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The main functions of the avian respiratory system is to move fresh air into the body while removing gaseous waste, and cooling the body by the lungs warming the entering air. Once the lungs have collected the oxygen, it is moved into the blood stream and spread throughout the body.
The main functions of the avian respiratory system is to move fresh air into the body while removing gaseous waste, and cooling the body by the lungs warming the entering air. Once the lungs have collected the oxygen, it is moved into the blood stream and spread throughout the body.
Nares
Nares
Oxygen enters the nasal passageway first. Chickens have nares, small nostril-like openings, in their beaks that they breathe through. The nasal cavity’s main functions are olfaction, respiration, and aid in immunity and helps to monitor the air and temperature when air passes through.
Trachea
Trachea
Once entering the nose and mouth, the air then flows into the trachea and past the larynx. The opening of the trachea is the glottis.
The trachea is also referred to as a windpipe, and carries oxygen-rich air from the respiratory passages (nasal passages, throat, and larynx) into the bronchi of the lungs. It is made up of rings of cartilage.
Larynx
Larynx
The larynx is a cavity in the throat and contains vocal chords. The avian syrinx is called a lower larynx, and is located where the trachea forks into the lungs.
The syrinx enables some species of birds (such as parrots, crows, and mynas) to mimic human speech. For chickens, it is their voice box. They do not have vocal cords, so instead their "voice" is produced by air pressure on a valve and modified by muscle tension.
Lungs
Lungs
The trachea then branches into two smaller airways which are called the left and right bronchi which leads to the two lungs. Each lung is divided into sections called lobes. There are 3 lobes in the right lung and 2 in the left lung.
The left lung is smaller because it shares space in the thoracic cavity with the heart. The lungs in avians have 9 air sacs, 2 cervical sacs, 1 interclavicular sac, 2 anterior thoracic sacs, and 2 abdominal sacs.
Structural Support
Structural Support
Birds lack a diaphragm, instead they inhale by lowering the sternum relative to the spinal vertebrae, enlarging the chest cavity and expanding the air sacs. Contraction of the sternum and ribs compresses the air sacs, pushes fresh air from them through the lungs and exhales the air.
Birds replace nearly all the air in its lungs with each breath. No residual air is left in the lungs during the ventilation cycle. The air sacs can provide buoyancy for swimming birds and help birds fly.
One volume of air moves sequentially into the posterior air sacs, into the lung, and into the anterior air sacs and is then exhaled. Two full respiratory cycles—inspiration, expiration, inspiration, and expiration—are required to move one volume of air through its complete path.
Flow of air through the respiratory system
Flow of air through the respiratory system
On first inhalation air flows through the trachea and bronchi, primarily into the posterior air sacs. On exhalation the air moves from the posterior air sacs into the lungs.
With the second inhalation, air moves from the lungs into the anterior air sacs and with second exhalation the air moves from the anterior air sacs back into the trachea and then out of the body.
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