Heart Anatomy – Location, Function, Chambers, Diagram

The most amazing organ in our body is our “heart.” Since time immemorial, heart has been associated with many songs, poems, love and what not. If a person is in love, a sign of heart with an arrow mark shows the love.  If a person is depressed in love, he/she is said to be heartbroken.  This amazing organ is always used to describe human emotions. The human heart is the essential organ of our body. So what is this heart? What does it do in our body?  How does this heart function?  Let us know more about the amazing facts about heart.

Where Is The Heart Located?

Heart is located in the center of the chest. It is present behind the breastbone or sternum. A part of the heart is slightly tilted towards the left side of the chest. It is located in the middle of the mediastinum at the level of thoracic T5-T8 vertebrae.  A layer of membranous sac called pericardium surrounds the heart and this pericardium attaches to the mediastinum. The front surface of the heart is behind the sternum and rib cartilages.  The back surface of the heart is situated behind the vertebral column.  The upper part of the heart is near the third costal cartilage and the lower part of the heart, which is the tip or apex of heart, is located to the left of the sternum between the fourth and fifth ribs.

The heart is cone shaped and is the size of a fist.  The base of the heart is facing upwards and the apex of this cone is downwards.  Its largest part is offset to the left side of the chest.  The left side of heart is stronger and larger since it pumps blood to all body parts.  The heart is located in between the lungs.  The left lung is smaller than the right and has a cardiac notch in its border for the heart to fit there. An adult heart weighs about 250 to 350 grams.

What Are The Different Parts Of The Heart?

The human heart can be divided into:

• The four chambers of heart
• Muscular walls
• Blood vessels
• The conductive system

The Four Chambers Of Heart

Two upper chambers are called the atria (singular atrium)

• Right atrium
• Left atrium

Two lower chambers are called the ventricles

• Right ventricle
• Left ventricle

The Muscular Walls Of The Heart

The heart wall is made of three layers:

• Epicardium – The epicardium is the outer protective layer of the heart
• Myocardium- The myocardium is the middle muscular layer of the heart
• Endocardium – The endocardium is the inner layer of the heart

EpicardiumEpi means outer and cardium means heart, hence epicardium means the outer layer of the heart.  It is also the inner visceral layer of the pericardium which attaches the heart to the mediastinum. The epicardium is made up of loose connective tissue and adipose (fat) tissue. The function of epicardium is to protect the inner layers of heart and production of a fluid called pericardial fluid which helps reduce friction between the pericardial membranes. Epicardium also consists of coronary blood vessels which supply blood to the heart walls.

MyocardiumMyo means muscle, cardium means heart, myocardium means muscle layer of heart as this layer of heart contains the cardiac muscle fibers, which helps in contraction of heart.  Myocardium is the middle layer of the heart. Myocardium is the thickest layer of the heart wall and the myocardium of the left ventricle is thicker than the rest as it requires power to pump oxygenated blood to all parts of our body. Myocardium contains specialized type of muscle fibers which help in cardiac conduction. This bundle of fibers is made up of atrioventricular bundle and Purkinje fibers which carry electrical impulses that trigger the muscle fibers to contract.

Endocardium“Endo” means inside or inner. Endocardium is the innermost layer of heart. It is a thin layer that covers the chambers and valves of the heart and is continuous with the endothelium of the large blood vessels. Infection of endocardium is called as Endocarditis which can be a serious condition.

Blood Vessels Of Heart

The five major blood vessels of heart are

• Aorta
• Superior vena cava
• Inferior vena cava
• Pulmonary artery
• Pulmonary vein

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The three main types of blood vessels are

• Arteries
• Capillaries
• Veins

The AortaThe aorta is the largest artery in the body. It begins in the upper part of the left ventricle. The heart pumps blood into the aorta from the left ventricle through the aortic valve. The aorta is a tube like structure, an inch in diameter and about a foot long.  It is again divided into four parts:

• Ascending aorta
• Aortic arch
• Descending thoracic aorta
• Abdominal aorta

The ascending aorta arises from the heart about 2 inches long.  The coronary arteries are branches of ascending aorta supply the heart with blood. The aortic arch is a curved shape vessel over the heart which gives many branches that bring blood to head, neck and arms. The descending aorta goes down through the chest.  Its branches supply blood to ribs and chest structures. The abdominal aorta starts at the diaphragm which branches to become iliac arteries of the abdomen and supplies blood to the major organs of the body.

Superior Vena CavaThe superior vena cava is one of the two venae cavae which returns deoxygenated blood from upper half of the body above the diaphragm to the right atrium. The superior vena cava is formed by the left and right brachiocephalic veins. There is no valve to divide the right atrium and superior vena cava. Thus, the right atrial and right ventricular contractions reach the internal jugular vein through the sternocleidomastoid muscle and seen as jugular venous pressure.

Inferior Vena CavaThe inferior vena cava (posterior vena cava) carries deoxygenated blood from the lower part of the body to the right atrium.  It is located behind the abdominal cavity and runs along the right vertebral column of spine.  Iliac veins of leg combine to form the inferior vena cava.

Pulmonary ArteryPulmonary artery carries deoxygenated blood from the heart to lungs. The main pulmonary artery starts from the base of the right ventricle and then splits into right and left main pulmonary artery. The left main pulmonary artery is shorter and passes in front of the aorta to the root of the lung. The right main pulmonary artery is longer and has a horizontal course.  It reaches the hilum of the lung and divides again into two branches. The pulmonary artery pressure is a measure of Blood Pressure in the main pulmonary artery.  The wedge pressure is measured in the left atrium and is elevated in conditions like left heart failure, mitral stenosis etc.

