Lecture 3 - Mediastinum PDF

Lecture 3 Mediastinum Dr. Rasem Mustafa PhD. Dr.med.dent (Anatomy and Cell Biology) Dr. Rasem Mustafa 1  Mediastinum Thick midline partition between 2 lungs, that extends anteriorly to the sternum and posteriorly to...

Lecture 3 Mediastinum Dr. Rasem Mustafa PhD. Dr.med.dent (Anatomy and Cell Biology) Dr. Rasem Mustafa 1  Mediastinum Thick midline partition between 2 lungs, that extends anteriorly to the sternum and posteriorly to the vertebral column and from the superior thoracic aperture to the diaphragm Contains: the remains of the thymus, the heart and large blood vessels, the trachea and esophagus, the thoracic duct and lymph nodes, the vagus and phrenic nerves, and the sympathetic trunks. Divided into superior and inferior mediastina by an imaginary plane passing from the sternal angle, through T4 and T5. Dr. Rasem Mustafa 2  The inferior mediastinum is further subdivided into the middle mediastinum, which consists of the pericardium and heart; the anterior mediastinum, which is a space between the pericardium and the sternum; and the posterior mediastinum, which lies between the pericardium and the vertebral column. Dr. Rasem Mustafa 3  Superior mediastinum: (a) Thymus, (b) large veins, (c) large arteries, (d) trachea, (e) esophagus and thoracic duct, and (f) sympathetic trunks. Inferior Mediastinum: (a) Thymus, (b) heart within the pericardium with the phrenic nerves on each side, (c) esophagus and thoracic duct, (d) descending aorta, and (e) sympathetic trunks. Dr. Rasem Mustafa 4  Superior mediastinum  Boundaries Anteriorly: manubrium sterni. Posteriorly: T1-T4 Superior boundary :oblique plane passing from the jugular notch upward and posteriorly to the superior border of vertebra TI. Inferiorly : a transverse plane passing from the sternal angle to the intervertebral disc between vertebra TIV/V separates it from the inferior mediastinum. Laterally :it is bordered by the mediastinal part of the parietal pleura on either side. Dr. Rasem Mustafa 5  Content Thymus Three veins Left and right brachiocephelic v. Arch of azygos vein Superior vena cava Aortic arch and its three branches Nerves related to the vessels – Phrenic n. – Vagus n. – Cardiac plexus of nerve. Trachea, Esophagus and between them Left Recurrent laryngeal nerve. Thoracic duct and lymphatic trunk. Thoracic part of the sympathetic chain. Dr. Rasem Mustafa 6 Dr. Rasem Mustafa 7 Dr. Rasem Mustafa 8  Anterior mediastinum  Boundaries Anteriorly: body of the sternum and Transversus thoracis muscle. Posteriorly: pericardium Superior boundary : line between sternal angel and T4. Inferiorly : Diaphragm Laterally :it is bordered by the mediastinal part of the parietal pleura on each side. Dr. Rasem Mustafa 9  Content Connective tissue. Fat Remnants of thymus gland. Anterior mediastinal lymph nodes. Sterno-pericardial ligament -which pass from the posterior surface of the body of the sternum to the fibrous pericardium Branches of the internal thoracic vessels. Ant. Border of pleura &lung on the right side. Dr. Rasem Mustafa 10  Middle mediastinum  Boundaries Anteriorly and posteriorly-pericardium Superiorly by line between sternal angel and T4 Inferiorly Diaphragm  Content Heart Right and left phrenic nerves Pericardiacophrenic vessels Root of great vessels  Ascending aorta  SVC  Pulmonary trunk  Pulmonary veins Bifurcation of trachea. Dr. Rasem Mustafa 11  Posterior mediastinum  Boundaries In front -pericardium above and posterior surface of the diaphragm below. Behind -vertebral column from lower border of T4 to the upper border of T12. On each side mediastinal pleura. Superiorly by line between sternal angel and T4 Dr. Rasem Mustafa 12  Content Descending thoracic aorta and its branches. Thoracic duct Posterior mediastinal lymph nodes (e.g., tracheobronchial nodes) Azygos and hemiazygos veins Esophagus Esophageal plexus Thoracic sympathetic trunks Thoracic splanchnic nerves Dr. Rasem Mustafa 13  Large Veins of the Thorax  Brachiocephalic Veins:  The right brachiocephalic vein is formed at the root of the neck by the union of the right subclavian and the right internal jugular veins, posterior to the sternoclavicular joint.  The left brachiocephalic vein has a similar origin. It passes obliquely downward and to the right behind the manubrium sterni and in front of the large branches of the aortic arch. It joins the right brachiocephalic vein to form the superior vena cava.  