The Lymphatic Vessels of the Thorax

Human Body VIII. The Lymphatic System The Lymphatic Vessels of the Thorax

7. The Lymphatic Vessels of the Thorax

1. The Sternal Glands (lymphoglandulæ sternales; internal mammary glands) are placed at the anterior ends of the intercostal spaces, by the side of the internal mammary artery. They derive afferents from the mamma, from the deeper structures of the anterior abdominal wall above the level of the umbilicus, from the upper surface of the liver through a small group of glands which lie behind the xiphoid process, and from the deeper parts of the anterior portion of the thoracic wall. Their efferents usually unite to form a single trunk on either side; this may open directly into the junction of the internal jugular and subclavian veins, or that of the right side may join the right subclavian trunk, and that of the left the thoracic duct.

2. The Intercostal Glands (lymphoglandulæ intercostales) occupy the posterior parts of the intercostal spaces, in relation to the intercostal vessels. They receive the deep lymphatics from the postero lateral aspect of the chest; some of these vessels are interrupted by small lateral intercostal glands. The efferents of the glands in the lower four or five spaces unite to form a trunk, which descends and opens either into the cisterna chyli or into the commencement of the thoracic duct. The efferents of the glands in the upper spaces of the left side end in the thoracic duct; those of the corresponding right spaces, in the right lymphatic duct.

3. The Diaphragmatic Glands lie on the thoracic aspect of the diaphragm, and consist of three sets, anterior, middle, and posterior.

The anterior set comprises (a) two or three small glands behind the base of the xiphoid process, which receive afferents from the convex surface of the liver, and (b) one or two glands on either side near the junction of the seventh rib with its cartilage, which receive lymphatic vessels from the front part of the diaphragm. The efferent vessels of the anterior set pass to the sternal glands.

The middle set consists of two or three glands on either side close to where the phrenic nerves enter the diaphragm. On the right side some of the glands of this group lie within the fibrous sac of the pericardium, on the front of the termination of the inferior vena cava. The afferents of this set are derived from the middle part of the diaphragm, those on the right side also receiving afferents from the convex surface of the liver. Their efferents pass to the posterior mediastinal glands.

The posterior set consists of a few glands situated on the back of the crura of the diaphragm, and connected on the one hand with the lumbar glands and on the other with the posterior mediastinal glands.

The superficial lymphatic vessels of the thoracic wall ramify beneath the skin and converge to the axillary glands. Those over the Trapezius and Latissimus dorsi run forward and unite to form about ten or twelve trunks which end in the subscapular group. Those over the pectoral region, including the vessels from the skin covering the peripheral part of the mamma, run backward, and those over the Serratus anterior upward, to the pectoral group. Others near the lateral margin of the sternum pass inward between the rib cartilages and end in the sternal glands, while the vessels of opposite sides anastomose across the front of the sternum. A few vessels from the upper part of the pectoral region ascend over the clavicle to the supraclavicular group of cervical glands.

The Lymphatic Vessels of the Mamma originate in a plexus in the interlobular spaces and on the walls of the galactophorous ducts. Those from the central part of the gland pass to an intricate plexus situated beneath the areola, a plexus which receives also the lymphatics from the skin over the central part of the gland and those from the areola and nipple. Its efferents are collected into two trunks which pass to the pectoral group of axillary glands. The vessels which drain the medial part of the mamma pierce the thoracic wall and end in the sternal glands, while a vessel has occasionally been seen to emerge from the upper part of the mamma and, piercing the Pectoralis major, terminate in the subclavicular glands (Fig. 607).

The deep lymphatic vessels of the thoracic wall (Fig. 621) consist of:

1. The lymphatics of the muscles which lie on the ribs: most of these end in the axillary glands, but some from the Pectoralis major pass to the sternal glands. 2. The intercostal vessels which drain the Intercostales and parietal pleura. Those draining the Intercostales externi run backward and, after receiving the vessels which accompany the posterior branches of the intercostal arteries, end in the intercostal glands. Those of the Intercostales interni and parietal pleura consist of a single trunk in each space. These trunks run forward in the subpleural tissue and the upper six open separately into the sternal glands or into the vessels which unite them; those of the lower spaces unite to form a single trunk which terminates in the lowest of the sternal glands. 3. The lymphatic vessels of the diaphragm, which form two plexuses, one on its thoracic and another on its abdominal surface. These plexuses anastomose freely with each other, and are best marked on the parts covered respectively by the pleuræ and peritoneum. That on the thoracic surface communicates with the lymphatics of the costal and mediastinal parts of the pleura, and its efferents consist of three groups: (a) anterior, passing to the gland which lie near the junction of the seventh rib with its cartilage; (b) middle, to the glands on the esophagus and to those around the termination of the inferior vena cava; and (c) posterior, to the glands which surround the aorta at the point where this vessel leaves the thoracic cavity.

The plexus on the abdominal surface is composed of fine vessels, and anastomoses with the lymphatics of the liver and, at the periphery of the diaphragm, with those of the subperitoneal tissue. The efferents from the right half of this plexus terminate partly in a group of glands on the trunk of the corresponding inferior phrenic artery, while others end in the right lateral aortic glands. Those from the left half of the plexus pass to the pre- and lateral aortic glands and to the glands on the terminal portion of the esophagus.

