Fun Facts About The Respiratory System
The respiratory system is a vital organ system that allows for gas exchange. The lungs are the primary organ and contain numerous sacs known as alveoli, where gas exchange occurs. As the lungs expand, oxygen is brought into the lungs. This process of bringing in oxygen is called respiration, which is also referred to as breathing or ventilation. When we breathe in, our bodies use an internal pump to push air through the nose and down into the lungs. In addition to using the diaphragm (a muscle located at the base of the chest) to fill the lungs with air, the lungs also have specialized muscles around their openings. These muscles allow us to control the amount of air entering the lungs.
When we exhale, the same type of pumping mechanism takes place inside the body. After receiving oxygen from the lungs, the blood carries it throughout the body. Carbon dioxide, another byproduct of metabolism, diffuses out of the bloodstream and back into the lungs to be expelled. To maintain a healthy balance between these two substances, the entire respiratory system relies on various mechanisms that regulate how much air enters the lungs and how fast the heart pumps so that there is no excess of either one. One of these mechanisms is what’s known as the ventilatory cycle. It consists of four distinct stages – inspiration and expiration, inhalation and exhalation.
During each stage of the cycle, different parts of the respiratory system play distinctive roles. For example, during inspiration, the trachea narrows and expands the lungs. At the same time, the vocal cords in the larynx vibrate and create sound waves. During exhalation, the vocal folds return to their original position, and the diameter of the trachea opens up to its maximum extent. The purpose of this narrowing is to increase the pressure within the lung, allowing the lungs to become filled with more oxygen-rich air. Once the lungs are full, the airways must open wide enough to ensure that all of the air can leave the lungs. Because of the importance of maintaining a proper balance of oxygen and carbon dioxide, the respiratory system has a built-in reflex to respond to changes in the composition of the air inhaled and exhaled.
In order to understand how the respiratory system works, you need to know about some other important terms related to it. What happens when you exhale? You don’t just release air from your lungs; rather, it is taken up from the atmosphere and pumped through the rest of the respiratory system. The word breath is used interchangeably with both “exhaling” and “ventilation.” Another term often used in conjunction with ventilation is respiration. Breathing is usually defined as taking in air through the mouth or nose, but it may also include drawing in air through the skin.
Ventilation refers to the movement of air. Air moves because of pressure differences between the atmosphere outside your body and the interior of your body. The difference in atmospheric pressure is expressed in millimeters of mercury (mmHg). Atmospheric pressure is equal everywhere, regardless of location. However, the pressure inside your body varies according to height above sea level. Lower levels of elevation experience greater pressures than those who live higher up. A person living at an altitude of 1,000 feet would feel less atmospheric pressure than someone standing 20 stories below him. If you stand on the ground floor of a tall building, the force exerted against your body will be less than if you were to climb 30 stories.
Now let’s take a closer look at the components of the respiratory system. We’ll start with the nasal cavity. Before it reaches the lungs, the air passes first through the nasal passages. The nostrils serve as filters that remove dust particles, pollen, bacteria, viruses, and other foreign matter from the air before it enters the lungs. Nasal hairs also help filter particles from the air. The mucous membrane lining of the nasal cavities contains cilia, tiny hairlike structures that act like miniature vacuum cleaners. Cilia transport solid particles toward the pharynx. Each pair of nasal cilia acts like a handpump, pulling the solid particles across the mucous membrane toward them. Just like the lungs, the nasal membranes consist of millions of tiny channels, which allow for gas exchange. When the nasal cilia pull the solid particles forward, they deposit them on top of the goblet shaped turbinates, which are essentially small cushions made of cartilage. The nasal turbinates, together with the nasal septum, form part of the bony framework of the nasal passageways, and are connected to the facial skeleton. They provide additional protection for the delicate nasal tissues.
After passing through the nasal passages, the air enters the pharynx. Located behind the soft palate, the pharynx is a muscular tube that connects the nasal passages to the throat. The wall of the pharynx contains tonsils, which are lymphoid tissue that produce secretory IgA antibodies. Tonsils also serve as filters to protect the softer tissues of the upper airway. Behind the tonsils lies the epiglottis, a leaf-shaped flap that protects the lungs. It is attached to the root of the tongue, which helps keep food from going into the windpipe.
Once the air leaves the pharynx, it travels past the glottis, which separates the voice box from the trachea. The trachea branches off from the bronchii, which lead into the major airways. The bronchi branch into smaller tubes known as bronchioles. Bronchioles end in clusters of tiny sacs called alveoli. Alveolar capillaries separate the larger airways from the pulmonary interstitial tissue. Oxygen and carbon dioxide enter the lungs through the alveoli, where the exchange of gasses actually occurs.
Next, we’ll talk about how the lungs work. The lungs are enclosed in a protective envelope composed of several layers. The outermost layer is formed by thin sheets of connective tissue known as pleurae. Between the pleura and the inner surface of the rib cage lie three pleural membranes. An average adult human has approximately 500 million air sacs (or alveoli), distributed over the left and right sides of his or her chest. There are also thousands of connecting airways leading to the lungs.
Alveoli are microscopic sacks lined with a protein substance called surfactant. Surfactants prevent liquid from forming bubbles by reducing the surface tension of liquids. Inside the alveolus, red blood cells collect oxygen and expel carbon dioxide. Oxygen is carried through the walls of the alveolus by hemoglobin molecules. Hemoglobin collects oxygen along with ionic calcium and sodium ions, creating a chemical reaction that releases energy. This energy creates the forces needed for muscle contraction. Expelled carbon dioxide combines with water to form carbonic acid, which increases the pH of the blood and lowers the concentration of hydrogen ions.
Inside the alveolus, the exchanging of oxygen and carbon dioxide continues until the alveolus becomes saturated with oxygen. That means every square inch of the alveolar surface area receives roughly 21 percent of the total available supply of oxygen. When the alveolus fills up with oxygen, the remaining empty space is filled with air. The walls of the alveolus have special elastic fibers that contract and relax in response to changing concentrations of oxygen and carbon dioxide. These fibers also react when there is too much pressure buildup in the alveolus.
Finally, we’ll discuss how the lungs perform their main function: gas exchange. Gas exchange occurs once the air passes through the alveoli. Oxygen diffuses into the blood stream from the surrounding atmosphere through the walls of the alveoli, while carbon dioxide diffuses outwardly from the blood stream into the atmosphere. Carbon dioxide reacts with water in the blood stream to form carbonic acid, which raises the pH of the blood. By doing this, the carbonic acid prevents the formation of excessive amounts of free radicals, which damage cells and cause disease.
Oxygen that enters the blood stream combines with hemoglobin to form oxyhemoglobin, which delivers oxygen to the tissues. Enzymes present in the red blood cells break down the oxyhemoglobin molecule into smaller units of usable oxygen. Cells in the lungs convert most of the remaining portion of the oxygen into molecular form, releasing it directly into the fluid inside the alveoli. Some of the released oxygen attaches itself to fatty acids in phospholipids to form new lipoproteins. Lipoproteins carry fat droplets through the bloodstream to the liver, where the fats are converted into triglycerides for storage. Fatty acids produced in the liver combine with glycerol to form phosphoglycerides, which dissolve the triglycerides, freeing the fatty acids for use by the body.
As long as cells receive sufficient quantities of oxygen, they can continue functioning properly. But if oxygen supplies diminish, cell death results. Lack of oxygen triggers certain biochemical reactions that ultimately lead to cell death. Free radicals attack cellular DNA and enzymes degrade proteins. Mitochondria begin losing electrons, triggering chain reactions that eventually destroy the mitochondria. Cell death is caused primarily by lack of oxygen.
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