If there is not enough oxygen in the blood to accommodate adequate respiration, the lungs will adapt in order to bring in more oxygen. Think of when you go for a long run. You have increased the amount of work that your muscles are doing, so they are more active and need more energy from the glucose in your body. Therefore, respiration increases. Because respiration has increased, your body needs more oxygen to keep up with the demand.
This is why you breath quicker and more heavily when exercising. However, as cells respire, they use this oxygen up and produce carbon dioxide - which isn't as useful. As carbon dioxide is a waste product, and has little use in our body, we have to dispose of it. This time, the deoxygenated blood which is full of carbon dioxide comes to be filtered by the lungs.
The blood is topped up with oxygen, and the carbon dioxide is removed ready to be exhaled. This is important, as carbon dioxide dissolves in water to form an acid. By removing the carbon dioxide, the lungs also help to keep a healthy pH balance, essential to ensure that our cells and enzymes can work at the optimum efficiency!
Finally, the lungs also play a large part in maintaining sufficient water content. When we exhale, not only do we remove carbon dioxide, but we also remove lots of water vapor,. This is why when you breath on a cold window, it gets steamy - that's the water vapor in your breath condensing. So, as water leaves your body via the lungs, it is involved in keeping the right balance of water along with sweat and urine.
As one area increases or decreases, all the other ways of removing water will adjust to balance it out. Respiration is often referred to as breathing, but it can also mean cellular respiration, which is the main reason why breathing is important. Cells require oxygen from the air to extract energy from glucose through respiration, which produces carbon dioxide and water as a waste product.
Therefore, oxygen is vital for every part of normal cellular function, and oxygen deficiency can have severe pathological consequences. The respiratory system facilitates breathing. In the alveoli tissue of the lungs, the exchange of oxygen and carbon dioxide molecules between the air and the bloodstream occurs by passive transport, so that oxygen is taken in and carbon dioxide and water are removed.
Passive diffusion also called bulk flow is the term for the movement of these gases between the air and bloodstream based on their relative concentration, with the gas with the greater concentration moving across to the area with the lower concentration. This process consumes no energy. The circulatory system is deeply connected with the respiratory system because it distributes the dissolved oxygen to the tissues of the body and the waste carbon dioxide to the lungs.
Another key role of respiration is maintaining proper blood pH. The concentration of hydrogen ions in blood is partially determined by the amount of dissolved carbon dioxide in the blood, so that more carbon dioxide results in more hydrogen, causing the blood to have a lower pH and be more acidic.
When the blood becomes acidic, respiratory acidosis occurs, which can cause tissue damage if too severe. Acidosis can be caused by hypoventilation too little breathing , which reduces the removal rate of carbon dioxide, causing it to build up in the bloodstream along with hydrogen. There are many symptoms of acidosis, such as headache, confusion, increased heart rate, and muscle weakness. Respiratory alkalosis happens when the opposite effect occurs. When the blood pH becomes too high, from too few hydrogen ions because of too little carbon dioxide, the blood will become alkaline, which is also harmful to the body.
Alkalosis can happen from hyperventilation too much breathing which removes too much carbon dioxide from the bloodstream. Thankfully, negative feedback mechanisms exist so that hyperventilation and hypoventilation can be corrected. These feedback mechanisms can fail in people with chronic respiratory diseases like emphysema and bronchitis, or from the side effects of certain drugs, in which acidosis and alkalosis will occur regardless. The respiratory system include lungs, airways and respiratory muscles.
Ventilation is the rate at which gas enters or leaves the lung. In humans and other mammals, this exchange balances oxygenation of the blood with the removal of carbon dioxide and other metabolic wastes from the circulation. Bronchial anatomy : The pulmonary alveoli are the terminal ends of the respiratory tree, outcropping from either alveolar sacs or alveolar ducts, which are both sites of gas exchange with the blood.
As gas exchange occurs, the acid-base balance of the body is maintained as part of homeostasis. If proper ventilation is not maintained, two opposing conditions could occur: respiratory acidosis a life threatening condition and respiratory alkalosis. Changing the pressure of this fluid also allows the lungs and the thoracic wall to move together during normal breathing.
