HOW THE LUNGS WORK
Breathing involves two phases: breathing in and breathing out.
Breathing in
When you breathe in, or inhale, your diaphragm contracts and moves downward. This increases the space in your chest cavity, and your lungs expand into it. The muscles between your ribs also help enlarge the chest cavity. They contract to pull your rib cage both upward and outward when you inhale.
As your lungs expand, air is sucked in through your nose or mouth. The air travels down your trachea, or windpipe, and into your lungs. After passing through your bronchial tubes, the air travels to the alveoli, or air sacs.
Gas exchange
Every time you breathe in, oxygen from the air you inhale passes through the thin walls of the alveoli into the surrounding capillaries, where red blood cells pick it up using a protein called haemoglobin. At the same time, carbon dioxide, the waste gas carried back to the lungs from the cells of the body, trades places with the oxygen, moving from the blood in the capillaries back into the alveoli.
Blood loaded up with oxygen-rich red blood cells travels to the left side of the heart through the pulmonary veins. The heart then pumps the oxygenated blood to the rest of the body, where it moves from your blood vessels to your cells. The cells need this oxygen to make the energy your body needs to work. When cells make that energy, they create the waste product carbon dioxide. That carbon dioxide has to be removed from the blood and the body, which is why it is pushed from the cells back to the blood.
The carbon dioxide, once in the bloodstream, travels back to the heart, where it enters the right side. From there, it travels through the pulmonary artery to the lungs, where it flows from the capillaries back into the alveoli in exchange for the incoming oxygen. From the alveoli, the carbon dioxide is breathed back out.
Breathing 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 how air releases 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.
Air and Gas Exchange - You Tube
https://www.youtube.com/watch?v=Y7KsJ-wHRQI
HOW THE HEART WORKS
The heart is an organ about the size of your fist that pumps blood through your body. It is made up of multiple layers of tissue.
Your heart is at the center of your circulatory system. This system is a network of blood vessels, such as arteries, veins, and capillaries, that carries blood to and from all areas of your body. Your blood carries the oxygen and nutrients that your organs need to work properly. Blood also carries carbon dioxide to your lungs so you can breathe it out. Inside your heart, valves keep blood flowing in the right direction.
Your heart’s electrical system controls the rate and rhythm of your heartbeat. A healthy heart supplies your body with the right amount of blood at the rate needed to work well. If disease or injury weakens your heart, your body’s organs will not receive enough blood to work normally. A problem with the electrical system — or the nervous or endocrine systems, which control your heart rate and blood pressure — can also make it harder for the heart to pump blood.