The document provides a histological review of human blood, detailing various blood cell types observed in a Wright-stained blood film. It describes neutrophils, eosinophils, basophils, monocytes, and lymphocytes, highlighting their sizes, functions, and identifying characteristics. Each cell type is associated with specific roles in immune response and blood functions.

1. HISTOLOGY REVIEW
Human Blood
Dr. Tim Ballard
Department of Biology and Marine Biology

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Blood film -- human – Wright – 40x objective
thrombocytes
(2 μ diameter)
erythrocytes
(10 μ diameter)
leukocytes
(20-30 μ diameter)
A blood film is a smear of whole blood. Done properly, the cells lie in a sheet of
single cells.

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Blood film -- human – Wright – 40x objective
neutrophil
Neutrophils (~60%) are named for their lack of characteristic cytoplasmic staining,
but are readily identified by their multilobed nucleus (hence their name
polymorphonuclear leukocytes or polymorphs or PMNs). Their nucleus typically
contains 2 – 4 lobes. The cytoplasm contains three kinds of granules, all of which
are related to the cell’s function as a phagocyte.

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Blood film -- human – Wright – 40x objective
neutrophils

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Blood film -- human – Wright – 40x objective
eosinophil
Eosinophils (2-4%) are about the same size as neutrophils. Their nuclei are
typically bilobed. The cytoplasm contains two specific types of granules, the
contents of which are responsible for the intense acidophilia (red stain) seen with
Wright’s stain. The granule contents include histaminases (anti-histamines) and
materials that have a strong cytotoxic effect on parasites.

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Blood film -- human – Wright – 40x objective
neutrophil
eosinophil

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Blood film -- human – Wright – 40x objective
basophil
Basophils (<1%) are about the same size of neutrophils (maybe a little smaller) and
are so named because of the numerous large granules in the cytoplasm that stain
purple (basophilia) with the basic dyes of Wright’s stain. The granules contain
heparin and histamine, mediators of the inflammatory response. Basophils are
related to mast cells located in the tissues.

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Blood film -- human – Wright – 40x objective
eosinophil
basophil

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Blood film -- human – Wright – 40x objective
monocyte
Monocytes (3-8%) are the largest of the WBCs. They leave the general circulation
in 1.5 – 2 days to become wandering macrophages in the tissues and osteoclasts
in the bone. The nucleus of the monocyte is typically flattened or indented. The
cells are classified as agranulocytes because their granules are small and hard to
visualize. The granules are lysosomes in keeping with the function of the cells as
macrophages.

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Blood film -- human – Wright – 40x objective
monocyte
neutrophils

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Blood film -- human – Wright – 40x objective
lymphocyte
Lymphocytes (~30%) are the smallest of the WBCs. They come as small, medium,
and large, the smallest of which are about the size of the RBCs. The nucleus is
intensely staining, slightly indented, and mostly spherical. There is a thin rim of
bluish-gray cytoplasm. They function in either cell-mediated or antibody-mediated
immunity.

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Blood film -- human – Wright – 40x objective
lymphocyte
This is a large lymphocyte, not a macrophage.
To call it a macrophage, the cell should be larger
and have a flattened or indented nucleus.

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Blood film -- human – Wright – 40x objective
lymphocyte
neutrophil

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Blood film -- human – Wright – 40x objective
monocyte
lymphocyte
end