Both lies posterior to the thymus  The left brachiocephalic vein crosses the midline posterior to the manubrium in the adult. In infants and children the left brachiocephalic vein rises above the superior border of the manubrium and Dr. Rasem Mustafa 14 therefore is less protected.  Right brachiocephalic venous tributaries include the vertebral, first posterior intercostal, and internal thoracic veins. The inferior thyroid and thymic veins may also drain into it.  Left brachiocephalic venous tributaries include the vertebral, first posterior intercostal, left superior intercostal, inferior thyroid, and internal thoracic veins. It may also receive thymic and pericardial veins. Dr. Rasem Mustafa 15  Superior Vena Cava:  Contains all the venous blood from the head and neck and both upper limbs.  Is formed by the union of the two brachiocephalic veins. It passes downward to end in the right atrium of the heart.  The vena azygos joins the posterior aspect of the superior vena cava just before it enters the pericardium, may also receive pericardial and mediastinal veins. Dr. Rasem Mustafa 16  The vertically oriented superior vena cava begins posterior to the lower edge of the right first costal cartilage, where the right and left brachiocephalic veins join, and terminates at the lower edge of the right third costal cartilage, where it joins the right atrium.  The lower half of the superior vena cava is within the pericardial sac and is therefore contained in the middle mediastinum. Dr. Rasem Mustafa 17  Clinical Correlation  Venous access for central and dialysis lines Large systemic veins are used to establish central venous access for administering large amounts of fluid, drugs, and blood. Most of these lines (small-bore tubes) are introduced through venous puncture into the axillary, subclavian, or internal jugular veins. The lines are then passed through the main veins of the superior mediastinum, with the tips of the lines usually residing in the distal portion of the superior vena cava or in the right atrium. Similar devices, such as dialysis lines, are inserted into patients who have renal failure, so that a large volume of blood can be aspirated through one channel and reinfused through a second channel. Dr. Rasem Mustafa 18  Azygos vein:  Consist of the main azygos vein, the inferior hemiazygos vein (hemiazygous), and the superior hemiazygos vein (Accessory hemiazygos).  They drain blood from the posterior parts of the intercostal spaces, the posterior abdominal wall, the pericardium, the diaphragm, the bronchi, and the esophagus.  Azygos Vein: The origin of the azygos vein is variable. It is often formed by the union of the right ascending lumbar vein and the right subcostal vein, at the level opposite vertebra LI or LII. Dr. Rasem Mustafa 19  It ascends through the aortic opening in the diaphragm on the right side of the aorta to the level of the fifth thoracic vertebra. Here it arches forward above the root of the right lung to empty into the posterior surface of the superior vena cava. Tributaries of the azygos vein include: the right superior intercostal vein (a single vessel formed by the junction of the second, third, and fourth intercostal veins), fifth to eleventh right posterior intercostal veins, the hemiazygos vein, the accessory hemiazygos vein, esophageal veins, mediastinal veins, pericardial veins, and right bronchial veins. Dr. Rasem Mustafa 20  Superior Hemiazygos Vein The superior hemiazygos vein is formed by the union of the fourth to the eighth intercostal veins and sometimes, the left bronchial veins. It joins the azygos vein at the level of the seventh or eighth thoracic vertebra. Usually, it also has a connection superiorly to the left superior intercostal vein. Dr. Rasem Mustafa 21  Inferior Hemiazygos Vein (Hemiazygos) Is often formed by the union of the left ascending lumbar vein and the left subcostal vein. It may also arise from either of these veins alone and often has a connection to the left renal vein. It ascends through the left crus of the diaphragm but may enter through the aortic hiatus. At level of the eighth thoracic vertebra or nine, turns to the right and joins the azygos vein, posterior to the thoracic aorta, esophagus, and thoracic duct. It receives as tributaries some lower left four or five intercostal veins, esophagreal veins and mediastinal veins. Dr. Rasem Mustafa 22  Inferior Vena Cava: A vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart. It is formed by the joining of the right and the left common iliac veins, usually at the level of the fifth lumbar vertebra. The inferior vena cava pierces the central tendon of the diaphragm opposite the eighth thoracic vertebra and almost immediately enters the lowest part of the right atrium.  