Circulatory System of Human Body

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Circulatory System of Human Body

Human Heart and its Functioning

Size 12 x 9 cm and 300 gm weight.

Enclosed in a tough, 2 – Layered Connective Tissue Sac, the Pericardium.

Has 4 Chambers : 2 upper Smaller Auricles and 2 Lower Larger Ventricles.

The right auricle receives 2 Large Veins : superior vena cava and inferior vena cava.

The right auricle opens into right ventricle through tricuspid valve.

The right ventricle gives off a large blood vessel which carries deoxygenated blood to the lungs.

This blood vessel is guarded by semi – lunar valve to prevent backflow of blood into ventricles.

Blood again returns to heart from the lungs in left auricle. Now the blood is oxygenated.

The left auricle opens into left ventricle through a bicuspid valve.

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From the left ventricle the blood flows throughout the body through a large blood vessel called aorta.

It is again guarded by semi – lunar valves to prevent back – flow of blood.

To pump – out blood, the heart chambers undergo alternate contraction called systole and relaxation called diastole.

To pump – out blood, the heart chambers undergo alternate contraction called systole and relaxation called diastole.

The regular sequence of these systole and diastole causes the heart sound LUBB and DUPP.

Lubb is produced by the closing of tricuspid and bicuspid valves while dupp is produced by the closing of semi – lunar valves.

Our heart – beat is myogenic in nature ie, it is initiated by a patch of modified heart muscles itself without requiring an external stimulation.

This patch is the sino – auricular node which is called the Pacemaker’. Normal heart beat is 72 /min.

Heart Failure : When S.A. node does not initiate any impulse.

Sphygmomanometer measure the BP. There are 2 limits of BP :

  • Higher Limit
  • Lower Limit
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Higher limit is the systolic BP at the time of ventricular systole while lower limit is the diastolic BP at the time of ventricular diastole. BP is 120/80 mm of Hg.

Note :

Pulmonary Artery : The only artery which carries deoxygenated blood. It carries blood from right ventricle to lungs.

Pulmonary Vein : The only vein which carries oxygenated blood. It carries blood from lungs to left auricle.

All pulmonary volume and capacities are about 20% to 25% less in women than in men, more in athletic people than non-exercising ones and more in non smokers than the smokers.

Diseases of Heart

Course SC / ST OBCOthers
MBBS Two One One

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