Two main causes of decreased gas exchange are compliance how elastic the lung is and resistance how much obstruction exists in the airways. A change in either can dramatically alter breathing and the ability to take in oxygen and release carbon dioxide. Examples of restrictive diseases are respiratory distress syndrome and pulmonary fibrosis.
In both diseases, the airways are less compliant and stiff or fibrotic, resulting in a decrease in compliance because the lung tissue cannot bend and move. In these types of restrictive diseases, the intrapleural pressure is more positive and the airways collapse upon exhalation, which traps air in the lungs.
Forced or functional vital capacity FVC , which is the amount of air that can be forcibly exhaled after taking the deepest breath possible, is much lower than in normal patients; the time it takes to exhale most of the air is greatly prolonged.
A patient suffering from these diseases cannot exhale the normal amount of air. Obstructive diseases and conditions include emphysema, asthma, and pulmonary edema. In emphysema, which mostly arises from smoking tobacco, the walls of the alveoli are destroyed, decreasing the surface area for gas exchange.
The overall compliance of the lungs is increased, because as the alveolar walls are damaged, lung elastic recoil decreases due to a loss of elastic fibers; more air is trapped in the lungs at the end of exhalation.
Asthma is a disease in which inflammation is triggered by environmental factors, obstructing the airways. The obstruction may be due to edema, smooth muscle spasms in the walls of the bronchioles, increased mucus secretion, damage to the epithelia of the airways, or a combination of these events.
Those with asthma or edema experience increased occlusion from increased inflammation of the airways. This tends to block the airways, preventing the proper movement of gases. Those with obstructive diseases have large volumes of air trapped after exhalation.
They breathe at a very high lung volume to compensate for the lack of airway recruitment. The pulmonary circulation pressure is very low compared to that of the systemic circulation; it is also independent of cardiac output.
Recruitment is the process of opening airways that normally remain closed when cardiac output increases. As cardiac output increases, the number of capillaries and arteries that are perfused filled with blood increases. These capillaries and arteries are not always in use, but are ready if needed. However, at times, there is a mismatch between the amount of air ventilation, V and the amount of blood perfusion, Q in the lungs. Dead space is characterized by regions of broken down or blocked lung tissue.
Dead spaces can severely impact breathing due to the reduction in surface area available for gas diffusion. As a result, the amount of oxygen in the blood decreases, whereas the carbon dioxide level increases. Anatomical dead space, or anatomical shunt, arises from an anatomical failure, while physiological dead space, or physiological shunt, arises from a functional impairment of the lung or arteries. An example of an anatomical shunt is the effect of gravity on the lungs. The lung is particularly susceptible to changes in the magnitude and direction of gravitational forces.
When someone is standing or sitting upright, the pleural pressure gradient leads to increased ventilation further down in the lung.
As a result, the intrapleural pressure is more negative at the base of the lung than at the top; more air fills the bottom of the lung than the top. Likewise, it takes less energy to pump blood to the bottom of the lung than to the top when in a prone position lying down.
Perfusion of the lung is not uniform while standing or sitting. This is a result of hydrostatic forces combined with the effect of airway pressure. An anatomical shunt develops because the ventilation of the airways does not match the perfusion of the arteries surrounding those airways. As a result, the rate of gas exchange is reduced. Note that this does not occur when lying down because in this position, gravity does not preferentially pull the bottom of the lung down. When a healthy individual stands up quickly after lying down for a while, both ventilation and perfusion increase.
A physiological shunt can develop if there is infection or edema in the lung that obstructs an area. The lung has the capability to compensate for mismatches in ventilation and perfusion. If ventilation is greater than perfusion, the arterioles dilate and the bronchioles constrict, increasing perfusion while reducing ventilation. Likewise, if ventilation is less than perfusion, the arterioles constrict while the bronchioles dilate to correct the imbalance.
Privacy Policy. Skip to main content. The Respiratory System. Search for:. The Mechanics of Human Breathing Both inhalation and exhalation depend on pressure gradients between the lungs and atmosphere, as well as the muscles in the thoracic cavity. Learning Objectives Describe how the structures of the lungs and thoracic cavity control the mechanics of breathing. The process of inhalation occurs due to an increase in the lung volume diaphragm contraction and chest wall expansion which results in a decrease in lung pressure in comparison to the atmosphere; thus, air rushes in the airway.
