Rav Hirsch: Prayer V
The trachea, and probably also the esophagus, the heart and the lungs, together with the breast, which covers them, and the upper ribs on either side, form the fourth group.
Here we have together all the vital organs and their protective encasement, on whose unimpeded functioning the very existence of the living creature is dependent.
Without the functioning of the esophagus – which, by bringing the food to be digested into nutritive substances distributed to the body in the blood stream by the heart pump – the body would become entirely impoverished; without the functioning of the trachea and the lungs the whole life process comes to a deadlock, and the living individual falls as dead matter.
The deliverance from all dangers to our existence – Geula – the protection from impoverishment – Oni- and all struggle – Riv – form the subjects of the fourth of the middle blessings, which correspond to the organs representing the vital and indispensable requirements for our existence.