Pulmonary Veins Two pulmonary veins leave each lung carrying oxygenated blood to the left atrium of the heart. Dr. Rasem Mustafa 23  Large Arteries of the Thorax  Aorta :  The aorta is the main arterial trunk that delivers oxygenated blood from the left ventricle of the heart to the tissues of the body.  It is divided for purposes of description into the following parts:  Ascending aorta.  Arch of the aorta.  Descending thoracic aorta.  Abdominal aorta. Dr. Rasem Mustafa 24  Ascending Aorta  Begins at the base of the left ventricle and runs upward and forward to come to lie behind the right half of the sternum.  At the level of the sternal angle, where it becomes continuous with the arch of the aorta.  The ascending aorta lies within the fibrous pericardium and is enclosed with the pulmonary trunk in a sheath of serous pericardium.  At its root, it possesses three bulges, the sinuses of the aorta, one behind each aortic valve cusp.  Branches: The right coronary artery arises from the anterior aortic sinus, and the left coronary artery arises from the Dr. Rasem Mustafa 25 left posterior aortic sinus  Arch of the Aorta  Lies behind the manubrium sterni and arches upward, backward, and to the left in front of the trachea (its main direction is backward).  Extending as high as the midlevel of the manubrium. It then passes downward to the left of the trachea and, at the level of the sternal angle, becomes continuous with the descending aorta.  Branches (crossed anteriorly by the left brachiocephalic vein): 1. The brachiocephalic artery arises from the convex surface of the aortic arch. It passes upward and to the right of the trachea. Largest and slightly anterior to the other branches Dr. Rasem Mustafa 26  At the level of the upper edge of the right sternoclavicular joint, the brachiocephalic trunk divides into: The right common carotid artery The right subclavian artery.  The arteries mainly supply the right side of the head and neck and the right upper limb, respectively.  Occasionally, the brachiocephalic trunk has a small branch, the thyroid ima artery, which contributes to the vascular supply of the thyroid gland. Dr. Rasem Mustafa 27 2. The left common carotid artery arises from the convex surface of the aortic arch on the left side of the brachiocephalic artery. It runs upward and to the left of the trachea and enters the neck behind the left sternoclavicular joint. The left common carotid artery supplies the left side of the head and neck. 3. The left subclavian artery arises from the aortic arch behind the left common carotid artery. It runs upward along the left side of the trachea and the esophagus to enter the root of the neck. It arches over the apex of the left lung, major blood supply to the left upper limb. Dr. Rasem Mustafa 28  Descending Thoracic Aorta  The descending thoracic aorta lies in the posterior mediastinum and begins as a continuation of the arch of the aorta on the left side of the lower border of the body of the 4th thoracic vertebra (i.e., opposite the sternal angle).  It runs downward in the posterior mediastinum, inclining forward and medially to reach the anterior surface of the vertebral column.  At the level of the 12th thoracic vertebra, it passes behind the diaphragm (through the aortic opening) in the midline and becomes continuous with the abdominal aorta.  Branches: Posterior intercostal arteries are given off to the lower nine intercostal spaces on each side. Subcostal arteries are given off on each side and run along the lower border of the 12th rib to enter the abdominal wall. Pericardial, esophageal, and bronchial arteries are small branches that are distributed to these organs. Dr. Rasem Mustafa 29 Dr. Rasem Mustafa 30  Pulmonary Trunk  The pulmonary trunk conveys deoxygenated blood from the right ventricle of the heart to the lungs.  It leaves the upper part of the right ventricle and runs upward, backward, and to the left conus arteriosus.  It is about 2 in. (5 cm) long.  Terminates in the concavity of the aortic arch by dividing into right and left pulmonary arteries.  Together with the ascending aorta, it is enclosed in the fibrous pericardium and a sheath of serous pericardium. Dr. Rasem Mustafa 31  Branches: right pulmonary artery, left pulmonary artery  The pulmonary trunk is contained within the pericardial sac.It is covered by the visceral layer of serous pericardium, and is associated with the ascending aorta in a common sheath.  