4.1.6 Blood Cells

Question 1

How do you draw cells from blood smears?

Answer 1

To record the observations seen under the microscope (or from photomicrographs taken) a labelled biological drawing is often made

Biological drawings are line pictures which show specific features that have been observed when the specimen was viewed

There are a number of rules/conventions that are followed when making a biological drawing

The conventions are:
The drawing must have a title
The magnification under which the observations shown by the drawing are made must be recorded
A sharp HB pencil should be used (and a good eraser!)
Drawings should be on plain white paper
Lines should be clear, single lines (no thick shading)
No shading
The drawing should take up as much of the space on the page as possible
Well-defined structures should be drawn
The drawing should be made with proper proportions
Label lines should not cross or have arrowheads and should connect directly to the part of the drawing being labelled
Label lines should be kept to one side of the drawing (in parallel to the top of the page) and drawn with a ruler

Drawings of cells are typically made when visualizing cells at a higher magnification power, whereas plan drawings are typically made of tissues viewed under lower magnifications (individual cells are never drawn in a plan diagram)

Question 2

What are blood smears?

Answer 2

A blood smear is when a small amount of blood is spread on a glass microscope slide, stained and covered with a coverslip

The different blood cells can then be examined using a microscope
Red blood cells have no nuclei and a distinct biconcave shape
White blood cells have irregular shapes
Neutrophils have distinctive lobed nuclei
They make up roughly 70% of all white blood cells
Lymphocytes have very large nuclei that nearly occupy the entire cell