Page 1032 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

H aemolymphatic system 1007

VetBooks.ir ×1000 magnification for optimal evaluation. A dif- 9.4
Equine leucocytes are examined at ×400 to

ferential examination of a minimum of 100 cells is
performed to determine the percentages and then
the absolute numbers of individual cell types pres-
ent (Fig. 9.4).
Equine neutrophils, the most abundant blood
leucocyte, have segmented nuclei, often with jagged a b
projections off the nuclear lobes, and very clumped
chromatin. The cytoplasm typically stains neutrally,
with occasional fine pink granules. Toxic changes
such as cytoplasmic basophilia and vacuolation,
Dohle body formation and nuclear degeneration can
be observed with interference with cellular develop-
ment in the bone marrow during endotoxaemia and
other inflammatory diseases.
Lymphocytes are the next most common leuco- c d
cyte. They are small round cells with round nuclei. Fig. 9.4 Blood smear demonstrating morphology of
Only scant, slightly basophilic cytoplasm is com- normal white blood cells and platelets: (a) neutrophil
monly observed. Nuclear chromatin is clumped, and with an eosinophil below; (b) basophil; (c) neutrophil;
nucleoli are typically absent. (d) monocyte with two lymphocytes below. The
Monocytes are infrequently observed on equine arrows indicate clumps of platelets (Wright’s stain).
blood smears, but they are the largest appearing
leucocyte. They have abundant grey-blue cyto-
plasm that frequently contains small discrete vac- 9.5
uoles. Nuclei can be any shape except round and
are not segmented. Nuclear chromatin is often
described as ‘lacy’ and is more pale staining than
other cell types.
Equine eosinophils are uncommonly observed
but are the most distinctive leucocyte. Nuclei are
segmented and similar to neutrophils, but nuclear
detail is often obscured by the numerous large round
pink-orange granules that fill the cytoplasm.
Equine basophils are rare leucocytes, but again
they have a segmented nucleus with clumped nuclear
chromatin and few to many small purple cytoplas-
mic granules. The cytoplasm, when visible, tends to Fig. 9.5 Collection of bone marrow from the wing
be slightly basophilic. of the ilium using an 11-gauge, 4-inch Jamshidi needle
and a heparinised 12 ml syringe.
Collection and evaluation
of bone marrow
Bone marrow is most commonly collected from collected and evaluated concurrently, as results are
the wing of the ilium or sternebrae in the horse complementary. Bone marrow samples are usually
(Fig. 9.5). Bone marrow can be aspirated for cyto- interpreted by pathologists and are evaluated for cel-
logical evaluation, or a core of bone marrow tissue lularity, synchronous maturation and adequate pro-
can be removed and fixed in formalin for histo- portions of developing erythrocytic, granulocytic
pathological evaluation. Ideally, both specimens are and megakaryocytic cells.