Components of Blood
- Blood consists of red blood cells, white blood cells, platelets and plasma
- Over half of the volume of the blood is made up of plasma
- Around 45 % is made up of red blood cells
- The remaining fraction consists of white blood cells and platelets
Blood micrograph diagram
Red blood cells, white blood cells and platelets can be observed when blood is viewed under a microscope
Blood parts functions table
| Part of the blood | Function |
| Red blood cell | Contains haemoglobin which binds to oxygen and transports it around the body |
| White blood cell, e.g. phagocytes | Part of the immune system; these cells detect and destroy pathogens |
| Platelets | Enable blood clotting; this reduces bleeding and infection at wound sites |
| Plasma |
The liquid part of the blood, containing water and other dissolved solutes, e.g. glucose and other soluble food, carbon dioxide, hormones and urea Plasma aids the distribution of heat around the body |
Drawing Blood Cells
- In an exam you may be asked to draw two types of blood cells: red blood cells and phagocytes (which are a type of white blood cell)
Labelled drawing of a red blood cell diagram
A drawing of a red blood cell in an exam would only need to be very basic, as shown in the image here
- When drawing a red blood cell remember the following points:
- A red blood cell has a circular structure and is sometimes drawn with a secondary inner circle to represent the biconcave shape
- It has no nucleus
- You need to be able to label the cell membrane
Labelled drawing of a phagocyte diagram
A drawing of a phagocyte in an exam would only need to be very basic, as shown in the image here
- When drawing a phagocyte remember the following points:
- It does not have a fixed shape because it can flex its shape to engulf pathogens
- It has a three-lobed nucleus (three circles joined by thin stems)
- You need to be able to label the cell membrane, the nucleus and the cytoplasm
Examiner Tip
When drawing in an exam always make sure to draw crisp, clear lines and avoid being too sketchy. Make sure you draw straight lines from your labels to your sketch to avoid ambiguity about what the label is for.
