Gas exchange takes place in the millions of alveoli in the lungs and the capillaries that envelop them. As shown below, inhaled oxygen moves from the alveoli to the blood in the capillaries, and carbon dioxide moves from the blood in the capillaries to the air in the alveoli. Three processes are essential for the transfer of oxygen from the outside air to the blood flowing through the lungs: ventilation, diffusion, and perfusion. Diffusion is the spontaneous movement of gases, without the use of any energy or effort by the body, between the alveoli and the capillaries in the lungs.
The body's circulation is an essential link between the atmosphere, which contains oxygen, and the cells of the body, which consume oxygen. For example, the delivery of oxygen to the muscle cells throughout the body depends not only on the lungs but also on the ability of the blood to carry oxygen and on the ability of the circulation to transport blood to muscle.
In addition, a small fraction of the blood pumped from the heart Function of the Heart The heart and blood vessels constitute the cardiovascular circulatory system. Merck and Co. 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.
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This site complies with the HONcode standard for trustworthy health information: verify here. Common Health Topics. Courtesy of. Biology of the Lungs and Airways. Air also enters through the MOUTH , especially for those who have a mouth-breathing habit, whose nasal passages may be temporarily blocked by a cold, or during heavy exercise.
These, in turn, split further into bronchioles. Each lobe is like a balloon filled with sponge-like tissue. Air moves in and out through one opening—a branch of the bronchial tube. The PLEURA are the two membranes, actually, one continuous one folded on itself, that surround each lobe of the lungs and separate your lungs from your chest wall. This motion carries MUCUS sticky phlegm or liquid upward and out into your throat, where it is either coughed up or swallowed.
Mucus catches and holds much of the dust, germs, and other unwanted matter that has invaded your lungs. You get rid of this matter when you cough, sneeze, clear your throat or swallow. While in the capillaries, blood gives off carbon dioxide through the capillary wall into the alveoli and takes up oxygen from air in the alveoli. By moving downward, it creates suction in the chest, drawing in air and expanding the lungs. RIBS are bones that support and protect your chest cavity.
They move slightly to help your lungs expand and contract. Keeping Lungs Healthy Lung capacity declines as you age. Make a Donation Your tax-deductible donation funds lung disease and lung cancer research, new treatments, lung health education, and more.
Make a Donation. Sign Up for Email Updates Join over , people who receive the latest news about lung health, including COVID, research, air quality, inspiring stories and resources. The chest walls form a protective cage around the lungs and other contents of the chest cavity. The cells in our bodies need oxygen to stay alive. Carbon dioxide is made in our bodies as cells do their jobs. The lungs and respiratory system allow oxygen in the air to be taken into the body, while also letting the body get rid of carbon dioxide in the air breathed out.
When you breathe in, the diaphragm moves downward toward the abdomen, and the rib muscles pull the ribs upward and outward. This makes the chest cavity bigger and pulls air through the nose or mouth into the lungs. In exhalation, the diaphragm moves upward and the chest wall muscles relax, causing the chest cavity to get smaller and push air out of respiratory system through the nose or mouth.
Every few seconds, with each inhalation, air fills a large portion of the millions of alveoli. In a process called diffusion, oxygen moves from the alveoli to the blood through the capillaries tiny blood vessels lining the alveolar walls. Once in the bloodstream, oxygen gets picked up by the hemoglobin in red blood cells. This oxygen-rich blood then flows back to the heart, which pumps it through the arteries to oxygen-hungry tissues throughout the body. In the tiny capillaries of the body tissues, oxygen is freed from the hemoglobin and moves into the cells.
Carbon dioxide, made by the cells as they do their work, moves out of the cells into the capillaries, where most of it dissolves in the plasma of the blood. Blood rich in carbon dioxide then returns to the heart via the veins.
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