The brochioles end in tiny air sacs, called alveoli. In the alveoli, the oxygen you inhaled passes into the bloodstream, and carbon dioxide from your body passes out of the bloodstream.
Through the thin walls of the alveoli, oxygen from the air passes into your blood in the surrounding capillaries. At the same time, carbon dioxide moves from your blood into the air sacs. The oxygen in your blood is carried inside your red blood cells by a protein called hemoglobin. The oxygen-rich blood from your lungs is carried to the left side of the heart through the pulmonary veins. The heart pumps the blood to the rest of the body, where oxygen in the red blood cells moves from blood vessels into your cells.
Your cells use oxygen to make energy so your body can work. During this process, your cells also make a waste gas called carbon dioxide. Carbon dioxide needs to be breathed out or it can damage your cells. Carbon dioxide moves from the cells into the bloodstream, where it travels to the right side of your heart. The blood rich in carbon dioxide is then pumped from the heart through the pulmonary artery to the lungs, where it is breathed out.
When you breathe out, or exhale, your diaphragm and rib muscles relax, reducing the space in the chest cavity. As the chest cavity gets smaller, your lungs deflate, similar to releasing of air from a balloon. At the same time, carbon dioxide-rich air flows out of your lungs through the windpipe and then out of your nose or mouth.
Breathing out requires no effort from your body unless you have a lung disease or are doing physical activity. When you are physically active, your abdominal muscles contract and push your diaphragm against your lungs even more than usual. This rapidly pushes air out of your lungs. Damage, infection, or inflammation in the lungs or airways or both, can lead to the following conditions. Exposure to cigarette smoke, air pollutants, or other substances can damage the airways, causing disease of the airways or making a disease more severe.
You can take these steps to help protect your lungs from injury or disease:. As you age, the lung tissue that helps keep your airways open can lose elasticity, which means they cannot expand or contract as easily as when you were younger.
The muscles your body uses for breathing may get smaller or weaker, and your spine can curve more, leaving less space for your lungs to expand. It can take longer to clear mucus and particles from your airways. It can also become harder to cough. These changes can make it harder to breathe during physical activity as you get older. We are committed to advancing science and translating discoveries into clinical practice to promote the prevention and treatment of heart, lung, blood, and sleep disorders.
Learn about current and future NHLBI efforts to improve health through research and scientific discovery. Learn about the following ways the NHLBI continues to translate current research to prevent and treat lung problems. Learn about some of the pioneering research contributions we have made over the years that have improved clinical care. In support of our mission , we are committed to advancing lung research in part through the following ways.
We lead or sponsor studies on the lungs. See if you or someone you know is eligible to participate in a clinical trials. To learn more about clinical trials at the NIH Clinical Center or to talk to someone about a study that might fit your needs, call the Office of Patient Recruitment Learn more about participating in a clinical trial. View all trials from ClinicalTrials. After reading our How the Lungs Work Health Topic, you may be interested in additional information found in the following resources.
This Symposium will highlight important scientific advances in pulmonary health and disease since the creation of t How the Lungs Work. Also known as Respiratory System. Read more. The pleura Cross-section of lungs to show the pleura. The main image shows the location of the lungs, pleura, and diaphragm.
The inset image shows a closer view of the two layers of the pleura and the pleural space. Read less. The muscles used for breathing The lungs are like sponges; they cannot expand get bigger on their own.
The breathing muscles include the: Diaphragm, which is a dome-shaped muscle below your lungs. It separates the chest cavity from the abdominal cavity.
The diaphragm is the main muscle used for breathing. The muscles between your ribs, called intercostal muscles, play a role in breathing during physical activity. Abdominal muscles help you breathe out when you are breathing fast, such as during physical activity. Muscles of the face, mouth, and pharynx.
The pharynx is the part of the throat right behind the mouth. These muscles control the lips, tongue, soft palate, and other structures to help with breathing. Problems with these muscles can narrow the airway, make it more difficult to breathe, and contribute to sleep apnea. Muscles in the neck and collarbone area help you breathe in.
Cross-section of lungs to show the diaphragm. The nervous system Your breathing usually does not require any thought, because it is controlled by the autonomic nervous system, also called the involuntary nervous system.
The parasympathetic system slows your breathing rate. When arterial CO2 levels are abnormally low hypocapnia , respirations become shallow and slow hypoventilation and periods of apnoea may occur as the stimulus to breathe is absent.
This reaction can occur as a result of a panic attack and can usually be rectified by rebreathing into a paper bag. Rebreathing expired CO2 leads to a rise in arterial CO2 levels which triggers the chemoreceptor response. A fall in the pH of CSF can be triggered not only by respiratory changes but by metabolic causes.
Typical causes of metabolic acidosis are poorly controlled diabetes mellitus, which allows organic acids to build up, or the increased production and accumulation of lactic acid during exercise. Whether the cause of the reduction of pH in the CSF is respiratory or metabolic, the central chemoreceptors will be stimulated.
The body will react in an attempt to rid itself of excess acids and raise the pH by eliminating CO2 via the lungs. Peripheral chemoreceptors, bathed as they are in newly oxygenated blood, are sensitive to arterial O2 levels. While they are involved in the response to increased acidity rise in arterial partial pressure of CO2, fall in pH they also respond to falls in the arterial partial pressure of oxygen PO2.