The ligamentum arteriosum is a fibrous band that connects the bifurcation of the pulmonary trunk to the lower concave surface of the aortic arch. Dr. Rasem Mustafa 32  Clinical Correlation  Coarctation of the aorta Is a congenital abnormality in which the aortic lumen is constricted just distal to the origin of the left subclavian artery. At this point, the aorta becomes significantly narrowed and the blood supply to the lower limbs and abdomen is diminished. Over time, collateral vessels develop around the chest wall and abdomen to supply the lower body. Dilated and tortuous intercostal vessels, which form a bypass to supply the descending thoracic aorta, may lead to erosions of the inferior margins of the ribs. This can be appreciated on chest radiographs as inferior rib notching and is usually seen in long standing cases. The coarctation also affects the heart, which has to pump the blood at higher pressure to maintain peripheral perfusion. This in turn may Dr. Rasem Mustafa 33 produce cardiac failure.  Thoracic aorta Diffuse atherosclerosis of the thoracic aorta may occur in patients with vascular disease, but this rarely produces symptoms. There are, however, two clinical situations in which aortic pathology can produce life-threatening situations.  Trauma The aorta has three fixed points of attachment: the aortic valve, the ligamentum arteriosum, and the point of passing behind the median arcuate ligament of the diaphragm to enter the abdomen. The rest of the aorta is relatively free from attachment to other structures of the mediastinum. A serious deceleration injury (e.g., in a road traffic accident) is most likely to cause aortic trauma at these fixed points. Dr. Rasem Mustafa 34  Aortic dissection In certain conditions, such as in severe arteriovascular disease, the wall of the aorta can split longitudinally, creating a false channel, which may or may not rejoin into the true lumen distally. This aortic dissection occurs between the intima and media anywhere along its length. If it occurs in the ascending aorta or arch of the aorta, blood flow in the coronary and cerebral arteries may be disrupted, resulting in myocardial infarction or stroke. In the abdomen the visceral vessels may be disrupted, producing ischemia to the gut or kidneys. Dr. Rasem Mustafa 35  Abnormal origin of great vessels Great vessels occasionally have an abnormal origin, including: a common origin of the brachiocephalic trunk and the left common carotid artery, the left vertebral artery originating from the aortic arch, and the right subclavian artery originating from the distal portion of the aortic arch and passing behind the esophagus to supply the right arm—as a result, the great vessels form a vascular ring around the trachea and the esophagus, which can potentially produce difficulty swallowing. This configuration is one of the most common aortic arch abnormalities. Dr. Rasem Mustafa 36  Esophagus  Begins: Muscular tube 10 inch= 25 cm that begin as continuation of the pharynx at the level of cricoid cartilage (lower border of c6v)  Ends: in the cardiac orifice of the stomach at the level of the 10th thoracic vertebra to join the stomach, reaching the level of T11.  It is the narrowest part of GIT after the pylorus & appendix Dr. Rasem Mustafa 37  Constrictions The esophagus is a flexible, muscular tube that can be compressed or narrowed by surrounding structures at four locations:  Junction of the esophagus with the pharynx in the neck;  In the superior mediastinum where the esophagus is crossed by the arch of the aorta;  In the posterior mediastinum where the esophagus is compressed by the left main bronchus;  In the posterior mediastinum at the esophageal hiatus in the diaphragm. FIGURE 3.50 The approximate respective distances from the incisor teeth (blue) and the nostrils (red) to the normal three constrictions of the esophagus. To assist in the passage of a tube to the duodenum, the distances to the first part of the Dr. Rasem Mustafa 38 duodenum are also included.  Surface anatomy of Esophageal opening  1 inch to the Left from the mid.line  At the level of T10th. Vertebra  In the Rt.crus of the diaphragm In the neck  The esophagus lies in front of the vertebral column; laterally, it is related to the lobes of the thyroid gland; and anteriorly, it is in contact with the trachea and the recurrent laryngeal nerves. Dr. Rasem Mustafa 39  In the thorax  It passes downward and to the left through the superior and then the posterior mediastinum. At the level of the sternal angle, the aortic arch pushes the esophagus over to the midline.  