Heart
Dr.V.S.SURESH Phd., Email :bksureshv@gmail.com
The human heart is a marvelous organ.Its function is to move the living stream of blood through all parts of the body,never stopping even for a moment in its endless activity.Although the heart is one single organ,it actually consists of two chambers,receives blood from all parts of the body and propels it to the lungs.There the blood drops its load of carbon dioxide and receives a fresh supply of oxygen,then passes to the left side of the heart(with its two chambers also) and from there it is pumped to all parts of the body.
Each side of the heart operates independently of the other,but they act together in keeping the blood circulation normally.The walls of the heart consist of powerful muscle fibers that have the power to contract or beat rhythmically.This constant rhythmic beating keeps the circulation going.
Your heart does an enormous amount of work.It beats over one hundred thousand times a day,continually pumping the blood through more than 60,000 miles or tiny blood-vessels.these tiny capillaries are only a tenth of an inch long,but if they could be placed end to end,they would nstretch two and half times around thje earth at the equator.To maintain the right pressure,all these vessels must be filled with the right amount of blood;otherwise the tissus of the body would waste away and die.
How the heart beats
The motions of the heart are maintained by a specially designed structure known as the senatorial node or SA node.This little structure is capable of initiating a regular rhythm,and transmitting these electrical impulses to all the muscle fibres of the heart wall.This is how the constant rhythmic contractions are maintained.
This SA node or pace-maker is located near the top of the heart.It really operates like a small radio station,flashing out its signals in regular electric waves.These are the P waves seen on the electro cardiogram or tracing of the heart.These P waves make the atria or auricles(the left and right upper chambers) contract to fill the ventricles(the two lower chambers)
Lower down near the main valves of the heart,another small structure,the atrioventricular or AV node,picks up these radio signals and transmits them through the special conduction fibres or filaments of all the muscle cells of the powerful ventricles or pumping chambers of the heart.These electrical impulses are the QRS waves seen on the electrocardiogram.Almost instantly after the QRS waves the ventricular walls contract,emptying the pumping chambers into the aorta and out to all the arteries.This is the pulse you can feel at your wrist
Then for a split second the heart relaxes and fills with blood.It is now ready for the next contraction or beat.This whole amazing process is an engineering feat without any equal.Because of the simultaneous electric flash,all the heart muscle cells contract as one unit,even though they are each stimulated individually by these electrical impulses coming from above.
The coronary arteries
Naturally,to maintain all this activity,the heart must feed itself. It must also be constantly supplied with oxygen.The heart's own blood supply is maintained by two very important vessels known as the coronary arteries.Centuries ago early students of anatomy discovered these vessel winding their way around the heart and thought they resembled a crown-hence the name coronary.They are among the most important vessels in the body.If one of these should fail,the heart might stop and that would be the end.
As the blood leaves the left side of the heart,it passes through a large artery known as the aorta.This great vessels,nearly an inch in diameter,passes upward from the heart,then curves over to the left,and passes down behind the heart into the abdomen.As mentioned above,the first branches of the aorta are the left and right coronary arteries.These supply the heart itself withy blood.Other large branches supply the head,neck,upper extremities,and all the organs of the chest and abdomen.Down near the pelvis the aorta divides into two major vessels that supply the pelvic organs and the lower extremities.
This great network of vessels is known as the arterial system of the body.Out in the tissues the smaller arteries divide into endless tiny hair-sized vessels called arterioles,and these in turn divide into still smaller vessels called capillaries.It is through these innumerable tiny capillaries that the exchange of oxygen and food substances takes place.
The waste products and carbon dioxide from the tissues are then picked up by the blood stream and brought back through the smaller veins.These,like the tributaries of a river,join together forming larger vessels until eventually the blood reaches the two largest veins,the superior and inferior vena cava and through them returns to the right side of the heart.
Blood coming toward the heart from distant areas of the body is dark red in colour,as you will see whenever you cut yourself.From the right side of the heart this darker blood is pumped to the lungs.There it gives up itd surplus amount to carbon dioxide and takes on a fresh supply of oxygen.This extra oxygen immediately changes the colour of blood to a brighter red.The freshly oxygenated blood then passes through the large pulmonary veins to the left atrium(auricle)of the heart.As soon as the mitral valve opens,the bright red blood flows down into the left ventricle and is immediately pumped by way of the aorta to the entire body.The left ventricle contracts or beats about 70 times each minute,not for an hour,a day,or a year,but for a entire lifetime!
