The respiratory system of birds is unique. In birds, air currents go only in one direction, which is not characteristic of other vertebrates. How can you inhale and exhale through one trachea? The solution is an amazing combination of unique anatomical features and atmospheric flow manipulation. Features of the respiratory system of birds determine the complex mechanisms of the air sacs. They are not present in mammals.
Bird respiratory system: diagram
The process in winged animals is carried out somewhat differently than in mammals. In addition to lungs, they also have air sacs. Depending on the species, the respiratory system of birds may include seven or nine of these lobes, which have access to the humerus and femur, vertebrae, and even the skull. Due to the lack of a diaphragm, air is moved by changing the pressure in the air sacs with the help of the pectoral muscles. This creates negative pressure in the vanes, forcing air into the respiratory system. Such actions are not passive. They require certain muscle contractions to increase pressure on the air sacs and push the air out.
The structure of the respiratory system of birds involves raising the sternum during the process. Feather lungs do not expand or contract like mammalian organs. In animals, the exchange of oxygen and carbon dioxide takes place in microscopic sacs called alveoli. In winged relatives, gas exchange takes place in the walls of microscopic tubes called air capillaries. The respiratory organs of birds work more efficiently than those of mammals. They are able to carry more oxygen with each breath. When compared to animals of similar weight, there are slower breathing rates.
How do birds breathe?
Birds have three different sets of respiratory organs. These are the anterior air sacs, the lungs and the posterior air sacs. During the first breath, oxygen passes through the nostrils at the junction between the top of the beak and the head. Here it is heated, moistened and filtered. The fleshy tissue that surrounds them is called cere in some species. The flow then moves into the nasal cavity. The inhaled air travels further down into the trachea, or windpipe, which divides into two bronchi. They then branch into many paths in each lung.
Most of the tissue of this organ is about 1800 small adjacent tertiary bronchi. They lead to tiny air capillaries that intertwine with blood vessels, where gas exchange takes place. The air flow does not go directly to the lungs. Instead, it follows into the caudal sacs. A small amount passes through the tail formations through the bronchi,which, in turn, are divided into smaller capillaries in diameter. When the bird inhales a second time, oxygen moves into the cranial air sacs and back out through the fistula into the trachea through the larynx. And finally through the nasal cavity and out of the nostrils.
Complex system
The respiratory system of birds consists of paired lungs. They contain static structures on the surface for gas exchange. Only the air sacs expand and contract, forcing oxygen to move through the immobile lungs. The inhaled air remains in the system for two complete cycles before it is completely used up. Which part of the bird's respiratory system is responsible for gas exchange? The lungs play this important role. The air exhausted there begins to leave the body through the trachea. During the first breath, the waste gases pass into the anterior air sacs.
They cannot immediately leave the body, because during the second breath, fresh air again enters both back bags and lungs. Then, during the second exhalation, the first flow flows out through the trachea, and fresh oxygen from the posterior sacs enters the organs for gas exchange. The structure of the respiratory system of birds has a structure that allows you to create a unidirectional (one-sided) influx of fresh air above the surface of the ongoing gas exchange in the lungs. In addition, this flow passes there during both inhalation and exhalation. As a result, the exchange of oxygen and carbon dioxide is carried out continuously.
System efficiency
Features of the respiratory system of birds allow you to get the amount of oxygen necessary for the cells of the body. The big advantage is the unidirectional nature and structure of the bronchi. Here, the air capillaries have a larger total surface area than, for example, in mammals. The higher this figure, the more oxygen and carbon dioxide can circulate in the blood and tissues, which ensures more efficient breathing.
Structure and anatomy of the air sacs
The bird has several sets of air tanks, including caudal ventral and caudal thoracic. The composition of the cranial includes the cervical, clavicular and cranial thoracic sacs. Their contraction or expansion occurs when the part of the body in which they are placed changes. The size of the cavity is controlled by muscle movement. The largest container for air is located inside the wall of the peritoneum and surrounds the organs located in it. In an active state, for example during flight, the bird needs more oxygen. The ability to contract and expand body cavities allows not only to quickly drive more air through the lungs, but also to lighten the weight of the feathered creature.
During flight, the rapid movement of the wings creates an atmospheric flow that fills the air sacs. The abdominal muscles are largely responsible for the process while at rest. The respiratory system of birds differs both structurally and functionally from that of mammals. Birds have lungs - small, compact spongy structures formed among the ribs on either side of the spine in the thoracic cavity. The dense tissues of these winged organs weigh as much as those of mammals of equal body weight, but occupy only half the volume. He althy specimens tend to have light pink lungs.
Singing
The functions of the respiratory system of birds are not limited to breathing and oxygenation of body cells. This also includes singing, through which communication occurs between individuals. Whistling is the sound produced by the vocal organ located at the base of the height of the trachea. As with the mammalian larynx, it is produced by the vibration of air flowing through the organ. This peculiar property allows some species of birds to produce extremely complex vocalizations, up to the imitation of human speech. Some song species can produce many different sounds.
Stages of breathing cycles
The inhaled air passes through two respiratory cycles. In their totality, they consist of four stages. A series of several interrelated steps maximizes fresh air contact with the respiratory surface of the lungs. The process is as follows:
- Most of the air inhaled during the first step passes through the primary bronchi into the posterior air lobes.
- The inhaled oxygen moves from the rear sacs to the lungs. This is where gas exchange takes place.
- The next time the bird inhales, satedoxygen flow moves from the lungs to the front tanks.
- The second exhalation pushes carbon dioxide-enriched air out of the anterior sacs through the bronchi and trachea back into the atmosphere.
High oxygen demand
Due to the high metabolic rate required for flight, there is always a high demand for oxygen. Considering in detail what kind of respiratory system birds have, we can conclude: the features of its device quite help to satisfy this need. Although birds have lungs, they mostly rely on air sacs for ventilation, which make up 15% of their total body volume. At the same time, their walls do not have a good blood supply, therefore they do not play a direct role in gas exchange. They act as intermediaries to move air through the respiratory system.
The winged ones have no diaphragm. Therefore, instead of the regular expansion and contraction of the respiratory organs, as is observed in mammals, the active phase in birds is expiration, which requires muscle contraction. There are various theories about how birds breathe. Many scientists are still studying the process. Structural features of the respiratory system of birds and mammals do not always coincide. These differences allow our winged brethren to have the necessary adaptations for flying and singing. It is also a necessary adaptation to maintain a high metabolic rate for all flying creatures.
