Question

a) Figure 4 shows the pressure and velocity profiles in the systemic circulation. Discuss how the profiles change from the arteries to the veins, making reference to the anatomy of the vessel walls and how the anatomy changes throughout the vascular tree. In your answer, comment on the region of highest vascular resistance. [12 marks] 120 50 100 80 60 Pressure (mm Hg) Velocity (cm/sec) 40 20 0 -50 Aorta Large Small Small Large Vena arteries arteries veins veins cava Arterioles Venules Capillaries Figure 3 b) What is Osmotic pressure and why is it important in capillary filtration? [7 marks]

Answer 1

a) in the systemic circulation, the pressure profile decreases from the arteries to the veins and the velocity profile decreases from aorta to Capillaries then it increases from venules to vena cava. anatomically we can say that when the blood goes through the vessels and exert force against the vessel wall. the measurement of the force is called pressure. blood always flows from a higher pressure area to a lower pressure region. it flows the same direction as the decrease in pressure gradient that is artery to Capillary to vein. the velocity profile is related to the total cross sectional area of the blood vessels. they are inversely proportional each other. in the arterial system , blood pressure increases with velocity of flow decreases. in the venous system, increased blood pressure with velocity of flow increases. because increased blood pressure helps to return blood to the heart.

highest vascular resistance during systemic circulation seen in the region of arterioles. more viscosity is seen in the area. arterioles are with small dimeter an few in number. so their total cross sectional area is small due to the small diameter and few in number.

b) osmotic pressure is the minimum pressure that need in a solution to prevent the inward force of its pure solvent across the SPM. in other words it is the measure of tendency of a solution to take in pure solvent by osmosis. dissolved compounds have Osmotic pressure throughout the body. the reabsorption from the intestinal fluid back to the Capillaries is greatly affected by osmotic pressure. osmotic pressure draws fluids back in to the capillaries. it also contribute to the transcapillary movement of fluid in the Cardiovascular system.