As it approaches the diaphragm, it moves anteriorly and to the left, crossing from the right side of the thoracic aorta to eventually assume a position anterior to it. It then passes through the esophageal hiatus, an opening in the muscular part of the diaphragm, at vertebral level TX. Dr. Rasem Mustafa 40  Relationship: Anteriorly: The trachea and the left recurrent laryngeal nerve; the left principal bronchus, which constricts it; and the pericardium, which separates the esophagus from the left atrium. Posteriorly: The bodies of the thoracic vertebrae; the thoracic duct; the hemiazygos veins; the right posterior intercostal arteries; and, at its lower end, the descending thoracic aorta Right: The mediastinal pleura and the terminal part of the azygos vein. Left: The left subclavian artery, the aortic arch, the thoracic duct, and the mediastinal pleura Dr. Rasem Mustafa 41  Inferiorly to the level of the roots of the lungs The vagus nerves leave the pulmonary plexus and join with sympathetic nerves to form the esophageal plexus. The left vagus lies anterior to the esophagus. The right vagus lies posterior.  At the opening in the diaphragm The esophagus is accompanied by the two vagi, branches of the left gastric blood vessels, and lymphatic vessels. Fibers from the right crus of the diaphragm pass around the esophagus in the form of a sling.  In the abdomen The esophagus descends for about 0.5 in. (1.3 cm) and then enters the stomach. It is related to the left lobe of the liver anteriorly and to the left crus of the diaphragm posteriorly. Dr. Rasem Mustafa 42  Blood Supply of the Esophagus  The upper third of the esophagus is supplied by the inferior thyroid artery.  The middle third by branches from the descending thoracic aorta and branches from the bronchial arteries.  The lower third by branches from the left gastric artery.  The veins from the upper third drain into the inferior thyroid veins.  From the middle third into the azygos and hemiazygous veins.  From the lower third into the left gastric vein, a tributary of the portal vein. Dr. Rasem Mustafa 43  Lymph Drainage of the Esophagus  Lymph vessels from the upper third of the esophagus drain into the deep cervical nodes.  From the middle third into the superior and posterior mediastinal nodes.  From the lower third into nodes along the left gastric blood vessels and the celiac nodes Dr. Rasem Mustafa 44  Nerve Supply of the Esophagus  The esophagus is supplied by parasympathetic and sympathetic efferent and afferent fibers via the vagus and sympathetic trunks. In the lower part of its thoracic course, the esophagus is surrounded by the esophageal nerve plexus.  After passing posteriorly to the root of the lungs, the right and left vagus nerves approach the esophagus, forming the esophageal plexus. Dr. Rasem Mustafa 45  Clinical Correlation  Esophageal cancer When patients present with esophageal cancer, it is important to note which portion of the esophagus contains the tumor because tumor location determines the sites to which the disease will spread. Esophageal cancer spreads quickly to lymphatics, draining to lymph nodes in the neck and around the celiac artery. Endoscopy or barium swallow is used to assess the site. CT and MRI may be necessary to stage the disease. Once the extent of the disease has been assessed, treatment can be planned. Dr. Rasem Mustafa 46  Esophageal rupture The first case of esophageal rupture was described by Herman Boerhaave in 1724. This case was fatal, but early diagnosis has increased the survival rate up to 65%. If the disease is left untreated, mortality is 100%. Typically, the rupture occurs in the lower third of the esophagus with a sudden rise in intraluminal esophageal pressure produced by vomiting secondary to an uncoordination and failure of the cricopharyngeus muscle to relax. Because the tears typically occur on the left, they are often associated with a large left pleural effusion that contains the gastric contents. In some patients, subcutaneous emphysema may be demonstrated. Treatment is optimal with urgent surgical repair. Dr. Rasem Mustafa 47  Thymus  The thymus is a flattened, bilobed structure lying between the sternum and the pericardium in the anterior mediastinum.  