Cells of the Blood (Cambridge International AS Biology)

Spec point — 8.1.5 · recognise and draw red blood cells, monocytes, neutrophils and lymphocytes from microscope slides, photomicrographs and electron micrographs

Cells of the blood

• Blood is a tissue composed of a number of important specialised cells, including:

  • Red blood cells
  • Monocytes
  • Neutrophils
  • Lymphocytes

• These cells all have distinguishable structures which enable them to be recognised on microscope slides, in photomicrographs and in electron micrographs

Diagram of the structure of a red blood cell

• Red blood cells contain haemoglobin

  • This is a protein with a quaternary structure that contains haem iron groups which can bind reversibly to oxygen

• Distinctive features of red blood cells when viewed under a microscope, are their distinctive biconcave disc shape (caused by their lack of nucleus)

Red blood cell micrograph

A monocyte is a type of white blood cell

• Monocytes are identifiable by their size

  • They are the largest of the leukocytes and have a nucleus shaped like a kidney or a bean

• The nucleus of monocytes tends to appear lighter after staining than other leukocytes

• The nucleus should appear a light blue colour, while the chromatin inside is distinct and fine

A micrograph of a monocyte cell

• Neutrophils are distinguished by their multi-lobed nuclei

• Up to 70% of all leukocytes are neutrophils

  • This makes them easy to spot on a micrograph

• The granules of neutrophils typically stain pink or purple-blue

A neutrophil is a type of white blood cell

A micrograph of a neutrophil cell

• Lymphocytes are small leukocytes that are identifiable by their very large nuclei, which typically stains a dark colour
• Lymphocytes constitute around 20-25% of all leukocytes
• Lymphocytes are around the size of red blood cells

A lymphocyte is a type of white blood cell

A micrograph of some lymphocyte cells

Exam Hint When looking at micrographs, ensure you distinguish between the kidney-shaped nucleus of a monocyte and the multi-lobed nucleus of a neutrophil, as these can appear similar at first. As with all things, practice is key here!