Much the way two glass slides with water in-between them are difficult to pull apart, such is the relationship of the lungs to the thoracic wall. The rhythm of ventilation is also controlled by the "Respiratory Center" which is located largely in the medulla oblongata of the brain stem. This is part of the autonomic system and as such is not controlled voluntarily one can increase or decrease breathing rate voluntarily, but that involves a different part of the brain.
While resting, the respiratory center sends out action potentials that travel along the phrenic nerves into the diaphragm and the external intercostal muscles of the rib cage, causing inhalation. Relaxed exhalation occurs between impulses when the muscles relax. Normal adults have a breathing rate of respirations per minute.
When one breathes air in at sea level, the inhalation is composed of different gases. In the process of breathing, air enters into the nasal cavity through the nostrils and is filtered by coarse hairs vibrissae and mucous that are found there. The vibrissae filter macroparticles, which are particles of large size. Dust, pollen, smoke, and fine particles are trapped in the mucous that lines the nasal cavities hollow spaces within the bones of the skull that warm, moisten, and filter the air.
There are three bony projections inside the nasal cavity. The superior, middle, and inferior nasal conchae. Air passes between these conchae via the nasal meatuses. Air then travels past the nasopharynx, oropharynx, and laryngopharynx, which are the three portions that make up the pharynx.
The pharynx is a funnel-shaped tube that connects our nasal and oral cavities to the larynx. The tonsils which are part of the lymphatic system, form a ring at the connection of the oral cavity and the pharynx. Here, they protect against foreign invasion of antigens. Therefore, the respiratory tract aids the immune system through this protection. Then the air travels through the larynx. The larynx closes at the epiglottis to prevent the passage of food or drink as a protection to our trachea and lungs.
The larynx is also our voicebox; it contains vocal cords, in which it produces sound. Sound is produced from the vibration of the vocal cords when air passes through them. The trachea , which is also known as our windpipe, has ciliated cells and mucous secreting cells lining it, and is held open by C-shaped cartilage rings. One of its functions is similar to the larynx and nasal cavity, by way of protection from dust and other particles. The dust will adhere to the sticky mucous and the cilia helps propel it back up the trachea, to where it is either swallowed or coughed up.
The mucociliary escalator extends from the top of the trachea all the way down to the bronchioles , which we will discuss later. Through the trachea, the air is now able to pass into the bronchi, bronchioles and finally alveoli before entering the pulmonary capillaries. There is lots of oxygen and then there is less carbon dioxide when the air comes in, but when it diffuses, the amounts exchange. All of this happens in seconds. Inspiration is initiated by contraction of the diaphragm and in some cases the intercostals muscles when they receive nervous impulses.
During normal quiet breathing, the phrenic nerve stimulates the diaphragm to contract and move downward into the abdomen. This downward movement of the diaphragm enlarges the thorax. When necessary, the intercostal muscles also increase the thorax by contacting and drawing the ribs upward and outward. As the diaphragm contracts inferiorly and thoracic muscles pull the chest wall outwardly, the volume of the thoracic cavity increases.
The lungs are held to the thoracic wall by negative pressure in the pleural cavity, a very thin space filled with a few millilitres of lubricating pleural fluid.
The negative pressure in the pleural cavity is enough to hold the lungs open in spite of the inherent elasticity of the tissue. Hence, as the thoracic cavity increases in volume the lungs are pulled from all sides to expand, causing a drop in the pressure a partial vacuum within the lung itself but note that this negative pressure is still not as great as the negative pressure within the pleural cavity--otherwise the lungs would pull away from the chest wall.
Assuming the airway is open, air from the external environment then follows its pressure gradient down and expands the alveoli of the lungs, where gas exchange with the blood takes place. As long as pressure within the alveoli is lower than atmospheric pressure air will continue to move inwardly, but as soon as the pressure is stabilized air movement stops.
During quiet breathing, expiration is normally a passive process and does not require muscles to work rather it is the result of the muscles relaxing. When the lungs are stretched and expanded, stretch receptors within the alveoli send inhibitory nerve impulses to the medulla oblongata, causing it to stop sending signals to the rib cage and diaphragm to contract.
The muscles of respiration and the lungs themselves are elastic, so when the diaphragm and intercostal muscles relax there is an elastic recoil, which creates a positive pressure pressure in the lungs becomes greater than atmospheric pressure , and air moves out of the lungs by flowing down its pressure gradient.