In the newborn infant, it reaches its largest size relative to the size of the body, at which time it may extend up through the superior mediastinum in front of the great vessels into the root of the neck.  The thymus continues to grow until puberty but thereafter undergoes involution.  It has a pink, lobulated appearance and is the site for development of T (thymic) lymphocytes. Dr. Rasem Mustafa 48  The most anterior component of the superior mediastinum, lying immediately posterior to the manubrium of the sternum and extends into the anterior mediastinum over the pericardial sac.  The upper extent of the thymus can reach into the neck as high as the thyroid gland; a lower portion typically extends into the anterior mediastinum over the pericardial sac. Dr. Rasem Mustafa 49  The blood supply of the thymus is from the inferior thyroid and internal thoracic arteries. Venous drainage is usually into the left brachiocephalic vein and possibly into the internal thoracic veins. Thymus Lymphatic drainage  Lymphatic drainage returns to multiple groups of nodes at one or more of the following locations:  Internal thoracic arteries (parasternal);  Tracheal bifurcation (tracheobronchial).  Root of the neck. Dr. Rasem Mustafa 50  Clinical Correlation  Ectopic parathyroid glands in the thymus The parathyroid glands develop from the third pharyngeal pouch, which also forms the thymus. The thymus is therefore a common site for ectopic parathyroid glands and, potentially, ectopic parathyroid hormone production. Dr. Rasem Mustafa 51  Nerves of the superior mediastinum  Vagus nerve  The vagus nerves [X] pass through the superior and posterior mediastinum on their way to the abdominal cavity.  Each nerve enters the superior mediastinum posterior to the respective sternoclavicular joint and brachiocephalic vein  They provide parasympathetic innervation to the thoracic viscera.  Visceral afferents in the vagus nerves relay information to the central nervous system about normal physiological processes and reflex activities. They do not transmit pain sensation. Dr. Rasem Mustafa 52  Right vagus nerve The right vagus nerve enters the superior mediastinum and lies between the right brachiocephalic vein and the brachiocephalic trunk. It descends in a posterior direction toward the trachea, crosses the lateral surface of the trachea, and passes posteriorly to the root of the right lung to reach the esophagus. Just before the esophagus, it is crossed by the arch of the azygos vein. As the right vagus nerve passes through the superior mediastinum, it gives branches to the esophagus, cardiac plexus, and pulmonary plexus. Dr. Rasem Mustafa 53  Left vagus nerve The left vagus nerve descends in the neck and enters the thorax and mediastinum between the left common carotid and the left subclavian arteries and posterior to the left brachiocephalic vein. As the left vagus nerve curves medially at the inferior border of the arch of the aorta, it gives off the left recurrent laryngeal nerve. The left vagus nerve continues on to pass posterior to the root of the left lung, where it breaks up into many branches to the esophagus, the cardiac plexus, and the pulmonary plexus Dr. Rasem Mustafa 54  The left vagus nerve also gives rise to the left recurrent laryngeal nerve, which arises from it at the inferior margin of the arch of the aorta just lateral to the ligamentum arteriosum. The left recurrent laryngeal nerve passes inferior to the arch of the aorta before ascending on its medial surface. Entering a groove between the trachea and esophagus, the left recurrent laryngeal nerve continues superiorly to enter the neck and terminate in the larynx Dr. Rasem Mustafa 55 Dr. Rasem Mustafa 56  Phrenic nerves  The phrenic nerves arise in the cervical region mainly from the fourth, but also from the third and fifth, cervical spinal cord segments.  The phrenic nerves descend through the thorax to supply motor and sensory innervation to the diaphragm. Dr. Rasem Mustafa 57  Right phrenic nerve Enters the superior mediastinum lateral to the right vagus nerve and lateral and slightly posterior to the beginning of the right brachiocephalic vein. It continues inferiorly along the right side of this vein and the right side of the superior vena cava. On entering the middle mediastinum, the right phrenic nerve descends along the right side of the pericardial sac, within the fibrous pericardium, anterior to the root of the right lung. It leaves the thorax by passing through the diaphragm with the inferior vena Dr. Rasem Mustafa 58 cava.  