odds & ends item from APRIL-MAY 2007 ISSUE
Marvels of the Human BodyReady, Set, Breathe!
What do you do between 15 to 25 times per minute and is essential for life? You breathe! The respiratory system is one of the many marvels of the human body.
Source: MCT
Here’s how it works. The respiratory system includes your nose, throat, voice box, windpipe and lungs. As you inhale through your nose or mouth, oxygen is sent through a filtration system made up of tiny hairs called cilia. Cilia function to protect the nasal passage and respiratory tract. As you inhale, the tiny hairs move back and forth, filtering out dust and other foreign particles. When found, these are either pushed back toward the nostril to be blown out or toward the pharynx (or throat) where they will journey through your digestive tract and be eliminated with other waste.
The pharynx is part of the digestive tract and respiratory system because it carries food, water and air into the body. At the end of the pharynx begins the esophagus, which takes food to the stomach, and the epiglottis, which is a small flap of tissue that covers the air-passage to prevent food from entering the lungs. The larynx (voice box) is located at the top of the air-passage. This is a small tube with a pair of vocal cords that vibrate to make sounds. The trachea (windpipe) is attached to the bottom of the larynx. The trachea walls are lined with cilia and strengthened by rings of cartilage to keep it open for air to flow to the lungs.
The end of the trachea divides into two air tubes called bronchi, which attach to the right and left lungs. In the lungs, the bronchi continue to branch into smaller tubes. The smallest tubes, the bronchioles, are as thin as a strand of hair! At the end of these are tiny air sacs called alveoli, where the exchange of oxygen and carbon dioxide takes place. There are approximately 300 to 400 million alveoli in each lung! Together, the alveoli, bronchioles and bronchi are known as the bronchial tree.
Each time you inhale, millions of alveoli are filled with air. Then a process called diffusion takes place. This is when oxygen is moved from the alveoli into your bloodstream through tiny blood vessels called capillaries, which line the alveolar walls. In the bloodstream, oxygen is picked up by a molecule in the red blood cells called hemoglobin. This oxygen-filled blood is then taken to the heart and finally pumped throughout the body via arteries. Carbon dioxide is produced during the diffusion process and then released from the cells back into the capillaries that just delivered the oxygen. Most of the carbon dioxide dissolves into the plasma of the blood. The carbon dioxide-rich blood travels through the veins to the heart and then back to the lungs, where it passes into the alveoli to be exhaled.
The lungs are enclosed in the chest cavity, or thorax. This also includes the bronchial tree, the heart and other structures. The top and sides of the thorax are comprised of 12 ribs and attached muscles, and also protect the lungs and heart. The bottom is the diaphragm, a large muscle that separates the chest from the abdomen.
When you inhale and exhale, your chest inflates and deflates. How does this work? When inhaling, the diaphragm moves down toward the abdomen and the muscles along your rib cage pull your ribs up and out, allowing the chest cavity to expand and fill with air. When exhaling, the diaphragm moves upward, causing the chest to shrink, pushing all the gases in the lungs out. Elastic tissue in the lungs allows this to happen without the lungs losing their shape.
The respiratory system is certainly another incredible marvel of the human body, which of course God created. But there is much more to learn!
Sources: www.kidshealth.org; www.howstuffworks.com