The human respiratory system consists of a series of organs that form a passageway for the air flowing to and from the alveoli of the lungs. The larynx is the central portion.
The other organs are grouped as supra laryngeal or infra-laryngeal. The general functions of the supra laryngeal structures are to condition the in flowing air and to test it.
The larynx is located in the lower anterior neck region. The larynx is suspended from the hyoid bone by a membrane. The larynx performs several functions in humans.
Its primary function is to control the volume of the air passing through the air passageways, to and from the alveoli of the lungs. The larynx also produces selected vibration frequencies in the moving column of air.
The respiratory tree is so named because it has the appearance of an inverted tree, with its trunk and branches. The "trunk" of the tree is the trachea.
The trachea extends from the inferior margin of the larynx, down through the neck, and into the center of the thorax.
In the center of the thorax, the trachea divides into right and left primary bronchi. The right is somewhat more vertical than the left.
At the terminals of the branching tubes are groups of spherical alveoli. This gives the appearance of a bunch of grapes. A variety of situations may occlude these tubular air passageways.
External respiration takes place in the alveoli. As we indicated earlier, external respiration is a surface phenomenon in which the gases pass through the wall of the alveolus.
Respiratory reflexes are controlled by the respiratory center. The level of carbon dioxide in the circulating blood is one of the major influences upon the respiratory reflex.
The individual intercostal nerves innervate the intercostal muscles.
The muscles attached to and moving the rib cage are innervated by their appropriate nerves.
The diaphragm is innervated by its own individual pair of phrenic nerves.
Nutrient blood provides nourishment and oxygen to the tissues of the lung.
Functional blood is actually involved in the respiratory exchange of gases between the alveoli and the capillaries.
The pulmonary cycle originates in the right ventricle of the heart. Contraction of the right ventricle forces the blood into the pulmonary arch, which divides into the right and left pulmonary arteries to their respective lungs.