cardiovasicular system
The blood is pumped by contraction of the heart muscles from left vertical at pressure of 125 mmHg and finally into very fine meshwork or capillary bed for few seconds the blood supplies O2 to cells and pick CO2. Adult has about 4.5 liters of blood, each section of the heart pumps 80 ml on each contraction. The combination of R.B.C and plasma causes blood to have flow properties different from those of fluid like water starting law , fluid movement through capillary wall = the hydrostatic pressure p across the capillary wall+ osmotic pressure bringing fluid in.
Work done by the heart:
Left side of heart has greater thickness muscles systole pressure =120 mmHg, right side of heart diastole pressure =80 mmHg , this caused by following :
1. the left side of the heart three times thicker from right side
2. the circular shape of left ventricle producing pressure greater than elliptical shape of right ventricle
the work done by heart W= P V
Blood pressure and its measurement:
the instrument called sphygmomanometer the sound heard with stethoscope called korotkoff or k sound, the on set of k indicated systolic pressure precision ± 2 mmHg . The fade of k indicates diastolic pressure precision ± 5 mmHg.
Pressure across blood vessel wall
The drop pressure in capillaries which have thin walls 1 micrometer permit easy diffusion of O2 and CO2 , the capillary don t burst according to Laplace s law for tube of radius R:
F=2RP where p blood pressure.
T=RP ......... tension in the wall
Bernoulli s principle applied to cardiovascular system is based on the law of conservation of energy. Increasing K.E. obtained by reduction of P.E. the pressure in the tube
Average K.E. of 1 gm = 1cm3 of blood as it leaves the heart , E.K.= 1/2 mv2 , v=30 cm/sec , so K.E.= 450 erg/cm3
How fast does your blood flow
Capillaries about 20 micrometer diameter with cross sectional area 30 cm2. The blood velocity V inversely related to the cross sectional area of the vessel carrying blood.
V=flow rate/cross sectional area
The viscosity of blood = 3*10-3 pas depends on R.B.C. in blood or hematocrit a change from 37 C to 0 C increase the viscosity of blood by a factor of 2.5 , If increase the velocity of fluid in tube by reducing the radius it will reach the critical velocity vc when laminar flow changes into turbulent flow, the critical velocity will be lower if there are restriction obstruction in the tube.
VC=K?/?R
R: radius of tube
K= 1000 (const.) for many fluid
For aorta has radius =1 cm
Vc=1000*4*10-3/103 kg/cm*10-2 m= 0.4m/sec