How do human achieve inhalation?

Human inhalation is achieved by relaxation movements of the diaphragm, a dome-shaped muscular partition that seperates the cavity of the chest and that of the abdomen. When the dome-shaped diaphragm flattens, the chest volume increases and accordingly the expansion of the lungs (left and right). Air from outside the human body is thereby sucked into our lungs via our bronchi through the nostrils.