THORACIC ANATOMY Extramediastinal

1. THORACIC ANATOMYExtramediastinal

2. Boundaries • Anterior • manubrium, sternum and xiphisternum • Posterior • vertebral column and the ribs • Superior • continuous with the neck • Inferior • diaphragm • Thoracic wall is topographically & developmentally continuous with the abdominal wall

3. Skin & Subcutaneous Tissue • Essentially the same as elsewhere in the body

4. Bones • Sternum • manubrium, body and xiphoid process • gives rise to and is the area of attachment of a number of different muscles • Vertebral column • Scapula & clavicle

5. Bones cont… • Ribs • 12 pairs • first seven pairs directly articulate with the sternum • pairs 8-10 articulate with the rib above and then via 7th rib with the sternum • pairs 11&12 are capped with an apex of cartilage but do not articulate with the sternum • atypical: 1st, 11th and 12th • remainder are typical

6. Joints • Variety of joints • Ribs • articulations between the ribs and the vertebral column: costovertebral joints • articulation between the ribs and the sternum: costosternal joints • Sternoclavicular joint • synovial joint • medial end of the clavicle and the manubrium

8. Muscles: Outer Layer • Consists of: external intercostals, levator costae and serratus posterior • External intercostals: corresponds to the external oblique in the abdomen • Levator costae: 12 pairs of fan-shaped muscles • Serratus posterior: superior and inferior

9. Muscles: Inner Layer • Consists of: internal intercostals • Internal intercostals: corresponds with the internal oblique in the abdomen

10. Muscles: Innermost Layer • Consists of : subcostals, innermost intercostals and tranversus thoracis • Together referred to as the transversus thoracis group • Line the rib cage • subcostals: posteriorly • innermost intercostals: laterally • transversus thoracis: anteriorly

11. Intercostal Spaces • Filled with the muscles of the thoracic wall • external/internal/innermost • Neurovascular bundle lies in the plane between the internal and innermost layer • vein, artery and nerve • protected by the lower border of the rib above • Intercostal nerve: anterior ramus of the spinal nerve • segmentally supplies the muscles and skin of the thorax and the abdominal wall

12. Intercostal Spaces cont… • Intercostal arteries: anterior and posterior • branches from the descending thoracic aorta and the internal thoracic artery for all intercostal spaces except for the first two • supplied by the superior intercostal artery • Intercostal veins: more complex • each space has one posterior and two anterior veins • complex drainage pattern

13. Contents: Lungs • Surfaces: inferior, mediastinal & costal • Hilum • area on the mediastinal surface where structures running to and from the lung enter and leave • different between the right and the left lung

14. Contents: Lungs cont… • Structure of the alveolar tree • multiple divisions from the trachea to the respiratory bronchioles • 20-25 divisions in total • Relationship of the alveolar tree to vascular supply • pulmonary artery divides alongside the bronchi however, it does not supply it • ultimately ramifies around the walls of the alveoli and feeds it with deoxygenated blood • branches of the pulmonary vein drain the area

15. Contents: Diaphragm • Separates the thoracic and abdominal cavities • Arises from within the costal margin: directly from the ribs and via two large crura • Relationships • right dome to the level of 4th ICS on expiration • left dome to the level of the 5th rib • central tendon level with the xiphisternal joint (T8) • Openings • three: aortic, oesophageal and caval

16. Contents: Diaphragm cont… • Nerve supply • sole muscular supply is from the phrenic nerve (C4, 5 & 6)