Structure and Function of the Respiratory Tract in Dogs

Below is information about the structure and function of the canine respiratory system. We will tell you about the general structure of respiratory system, how lungs work in dogs, common diseases that affect the respiratory system and common diagnostic tests performed to evaluate the lungs and airways of dogs.

What Is the Respiratory System?

The respiratory system in humans, dogs, and other pets is a series of tracts and organs responsible for respiration, without which life would not be possible. Respiration is the term used to describe breathing. It involves the inhalation of air and the intake of oxygen, as well as the exhalation of waste gases such as carbon dioxide from the lungs.

Besides breathing, the respiratory tract serves other important roles, such as the humidification and warming of air before it enters the body, the trapping and expelling of foreign substances, facilitation of the sense of smell, and the production of vocal sounds (e.g. barking, growling). The respiratory system consists of the nasal passages, the back of the mouth (nasopharynx), the voice box (larynx), the windpipe (trachea), the lower airway passages, and the lungs.

Where Is the Respiratory Tract Located in Dogs?

The respiratory tract is a large, contiguous system comprised of several structures. The respiratory system begins at the nostrils, involves several structures of the head, continues down the neck and ends at the lungs that lie in the chest cavity.

What Is the General Structure of the Canine Respiratory Tract?

The respiratory tract is a very structurally diverse system.

What Are the Functions of the Respiratory Tract?

What Are Some Common Diseases of the Respiratory Tract in Dogs?

There are many primary disorders that affect the respiratory tract. Generally speaking, coughing, sneezing, and/or difficult breathing are the most common signs seen with respiratory disease.

Laryngitis is inflammation of the larynx. It most commonly occurs with tracheitis and upper respiratory infections. Clinical signs may include coughing, nasal discharge, difficulty or noisy breathing and a change in voice.

Brachycephalic syndrome is a condition of brachycephalic dogs in which several upper airway abnormalities occur together and seriously decrease the passage of air. Dogs with this syndrome may have congenitally small nostrils (stenotic nares), overly long soft palates that hang down into the nasopharynx, underdeveloped tracheas (tracheal hypoplasia), herniation of the vocal folds into the larynx (everted laryngeal saccules), and laryngeal paralysis. All of these conditions predispose the dog to respiratory difficulties, particularly if they become excited or overactive, are confined to small areas, are obese, or are exposed to heat and humidity. Clinical signs may be mild (noisy breathing, snoring, gagging or retching phlegm, exercise intolerance) to severe (respiratory distress, cyanosis, overheating, collapse, shock) with this condition.

Laryngeal paralysis is an acquired disease of some older, large breed dogs. The cartilages that normally control the opening and closing of the larynx become paralyzed and the larynx does not open well. These dogs exhibit changes in their voice (hoarse, raspy bark), noisy breathing, and exercise intolerance. They may also overheat and collapse in respiratory distress.

Polyps and tumors may also develop within the larynx.

Edema or fluid in the lungs may occur with a variety of conditions, including heart disease, electric cord shock, trauma, snake bite and other exposure to other toxins, smoke inhalation, near drowning, overdosage of intravenous fluids, and numerous other systemic diseases.

Cancer of the lungs may be primary or secondary (metastatic). Primary lung tumors are usually malignant and arise from either cells of the lungs or airways. They include squamous cell carcinomas, the bronchoalveolar carcinomas, and pulmonary adenocarcinomas. Many cancerous tumors in the body can spread to the lungs via the blood vessels. Such tumors include cancers of the kidneys, spleen, bones, skin, mammary glands, and soft tissues of the body.

Pulmonary contusions or bruises may develop when trauma causes hemorrhaging into the lungs. They are common after automobile accidents, dog bite wounds, falling from heights, and other forms of blunt chest trauma.

What Types of Diagnostic Tests Are Used to Evaluate the Respiratory Tract?

Depending on the history and clinical signs, the following tests may be indicated to help make a diagnosis and design a proper treatment protocol.