Published by Australian Academy of Science
Activity 1 | Singing the praises of colony stimulating factors

Blood cells

The two main types of cells found in the blood are red blood cells and white blood cells. There are also fragments of cells called platelets.

Materials (per student)

• prepared slide of stained blood smear
• monocular microscope

Procedure

1. Focus the prepared blood smear under low power and then high power.

2. Identify the red blood cells (erythrocytes) and white blood cells (leucocytes). (With Leishman's stain, the red blood cells appear yellowish-red; the nuclei of the white blood cells stain a purple colour and any granules in these cells may range from orange to black in colour.)

3. Draw and label each of the different cell types. (You may distinguish different white blood cell types according to the shape of the nucleus.)

4. Estimate the approximate ratio of red blood cells to white blood cells. Work out a way to do this that does not involve counting every cell in the field. Combine your results with those of other students for a more accurate result.

Questions

1. Describe the appearance of a red blood cell. Find out why they appear lighter in colour in the middle of the cell.

2. Describe the appearance of a white blood cell. In what ways do white and red blood cells differ?

3. How many different types of white blood cells are visible? How do they differ from each other?

4. What is the function of any platelets that are visible?

Teachers notes

Red blood cells have a characteristic biconcave shape and, unusually for cells, lack a nucleus. (Red blood cells cannot repair themselves if they are damaged. They live for only about four months before being replaced by new red blood cells produced from stem cells in the bone marrow.)

White blood cells contain a nucleus, and are larger than red blood cells. Some white blood cells have granules in their cytoplasm. These cells are made in the bone marrow and three types are recognised – neutrophils (the most common of the white blood cells), eosinophils and basophils. Other white blood cells have no granules in their cytoplasm. These cells mature in the lymph tissue as well as the bone marrow and two types are recognised – monocytes (the largest of the white blood cells) and lymphocytes.

Platelets are much smaller than either red cells or white cells and are not really cells at all. They are formed in the bone marrow when large cells pinch off pieces of their cytoplasm. There are about 250,000 platelets per cubic millimetre of blood and they play a vital role in blood clotting.

The red blood cells are the most numerous of the blood cells - there are about 5 million red blood cells in each cubic millimetre of blood. There are normally 4000 to 11,000 white cells per cubic millimetre of blood. (Leukemias are a range of cancers that involve the production of large numbers of abnormal white blood cells.)