GROSS ANATOMY

Detailed explanation-1: -Blood flow is slowest in the capillaries, which allows time for exchange of gases and nutrients. Resistance is a force that opposes the flow of a fluid. In blood vessels, most of the resistance is due to vessel diameter. As vessel diameter decreases, the resistance increases and blood flow decreases.

Detailed explanation-2: -For example, blood flow is slow at the capillaries because of the high total cross-sectional area, which allows for proper nutrient exchange. Blood flow is pressure gradient over resistance or the difference between mean arterial pressure and right atrial pressure over peripheral vascular resistance.

Detailed explanation-3: -The velocity of blood is slowest in the capillaries and the pressure of blood is lowest in the veins. slower blood flow through the capillaries allows more time for diffusion to take place in the capillary bed.

Detailed explanation-4: -In the aorta, the blood travels at 30 cm/sec. As blood moves into the arteries, arterioles, and ultimately to the capillary beds, the rate of movement slows dramatically to about 0.026 cm/sec, one-thousand times slower than the rate of movement in the aorta.

Detailed explanation-5: -The slowest flow of blood is at the capillaries to allow more time to exchange substances between the blood and the tissues. The rate of velocity increases as blood flows through the veins but not to the extent seen in large arteries due to decreasing blood pressure and increasing compliance in these vessels. Fig. 2.7.