Pulmonary Respiration

Pulmonary Respiration

What is lung breathing?

The breath through the lungs is called pulmonary respiration.

The mechanism of lung breathing: Includes breathing movement, exchange of gases, lungs, transport of gases through the blood and exchange of gas by tissue.

Breathing Movement

The thoracic cavity is a compressed air chamber that is closed by the dorsal vertebral column, ventrally by the sternum, laterally by the ribs, anteriorly by the neck and later by the diaphragm. Diaphragm is a dome-shaped partition of skeletal muscle between the thoracic cavity and the abdominal cavity.

Breathing includes two processes of inspiration and expiration.

Inspiration is a process of entering air into the lungs. It is an active process. When the external intercostal muscles contract the diaphragm becomes flat and space inside increases thoracic cavity. At the same time, high pressure outside air flows into the lungs.

Expiration is a process of expelling air from the lungs.

In this process, the internal intercostals contract and diphragam muscles makes dome-shaped originals and decreases the space within the thoracic cavity, the lungs are compressed and air is expelled outward. Therefore, ribs play important roles in women while diaphragm in males.

Pulmonary volume

The recoding of volume of air circulation into and out of the lungs is called spirometry and is measured with the help of a spirometer.

The volume of air inhaled by the animals and exhaled with each breath is called tidal volume. The average is about 500 ml in humans.

The maximum volume of air that can be inhaled and exhaled during forced breathing is called vital capacity. It’s about 3.5-4.5 liters.

The vital capacity is greater in athletes, mountain dwellers and the lower women, by old age, and people smokers.

The volume of air is left in the lungs after forced expiration called residual volume.

It is 1200ml. the volume of air that can not be inspired, above normal tidal volume is called inspiratory reserve volume, or IRS (3000ml).

The amount of air that can not be expired forcefully beyond normal current expiration is called the expiratory reserve volume. It is about 1100 ml.

The dead space is the volume of air (150 ml) in nasopharynx, trachea, bronchi, which is not available for gas exchange.

Rate of breathing

The respiration rate in humans is 15-25 per minute. In babies, it is 35 per minute.

Breath control

Our respiratory centers are located in two regions of the brain-bulb (with inspiratory center and expiratory center) and varolii bridge (with pneumotaxic center).

The inspiratory center stimulates inspiratory muscles (diaphragm) to control the rate of breathing. The expiratory center remains inactive during normal breathing, but it controls both expiration and inspiration during exercise.

Pneumotaxic Center controls the shutdown of the breathing point by sending a signal to the inspiratory center.

The core control center detects the low pH of the tissue fluid, during the formation of more carbonic acids, the center increases the respiration rate to eliminate excess CO2.

The concentration of O2 has little effect on respiratory centers.

However, when the level of O2 is severely depressed, O2 sensors in the aorta and carotid arteries send signals to breathe control center to increase respiration rate.

Pulmonary gas rates (external respiration)

External breathing occurs between the blood in the alveolar capillaries and alveolar air.

The partial pressure of O2 (PO2) in the alveolar air is 100 mm Hg and in the venous blood has 40 mm Hg.

Thus, alveolar air oxygen diffuses into the venous blood and into the lungs, the CO2 or PCO2 partial pressure in the venous blood is 46 mm Hg and in the alveolar air is 40 mm Hg.

Therefore, CO2 diffuses from venous blood into the lungs of alveolar air.

However, N 2 is physiologically inert to respiration.

It is the breath that allowed the existence of large animals in terrestrial environment. The air enters through some hole in the being and goes to the lung, an organ extremely vascularized and with an incredible surface of contact.

The function of respiration is essential to life and can be defined, in a simplified way, as the exchange of gases (O2 and CO2) between the cells of the organism and the atmosphere.

The pulmonary respiration is represented by ventilation (mechanical process input and output air from the lungs) and gas exchange.

Pulmonary Respiration – is the exchange of gases (O2 and CO2) in the lungs (Ventilation).

Ambient air is taken and exchanged for air present in the lungs through the lung ventilation process.


The pulmonary respiration is the process by which air enters the lungs and then sa i. It is a repetitive event that involves the whole set of organs of the respiratory system.

