Q.(a) Distinguish between arteries and veins. OR

Arteries carry blood away from the heart under high pressure through thick, muscular, narrow-lumened, valveless vessels, while veins carry blood back to the heart under low pressure through thin-walled, wide-lumened vessels equipped with valves.

Answering part (a): Distinguish between arteries and veins.

Arteries:

1. Direction of flow: carry blood AWAY from the heart to the body's organs and tissues.
2. Oxygen content: carry oxygenated blood, EXCEPT the pulmonary artery, which carries deoxygenated blood from the heart to the lungs.
3. Wall structure: have thick, strong, elastic and muscular walls, able to withstand the high pressure of blood pumped directly from the heart, and to expand and recoil with each heartbeat (giving a pulse).
4. Lumen: comparatively narrow lumen (internal space).
5. Pressure and flow: blood flows under high pressure, in a pulsatile (surging) manner corresponding to the heartbeat.
6. Valves: generally lack valves along their length (except semilunar valves at the base of the aorta and pulmonary artery, where they leave the heart), since the heart's pumping pressure alone keeps blood moving forward.
7. Location: usually located deeper within the body, well protected by surrounding tissue.

Veins:

1. Direction of flow: carry blood TOWARD the heart from the body's organs and tissues.
2. Oxygen content: carry deoxygenated blood, EXCEPT the pulmonary vein, which carries oxygenated blood from the lungs to the heart.
3. Wall structure: have thin, less muscular and less elastic walls compared to arteries, since blood pressure in veins is much lower.
4. Lumen: comparatively wide lumen. …