QS Study

The thorax is the superior part of the trunk between the neck and the abdomen. The thoracic cage provides attachments for muscles of the neck, thorax, upper limbs, abdomen, and back.

Role of ribs in respiration:

The ribs help in the expansion and contraction of the thoracic cavity (though that is primarily the function of the diaphragm) and also protect the lungs and heart. The rib cage assists with breathing by using a pair of muscles located between each rib known as the internal intercostals and external intercostals. The ribs play an important role in respiration by increasing the anteroposterior and transverse diameters of the thorax in the following ways:

(a) Antero-posterior diameter is increased

  1. Mainly by the pump-handle movements of the sternum brought by the elevation of vertebrosternal ribs (2nd to 6th).
  2. Partly by the elevation of vertebrochondral ribs (7th to 10th).

(b) Transverse diameter is increased

  1. Mainly by the bucket-handle movements of vertebrochondral ribs (7th to 10th).
  2. Partly by elevation of the vertebrosternal ribs.