There are vast reserves of arterial oxygen bound to haemoglobin in the blood Richardson, , and a large fall in PO2 is needed before these begin to be depleted and the peripheral chemoreceptors are stimulated.
Neuronal messages via the glossopharyngeal nerves from carotid receptors and the vagus nerve from the aortic receptors , stimulate the medullary inspiratory neurones. Rate and depth of respiration are increased and more O2 is inhaled and absorbed into the blood. Once arterial O2 levels return to normal, the stimulus ceases. These peripheral receptors assume a vital importance in patients who retain CO2 due to pulmonary disease such as emphysema or chronic bronchitis.
In these patients, the central chemoreceptors become unresponsive to the constant stimulus of CO2 and the peripheral chemoreceptors assume the function of driving respiration the hypoxic drive. These patients will only breathe when arterial PO2 is low enough to trigger the peripheral chemoreceptors. It is essential that nurses understand this physiological alteration as giving high doses of oxygen therapy to these patients will stop them breathing because O2 levels do not fall low enough to stimulate respiration.
Hormones are not only involved in the transmission of nerve impulses within the respiratory system, but recent work suggests that many are involved in the control of respiration Saaresranta and Polo, Progesterone and thyroxine, for example, are known to stimulate respiration, while somostatin and dopamine have a depressant effect.
Many different drugs affect our respiratory rate. From developing new therapies that treat and prevent disease to helping people in need, we are committed to improving health and well-being around the world.
The Manual was first published in as a service to the community. Learn more about our commitment to Global Medical Knowledge. This site complies with the HONcode standard for trustworthy health information: verify here. Common Health Topics. Respiratory muscles. Biology of the Lungs and Airways. Test your knowledge. Coughing up blood from the respiratory tract is called hemoptysis. Which of the following is the most likely cause of hemoptysis in adults? More Content.
The dorsal respiratory group stimulates inspiratory movements. The Pons The pons is the other respiratory center and is located underneath the medulla. It has two main functional regions that perform this role: The apneustic center sends signals for inspiration for long and deep breaths. It controls the intensity of breathing and is inhibited by the stretch receptors of the pulmonary muscles at maximum depth of inspiration, or by signals from the pnuemotaxic center.
It increases tidal volume. The pnuemotaxic center sends signals to inhibit inspiration that allows it to finely control the respiratory rate.
Its signals limit the activity of the phrenic nerve and inhibits the signals of the apneustic center. It decreases tidal volume. Neural Mechanisms Cortex The cerebral cortex of the brain controls voluntary respiration.
Learning Objectives Describe the mechanism of the neural cortex in respiration control. Key Takeaways Key Points The motor cortex within the cerebral cortex of the brain controls voluntary respiration the ascending respiratory pathway. Voluntary respiration may be overridden by aspects of involuntary respiration, such as chemoreceptor stimulus, and hypothalamus stress response.
The phrenic nerves, vagus nerves, and posterior thoracic nerves are the major nerves involved in respiration. Voluntary respiration is needed to perform higher functions, such as voice control. Key Terms The Phrenic Nerves : A set of two nerves that brings nerve impulses from the spinal cord to the diaphragm. Chemoreceptor Regulation of Breathing Chemoreceptors detect the levels of carbon dioxide in the blood by monitoring the concentrations of hydrogen ions in the blood. Learning Objectives Describe the role of chemoreceptors in the regulation of breathing.
In response to a decrease in blood pH, the respiratory center in the medulla sends nervous impulses to the external intercostal muscles and the diaphragm, to increase the breathing rate and the volume of the lungs during inhalation. Hyperventilation causes alakalosis, which causes a feedback response of decreased ventilation to increase carbon dioxide , while hypoventilation causes acidosis, which causes a feedback response of increased ventilation to remove carbon dioxide.
Any situation with hypoxia too low oxygen levels will cause a feedback response that increases ventilation to increase oxygen intake. Vomiting causes alkalosis and diarrhea causes acidosis, which will cause an appropriate respiratory feedback response. Key Terms hypoxia : A system-wide deficiency in the levels of oxygen that reach the tissues. Proprioceptor Regulation of Breathing The Hering—Breuer inflation reflex prevents overinflation of the lungs.
Learning Objectives Evaluate the effect of proprioception the sense of the relative position of the body and effort being employed in movement on breathing.
Key Takeaways Key Points Pulmonary stretch receptors present in the smooth muscle of the airways and the pleura respond to excessive stretching of the lung during large inspirations.
The Hering—Breuer inflation reflex is initiated by stimulation of stretch receptors. The deflation reflex is initiated by stimulation of the compression receptors called proprioceptors or deactivation of stretch receptors when the lungs deflate. Activation of the pulmonary stretch receptors via the vagus nerve results in inhibition of the inspiratory stimlus in the medulla, and thus inhibition of inspiration and initiation of expiration.
An increase in pulmonary stretch receptor activity leads to an elevation of heart rate tachycardia. A cyclical, elevated heart rate from inspiration is called sinus arrhythmia and is a normal response in youth. Inhibition of inspiration is important to allow expiration to occur. Key Terms sinus arryhthmia : A normal cyclical heart rate change in which an increase in heart rate occurs during inspiration, but returns to normal during expiration.
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