Table of Contents (click to enlarge)
- The human heart – a miracle!
- What does the heart look like from the inside?
- The flow of blood in and out of the heart
- Why does our heart go LUB-DUB-LUB-DUB?
- Final remarks
The heart is a muscle that contracts and relaxes as it pumpsbloodthrough the body. The right side of the heart pumps blood to the lungs for oxygen. The left side of the heart pumps blood to the rest of the body. The heart has four chambers: the right and left atria and the right and left ventricles. The heart has four valves: the tricuspid valve, the mitral valve, the pulmonary valve, and the aortic valve. The heart beats about 72-80 times a minute, or 115,000 times a day.
You've had a long and tiring day at work/school/university/playground etc. and all you want to do is go home and go to bed. Imagine how tired your heart must be! Yes, your heart, the organ that continually pumps blood throughout your body and helps you work/play/walk/rest - it basically helps you live! You will be surprised to know that your tiny little heart was working and pumping blood long before you were born!! Her heart started beating barely 18-21 days after her conception. Your tiny little heartbeat lets your parents know of your existence in the womb. Since then, your heart has been working tirelessly and, mind you, don't treat yourself to a power nap in between!
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The human heart – a miracle!
We know that our bodies are made up of skin, bones, cartilage, tendons, etc. Have you ever wondered which of these substances makes up your heart? Your heart is a muscle, but not just an ordinary muscle like your biceps or triceps. The heart is the hardest working muscle in the body and works 24/7 until life ends. It has no bones, just layers of muscle fibers laid over a fibrous skeleton to give the heart's chambers their shape. The heart is located roughly in the center of the chest cavity and is about the size of your fist. The heart beats about 72-80 times a minute, or 115,000 times a day! If you lived to be 70, your heart would beat more than 2.5 billion times. The adult heart is conical in shape and measures about 12 cm. in length and 8 to 9 cm. in width at the widest point. In males, it weighs slightly more than in females, ranging from 280 to 340 grams, while in females it ranges from 230 to 280 grams.
Also read:Two & Three Chamber Hearts: How Do They Work?
What does the heart look like from the inside?
The heart is divided into two sides - the right side and the left side. This is then further divided by a constriction into the upper and lower chambers, resulting in 4 heart chambers. The 2 upper chambers are called the atria and the 2 lower chambers are called the ventricles. Thus, the 4 chambers of the heart are:
- Right atrial
- right ventricle
- Left Atrium
- Left Ventricle
The two atria are thin-walled structures separated into right and left halves by a septum that runs between them, called the interatrial septum. The two ventricles are relatively thick-walled and separated by the interventricular septum that runs between them. A large circulatory vessel, either an artery or a vein, enters and exits each chamber of the heart, thereby helping to transport blood. Blood flow through the heart is controlled by a one-way valve system, which is extremely necessary to prevent backflow of blood from the ventricles. The valve present between the right atrium and right ventricle is called the tricuspid valve; a similar valve on the left is called the mitral valve.
The flow of blood in and out of the heart
- Right Atrium – The blood circulating in the body becomes deoxygenated and enters the right atrium via two vessels called the superior and inferior vena cava.
- Blood flows from the right atrium through the tricuspid valve into the right ventricle. This valve only allows blood to flow from the right atrium to the right ventricle, but not vice versa.
- Right Ventricle - The blood in this chamber is then pumped from the heart through the pulmonary artery to the lungs, where the blood is reoxygenated and sent back to the heart. Entry into the pulmonary artery is controlled by a valve called the pulmonary valve.
- Left Atrium - This chamber now receives the blood that has been oxygenated from the lungs and is now oxygenated. The blood is supplied via the pulmonary veins.
- The blood flows from the left atrium through the mitral valve into the left ventricle, which also only allows a unidirectional flow from the atrium to the ventricle.
- Left Ventricle - This chamber of the heart is now filled with oxygenated blood for use by the various tissues throughout the body. This oxygenated blood is sent from the aorta to the systemic circulation and is controlled by the aortic valve.
The best way to visualize this complex mechanism is to think of the heart as two pumps working side by side. The right side of the pump receives blood that has been used up by the body and is now depleted of oxygen. This deoxygenated (bad) blood enters the right side of the heart and is pumped and sent to the lungs where it is oxygenated and is now oxygenated (good) blood ready to be circulated and used by the body. The left side of the pump receives oxygenated blood and its main function is to pump that blood around the body. The main purpose of all this blood going in and out of the heart is to carry nutrients and oxygen to all tissues of the body and to carry waste products out of the tissues. This entire circulation system is divided into two types:
- Systemic Circulatory System – The left side of the heart pumps good blood into a vessel called the aorta, which then supplies blood to all of the body's systems.
- Pulmonary Circulation – The right side of the heart pumps bad blood to the lungsarteries, where it eventually travels to the lungs to pick up oxygen and eventually returns to the heart.
Why does our heart go LUB-DUB-LUB-DUB?
Our heart beats around 60-80 beats/min (average 72 beats/min); Each time it beats, it makes a sound similar to LUB-DUB, and between each LUB and DUB of the heart, the heart pumps blood through our circulatory system. Have you ever wondered where these sounds come from? Well, the valves that we talked about earlier, namely the tricuspid, mitral, pulmonary, and aortic valves, are responsible for these sounds. When the tricuspid and mitral valves close between their respective atria and ventricles, the sound LUB is produced; The DUB tone is produced whenever the pulmonary and aortic valves close to prevent backflow to the ventricles. Of course, these valves don't close as loudly as you slam your bedroom door, but the LUB-DUB sounds can definitely be heard listening to the recorded audio of a heartbeat or pressing your ear to someone else's chest!
Also read:How does the human circulatory system work?
We must understand that this is not all when it comes to the functioning of the heart. Aside from this basic structure, there is a blood supply, conduction system, etc., which is beyond the scope of this article, but it's safe to assume that for a fully functioning heart we need all of these things to work in a 24/7 syncronized fashion ! Any abnormality in the heart's blood vessels or conduction system leads to various heart conditions and diseases that make it difficult for the heart to do its job of circulating blood and keeping us alive.
References (click to enlarge)
- Basic Anatomy of the Heart - Health Encyclopedia - URMC. The University of Rochester Medical Center
- V. Angiology. 4b. The heart. Grey, Henry. 1918. Anatomy by .... Bartleby.com
- Tripathi (2006). Text-book of physiology for students of dentistry. Elsevier India
- (2021) Anatomy, Thoracic, Cardiac - StatPearls - NCBI Bookshelf. The National Center for Information on Biotechnology
- How the Heart Works - The Heart | NHLBI, NIH. The National Heart, Lung and Blood Institute
- (Video) How does the heart pump blood?
- (Video) Blood Flow through the Heart in 2 MINUTES
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