Explain the composition and functions of blood.

1. 1 · Define in one line. Blood is a fluid connective tissue made of plasma and formed elements.
2. 2 · Plasma. About 55% of blood; about 90% water, with proteins, food, salts, hormones and wastes.
3. 3 · Formed elements.
   • Red cells: biconcave, no nucleus, haemoglobin; carry oxygen; live 120 days.
   • White cells: neutrophils, eosinophils, basophils, lymphocytes and monocytes; defence.
   • Platelets: cell fragments; clotting.
4. 4 · Draw the blood cells. [Red cell (biconcave disc, no nucleus), neutrophil (lobed nucleus), lymphocyte (large round nucleus), platelets (small fragments)]
5. 5 · Functions. Transport of gases, food, hormones and wastes; defence; clotting; temperature and pH balance.
6. 6 · Real life. Iron-rich foods such as greens and pulses help make haemoglobin and prevent anaemia.
7. 7 · Close in one line. Blood is the body's transport and defence system.

Scoring tip: A small table of the three formed elements with one job each scores well. Name haemoglobin and antibodies.