Each side of the heart operates independently of the other,but they act together in keeping the blood circulation normally.The walls of the heart consist of powerful muscle fibers that have the power to contract or beat rhythmically.This constant rhythmic beating keeps the circulation going.
Your heart does an enormous amount of work.It beats over one hundred thousand times a day,continually pumping the blood through more than 60,000 miles or tiny blood-vessels.these tiny capillaries are only a tenth of an inch long,but if they could be placed end to end,they would nstretch two and half times around thje earth at the equator.To maintain the right pressure,all these vessels must be filled with the right amount of blood;otherwise the tissus of the body would waste away and die.
How the heart beats
The motions of the heart are maintained by a specially designed structure known as the senatorial node or SA node.This little structure is capable of initiating a regular rhythm,and transmitting these electrical impulses to all the muscle fibres of the heart wall.This is how the constant rhythmic contractions are maintained.
This SA node or pace-maker is located near the top of the heart.It really operates like a small radio station,flashing out its signals in regular electric waves.These are the P waves seen on the electro cardiogram or tracing of the heart.These P waves make the atria or auricles(the left and right upper chambers) contract to fill the ventricles(the two lower chambers)
Lower down near the main valves of the heart,another small structure,the atrioventricular or AV node,picks up these radio signals and transmits them through the special conduction fibres or filaments of all the muscle cells of the powerful ventricles or pumping chambers of the heart.These electrical impulses are the QRS waves seen on the electrocardiogram.Almost instantly after the QRS waves the ventricular walls contract,emptying the pumping chambers into the aorta and out to all the arteries.This is the pulse you can feel at your wrist
Then for a split second the heart relaxes and fills with blood.It is now ready for the next contraction or beat.This whole amazing process is an engineering feat without any equal.Because of the simultaneous electric flash,all the heart muscle cells contract as one unit,even though they are each stimulated individually by these electrical impulses coming from above.
The coronary arteries
Naturally,to maintain all this activity,the heart must feed itself. It must also be constantly supplied with oxygen.The heart's own blood supply is maintained by two very important vessels known as the coronary arteries.Centuries ago early students of anatomy discovered these vessel winding their way around the heart and thought they resembled a crown-hence the name coronary.They are among the most important vessels in the body.If one of these should fail,the heart might stop and that would be the end.
As the blood leaves the left side of the heart,it passes through a large artery known as the aorta.This great vessels,nearly an inch in diameter,passes upward from the heart,then curves over to the left,and passes down behind the heart into the abdomen.As mentioned above,the first branches of the aorta are the left and right coronary arteries.These supply the heart itself withy blood.Other large branches supply the head,neck,upper extremities,and all the organs of the chest and abdomen.Down near the pelvis the aorta divides into two major vessels that supply the pelvic organs and the lower extremities.
This great network of vessels is known as the arterial system of the body.Out in the tissues the smaller arteries divide into endless tiny hair-sized vessels called arterioles,and these in turn divide into still smaller vessels called capillaries.It is through these innumerable tiny capillaries that the exchange of oxygen and food substances takes place.
The waste products and carbon dioxide from the tissues are then picked up by the blood stream and brought back through the smaller veins.These,like the tributaries of a river,join together forming larger vessels until eventually the blood reaches the two largest veins,the superior and inferior vena cava and through them returns to the right side of the heart.
Blood coming toward the heart from distant areas of the body is dark red in colour,as you will see whenever you cut yourself.From the right side of the heart this darker blood is pumped to the lungs.There it gives up itd surplus amount to carbon dioxide and takes on a fresh supply of oxygen.This extra oxygen immediately changes the colour of blood to a brighter red.The freshly oxygenated blood then passes through the large pulmonary veins to the left atrium(auricle)of the heart.As soon as the mitral valve opens,the bright red blood flows down into the left ventricle and is immediately pumped by way of the aorta to the entire body.The left ventricle contracts or beats about 70 times each minute,not for an hour,a day,or a year,but for a entire lifetime!
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