Pulmonary Circulation

Pulmonary blood flow is peculiar in the sense that it occurs under relatively lower pressures than those of systemic arterioles.

The pulmonary blood vessels, especially the capillaries and venules, are made up of very thin and flexible walls. Unlike the systemic capillaries, the pulmonary capillaries increase in diameter.

The pulmonary capillaries within the alveolar walls separate adjacent alveoli with increases in blood pressure or decreases in alveolar pressure.

Blood flow in the lung is therefore significantly influenced by elastic deformation. Although pulmonary circulation is not significantly affected by neuronal and chemical controls, it responds readily to hypoxia. There is also a systemic blood circulation system at high pressures around the bronchi that is completely independent of the low pressure pulmonary circulation (~ 3330 N / m 2) in healthy individuals.

The Human Breath

In the human species the gases travel through a series of organs that make up the Respiratory Tube.

Obtaining the sequence of: Nasal Cavities, Pharynx, Larynx, Trachea, Bronchi, Lungs.

Inhaling and exhaling

Pulmonary Respiration

Pulmonary Respiration

Inhaling comprises the penetration of atmospheric air into the pulmonary alveoli. The exhaling is the elimination of the air contained in the lungs to the external environment. In these mechanisms, the participation of the diaphragm – a flattened muscle that separates the thoracic cavity from the abdominal cavity – and external intercostal muscles – is located between the ribs.

Pulmonary Ventilation

Pulmonary Respiration
Pulmonary Ventilation

It is the process of conducting atmospheric air to the alveoli.

The air penetrates through the nose and mouth and flows to the conductive portion of the system

Adjusted to body temperature, filtered and moistened when passing through trachea

Air conditioning continues as it enters the two bronchi (leads to the lungs)

Bronchi subdivide into numerous bronchioles (leads to alveolar ducts)

Terminal branches of the duct are completely surrounded by alveoli (small pockets grouped around the respiratory bronchioles, whose shape and distribution resemble a hive).


Main function is gas exchange

Transfer the O2 from the air to the venous blood and transfer the CO2 from that blood to the alveolar chambers (vital for the gas exchange – surfactant – Kohn pores)

Average volume of 4 to 6 L …


Pulmonary Respiratory System

It is responsible for gas exchange between the body and the environment, a process known as lung breathing .

It is in the lungs that the exchanges with the blood capillaries occur, through millions of pulmonary alveoli.

These changes (called hematosis: oxygen uptake and carbon dioxide output) are effected by diffusion: the oxygen gas passes from the alveoli to the blood cells.

Pulmonary Respiration: The lungs are specific to air pockets located inside the body of some living beings, in which air enters and leaves in a process of pulmonary ventilation. In them the gas exchanges are carried out and the oxygen is taken to the whole body through the blood or the hemolymph, having a relation with the circulatory system.

Pulmonary Breathing: consists of gas exchanges between air and blood. The name of this process is hematosis , and it occurs in the pulmonary alveoli. In this case, the respiratory gases are O2, used in the process of cellular respiration, and CO2, resulting from this same process.

Pulmonary ventilation

The inspiration , which promotes the entry of air into the lungs, is caused by the contraction of the muscles of the diaphragm and the intercostal muscles. The diaphragm lowers and the ribs rise, promoting the increase of the rib cage, with consequent reduction of the internal pressure (in relation to the external one), forcing the air to enter the lungs.

The expiration , which promotes the exit of air from the lungs, occurs by relaxing the muscles of the diaphragm and intercostal muscles. The diaphragm rises and the ribs lower, which reduces the volume of the rib cage, with consequent increase of internal pressure, forcing the air out of the lungs.


Our cells need, while alive and performing their functions, a continuous supply of oxygen so that, in a chemical process of cellular respiration, they can generate the energy necessary for their perfect functioning and production of work.

In the same way that an automobile engine needs, to produce its mechanical work, in addition to the source of organic energy provided by the fuel (gasoline, alcohol or diesel), of constant oxygen supply; in the same way as a flame in a phosphorus stick, in order to remain lit it needs, besides the organic matter present in the wood of the toothpick, also of oxygen, our cells also, in order to maintain their perfect functioning they need, besides the source of energy provided by the various foods , of a constant supply of oxygen.

