CHAPTER 8
Blood and Hemopoiesis
139
Erythrocytes
Platelet
Capillary endothelial cell
B
Figure 8-3B.
Erythrocytes and a platelet in a small blood vessel.
EM,
3
10,000
The lumen of this
capillary
(or
venule
) contains proF
les of several
erythrocytes
and a
platelet
. The erythrocytes in this thin section
present a variety of proF le shapes owing to two effects: the random orientation of the plane of section and the fl
exibility that allows
the cells to bend in compliance with surrounding pressures. The platelet here is cut transversely through its biconvex shape, which
is maintained by microtubules arranged as a hoop at the edge of the disk. The magniF cation of this view is not quite sufF
cient to
reveal the microtubules. It can be seen here that the platelet contains a variety of granules and tubules.
Figure 8-3A.
Erythrocytes, small artery.
SEM,
3
1,140
This scanning electron micrograph demon-
strates the various shapes of the blood cells
contained in the lumen of a
small
artery
.
The
erythrocytes
appear as biconcave disks;
that is, “doughnuts” with thin diaphragms
across the holes. By contrast, the
leukocytes
are
spherical, and the different types cannot
be distinguished. No platelets are visible in
this view. The inner layer of the artery wall is
tunica intima, composed mainly of
endothe-
lium
and a thin
internal elastic lamina
.
Erythrocytes
Erythrocytes
Erythrocytes
Internal elastic lamina
Internal elastic lamina
Internal elastic lamina
Endothelium
Endothelium
of small artery
of small artery
Endothelium
of small artery
Leukocytes
Leukocytes
Leukocytes
A
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