Lesson 2 ·Class 10 · The Circulatory System · Label Lab
Blood Composition and Its Two Big Jobs
Transport and protection, in one fluid.
Tap any part of the diagram to learn its name and its job. Try: Spin a sample: 55 to 60 per cent settles as plasma on top, 40 to 45 per cent as cells below. Predict which layer the fibrinogen is in.
Free play — explore the diagram, or switch to "Label it yourself" and place every label. Switch to when you're ready to test yourself.
Blood does two jobs, not one. Transport: digested food, oxygen, carbon dioxide, excretory wastes, hormones and body heat. Protection: clotting, phagocytosis, and antibodies and antitoxins. Examiners almost always want both headings, so learn them as a pair.
What this lesson covers
What you do
- Spin a sample: 55 to 60 per cent settles as plasma on top, 40 to 45 per cent as cells below. Predict which layer the fibrinogen is in.
- Name the one component that has no nucleus of its own and yet carries nearly all the oxygen.
The parts you label
- Plasma — The pale yellow, slightly alkaline liquid part — 55 to 60 per cent of the blood. It is 90 to 92 per cent water, 7 to 8 per cent proteins and about 1 per cent inorganic salts, mainly sodium chloride and sodium bicarbonate, with glucose, amino acids, urea, hormones and fibrinogen dissolved in traces. Take the fibrinogen out and the liquid left is called serum.
- Red blood cell — The erythrocyte — a biconcave disc about 7 micron across, packed with haemoglobin. About 5 million per cubic millimetre in an adult male and about 4.5 million in an adult female. It carries oxygen as unstable oxyhaemoglobin and a small amount of carbon dioxide as carbamino-haemoglobin. This is the transport half of the blood.
- White blood cell — The leukocyte — has a nucleus, carries no haemoglobin, and numbers only 4000 to 8000 per cubic millimetre. Most are amoeboid and squeeze out through capillary walls by diapedesis to reach infected tissue, where they engulf bacteria by phagocytosis or make antibodies. This is the protection half of the blood.
- Platelet — The thrombocyte — a minute, non-nucleated oval body, 200,000 to 400,000 per cubic millimetre, budded off from giant megakaryocytes in the red bone marrow. It lives only 3 to 5 days and is destroyed in the spleen. At a wound it disintegrates and releases thrombokinase, which starts clotting.
Challenges to clear
- Find the part that makes up more than half the blood by volume.
- Now find the smallest one — the one that lives only 3 to 5 days.
- Label every component of blood.
Hint
Blood does two jobs, not one. Transport: digested food, oxygen, carbon dioxide, excretory wastes, hormones and body heat. Protection: clotting, phagocytosis, and antibodies and antitoxins. Examiners almost always want both headings, so learn them as a pair.