How the Canine Respiratory System Works

By Tess Thompson



There is a minor difference between the human and canine respiratory systems. In humans, body temperature is controlled by sweat glands, but dogs need to breathe hard to cool their bodies because they do not have sweat glands. Besides that, dog respiratory problems are treated and managed differently compared to human respiratory issues.

The dog respiratory system is comprised of the upper (nasal cavities, nasopharynx, larynx and trachea) and lower respiratory tract (bronchi and lungs).

The nasal cavities that open out through the dog’s nose are comprised of the nasal bone, premaxilla, maxillary bone, lateral cartilage and the nasal septum (the partition of bone and cartilage between the two cavities). They include the turbinate bones and the nasal sinuses. The turbinate bones are little spongy bones that are scrolled together and form into a cone. This provides a bigger surface area to the mucous membrane that covers them. It is here that the inhaled air is warmed and moistened. The turbinate bones and the nasal sinuses are partitioned by a middle bony partition.

Air enters through the anterior nares (nostrils). Dust, disease-causing germs, and other potentially harmful particles are trapped in the mucus that is secreted by the nasal glands within the nasal cavities. One portion of the mucous membrane is responsible for the dog’s sharp sense of smell. On the other end, there are posterior nares through which the air (at body temperature and void of any impurities) enters the nasopharynx, a cavity forming the upper part of the pharynx.

However, it is through the larynx and trachea that air moves onwards to the stomach and lungs. The larynx is attached to the skull bones by the hyoid bone (a U-shaped bone under the tongue) and is comprised of four different cartilage structures, including the epiglottis. During the swallowing process, the backward motion of the tongue forces the epiglottis cartilage to close the laryngeal opening so that the swallowed material does not enter the wind pipe. Besides avoiding entry of food into the trachea, the epiglottis is also responsible for controlling the flow of air.

The trachea is a common term used for an airway through which air is transported. Hair-like projections on the surface of tracheal cells trap any remaining dust to prevent it from entering the lungs, which are then removed by coughing. The trachea conveys inhaled air from the larynx to the bronchi, where it moves to the lungs. At the top of the trachea is a cartilaginous structure which contains elastic vocal cords that determine the vocal tone of the dog’s bark.

There are seven pulmonary lobes in a dog lungs, and as many bronchi. A tiny sac for holding air in the lungs is formed by the terminal dilation of air. The lungs have a large surface area and get a vast supply of blood. It is here that oxygen is exchanged with carbon dioxide and passed out through the mouth or the nostrils the same way it came in.

References:

http://www.caninehealthnutrition.com/KnowYourDog/canine-respiratory-system.html

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