Although the respiratory system is primarily under involuntary control, and regulated by the medulla oblongata, we have some voluntary control over it also.
This is due to the higher brain function of the cerebral cortex. When under physical or emotional stress, more frequent and deep breathing is needed, and both inspiration and expiration will work as active processes. Additional muscles in the rib cage forcefully contract and push air quickly out of the lungs.
In addition to deeper breathing, when coughing or sneezing we exhale forcibly. Our abdominal muscles will contract suddenly when there is an urge to cough or sneeze , raising the abdominal pressure. The rapid increase in pressure pushes the relaxed diaphragm up against the pleural cavity. This causes air to be forced out of the lungs. Another function of the respiratory system is to sing and to speak. By exerting conscious control over our breathing and regulating flow of air across the vocal cords we are able to create and modify sounds.
Lung Compliance is the magnitude of the change in lung volume produced by a change in pulmonary pressure. Compliance can be considered the opposite of stiffness.
A low lung compliance would mean that the lungs would need a greater than average change in intrapleural pressure to change the volume of the lungs. A high lung compliance would indicate that little pressure difference in intrapleural pressure is needed to change the volume of the lungs. More energy is required to breathe normally in a person with low lung compliance. Persons with low lung compliance due to disease therefore tend to take shallow breaths and breathe more frequently.
Determination of Lung Compliance Two major things determine lung compliance. The first is the elasticity of the lung tissue. Any thickening of lung tissues due to disease will decrease lung compliance. The second is surface tensions at air water interfaces in the alveoli. The surface of the alveoli cells is moist. The attractive force, between the water cells on the alveoli, is called surface tension.
Thus, energy is required not only to expand the tissues of the lung but also to overcome the surface tension of the water that lines the alveoli. Its main function is to send signals to the muscles that control respiration to cause breathing to occur.
For the sake of convenience, we will divide the respiratory system in to the upper and lower respiratory tracts:. The upper respiratory tract consists of the nose and the pharynx. Its primary function is to receive the air from the external environment and filter, warm, and humidify it before it reaches the delicate lungs where gas exchange will occur. Air enters through the nostrils of the nose and is partially filtered by the nose hairs, then flows into the nasal cavity.
The nasal cavity is lined with epithelial tissue, containing blood vessels, which help warm the air; and secrete mucous, which further filters the air. The endothelial lining of the nasal cavity also contains tiny hairlike projections, called cilia.
The cilia serve to transport dust and other foreign particles, trapped in mucous, to the back of the nasal cavity and to the pharynx. There the mucus is either coughed out, or swallowed and digested by powerful stomach acids. After passing through the nasal cavity, the air flows down the pharynx to the larynx.
The lower respiratory tract starts with the larynx, and includes the trachea, the two bronchi that branch from the trachea, and the lungs themselves. This is where gas exchange actually takes place. The larynx plural larynges , colloquially known as the voice box, is an organ in our neck involved in protection of the trachea and sound production.
The larynx houses the vocal cords, and is situated just below where the tract of the pharynx splits into the trachea and the esophagus. The larynx contains two important structures: the epiglottis and the vocal cords. The epiglottis is a flap of cartilage located at the opening to the larynx. During swallowing, the larynx at the epiglottis and at the glottis closes to prevent swallowed material from entering the lungs; the larynx is also pulled upwards to assist this process.
Stimulation of the larynx by ingested matter produces a strong cough reflex to protect the lungs. Note: choking occurs when the epiglottis fails to cover the trachea, and food becomes lodged in our windpipe.
The vocal cords consist of two folds of connective tissue that stretch and vibrate when air passes through them, causing vocalization. The length the vocal cords are stretched determines what pitch the sound will have.
The strength of expiration from the lungs also contributes to the loudness of the sound. Our ability to have some voluntary control over the respiratory system enables us to sing and to speak. In order for the larynx to function and produce sound, we need air.
That is why we can't talk when we're swallowing. Homeostasis is maintained by the respiratory system in two ways: gas exchange and regulation of blood pH. Gas exchange is performed by the lungs by eliminating carbon dioxide, a waste product given off by cellular respiration. As carbon dioxide exits the body, oxygen needed for cellular respiration enters the body through the lungs.
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