Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Discover World-Changing Science. Materials Disposable empty transparent bottle 10—16 fluid ounces made of hard plastic such as a sports drink bottle Ruler Two balloons 8-inch balloons work well Utility knife have an adult help and use caution when using the knife Adult helper Scissors Drinking straw optional Modeling clay optional Tape optional Additional balloon optional Preparation Ask an adult to cut the plastic bottle.
Place the cut bottle down on the wide opening. Lower a balloon into the bottle until only part of the balloon's neck sticks out. Fold the neck of the balloon over the top of the bottle. The balloon represents a lung.
Turn the bottle over keeping the balloon inside so the bottle top rests on the table. In the next steps you will create and add the diaphragm to your model. Make a knot in the neck of the second balloon. At the opposite side of this balloon cut off about a third of the balloon so you are left with a wide opening. Stretch the wide opening of the cut balloon over the wide opening of the bottle.
Pull the edges of the balloon far enough up the bottle so the balloon surface is gently stretched. Make sure that the knot is on the outside and located near the middle of the bottle opening.
Like an inflated balloon our lungs are full of air. We have two lungs, which are enclosed in the ribcage and protected by 24 ribs. When you breathe in, air flows into your lungs. When you breathe out, air flows out of your lungs.
The balloon inside the bottle is like one of your lungs. The bottle is like your ribcage. Procedure Hold the bottle so you can see the balloon inside representing the lung. Gently pull down on the knot. What happens to the balloon inside the bottle? Let the knot come back to its neutral position and then gently push it in. What happens to the balloon inside the bottle now? Our body needs oxygen to obtain energy to fuel all our living processes.
Carbon dioxide is a waste product of that process. The respiratory system, with its conduction and respiratory zones, brings air from the environment to the lungs and facilitates gas exchange both in the lungs and within the cells. Nurses need a solid understanding of how breathing works, and of vital signs of breathing and breathing patterns, to be able to care for patients with respiratory problems and potentially save lives in acute situations. Citation: Cedar SH Every breath you take: the process of breathing explained.
Nursing Times [online]; 1, It is also often the first question asked about newborns and the last one asked about the dying. Why is breathing so important? What is in the breath that we need so much? What happens when we stop breathing? These might seem obvious questions, but the mechanisms of respiration are often poorly understood, and their importance in health assessments and diagnostics often missed. This article describes the anatomy and physiology of breathing. We need energy to fuel all the activities in our bodies, such as contracting muscles and maintaining a resting potential in our neurons, and we have to work to obtain the energy we use.
Green plants take their energy directly from sunlight and convert it into carbohydrates sugars. We cannot do that, but we can use the energy stored in carbohydrates to fuel all other reactions in our bodies.
To do this, we need to combine sugar with oxygen. We therefore need to accumulate both sugar and oxygen, which requires us to work. As a matter of fact, we spend much of our energy obtaining the sugar and oxygen we need to produce energy.
We source carbohydrates from green plants or animals that have eaten green plants, and we source oxygen from the air. Green plants release oxygen as a waste product of photosynthesis; we use that oxygen to fuel our metabolic reactions, releasing carbon dioxide as a waste product.
Plants use our waste product as the carbon source for carbohydrates. To obtain energy we must release the energy contained in the chemical bonds of molecules such as sugars. The foods we eat such as carbohydrates and proteins are digested in our gastrointestinal tract into molecules such as sugars and amino acids that are small enough to pass into the blood. The blood transports the sugars to the cells, where the mitochondria break up their chemical bonds to release the energy they contain.
Cells need oxygen to be able to carry out that process. As every cell in our body needs energy, every one of them needs oxygen. The energy released is stored in a chemical compound called adenosine triphosphate ATP , which contains three phosphate groups. When we need energy to carry out an activity, ATP is broken down into adenosine diphosphate ADP , containing only two phosphate groups.
Breaking the chemical bond between the third phosphate group and ATP releases a high amount of energy. Our lungs supply oxygen from the outside air to the cells via the blood and cardiovascular system to enable us to obtain energy. As we breathe in, oxygen enters the lungs and diffuses into the blood. It is taken to the heart and pumped into the cells. At the same time, the carbon dioxide waste from the breakdown of sugars in the cells of the body diffuses into the blood and then diffuses from the blood into the lungs and is expelled as we breathe out.
One gas oxygen is exchanged for another carbon dioxide. This exchange of gases takes places both in the lungs external respiration and in the cells internal respiration. Fig 1 summarises gas exchange in humans. Our respiratory system comprises a conduction zone and a respiratory zone. The conduction zone brings air from the external environment to the lungs via a series of tubes through which the air travels.
These are the:. 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.
Learning Objectives Differentiate among the types of breathing in humans, amphibians, and birds. Key Takeaways Key Points Eupnea is normal quiet breathing that requires contraction of the diaphragm and external intercostal muscles.
Diaphragmatic breathing requires contraction of the diaphragm and is also called deep breathing. Costal breathing requires contraction of the intercostal muscles and is also called shallow breathing. Hyperpnea is forced breathing and requires muscle contractions during both inspiration and expiration such as contraction of the diaphragm, intercostal muscles, and accessory muscles.
The hemoglobin then returns the carbon dioxide back to the lungs where it is exhaled. The air is less dense at higher altitudes because there is less atmospheric pressure. This means the oxygen molecules are spread further apart. Less oxygen will enter the lungs with each breath. Atmospheric pressure also helps to push oxygen across the membrane of the cells in the lungs. In Denver, the altitude is 5, ft. We breathe in 50 percent less oxygen at 18, feet. Our bodies adjust to higher altitude by creating more red blood cells.
It takes 21 to 28 days for this process to occur. The amount of oxygen needed by the body varies. Individuals who are ill or injured may require more oxygen to help their bodies function and heal. Respiratory Failure: Spinal cord injuries at the C3 level or higher effect the phrenic nerve.
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