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Cross-Sectional Anatomy of Thorax

In this article, we are going to describe the cross-sectional anatomy of thorax which is essential in understanding cross-sectional imaging.

Cross-Sectional Anatomy of Thorax Level T3:

  • It is the level of superior mediastinum.
  • The trachea lies in the midline with the right brachiocephalic artery, left common carotid artery and left subclavian artery anteriorly.
  • The esophagus is seen behind the trachea and anterior to the vertebra.
  • The brachiocephalic veins are anterior and lateral to the arteries and unite to form the superior vena cava.
  • The left brachiocephalic vein is seen passing anterior to the branches of the aortic arch.
Cross-Sectional Anatomy of Thorax: Level T3
Cross-Sectional Anatomy of Thorax: Level T3
CT Scan of Thorax (Axial View) Level T3
CT Scan of Thorax (Axial View) Level T3

Cross-Sectional Anatomy of Thorax Level T4:

  • This plane passes through the lower board of T4 and the sternal angle.
  • This plane demarcates the superior and the inferior mediastinum.
  • The lower part of the aortic arch is seen to the left of the trachea.
  • The arch of an azygous vein crosses the right hilum to drain into the posterior aspect of superior vena cava at this level.
  • The oblique fissure can be seen at the level on CT.
Cross-Sectional Anatomy of Thorax: Level T4
Cross-Sectional Anatomy of Thorax: Level T4
CT Scan of Thorax (Axial View) Level T4
CT Scan of Thorax (Axial View) Level T4

Cross-Sectional Anatomy of Thorax Level T5:

  • This plane is at or just below the tracheal bifurcation.
  • The main pulmonary artery divides into right pulmonary artery and the left pulmonary artery
  • The right pulmonary artery runs anteriorly to its bronchus.
  • The left pulmonary artery arches superiorly out of the plane to pass over the left bronchus.
  • The superior pulmonary veins are seen anteriorly.
  • The right superior pulmonary vein is anterior to the interlobar artery.
  • The left superior pulmonary artery is separated from lower lobe artery by the left bronchus.
  • The ascending aorta is seen lying to the right of the main pulmonary artery.
  • Most anteriorly is the anterior junctional line that is the junction of the anterior pleurae of the lungs
  • The esophagus, azygous vein, and the descending aorta are seen in the posterior mediastinum.
  • The azygo-oesophageal recess may be seen.
Cross-Sectional Anatomy of Thorax: Level T5
Cross-Sectional Anatomy of Thorax: Level T5
CT Scan of Thorax (Axial View) Level T5
CT Scan of Thorax (Axial View) Level T5

Cross-Sectional Anatomy of Thorax Level T6:

  • This level passes through the upper part of the heart.
  • The right atrial appendage is seen overlapping the origin of the aorta.
  • The coronary artery arises from the at this level.
  • The right ventricular outflow tract is seen anterior to the origin of the aorta.
  • The esophagus is seen left to the left atrium.
Cross-Sectional Anatomy of Thorax Level T6
Cross-Sectional Anatomy of Thorax Level T6

Cross-Sectional Anatomy of Thorax Level T8:

  • At this level, we can see the relationship of heart chambers to each other.
  • The left ventricular inflow and outflow tracts are separated from each other by the anterior leaflet of the mitral valve.
  • The aortic sinuses are seen at this level.
  • The right border of the heart is formed by the right atrium.
  • The left ventricle forms the left border of the heart.
  • The right ventricle forms the anterior border of the heart.
Cross-Sectional Anatomy of Thorax Level T8
Cross-Sectional Anatomy of Thorax Level T8

Cross-Sectional Anatomy of Thorax Level T10:

  • Part of the abdominal cavity is seen at this level because the domes of the diaphragm reach the level of T9.
  • The esophagus traverses the diaphragm at the level of T10 through the esophageal opening.
  • The fundus of the stomach, part of liver and spleen are seen.
  • The inferior vena cava (IVC) is situated slightly anteriorly.
  • The descending aorta is seen posteriorly.
  • The azygous and hemizygous veins are on the right and left of the descending aorta respectively.
Cross-Sectional Anatomy of Thorax Level T10
Cross-Sectional Anatomy of Thorax Level T10

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