Left phrenic nerve Enters the superior mediastinum in a position similar to the path taken by the right phrenic nerve. It lies lateral to the left vagus nerve and lateral and slightly posterior to the beginning of the left brachiocephalic vein, and continues to descend across the left lateral surface of the arch of the aorta, passing superficially to the left vagus nerve and the left superior intercostal vein. On entering the middle mediastinum, the left phrenic nerve follows the left side of the pericardial sac, within the fibrous pericardium, anterior to the root of the left lung. It leaves the thorax by piercing the diaphragm near the apex of the heart.Dr. Rasem Mustafa 59  Lymph Nodes and Vessels of the Thorax  The lymph vessels of the skin(superficial regions ) of the anterior thoracic wall drain to the anterior axillary nodes.  The lymph vessels of the skin (Superficial regions ) of the posterior thoracic wall drain to the posterior axillary nodes.  The deep lymph vessels of the anterior parts of the intercostal spaces drain forward to the internal thoracic nodes (parasternal nodes) along the internal thoracic blood vessels. From here, the lymph passes to the thoracic duct on the left side and the bronchomediastinal trunk on the right side.  The deep lymph vessels of the posterior parts of the intercostal spaces drain backward to the posterior intercostal nodes lying near the heads of the ribs. From here, the lymph enters the thoracic duct. Dr. Rasem Mustafa 60 Intercostal nodes : in the upper thorax also drain into bronchomediastinal trunks, whereas intercostal nodes in the lower thorax drain into the thoracic duct. The deep lymph vessels of the diaphragm (diaphragmatic nodes). Diaphragmatic nodes are posterior to the xiphoid and at sites where the phrenic nerves penetrate the diaphragm. They also occur in regions where the diaphragm is attached to the vertebral column. Nodes associated with the diaphragm interconnect with parasternal, prevertebral, and juxta-esophageal nodes, brachiocephalic nodes (anterior to the brachiocephalic veins in the superior mediastinum), and lateral aortic/lumbar nodes (in the abdomen). Dr. Rasem Mustafa 61  Right Lymphatic Duct  The right jugular, subclavian, and bronchomediastinal trunks, which drain the right side of the head and neck, the right upper limb, and the right side of the thorax, respectively.  Is about 0.5 in. (1.3 cm) long.  Opens into the beginning of the right brachiocephalic vein. Dr. Rasem Mustafa 62  Thoracic Duct  Begins below in the abdomen as a dilated sac, the cisterna chyli.  It ascends through the aortic opening in the diaphragm, on the right side of the descending aorta.  It crosses the median plane behind the esophagus and reaches the left border of the esophagus at the level of sternal angle.  It then runs upward to enter the root of the neck. Here, it bends laterally behind the carotid sheath and in front of the vertebral vessels.  It turns downward in front of the left phrenic nerve and crosses the subclavian artery to enter the beginning of the left brachiocephalic vein. Dr. Rasem Mustafa 63  At the root of the neck, the thoracic duct receives the left jugular, subclavian, and bronchomediastinal lymph trunks.  The thoracic duct drain all lymph from the lower limbs, pelvic cavity, abdominal cavity, left side of the thorax, and left side of the head, neck, and left arm Dr. Rasem Mustafa 64  The autonomic nervous system  Is the part of the nervous system concerned with the innervation of involuntary structures such as the heart, smooth muscle, and glands throughout the body and is distributed throughout the central and peripheral nervous system.  The autonomic system divided into two parts—the sympathetic and the parasympathetic—and both parts have afferent and efferent nerve fibers.  The activities of the sympathetic part of the autonomic system prepare the body for an emergency. It accelerates the heart rate, causes constriction of the peripheral blood vessels, and raises the blood pressure, inhibits peristalsis of the intestinal tract and closes the sphincters.  The activities of the parasympathetic part of the autonomic system aim at conserving and restoring energy. They slow the heart rate, increase peristalsis of the intestine and glandular activity, and open the sphincters.  