Page 55 - 11-Bio-14 Transport
P. 55
14. Transport eLearn.Punjab
Table 14.3 Comparison in structure and function of an artery, capillary and vein
Arteries Veins Capillaries
1. These transport blood away 1. These collect blood from 1. These link arteries with veins.
from the heart to the various body through capillaries and
parts of the body through transp ort it towards heart.
capillaries.
2. All arteries carry oxygenated 2. All veins carry deoxygenated 2. Thesehavemixedoxygenated
blood except pulmonary blood except pulmonary and deoxygenated blood.
arteries. veins.
3. There are no valves in them 3. Valves are present. These 3. There are no valves.
except at the base of prevent the back flow of
pulmonary trunk and aorta. blood.
4. Have high blood pressure. 4. Have low blood pressure. 4. Falling pressure in these.
5. Wave of blood pressure or 5. No pulse. 5. No pulse.
pulse due toheartbeat can
be detected.
6. Blood flow rapid. 400-500mm 6 . Rate of blood flow increases 6. Blood flow slowest less than
per second in aorta and from smaller to larger veins. 1 mm per second.
decreasing in arteries and
arterioles.
7. Have smaller bore and thick 7. Have larger bore and thin 7. Larger bore; wall one cell in
wall. walls. thickness.
8. Thick muscle layer and elastic 8. Thin muscle layer and less 8. No muscles or elastic fibres.
fibres present. The elasticity elastic fibres. So they are less
helps changing the pulsating elastic.
flow of blood.
9. No exchange of materials. 9. No exchange of materials. 9. Responsible for exchange of
materials.
Blood Pressure and Rate of flow of Blood
It is the measure of force with which blood pushes up against the walls of blood vessels. It is
the force that keeps blood flowing from the heart to all the capillary networks in the body. This
pressure is generated by the contraction of ventricles (ventricle systole) and is the highest in aorta,
then gradually reduces in arteries. The walls of arteries are elastic and the flow of blood stretches
them, and it is felt as pulse. During diastole, the relaxation phase of the cardiac cycle, the heart is
not exerting pressure on the blood in the arteries and pressure in them falls. The pressure reaches
55 V: 1.1
