Lesson 1 of 12 · 6 min

Blood and plasma

NCERT §15 (opening text) and §15.1–§15.1.1

After the 800 m, Meher's legs are burning and her heart is hammering. Every one of her working muscle cells needs O₂ and food brought in and wastes carried out, all at once. What does the carrying?

The story this chapter follows: Meher's 800 m at Sports Day

Meher has just run the 800 m at her school's Sports Day. Her heart is pounding, her muscles are burning and she has grazed her knee on the last bend. Over the following weeks she gives blood at the school camp and has a routine ECG at a check-up. This chapter follows the blood and lymph that kept her going, and the heart that pumped them.

The lesson in notes

In short

Every living cell needs a steady supply of nutrients, O₂ and other essentials, and its wastes must be carried away. Animals solve this in different ways: sponges and coelenterates pass water from their surroundings through body cavities, while more complex animals move special body fluids.

Most higher animals, humans included, use blood for this transport; a second fluid, lymph, carries certain substances too.

Blood is a special connective tissue: a fluid matrix, plasma, with formed elements suspended in it.

Plasma is a viscous, straw-coloured fluid making up nearly 55 per cent of blood. Water forms 90–92 per cent of plasma and proteins 6–8 per cent.

The major plasma proteins and their jobs: fibrinogen for clotting (coagulation); globulins mainly for the body's defence; albumins for osmotic balance.

Plasma also carries small amounts of minerals such as Na⁺, Ca⁺⁺, Mg⁺⁺, HCO₃⁻ and Cl⁻, and glucose, amino acids and lipids that are always in transit through the body.

Clotting factors are present in plasma in an inactive form. Plasma from which the clotting factors have been removed is serum.