| Structure/Space | Description/Boundaries | Significance |
|---|---|---|
| midaxillary line | an imaginary vertical line passing through the middle of the axilla | used as a surface landmark for descriptive purposes |
| midclavicular line | an imaginary vertical line passing through the midshaft of the clavicle | used as a surface landmark for descriptive purposes |
| nipple | located superficial to the 4th intercostal space in the male and prepuberal female | location of the left nipple may be used to help locate the apex of heart, which is approximately 8 cm from the midline in the left 5th intercostal space; a surface landmark used to place the stethoscope for auscultation of the bicuspid valve |
| sternal angle | a protrusion on the anterior thoracic wall at the junction of the manubrium and body of the sternum (manubriosternal symphysis) | sternal angle is the location of the attachment of t the costal cartilage of the 2nd rib to the sternum; an imaginary horizontal plane through the sternal angle passes through the T4/T5 intervertebral disc and marks the inferior boundary of the superior mediastinum |
| suprasternal notch | the notch located at the superior border of the manubrium of the sternum, between the sternal ends of the clavicles | also known as: jugular notch |
| thoracic inlet | the opening at the superior end of the rib cage through which cervical structures enter the thorax; bounded by the T1 vertebral body, both of the 1st ribs and their costal cartilages, and the manubrium of the sternum | thoracic inlet marks the boundary between the neck and the superior mediastinum; also known as: superior thoracic aperture |
| thoracic outlet | the opening at the inferior end of the rib cage through which thoracic structures exit the thorax; it is bounded by the T12 vertebral body, both 12th ribs, the costal cartilages of ribs 7-12, and the xiphisternal joint | thoracic outlet is closed by the respiratory diaphragm which is attached at its boundary; also known as: inferior thoracic aperture |