich blood from the lungs and then pumps it into the left ventricle.
  • The left ventricle: It is the strongest chamber which pumps oxygen-rich blood to the rest of the body and the vigorous contractions of the ventricle create our blood pressure.

Valves: At the exit of each chamber there is a one-way valve which prevents blood from flowing backwards. During chamber contractions, the valve at its exit opens and when it is finished contracting, the valve closes to prevent the blood from flowing backwards. The four valves involved are:

  • Tricuspid valve: It separates the right atrium from the right ventricle and it opens allowing the de-oxygenated blood to flow into the right ventricle from the right atrium. It closes as the right ventricle contracts thus preventing blood from returning to the right atrium and forcing it to exit through the pulmonary valve into the pulmonary artery.
  • The mitral valve: It separates the left atrium from the left ventricle and it opens allowing oxygen-rich from the left atrium to flow into the left ventricle and as the left ventricle contracts the valve prevents blood from flowing into the left atrium; thereby, forcing the blood to exit through the aortic valve into the aorta.
  • The pulmonary valve: It separates the right ventricle from the pulmonary artery and as the ventricles contract; it opens to allow the de-oxygenated blood into the right ventricle which then flows into the lungs. It also closes as the ventricles relax which prevents blood from returning to the heart.
  • The aortic valve: It separates the left ventricle from the aorta and as the ventricles contract; it opens allowing the oxygen-rich blood collected in the left ventricle to flow throughout the body. The valve closes when the ventricles are relaxed and prevents blood from returning to the heart.

Blood vessels: These are tubes which carry blood to and from different body parts to the heart. Veins are blood vessels which carry blood from the body back to the heart and arteries are blood vessels which carry blood from the heart to the body. The aorta is the largest artery in our body which carries blood from the left ventricle to the rest of the body through smaller arteries. The right ventricle pumps blood into a large artery known as the pulmonary trunk and this split into pulmonary arteries which take the blood to the lungs. The pulmonary veins let the blood to flow from the lungs to the left atrium. All the other veins in our body dumps blood into the inferior vena cava or the superior vena cava. The superior vena cava brings de-oxygenated blood from the head and upper body and empties into the right atrium of the heart whereas the inferior vena cava brings de-oxygenated blood from the legs and lower torso to the right atrium.

Coronary Arteries: The heart is made of cardiac muscles tissues which need a constant supply of oxygen and nutrients and coronary arteries are the network of blood vessels that carry this oxygen- and nutrient-rich blood to the cardiac muscle tissue. Larger coronary vessels travel along the surface of the heart; whereas, the smaller branches penetrate the heart muscle. The capillaries are the smallest branches and they are so narrow that the red blood cells must travel in single file to pass through them.

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