The visceral lymph glands consist of three groups, viz.: anterior mediastinal, posterior mediastinal, and tracheobronchial.

The Anterior Mediastinal Glands (lymphoglandulæ mediastinales anteriores) are placed in the anterior part of the superior mediastinal cavity, in front of the aortic arch and in relation to the innominate veins and the large arterial trunks which arise from the aortic arch. They receive afferents from the thymus and pericardium, and from the sternal glands; their efferents unite with those of the tracheobronchial glands, to form the right and left bronchomediastinal trunks.

The Posterior Mediastinal Glands (lymphoglandulæ mediastinales posteriores) lie behind the pericardium in relation to the esophagus and descending thoracic aorta. Their afferents are derived from the esophagus, the posterior part of the pericardium, the diaphragm, and the convex surface of the liver. Their efferents mostly end in the thoracic duct, but some join the tracheobronchial glands.

The Tracheobronchial Glands (Fig. 622) form four main groups: (a) tracheal, on either side of the trachea; (b) bronchial, in the angles between the lower part of the trachea and bronchi and in the angle between the two bronchi; (c) bronchopulmonary, in the hilus of each lung; and (d) pulmonary, in the lung substance, on the larger branches of the bronchi. The afferents of the tracheobronchial glands drain the lungs and bronchi, the thoracic part of the trachea and the heart; some of the efferents of the posterior mediastinal glands also end in this group. Their efferent vessels ascend upon the trachea and unite with efferents of the internal mammary and anterior mediastinal glands to form the right and left bronchomediastinal trunks. The right bronchomediastinal trunk may join the right lymphatic duct, and the left the thoracic duct, but more frequently they open independently of these ducts into the junction of the internal jugular and subclavian veins of their own side.

In all town dwellers there are continually being swept into these glands from the bronchi and alveoli large quantities of the dust and black carbonaceous pigment that are so freely inhaled in cities. At first the glands are moderately enlarged, firm, inky black, and gritty on section; later they enlarge still further, often becoming fibrous from the irritation set up by the minute foreign bodies with which they are crammed, and may break down into a soft slimy mass or may calcify.

The lymphatic vessels of the thoracic viscera comprise those of the heart and pericardium, lungs and pleura, thymus, and esophagus.

The Lymphatic Vessels of the Heart consist of two plexuses: (a) deep, immediately under the endocardium; and (b) superficial, subjacent to the visceral pericardium. The deep plexus opens into the superficial, the efferents of which form right and left collecting trunks. The left trunks, two or three in number, ascend in the anterior longitudinal sulcus, receiving, in their course, vessels from both ventricles. On reaching the coronary sulcus they are joined by a large trunk from the diaphragmatic surface of the heart, and then unite to form a single vessel which ascends between the pulmonary artery and the left atrium and ends in one of the tracheobronchial glands. The right trunk receives its afferents from the right atrium and from the right border and diaphragmatic surface of the right ventricle. It ascends in the posterior longitudinal sulcus and then runs forward in the coronary sulcus, and passes up behind the pulmonary artery, to end in one of the tracheobronchial glands.

FIG. 622 - The tracheobronchial lymph glands. (From a figure designed by M. Hallé.)

The Lymphatic Vessels of the Lungs originate in two plexuses, a superficial and a deep. The superficial plexus is placed beneath the pulmonary pleura. The deep accompanies the branches of the pulmonary vessels and the ramifications of the bronchi. In the case of the larger bronchi the deep plexus consists of two net-works—one, submucous, beneath the mucous membrane, and another, peribronchial, outside the walls of the bronchi. In the smaller bronchi there is but a single plexus, which extends as far as the bronchioles, but fails to reach the alveoli, in the walls of which there are no traces of lymphatic vessels. The superficial efferents turn around the borders of the lungs and the margins of their fissures, and converge to end in some glands situated at the hilus; the deep efferents are conducted to the hilus along the pulmonary vessels and bronchi, and end in the tracheobronchial glands. Little or no anastomosis occurs between the superficial and deep lymphatics of the lungs, except in the region of the hilus.

The Lymphatic Vessels of the Pleura consist of two sets—one in the visceral and another in the parietal part of the membrane. Those of the visceral pleura drain into the superficial efferents of the lung, while the lymphatics of the parietal pleura have three modes of ending, viz.: (a) those of the costal portion join the lymphatics of the Intercostales interni and so reach the sternal glands; (b) those of the diaphragmatic part are drained by the efferents of the diaphragm; while (c) those of the mediastinal portion terminate in the posterior mediastinal glands.

The Lymphatic Vessels of the Thymus end in the anterior mediastinal, tracheobronchial, and sternal glands.

The Lymphatic Vessels of the Esophagus form a plexus around that tube, and the collecting vessels from the plexus drain into the posterior mediastinal glands.

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Human Body VIII. The Lymphatic System The Lymphatic Vessels of the Thorax

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7. The Lymphatic Vessels of the Thorax

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