Describe the three kinds of blood vessels and explain blood pressure.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Open in one line. Blood flows in three kinds of vessels: arteries, veins and capillaries.
2 · Draw the three vessels. [T.S. of an artery (thick wall, narrow lumen), a vein (thin wall, wide lumen, valve) and a capillary (endothelium only). Labels: tunica externa, tunica media, tunica interna]
3 · Arteries vs veins.
Away from the heart vs towards it.
Oxygenated vs deoxygenated blood (except the pulmonary vessels).
Thick, elastic wall vs thin wall.
No valves vs valves; narrow vs wide lumen.
4 · Capillaries. One cell thick; they link arteries and veins; gases, food and wastes are exchanged through them.
5 · Blood pressure. The pressure of blood on artery walls: systolic about 120 and diastolic about 80 mm Hg; measured by a sphygmomanometer; hypertension and hypotension.
6 · Real life. Less salt, regular exercise and a healthy weight help prevent hypertension.
7 · Close in one line. Together, the vessels and the pressure keep blood moving to every cell.
Scoring tip: Set out the differences as a two-column table; each correct row earns marks.
