Like all other body systems, a kitten is born with a fully functional respiratory system once the first breaths are taken. The 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. Without the organs and respiratory pathways, life would not be possible.
The feline’s respiratory system serves two purposes. First, it is the exchange mechanism by which the body’s carbon dioxide is replaced with oxygen. Second, it is a unique cooling system as they lake the sweat glands to perspire their body’s temperature like humans do. So like dogs, cats must pant, or breathe harder, so that warm war is exchanged from the body for the cooler outside air. Additionally, moisture within the respiratory system evaporates, further cooling the body.
Besides these two functions, the respiratory tract also serves other important roles such as: humidification and warming of air and trapping and expelling of foreign substances (nasal cavity), facilitation of the sense of smell (jacobson’s organ), and the production of vocal sounds (larynx).
The Organs
- Nostrils: Along with the mouth, the nose is responsible for taking air into the body. The fine hairs (cilia) that line the nasal cavity and the mucus that is produced is to filter debris and foreign material from the air.
- Nasal cavity: It holds the olfactory region, the area responsible for smell, is located in the back of the nasal cavity. The mucous membrane of this region contains special nerves designed for smell. It also warms and moistens the air before it enters the trachea.
- Sinuses within the skull
- Pharynx (back of the mouth)
- Larynx (voice box): It guards the entrance to the trachea, regulating both the inspiration and expiration of air. The valvular function of the larynx, formed by the epiglottis and arytenoid cartilages, is vital in protecting the airway, preventing the aspiration of food.
- Trachea (windpipe): It serves to conduct air downward into the lungs. Lined with cilia and mucus, it also traps any debris and foreign substances that manage to pass through the nasal cavity and mouth. The trachea returns those substances to the mouth through the act of coughing.
- Bronchi (the branches of the trachea going into the lungs)
- Lungs
How It Works
As a cat inhales, fresh air moves through the nose or mouth, pharynx, larynx, and to the trachea. From the trachea, the air is carried to the bronchi, which in turn supply the lungs. The bronchi divides into smaller and smaller tubes, called bronchioles, looking similar to the branches of trees. However, the actual air exchange occurs in the alveoli, where it meets thin capillaries running throughout the lungs to pick up oxygen and drop off carbon dioxide. The used air follows the opposite path of new air: passing into the bronchi, to the trachea, through the larynx and pharynx, and existing through the nose or mouth.
Breathing is accomplished by the actions of the rib muscles and movement of the diaphragm. The diaphragm muscle separates the chest, containing the heart and lungs, from the abdomen which holds the intestines, stomach, liver, bladder, etc. As it moves towards the abdomen, the muscle creates a negative pressure, pulling fresh air and oxygen into the lungs and causing the cat to inhale. The chest cavity holding the lungs is a vacuum, allowing the lungs to easily inflate to take in the air when the cat inhales. When the muscle moves upward, it causes the lungs to compress and exhale.
The physical act of breathing involves well-coordinated interactions between the lungs, the central nervous system, the diaphragm and the circulatory system.
Differences in Human and Feline Respiratory Systems
Though these two species have similar respiratory systems as mammals with well-developed lungs and respiratory structures, outside of proportions. However, because humans are bipedal, the epiglottis serves an important function to fight the effects of gravity more directly than cats, who are quadrupeds.
Specialization of the lung lobes also differ. Humans have three lobes in their left lung but only two in their right lung. But in cats, both the right and left lung each have three lobes for specialization. This difference most likely exists because the heart is normally located on the left side of humans, taking up space for only two lobes to be present in the left lung.
The respiratory rate in cats is also much higher than humans because of their smaller lung capacity.
Feline Respiratory Diseases
- Rhinitis: Inflammation of the mucosa (lining) of the nasal cavity is caused by infectious agents (bacteria, virus, fungal agents, parasites) or noninfectious disorders (foreign bodies, allergies, trauma, etc.). May extend into the adjacent sinuses of the face, resulting in sinusitis.
- Neoplasia: Tumors developed within the nose and are typically malignant cancers. May develop initially on one side of the nose, but with time, may affect both nasal passages.
- Pharyngeal disorders: Felines may develop inflammatory polyps in the benign soft tissue growths that grow from the lining of the back of the nasal passage, the pharynx, or the auditory tube. It may obstruct the flow of air, causing problems within the middle ear.
- Laryngitis: It is the inflammation of the larynx, most commonly occurs with tracheitis and upper respiratory infection.
- Laryngeal paralysis: A rare disease in cats, but in dogs, the cartilages that normally control the larynx become paralyzed and larynx does not open well.
- Infectious tracheobronchitis (Kennel Cough): Contagious upper respiratory disorder that typically occurring in a boarding facility, pet store, or animal shelter. Usually caused by a mixture of viruses and bacteria.
- Tracheitis: Also known as the inflammation of the trachea may occur with exposure to irritants such as smoke, chemicals, dust, or foreign bodies. Certain parasites that migrate to the trachea may also cause inflammation. Typically develops after the use of endotracheal tubes during general anesthesia.
- Tracheal collapse: The soft membrane across the top of the C-cartilage of the trachea becomes weak and stretches out. This allows the C-cartilages to collapse onto themselves, making it difficult to pass into the lungs
- Bronchitis: It is the inflammation of the lower airways that may arse with infections, irritants, allergies, diseases of the lungs, etc. May be acute or chronic in nature.
References + For More Reading
Respiratory System: Anatomy & Function in Cats
Overview of the Respiratory System
Structure and Function of the Respiratory Tract in Cats
For More In This Series
Don’t Skip A Beat: A Feline’s Circulatory System
Getting On A Cat’s Nerves: A Look Into the Feline Nervous System
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