How does the elasticity of aorta and vena cava relate to its ability to withstand pressure?

Answer 1

It is a very good question to answer. Pressure in Aorta is 120 mm of Mercury and speed of blood flow is 50 cm/ second.Aheadis peripheral resistance of capillaries, which are smaller in diameter than R.B.Cs, flowing through it.(It's a fact.) As left ventricle contract blood ispumpedin the aorta, large and small arteries. Now aorta is thick and muscular and elastic and along with entire arterial system, it dilates. When left ventricle relaxes, aortic valve close down. Now this entire arterial system contracts and maintains the diastolic blood pressure. Peripheral resistance has very important role to play in this. So it takes kinetic energy in systole and gives away in diastole. So in diastole aortic system works as a 'Heart'. In comparison pressure is very low in inferior venacave. Go onmeasuringthe height of from feet to heart. This much is the pressure in inferior vena cave as you ascend in term of mm of 'water' at that particular height in verticle position.(Density of mercury is 13.6.) For superior vena cave blood 'falls down' and pressure may be zero to minus. So both vena cave have very large diameter together. 10 to 12 times that of aorta and they are very thin walled and almost nonelastic.