Pulmonary Hypertension :  It is an increase in pulmonary artery pressure if mean PAP is more than 25 mmHg.  It may be due to heart failure, COPD, lung disease.

Pulmonary embolism :  It is an embolus found in the pulmonary circulation. It is a serious condition which may occur in patients with Cancer and Stroke may be fatal.

Pulmonary VeinPulmonary vein is the only vein that carries oxygenated blood from the lungs to the left atrium (other veins carry deoxygenated blood).  There are four pulmonary veins, two in each lung.  The right pulmonary veins pass behind the right atrium and superior vena cava.

Read more on Heart Attack

The Cardiac Conduction System

The cardiac conduction system is a group of specialized cardiac muscle cells that are present in the heart walls and that send signals to the heart muscles causing contraction.  This conduction system is made up of :

• SA node
• AV node
• Bundle of His
• Bundle branches
• Purkinje fibers

The SA node which is the heart’s anatomical pacemaker starts the sequence and causes contraction of atrial muscles.  The signal now travels to the AV node, bundle of His, bundle branches and Purkinje fibers and causes the ventricles to contract.  This signal is seen as an electrical current on graph called ECG or EKG which used to monitor patient’s electrical conduction system.

What Are The Four Chambers Of Heart?

The four chambers of heart as discussed above are:

• Right atrium
• Left atrium
• Right ventricle
• Left ventricle

The right atrium receives deoxygenated blood from the body and pumps into the right ventricle. The right ventricle pumps deoxygenated blood to the lungs. The left atrium receives oxygenated blood from the lungs and pumps into the left ventricle. The left ventricle pumps oxygenated blood to the body. The left ventricle is the largest of the four chambers of the heart and has about three times more muscle than the right ventricle. The atria/ atrium are one-third the size of ventricles.

What Is The Function Of The Heart?

The cardiovascular system is made up of heart, blood vessels and blood. The heart pumps deoxygenated and oxygenated blood to and from the body.  The heart acts like a pump, it pumps out and pumps in blood.  The arterial blood which is oxygenated and rich in nutrients is pumped out by the heart to different parts of the body and supplies nutrients to each and every cell in our body.  After the oxygen and nutrients are utilized by all the cells and organs in the body, the blood gets deoxygenated and this deoxygenated blood again reaches the heart through the atria.

The venous blood returns from the body to the right side of the heart which then pumps blood to the lungs.  The oxygen rich blood then returns from the lungs and reaches the left side of the heart.  The left side of the heart (left ventricle) pumps blood to the whole body and hence has to generate more pressure.  The flow of blood is controlled by the valves present in the heart called mitral, tricuspid, aortic, pulmonary valves.  The valves also prevent the backflow of blood from ventricles to atria during systole.

Heart is an important pumping organ that keeps all other organs in the human body alive.  Due to the pumping mechanism of the heart, blood containing oxygen and other nutrients reaches all the organs in our body helping them to carry out their functions.

Why Is The Left Ventricle The Strongest Part Of Your Heart?

The left ventricle is said to be the strongest pumping part of the heart.  It is also the largest chamber in the heart.  It pumps blood to the entire body hence it must have the most power.  The left ventricle contracts causing blood to pass through the left ventricular outflow tract across the aortic valve and into the aorta from where it reaches all the body parts through smaller arteries.

The upper part of the left ventricle is the base chamber and the farther lower part is the apex.  The left ventricle contracts, apex to base, causing as much blood to be pumped into the aorta.  This contraction is caused by the conduction system of the heart which causes depolarization from the atria to the ventricular myocardium.

The Left Ventricular Structures Are

• Mitral Valve – It is the atrioventricular valve and is bicuspid that is, having two cusps.  The blood flows from left atrium to the left ventricle through the mitral valve.
• Left Bundle Branches – The left bundles are responsible for the electrical activity to reach the left ventricle.  The main bundle splits into right and left branches and the left again subdivides into anterior and posterior bundles.  The conduction through the bundle is protected and thus the electrical activity does not reach the surrounding myocardium.
• Left Ventricular Papillary Muscles – These muscles are located near the apex of the ventricle.  The electrical activity exits here and the depolarization reach back to the base from the ventricular myocardium.
• Left Ventricular Outflow Tract (Lvot) – It is located below the aortic valve.  It is situated behind the right ventricular outflow tract and more posterior.  R wave visible in V1 and V2 in EKG originates from LVOT.
• Membranous Septum – This thin tissue separates the left ventricle from the right atrium.
• Aortic Valve – The aortic valve contains three cusps, the left, right and posterior cusps.  It is present between the left ventricle and aorta.

Some Interesting Facts About Heart

• The average heart is about the size of a fist
• Your heart pumps about 2000 gallons (1 gallon equals 3.7 liters) of blood every day
• The cardiac conduction system is an electrical system which controls the heart rhythm
• The first open-heart surgery was performed by Daniel Hale Williams in 1893
• The fair fly wasp has the smallest heart in any living creature
• Whales have the largest heart among mammals
• A woman’s heart beats slightly faster than a man’s
• The valves opening and closing cause the lub-dub sound of the heart
• Laughing is good for your heart.

Conclusion

The heart is no doubt the most important organ in our body.  Because of heart, other organs are able to function.  If the heart stops pumping blood, the organs and tissues will die as they will not receive oxygen and other nutrients and this will eventually lead to fatality.

As told by Dr. Lawrence Phillips, an eminent cardiologist, “the human heart basically comes down to structure, electricity and plumbing.”

A healthy heart means a healthy body.  Maintain your heart healthy by proper diet, regular exercise and leading a Stress-free life.