Subdivisions of the Thoracic Cavity

In preparation for studying the internal organs of the thoracic cavity, we will subdivide it artificially into several parts. It is thought that doing this will aid memorizing what is located in each subdivision. First, when looking at a cross section, we can subdivide the cavity into left and right pleural cavities and an intermediate area called the mediastinum.

Subdivisions of thorax as seen on cross section left and right pleural cavities mediastinum

Subdivision of the Mediastinum According to Anatomists

Subdivision of mediastinum as seen on cross section anterior mediastinum (1) middle mediastinum (2) posterior mediastinum (3)

Subdivision of mediastinum as seen on sagittal section superior mediastinum (1) anterior mediastinum (2) medial mediastinum (3) posterior mediastinum (4)

Boundaries of the mediastinum

• superior mediastinum (1)
• upper boundary -- plane of the thoracic inlet (jugular notch, first rib, first thoracic vertebra)
• lower boundary -- plane of sternal angle (from sternal angle to lower border of fourth thoracic vertebra
• lateral boundaries -- mediastinal pleurae
• anterior boundary -- manubrium of sternum
• posterior boundary -- bodies of thoracic vertebrae 1 thru 4
• inferior mediastinum (2)
anterior
• anterior -- body and xiphoid of sternum
• posterior -- pericardium
• lateral -- mediastinal pleura
• superior -- plane of sternal angle
• inferior -- diaphragm
middle
• anterior -- pericardium
• posterior -- pericardium
• lateral -- mediastinal pleura
• superior -- plane of sternal angle
• inferior -- diaphragm
posterior
• anterior -- pericardium
• posterior -- bodies of thoracic vertebrae 5 - 12
• lateral -- mediastinal pleura
• superior -- plane of sternal angle
• inferior -- diaphragm

Subdivision of the Mediastinum According to Some Clinical Radiologists

Clinical radiologists have described the subdivisions of the mediastinum in the following way: the anterior mediastinum by the clinician is the anterior and middle mediastina combined and it extends into the superior mediastinum anterior to the plane of the anterior surface of the trachea. the middle mediastinum includes the posterior mediastinum and the part of the superior mediastinum posterior to a plane anterior to the trachea the posterior mediastinum includes the bodies of the vertebrae which includes the paravertebral space and thus includes the sympathetic chains on each side. This is the region that neurogenic tumors might occur.

Pleural Cavity

Heart

This is copyrighted©1999 by Wesley Norman, PhD, DSc