a-short-review-of-histology

Neutrophils:

These are the most common of the white blood cells
They are granular leucocytes and represent 50-60% of white blood cells in normal peripheral blood
Neutrophils are 12-15 microns in diameter and have a lobed nucleus
Typically the nucleus has 3-5 lobes
The cytoplasm contains numerous granules which are weakly stained, ie are neutral, when a blood smear is stained with a Romanovsky-type staining method
(A Romanovsky staining method is a standard method for staining smears of whole blood cells - it allows for the easy identification of all the cell populations found in normal peripheral blood)
Neutrophils are endocytic (phagocytic) and involved in the endocytosis of bacteria
The cytoplasmic granules of neutrophils are of two types, small and large
The small granules are rich in lysozyme which breaks down bacterial cell walls
The larger ovoid granules contain a wide range of hydrolytic enzymes which are normally used to breakdown the contents of the lysed bacteria
An unusual feature of neutrophils is the presence of a Barr body (sometimes called a drumstick)
This extends, like a drumstick, from one of the lobes of the nucleus and represents the second X chromosome of females
It is not normally present in males
Neutrophils circulate in peripheral blood for between 6-10 hours then spend about 2-3 days in tissue spaces before dying

Neutrophils - 2:

In this image of a blood smear a neutrophil is labelled A. (B= basophil, C = small lymphocyte)

Notice that the diameter of the neutrophil is about 50% greater than the surrounding red blood cells

In this example, the nucleus appears to have four lobes

It is difficult to appreciate that the cytoplasm contains granules, in part because they are very weakly stained

Neutrophils - 3:

In this image of a blood smear identify the neutrophil with its four lobed nucleus

Notice a small projection of chromatin from the lower right lobe

This is a Barr body (or 'drumstick') representing the second X- chromosome of females

Neutrophils - 4

In this electron micrograph of a neutrophil notice:

The 4 lobes of the nucleus (these appear separate from each other but connections between the lobes would be present in a higher or lower plane of section)
A fine extension of chromatin, from the lower left lobe of the nucleus, expanding into a bulbous expansion. This may be the Barr body
Numerous cytoplasmic granules
These will contain the enzymes associated with breakdown of endocytosed bacteria