The hypothalamus of the brain controls the autonomic nervous system and integrates the activities of the autonomic and neuroendocrine systems, thus preserving homeostasis in the body. Dr. Rasem Mustafa 65  Sympathetic System  The gray matter of the spinal cord, from the 1st thoracic segment to the 2nd lumbar segment, possesses a lateral horn, or column, in which are located the cell bodies of the sympathetic connector neurons.  The myelinated axons of these cells (preganglionic) leave the spinal cord in the anterior nerve roots and then pass via the white rami communicantes to the paravertebral ganglia of the sympathetic trunk. Dr. Rasem Mustafa 66  These postganglionic nerve fibers Pass to the thoracic spinal nerves as gray rami communicantes and are distributed in the branches of the spinal nerves to supply the smooth muscle in the walls of blood vessels, the sweat glands, and the arrector pili muscles of the skin. Fibers entering the ganglia of the sympathetic trunk travel up to the ganglia in the cervical region where they synapse, the postganglionic nerve fibers leave the sympathetic trunk as gray rami communicantes, that join the cervical spinal nerves. Travel down to ganglia in the lower lumbar and sacral regions, where they synapse, the postganglionic fibers leave the sympathetic trunk as gray rami communicantes that join the lumbar, sacral, and coccygeal spinal nerves. Dr. Rasem Mustafa 67  The preganglionic fibers may pass through the ganglia on the thoracic part of the sympathetic trunk without synapsing forming three splanchnic nerves. 1. The greater splanchnic nerve arises from the 5th to 9th thoracic ganglia, pierces the diaphragm, and synapses with excitor cells in the ganglia of the celiac plexus. 2. The lesser splanchnic nerve arises from the 10th and 11th ganglia, pierces the diaphragm, and synapses with excitor cells in the ganglia of the lower part of the celiac plexus. 3. The lowest splanchnic nerve arises from the 12th thoracic ganglion, pierces the diaphragm, and synapses with excitor cells in the ganglia of the renal plexus. The postganglionic fibers distributed to the smooth muscle and glands of the viscera. Dr. Rasem Mustafa 68  Parasympathetic System  The connector cells of this part of the system are located in the brain and the sacral segments of the spinal cord.  In the brain form parts of the nuclei of origin of cranial nerves III, VII, IX, and X, and the axons emerge from the brain contained in the corresponding cranial nerves.  The sacral connector cells are found in the gray matter of the 2nd, 3rd and 4th sacral segments of the cord. The myelinated axons leave the spinal cord in the anterior nerve roots of the corresponding spinal nerves. They then leave the sacral nerves and form the pelvic splanchnic nerves. Dr. Rasem Mustafa 69  Thoracic part of the sympathetic trunks  Sympathetic trunks are two ganglionated nerve trunks that extend the whole length of the vertebral column.  There are 3 ganglia in each trunk of the neck, 11 or 12 ganglia in the thorax, 4 or 5 ganglia in the lumbar region, and 4 or 5 ganglia in the pelvis.  The two trunks lie close to the vertebral column and end below by joining together to form a single ganglion, the ganglion impar. Dr. Rasem Mustafa 70  The thoracic part of the sympathetic trunk  Is continuous above with the cervical and below with the lumbar parts of the sympathetic trunk.  It is the most laterally placed structure in the mediastinum and runs downward on the heads of the ribs.  It leaves the thorax on the side of the body of the 12th thoracic vertebra by passing behind the medial arcuate ligament.  Has 12 (often only 11) segmentally arranged ganglia, each with white and gray ramus communicans passing to the corresponding spinal nerve.  The first ganglion is often fused with the inferior cervical ganglion to form the stellate ganglion. Dr. Rasem Mustafa 71  Branches 1. Gray rami communicantes go to all the thoracic spinal nerves. The postganglionic fibers are distributed through the branches of the spinal nerves to the blood vessels, sweat glands, and arrector pili muscles of the skin. 2. The first five ganglia give postganglionic fibers to the heart, aorta, lungs, and esophagus. 3. The lower eight ganglia mainly give preganglionic fibers, which are grouped together to form the splanchnic nerves and supply the abdominal viscera. They enter the abdomen by piercing the crura of the diaphragm. The greater splanchnic nerve arises from ganglia 5 to 9, the lesser splanchnic nerve arises from ganglia 10 and 11, and the lowest splanchnic nerve arises from ganglion 12 Dr. Rasem Mustafa 72