THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -During inspiration, the diaphragm and external intercostal muscles contract, causing the rib cage to expand and move outward, and expanding the thoracic cavity and lung volume. This creates a lower pressure within the lung than that of the atmosphere, causing air to be drawn into the lungs.

Detailed explanation-2: -Inspiration (breathing in) The diaphragm contracts and moves downwards. The intercostal muscles contract and move the ribs upwards and outwards. This increases the size of the chest and decreases the air pressure inside it which sucks air into the lungs.

Detailed explanation-3: -Upon inhalation, the diaphragm contracts and flattens and the chest cavity enlarges. This contraction creates a vacuum, which pulls air into the lungs. Upon exhalation, the diaphragm relaxes and returns to its domelike shape, and air is forced out of the lungs.

Detailed explanation-4: -The diaphragm is controlled by the phrenic nerve, which originates from C3–C5 vertebrae; the external and internal intercostals are controlled by spinal nerves in the thoracic cord; the abdominal muscles are controlled by spinal nerves in the lumbar cord.