The thorax lies between the neck and the abdomen and lies within a cage formed by the vertebrae, the ribs, the sternum, the costal cartilages, and their attached muscles. The thoracic cage protects the contents of the thorax, whereas the muscles assist in breathing.
It is important to identify and count ribs as they form key landmarks to the positions of the internal organs.
In a fit muscular person one can identify a number of landmarks. For topographic anatomy of the chest wall
Jugular (suprasternal) notch: at the level of the inferior border of the T2 vertebra
Sternal angle (manubriosternal join): at the level of the T4/5 intervertebral disc and where the second costal cartilages articulate with the sternum.
Manubrium: The left brachiocephalic vein runs beneath the manubrium from the upper left to lower right, where it joins the right brachiocephalic vein to form the superior vena cava
Body of the sternum: Anterior to the T5 through T9 vertebrae and the right border of the heart
Nipple: Anterior to the 4th intercostal space in males and the dome of the right hemidiaphragm; sits on the pectoralis major muscle
Xiphoid process: At the level of the T10 vertebra
The costal margins: Comprises the 7th through 10th costal cartilages
On yourself, palpate the following:
The sternoclavicular joints, lateral to the jugular notch
The sternum and its parts: manubrium, body, and xiphoid process
The manubriosternal joint (sternal angle)
The second pair of ribs on either side of the sternal angle—the surface landmark for rib counting
Surface lines can be drawn to identify regions of the thorax
Imaginary perpendicular lines passing through the midpoint of each clavicle are called the midclavicular lines.
Midaxillary lines are perpendicular lines through the apex of the axilla on both sides
Cephalic vein can be seen in some subjects lying in the deltopectoral groove between the deltoid and pectoralis major muscles.
The sternum can be divided to gain access to the thoracic cavity for surgical operations. This is called a median sternotomy.
The middle ribs are most commonly fractured, and multiple rib fractures can manifest as a “flail chest,” where the injured region of the chest wall moves paradoxically, that is, in on inspiration and out on expiration.