Oxygen exists in abundance in our atmosphere. And to get it we need our respiratory system. Through it, part of the oxygen in the atmosphere diffuses through a respiratory membrane and reaches our bloodstream, is carried by our blood and taken to the various cells present in the various tissues. The cells, after using the oxygen, release carbon dioxide that, after being transported by the same bloodstream, is also eliminated in the atmosphere by the same respiratory apparatus.

In order to allow an adequate diffusion of gases through the respiratory membrane, oxygen passing from the inside of the alveoli to the blood present in the pulmonary capillaries and carbon dioxide diffusing in the opposite direction requires a constant process of pulmonary ventilation.

Pulmonary ventilation consists of a continuous renewal of the air present inside the alveoli. For this to occur, it is necessary that, during all the time, movements occur that provide insufflation and deflation of all or almost all the alveoli. This causes, within the alveoli, a pressure slightly, sometimes more negative, and sometimes more positive than that present in the atmosphere.

During inspiration, due to an intra-alveolar pressure of approximately 3 mmHg. more negative than atmospheric, a certain amount of atmospheric air is inhaled by the respiratory apparatus; during expiration, due to an intra-alveolar pressure of approximately 3 mmHg. more positive than atmospheric, the same amount of air is returned to the atmosphere.

In order for us to inflate and deflate our alveoli, we must inflate and deflate our lungs. This is possible through movements that lead to increase and reduction of the volume inside our rib cage, where our lungs are located.

We can expand the volume of our rib cage by lifting our ribs and contracting our diaphragm muscle.

To retract the volume of the rib cage we do exactly the opposite: we lower our ribs while we relax our diaphragm.

So we have several muscles that are very important to us during our breathing:

Muscles used in inspiration: diaphragm, sternocleidomastoids, external intercostals, scalenes, anterior serrations.
Muscles used in exhalation: internal intercostals, abdominal straight and other muscles located in the anterior wall of the abdomen.

During inspiration and during exhalation, the air passes through several different segments that are part of the respiratory system:

Nose: It is the first segment where, preferably, it passes the air during the inspiration. When passing through the nose, the air is filtered, humidified and heated. In the eventual impossibility of the passage of air through the nose, such passage can happen by a shortcut, the mouth. But unfortunately, when this happens, the air does not undergo the important modifications described above.
Pharynx: After passage through the nose, before reaching the larynx, the air must pass through the pharynx, a segment that also serves as a passageway for food.
Larynx:Usually allows only air passage. During swallowing of a food, a small membrane (epigloge) obstructs the opening of the larynx, which makes it difficult to pass fragments other than air into the lower respiratory tract. In the larynx are also located the vocal chords, responsible for the production of our voice.
Trachea: A small cartilage tube connecting the upper and lower airways, just below.
Bronchi: They are numerous and branching also numerous, like tree branches. Allow air to pass into the alveoli.
Bronchioles: More thin, are between the bronchi and the alveolar sacs, from where the alveoli come out.

Throughout the respiratory mucosa, from the nose to the bronchioles, there are numerous ciliated cells, with movable cilia, and large mucus production. All this helps a lot in the constant cleaning of the air that flows through the airways.

The alveoli have a tendency to collapse. Such a collapse does not normally occur due to the more negative pressure present in pleural space, which forces the lungs to remain expanded. The major factor responsible for the tendency of alveoli to collapse is a phenomenon called Surface Tension.

The superficial tension occurs inside the alveoli due to the large quantity of water molecules present and coating, also, all the internal wall of the alveoli. The superficial tension within the alveoli would certainly be much greater than it already is if it were not for the presence of a substance called pulmonary surfactant in the liquid lining the alveoli. Pulmonary surfactant is basically composed of phospholipids (dipalmitoyl lecithin) by cells present in the alveolar epithelium. The major importance of pulmonary surfactant is its ability to significantly reduce the surface tension of liquids lining the interior of the alleles and other airways.


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