How is a blood smear fixed and stained?

The air-dried film is fixed in methanol. The film is then stained with a Romanowsky stain, such as Leishman's or Giemsa, which colours nuclei purple.

Why are cells examined near the thin, feathered edge of a blood smear?

The cells near the feathered edge lie in a single layer without overlapping. Their shape and staining can be seen clearly.

How are red blood cells recognised in a stained blood smear?

Red blood cells are pink, round cells with no nucleus and a paler centre. The pale centre reflects their biconcave shape, and each is about 7 µm across.

CCEA A-Level Life and Health Sciences 0008

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Histology and Pathology

Blood smears and identifying blood cells

3 things to know
A2 8

Overview

Haematology and leukaemia, preparing, fixing and staining blood smears, recognising red cells, neutrophils, eosinophils, lymphocytes, monocytes and platelets, differential counts and the haematocrit.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is the role of the haematology department, and which specimens does it test?

Key term

How can haematology tests contribute to diagnosing leukaemia?

Key term

Describe how a thin blood smear is prepared.

Questions from this subtopic

Each one with the model answer underneath.

1
What is the role of the haematology department, and which specimens does it test?
Model answer
Haematology studies blood cells, blood clotting and the tissues that make blood. Specimens include EDTA whole blood, citrated plasma for clotting tests and bone marrow samples.
2
How can haematology tests contribute to diagnosing leukaemia?
Model answer
A blood count may show a very high or very low white cell count with anaemia and few platelets. A blood film may show immature blast cells, and a bone marrow sample confirms the diagnosis.
3
Describe how a thin blood smear is prepared.
Model answer
A small drop of blood is placed near one end of a clean slide. A spreader slide held at about 30 to 45° is drawn back into the drop, then pushed forward smoothly to spread a thin film.
4
How is a blood smear fixed and stained?
Model answer
The air-dried film is fixed in methanol. The film is then stained with a Romanowsky stain, such as Leishman's or Giemsa, which colours nuclei purple.
5
Why are cells examined near the thin, feathered edge of a blood smear?
Model answer
The cells near the feathered edge lie in a single layer without overlapping. Their shape and staining can be seen clearly.
6
How are red blood cells recognised in a stained blood smear?
Model answer
Red blood cells are pink, round cells with no nucleus and a paler centre. The pale centre reflects their biconcave shape, and each is about 7 µm across.

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