“Human Biological Systems Gas Exchange &amp

Transport" Diaphragm and external intercostal muscles are muscles of inspiration whereas internal intercostal muscle is the muscle of expiration. There are some accessory muscles that assist in forceful inspiration or expiration such as sternocleidomastoid, scalenus, pectoralis and abdominal muscles.
f) Spinal cord and peripheral nerves: C3, C4 and C5 spinal segments provide innervations to diaphragm via phrenic nerve. All the intercostal muscles get segmental innervations through intercostal nerves that run in the intercostal groove along with artery and vein.
Most of the structures of Ventilatory pump, such as muscles and skeleton, ensure appropriate movement of the chest wall and adequate change in the intrathoracic pressure during inspiration and expiration. All the components of airway provide an uninterrupted passage of air to and from the alveoli. The passage is also lined with special epithelium that produces mucus and is studded with cilia (Hlastala &amp. Berger, 1996, p.23). Mucus moist or warm the air whereas cilia traps any foreign particles and clear excess mucus. Parietal pleura line the chest wall and visceral pleura cover the outer surface of the lung. In between these two layers is a pleural space that contains a small amount of fluid. This pleural space plays a critical role in changing the intrathoracic pressure. Spinal cord and peripheral nerves provide a communication between controller and muscles of respiration. (Schwartzstein &amp. Parker, 2006, p.15-23)
Terminal bronchioles and alveoli are the sites of gas exchange (no gas exchange take place in the rest of the airway and is referred to as dead space). These alveoli provide abundant surface area for adequate diffusion of gases. Understandably, alveoli are surrounded by thousand of blood capillaries to ensure effective transfer of oxygen and carbon dioxide.
The process of

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