Lymphatic System
The lymphatic vascular system collects fluid from the tissues and returns it to the venous
circulation. The lymphatic system is able to remove debris from the fluid and sense and respond
to the presence of antigens. In almost all cases lymph passes through at least one lymph node
before returning to the circulation. The lymphatic vascular system is formed of superficial and
deep components. The superficial system drains the skin and superficial tissues to collections of
lymph nodes in the axilla and the inguinal region. From these two nodular areas the lymph passes
to join the deep system. The deep system of lymphatics accompanies the vessels. The inguinal
nodes continue into the external then common iliac nodes. The common iliac
nodes also receive
lymph from the internal iliac lymph nodes. The lymphatics then proceed cranially around the
aorta. Lymphatics draining the territories of the inferior and superior mesenteric arteries, and the
coeliac trunk drain into the para-aortic system. Lymphatics from the posterior abdominal wall
drain alongside the lumbar arteries to reach the para-aortic lymphatics. Below the diaphragm the
deep system of lymphatics drains into the cysterna chyli, a lymph sac lying behind the right crus of
the diaphragm.
The thoracic duct leaves the cysterna chyli lying on the right side of the aorta and
passes cranially lying in the posterior then superior mediastinum. As the thoracic duct passes
upwards it moves towards the left, lying on the azygos system of veins. The thoracic duct drains
into the venous system at the formation of the left brachiocephalic vein by the internal jugular and
subclavian veins. The lymphatic vessels from the left side of the head and neck also drain into the
venous system at this point, together with the lymphatics from the left axilla and left upper limb.
The lymphatics from the right axilla and upper limb join those from the right side of the head and
neck to drain into the formation of the right brachiocephalic vein.
Lymphatics of the thorax
The lymphatics of the thorax are considered fully in the Respiratory System Section. Lymph
drains from the visceral pleura covering the lungs towards bronchopulmonary nodes that are
located in the hilum of the lung. The lymph then passes to more proximal lymph nodes at the
bifurcation of the trachea, the tracheobronchial lymph nodes. The deep tissues of the lung are
drained by lymphatics that accompany the bronchi. These lymphatics again drain into the
bronchopulmonary lymph nodes. The tracheobronchial, parasternal and anteriormediastinal lymph
nodes on each side then form the bronchomediastinal limph nodes which drain towards the entry
point to the venous system at the formation of the brachiocephalic veins. These lymphatic
channels are in communication with the lymphatics of the breast and with those of the abdomen.
Return to Thorax