The process of exhalation occurs due to an elastic recoil of the lung tissue which causes a decrease in volume, resulting in increased pressure in comparison to the atmosphere; thus, air rushes out of the airway. There is no contraction of muscles during exhalation; it is considered a passive process. The lung is protected by layers of tissue referred to as the visceral pleura and parietal pleura; the intrapleural space contains a small amount of fluid that protects the tissue by reducing friction.
Key Terms visceral pleura : the portion of protective tissue that is attached directly to the lungs parietal pleura : the portion of the protective tissue that lines the inner surface of the chest wall and covers the diaphragm.
Types of Breathing Types of breathing in humans include eupnea, hyperpnea, diaphragmatic, and costal breathing; each requires slightly different processes.
Inhalation enables oxygen to enter our body, reaching the organs and absorbing itself into the bloodstream. Well, there are some substances that accidentally enter our system. For instance, inhalation of water can be caused due to drowning, smoke, bad food, and various other substances that can enter our body through the process of inhalation.
Apart from that, people also take some substances deliberately through inhalation, like drugs, helium, nitrous oxide, etc. These substances can prove to be fatal for the body. Some substances are used for medications, but the substances that are deliberately consumed by people drugs must be stopped. Inhalation means to 'breathe in,' i. But sometimes, smoke and other substances enter our body which might lead to certain infections.
Exhalation is defined as the process wherein the air moves out from the lungs through the airways in the body. The volume of air is decreased in the body leading to an increase in the pressure upon the body. When the pressure increases, the air tends to rush out from the body.
Exhalation is a passive process in which muscle contraction does not take place. Exhalation takes place for one simple reason, i. After inhalation, the body undertakes the exchange of oxygen in pulmonary capillaries. This process leads to the removal of CO2 and other substances from the body.
The process of exhalation is longer than inhalation. Along with carbon dioxide, substances like methanol, ketones, water, and other hydrocarbons are also moved out from the body. The brain controls the exhalation process. This process can be broken into two segments, i. In voluntary exhalation, the air is held and released at a fixed rate. Examples of voluntary exhalation include exercising, singing, playing some instrument, etc.
Involuntary exhalation takes place through respiratory organs in the body. Metabolic and behavioral breathing is often termed as involuntary exhalation. Now, there are certain points of difference between inhalation and exhalation.
So, let us discus them. So, these are some of the contrasting points between inhalation and exhalation. These breathing processes are essential for the sustenance of the human body. One must try to regulate their breathing through yoga practices.
According to B. K Iyengar, both inhalation and exhalation must be done through the nose. In this, the diaphragm gets relaxed and moves upward into the chest cavity. Even the intercostal muscles between the ribs also get relax, which reduces the area in the chest cavity. Gradually, the area in the chest gets decreased and air rich in carbon dioxide is forced to move out of the lungs and windpipe and finally out through the nose.
Though above we discuss the process of breathing, given below are the key differences between inhalation and exhalation:. Simply we can say that the giving and taking process is called breathing. In this process, while breathing we take in air rich in oxygen from the atmosphere and give out the carbon dioxide back to the atmosphere. This air carbon dioxide is utilized by the plant during day time in the process of photosynthesis.
And hence the cycle goes on continuously, which is significantly important for all the living beings. Hello, Thank you so much for creating this website! It has been a very informative and fantastic resource!
Without this site, we would have never been able to comprehend the primal human function. Its a very good website. There are answers for all question in this web site. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. Key Differences Between Inhalation and Exhalation Though above we discuss the process of breathing, given below are the key differences between inhalation and exhalation: Inhalation is the process of intake of air into lungs, whereas exhalation is the process of letting air out from lungs.
Inhalation is an active process , though exhalation is a passive process. The diaphragm contract during the inhalation and get flattens by moving down, while they relax during exhalation and turned into dome-shaped by moving up. The intercostal muscles relax and external costal muscles contract in the inhalation process, while in the exhalation process internal intercostal muscles contract and external intercostal muscles relax.
The volume of lungs increase during inhalation it means it gets inflated and it decreases during exhalation means it gets deflated. The size of chest cavity increase in inhalation and it decrease during exhalation. During the inhalation air rich in oxygen is taken into the blood but carbon dioxide is pushed out in exhalation process from the blood.
Due to the effect of intercostal muscles rib cage moves upward and outward in inhalation, while in exhalation the rib cage moves downward. The composition of air which is inhaled is oxygen and nitrogen mix, while the composition of air which is exhaled is carbon dioxide and nitrogen mix.
Inhalation results in a decrease in air pressure below atmospheric pressure. In exhalation, there is an increase in air pressure.
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