618
UNIT FOUR
jugular trunk
drains portions of the neck and head. These
lymphatic trunks then join one of two
collecting ducts
—the
thoracic duct or the right lymphatic duct.
Figure 16.4
shows
the location of the major lymphatic trunks and collecting
ducts, and
f gure 16.5
shows a lymphangiogram, or radio-
graph, of some lymphatic vessels and lymph nodes.
The
thoracic duct
is the larger and longer of the two col-
lecting ducts. It originates in the abdomen, passes upward
through the diaphragm beside the aorta, ascends anterior to
the vertebral column through the mediastinum, and empties
into the left subclavian vein near the junction of the left jugu-
lar vein. This duct drains lymph from the intestinal, lumbar,
and intercostal trunks, as well as from the left subclavian,
left jugular, and left bronchomediastinal trunks.
The
right lymphatic duct
originates in the right thorax
at the union of the right jugular, right subclavian, and right
bronchomediastinal trunks. It empties into the right subcla-
vian vein near the junction of the right jugular vein.
Lymph leaves the two collecting ducts, then enters the
venous system and becomes part of the plasma prior to the
Lymphatic
capillaries
Lymphatic
capillaries
Pulmonary
capillary
network
Lymph
node
Lymph
node
Systemic
capillary
network
Blood
flow
Lymph
flow
Lymphatic
vessels
FIGURE 16.1
Schematic representation of lymphatic vessels
transporting F
uid from interstitial spaces to the bloodstream.
Lymphatic
capillary
Tissue cells
Capillary
bed
Arteriole
Lymphatic
vessel
Venule
FIGURE 16.2
Lymphatic capillaries are microscopic, closed-ended
tubes that originate in the interstitial spaces of most tissues.
FIGURE 16.3
Light micrograph of the F
aplike valve (arrows) within
a lymphatic vessel (60×).
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