THORACIC ANATOMY Extramediastinal

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THORACIC ANATOMYExtramediastinal
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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

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Skin Subcutaneous Tissue

• Essentially the same as elsewhere in the body

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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

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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 1112 are capped with an apex of cartilage
  but do not articulate with the sternum
• atypical 1st, 11th and 12th
• remainder are typical

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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

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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

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Muscles Inner Layer

• Consists of internal intercostals
• Internal intercostals corresponds with the
  internal oblique in the abdomen

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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

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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

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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

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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

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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

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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

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Contents Diaphragm cont

• Nerve supply
• sole muscular supply is from the phrenic nerve
  (C4, 5 6)