THE THORACIC REGION DESCRIPTION: This is the part of the trunk, which is located between the root of the neck and the superior border of the abdominal region.  SHAPE It has the shape of a truncated cone with the apex located rostrally and the base caudally. APERTURES (Figs 1a & b): Superior thoracic aperture (Inlet): This communicates directly with the root of the neck. Inferior thoracic aperture (Outlet): This aperture is covered by the thoracoabdominal diaphragm.

BOUNDARIES OF THE THORAX (WALLS) (Fig. 1): Anterior: The sternum, anterior parts of the ribs and their costal cartilages. Lateral: Twelve pairs of ribs. The ribs and their cartilages are separated by 11 intercostal spaces, which are occupied by the intercostal muscles and membranes Posterior: The bodies of the twelve thoracic vertebrae and the intervertebral discs between them.

IMPORTANT LANDMARKS ON THE THORACIC WALL (Fig. 2) Understanding the applied anatomy of the thoracic wall is dependent on our knowledge of important landmark on this anatomical region of the body. This understanding is also vital to the correlation of internal structures to the chest wall. The following are the anatomical landmarks of the chest wall ANTERIOR THORACIC WALL Jugular notch (Suprasternal notch). This is the upper border of the manubrium: T2/T3 Manubrosternal (Sternomanubrial) junction. The manubrium articulates with the body of sternum at this point: T4/T5 3. This is also the point at which the second costal cartilages articulate with the sternum. 4. Xiphisternal (Xiphosternal) joint T9. 5. Subcostal plane (Tip of 10th costal cartilage) L3.

LANDMARKS ON THE POSTERIOR THORACIC WALL Superior angle of the scapular T2. Spine of the scapular T3. Inferior angle of the scapular T8.***

THE THORACIC CAVITY (Figure 3): SUBDIVISIONS: Two pleural (Lateral thoracic) cavities, which contain the lungs and the pleural membranes. The mediastinum: This is the bulky, mobile, midline septum sandwiched between the two pleural cavities. It extends anteroposteriorly (Front to back) from the sternum and the costal cartilages to the vertebral bodies of T1 to T12 and Rostrocaudally (From above downwards) from the thoracic inlet to the diaphragm, which seals the thoracic outlet.

COMPARTMENTS OF THE MEDIASTINUM: The compartments of the mediastinum consist of: Superior mediastinum above the manubriosternal junction and Inferior mediastinum below the manubriosternal junction. The inferior mediastinum is further subdivided by the pericardial sac into: Anterior mediastinum. Middle mediastinum (Formed by the pericardial sac) and Posterior mediastinum.

CONTENTS OF THE MEDIASTINAL COMPARTMENTS: THE SUPERIOR MEDIASTINUM The major contents of the superior mediastinum includes the following: Thymus gland or its degenerative remains in the adult The great vessels, which include: 2. Right and Left Brachiocephalic veins. 3. The Superior Vena cava. 4. The arch of the aorta 5. The Trachea 6. The Oesophagus The Phrenic nerve The Vagus nerve The Left Recurrent Laryngeal nerve The thoracic duct

THE ANTERIOR MEDIASTINUM The Thymus gland or its degenerative remains Lymph nodes and lymph vessels. Fat and loose connective tissues. Branches of the Internal thoracic (Internal mammary) artery. The sternopericardial ligaments

MAJOR CONTENTS OF THE MIDDLE MEDIASTINUM: 1. The fibrous pericardial sac, which contains: The heart. The parietal and visceral serous pericardium. The lower half of the superior Vena Cava. Terminal part of the inferior vena cava The ascending aorta. The pulmonary trunk. Serous fluid. 2. The pericardiacophrenic artery. 3. The phrenic nerve. 4. The pulmonary vessels 5. Termination of the azygos vein.

CONTENTS OF THE POSTERIOR MEDIASTINUM: The descending thoracic aorta. The oesophagus The oesophageal nerve plexus (Which is derived from the vagus nerve). The thoracic duct. The azygos vein. The hemiazygos. vein The accessory hemiazygos veins. Proximal parts of the posterior intercostal vessels The splanchnic nerves The posterior mediastinal lymph nodes and vessels