Inferior thoracic aperture (outlet)
1. Bounded by
a. T12 vertebrae
b. the six lower pairs of ribs (the cartilages of ribs 7-12)
c. xiphoid process anteriorly
2. Closed by diaphragm which attaches to the lower 6 ribs and to the vertebral bodies
3. Costal arch = sloping costal cartilages of ribs 7-10
4. Infrasternal angle = angle the costal arch makes as the ribs converge on the lower sternum
5. Inferior aperture is not in a flat plane
a. posteriorly at level of T12
b. anteriorly at level of T9 (xiphisternal junction)
c. laterally at level of L1-2 (subcostal plane)
d. diaphragm pushes up into the thorax as high as T8 (ICS 5 on left, ICS 4 on right)
Based on the above descriptions, tap on the image below where you would expect to find the inferior thoracic aperture and it will appear outlined.