The nasopulmonary and nasothoracic reflexes regulate the mechanism of breathing through deepening the inhale. Triggered by the flow of air, the pressure of the air in the nose, and the quality of the air, impulses from the nasal mucosa are transmitted by the trigeminal nerve to the breathing centres in the brainstem and the generated response is transmitted to the bronchi, the intercostal muscles and the diaphragm.

Stridor is a high-pitched breathing sound resulting from turbulent air flow in the larynx or lower in the bronchial tree. Stridor is a physical sign which is caused by a narrowed or obstructed airway.

Ventilatory rate (minute volume) is strictly controlled and determined primarily by blood levels of carbon dioxide as determined by metabolic rate. Blood levels of oxygen become important in hypoxia. These levels are sensed by chemoreceptors in the medulla oblongata for pH, and the carotid and aortic bodies for oxygen and carbon dioxide.

The nasal cavity conditions the air to be received by the other areas of the respiratory tract. Owing to the large surface area provided by the nasal conchae, the air passing through the nasal cavity is warmed or cooled to within 1 degree of body temperature.

This forms the Adam's apple. It is usually larger in males than in females. The thyrohyoid membrane is a ligament associated with the thyroid cartilage that connects the thyroid cartilage with the hyoid bone.

Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is emitted by the decaying corpses of a number of insects, including bees and Pogonomyrmex ants. Its RQ value is 0.71. Oxalic acid is a colorless crystalline solid that dissolves in water to give colorless solutions. Its RQ value is 4.

Posterior cricoarytenoid muscles abduct and externally rotate the arytenoid cartilages resulting in abducted vocal folds.

It is a genetic condition in which mucus does not clear easily from the airways. The excess mucus causes repeated episodes of bronchitis and pneumonia throughout life.

The esophagus lies posteriorly to the trachea. Circular bands of fibrous connective tissue called the annular ligaments of trachea join the tracheal rings together.

The middle lobe is the smallest lobe of the right lung. It is wedge-shaped and includes the part of the anterior border and the anterior part of the base of the lung.

Some amount of air remains in the various parts of the respiratory tract. The air in the trachea and bronchi (where no diffusion occurs) is called dead space air (350ml). The air remaining in the alveoli or air sacs is alveolar air (150ml).

As long as pressure within the alveoli is lower than atmospheric pressure, air will continue to move inwardly. But as soon as the pressure is stabilized, air movement stops.

Each body cell releases carbon dioxide into nearby capillaries by diffusion, because the level of carbon dioxide is higher in the body cells than in the blood. In the capillaries, some of the carbon dioxide is dissolved in plasma and some is taken by the hemoglobin, but most enters the red blood cells where it binds with water to form carbonic acid.

The citrate goes through a series of chemical transformations, losing two carboxyl groups as CO₂. The carbons donated by acetyl-CoA become part of the oxaloacetate carbon backbone after the first turn of the citric acid cycle.  

For simple fermentations, the metabolism of one molecule of glucose to two molecules of pyruvate has a net yield of two molecules of ATP. Most cells will then carry out further reactions to 'repay' the used NAD⁺ and produce a final product of ethanol or lactic acid.