The heart, made up mainly of cardiac muscle tissue, is an organ to pump blood to the whole of the body. The inside of the heart is divided into 4 chambers, 2 atria and 2 ventricles.
Atria and Ventricles
The atria are the chambers that receive blood from circulation. The ventricles are thicker walled chambers, located below the atria and connected with them by openings covered by heart valves. Their function is to pump blood from the heart into circulation.
Right Heart and Left Heart
The heart is divided into right and left sides by a septum. Each side consists of one atrium and one ventricle. So the chambers of the heart are named:
- Right atrium
- Right ventricle
- Left atrium
- Left ventricle
The concept of right and left hearts is important because it helps understand the way the heart works. While the right side of the heart is responsible for pulmonary circulation to the lungs, the left side of the heart deals with systemic circulation or circulation to the whole body. Normally, there is no communication between the right and left sides of the heart. Communications are present in abnormal conditions like atrial and ventricular septal defects, conditions that commonly go by the name ‘hole in the heart’.
Right Heart – Right Atrium and Right Ventricle
The right atrium basically receives venous blood from the whole of the body. It has the superior vena cava and inferior vena cava opening into its cavity. While the superior vena cava brings in venous blood from the upper limbs, head and neck regions and walls of the chest and upper abdomen, the inferior vena cava drains the abdomen and the lower limbs.
The right atrium also receives venous blood from the coronary sinus, anterior cardiac veins and venae cordis minimae which drain the heart muscle tissue.
The blood entering the right atrium is deoxygenated – that is, its oxygen has been used up by the tissues of the body and this blood is rich in carbon dioxide.
The right atrium opens into the right ventricle below through the atrioventricular orifice or opening covered by the tricuspid valve that ensures blood flow in one direction only. So when the right atrium contracts, this venous blood moves into the right ventricle.
The right ventricle is almost triangular in shape. It opens into the pulmonary artery. The deoxygenated blood in the right ventricle is carried by the pulmonary artery to the lungs for the process of gas exchange, where carbon dioxide is exchanged for oxygen.
Left Heart – Left Atrium and Left Ventricle
The left atrium contains the openings of the superior and inferior pulmonary veins above. These blood vessels bring oxygenated blood from the lungs into the left atrium. Below, the left atrium opens into the left ventricle through an opening covered by the mitral valve. When the left atrium contracts, the oxygen-rich blood in it is pumped into the left ventricle.
The left ventricle is larger and more muscular than the right ventricle. It opens into the aorta, the largest artery in the body. The left ventricle receives oxygen-rich blood from the left atrium which it pumps into the aorta for circulation to the entire body.
For more details about how the heart pumps blood, read about cardiac physiology and the cardiac cycle.
Sources
Romanes, G.J. “Cunningham’s Manual of Practical Anatomy” (Oxord University Press; 15th Edition, 2003)
Lakshmi Ananth - Lakshmi Ananth is a practising ENT, head and neck surgeon and has faculty position at a medical college. She is specially interested in ...
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