Heart Beats

The contractions of the heart chambers are known as heart beats which are rhythmically and regular. A human normal heart beats 72 times per minute at rest. These beast are audible and are known as heart sounds.
During the ventricular systole blood is forced against the closed AV-valves. This procedures the first heart sound LUB. Ventricular systole is followed by ventricular diastole. The high pressure developed in the aorta, tends to force some blood back towards the ventricles which closes the aorta valves. This impact of the back flow against the valves causes the second heart sound DUP.

Human Heart

The human heart is the most powerful organ in the circulatory system. It works continuously like a muscular pump and keeps the blood in circulation. The heart lies in the thoracic cavity between the lungs slightly towards left, enclosed with in the rib cage with the sternum in front and vertebral column behind. It is surrounded by a double layered Pericardium. A pericardia l fluid is secreted in between the two. It functions as a lubricant and reduces friction between the heart walls and surrounding tissue during the beating of heart.

Transport In Man

Blood Circulatory System (Cardio-vascular system)
The fluid circulatory system, with blood as the transporting material has assumed its highest development in man. It consists of a powerful heart, arteries, veins and capillaries.

Blood: Blood is viscous, red fluid connective tissues, comprising a colorless plasma in which the blood corpuscles float.

Plasma: It constitutes about 55% of the blood. It is a viscous fluid containing a mixture of inorganic salts in true solution form and blood proteins (albumins, globulins and fibrinogen) in colloidal form. In addition, plasma contains glucose, amino acids, triglycerides, urea, hormones, enzymes and auto toxins. The water is the most abundant component and forms 90% of plasma. The dissolved substances are only 10%.
Blood Corpuscles: These are the blood cells which form the remaining 45% of the blood.