Bird respiratory system: functions, structure

The respiratory system of birds is unique. In birds, airflows travel in only one direction, which is not the case with other vertebrates. How can one inhale and exhale through one trachea? The solution is an amazing combination of unique anatomical features and manipulations of the atmospheric flow. Peculiarities of the respiratory system of birds cause complex mechanisms for the operation of air bags. They are not present in the mammals.

Bird respiratory system: scheme

The process of winged animals is somewhat different than in mammals. In addition to the lungs, they also have air sacs. Depending on the species, the bird's respiratory system can include seven or nine of these blades, 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 bags with the help of the pectoral muscles. This creates a negative pressure in the blades, causing the air to enter 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. Light birds do not expand or contract as mammalian organs. In animals, the exchange of oxygen and carbon dioxide takes place in microscopic sacs called alveoli. In winged relatives gas exchange is carried out in the walls of microscopic tubes, called air capillaries. Respiratory organs of birds work more effectively than in mammals. They are able to carry more oxygen with each breath. When compared to animals of similar weight, there are slower respiratory rates.

How do birds breathe?

Birds have three different sets of respiratory organs. These are front air bags, light and rear air bags. During the first inhalation, oxygen passes through the nostrils at the junction between the upper part of the beak and the head. Here it is heated, moistened and filtered. The fleshy tissue that surrounds them, in some species, is called a waxen. Then the stream moves into the nasal cavity. The inhaled air goes further down into the trachea, or the respiratory throat, which is divided into two bronchi. Further they 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, which are intertwined with blood, where there is an exchange of gases. The air flow does not go directly to the lungs. Instead, he follows caudal sacs. A small amount passes through the caudal 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.

A complex system

The respiratory system of birds consists of paired lungs. They contain static structures on the surface for gas exchange. Expand and contract only air bags, forcing oxygen to move through the fixed lungs. The inhaled air remains in the system for two complete cycles before it is completely consumed. What part of the respiratory system of birds is responsible for gas exchange? This important role is played by the lungs. The air exhausted there begins to leave the body through the trachea. During the first inhalation, the exhaust gases pass into the front air sacs.

They can not immediately leave the body, because during the second breath fresh air again enters both the back bags and lungs. Then, during the second exhalation, the first flow flows out through the trachea, and fresh oxygen from the rear 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 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.

Efficiency of the system

Features of the respiratory system of birds allow you to get the amount of oxygen needed for the cells of the body. A great advantage is the unidirectional nature and structure of the bronchi. Here, air capillaries have a larger total surface area than, for example, in mammals. The more this figure is, the more oxygen and carbon dioxide can circulate in the blood and tissues, which provides more efficient breathing.

Structure and anatomy of air sacs

The bird has several sets of air tanks, including the caudal thoracic and caudal. The cranial structure includes cervical, clavic and cranial thoracic sacs. Their contraction or expansion occurs when the part of the body in which they are located changes. The size of the cavity is controlled by the movement of the muscles. The largest capacity for air is located inside the peritoneal wall and surrounds the organs located in it. In an active state, for example, during a flight, the bird needs more oxygen. The ability to squeeze and expand the body cavities allows you not only to speed up more air through the lungs, but also to facilitate the weight of the feathered creature.

During the flight, the rapid movement of the wings creates an atmospheric flow that fills the air sacs. Muscles of the abdominal press are largely responsible for the process, being in a calm state. The respiratory system of birds differs both structurally and functionally from that inherent in mammals. Birds have lungs - small, compact spongy structures formed among the ribs on both sides of the spine in the thoracic cavity. The dense tissues of these winged organs weigh as much as in mammals of equal body weight, but occupy only half the volume. Healthy individuals, as a rule, have light light pink color.

Singing

Functions of the respiratory system of birds are not limited to breathing alone and oxygenation of body cells. This also includes singing, through which there is communication between individuals. Whistling is the sound obtained by the vocal organ located at the base of the tracheal height. As in the case of the larynx of mammals, 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, right up to the imitation of human speech. Some singing species can produce many different sounds.

Stages of breathing cycles

The inhaled air passes through two breathing cycles. In their totality they consist of four stages. A series of several interconnected steps maximizes the contact of fresh air with the respiratory surface of the lungs. The process is as follows:

1. Most of the air, inhaled for the first step, passes through the primary bronchi into the rear air blades.
2. The inhaled oxygen moves from the back bags to the lungs. There is a gas exchange.
3. The next time the bird inhales, the oxygen-rich stream moves from the lungs to the front tanks.
4. The second exhale displaces carbon dioxide-enriched air from the anterior sacs through the bronchi and trachea back into the atmosphere.

High oxygen demand

Due to the high rate of metabolism required for flight, there is always a high demand for oxygen. In detail, considering what kind of respiratory system in birds, we can conclude: the features of its device quite help meet this need. Although birds have lungs, they rely heavily on air sacs for ventilation, which make up 15% of the total body volume. At the same time, their walls do not have a good blood supply, so they do not play a direct role in gas exchange. They act as intermediaries for the movement of air through the respiratory system.

The winged do not have a diaphragm. Therefore, instead of regularly expanding and contracting the respiratory organs, as observed in mammals, the active phase in birds is an exhalation that requires muscle contraction. There are various theories about how birds breathe. Many scientists are still studying the process. The peculiarities of the structure of the respiratory system of birds and mammals do not always coincide. These differences allow our winged brethren to have the necessary devices for flying and singing. It is also a necessary adaptation to maintain a high metabolic rate for all flying creatures.