It all starts with the inhalation. Oxygen that we breathe in goes in our lungs down bronchial tubes. The bronchial tubes that lead to the lungs split up into many different bronchial tubes that have sacs attached to them that are called Alveoli. The oxygen that is inhaled passes into these Alveoli’s and then diffuses through the capillaries into the arterial blood. Meanwhile, the waste-rich blood from the veins releases its carbon dioxide into the alveoli. The carbon dioxide follows the same path out of the lungs when you exhale.
The oxygen that we breathe in goes in our blood. Our blood needs more the just oxygen, it needs energy. The energy that it needs is sugar. The sugar comes from the digestive system, where enzymes to form sugars or glucose break down the food. The nutrients like sugar are all transformed into a thick liquid called Chyme. When the Chyme is at a good consistency, it is then squirted down into the Small intestine, where digestion of food continues so the body can absorb the nutrients into the bloodstream. Undigested food and water travels to the large intestine from the small intestine. Almost all the nutrients are gone and this waste gets excreted out of the body by the rectum. The blood cells use this system to get their energy. Now that the blood has oxygen and energy from the digestive system, cellular respiration can happen. Respiration in cells involves a series of chemical reactions that occur in the presence of oxygen. These reactions release energy from food substances and make it available so that the cells can function. Cells can obtain a compound known as adenosine troposphere (ATP). ATP is very important because it supplies energy to all cells. Cells require oxygen to obtain large amounts of ATP. When oxygen is present in a cell, pyruvic acid (In the cell's cytoplasm, the simple sugars are broken down into pyruvic acid) enters a series of chemical reactions called the Krebs cycle (is a series of chemical reactions through which tissues use carbohydrates, fats, and proteins to produce energy.). During the cycle, energy is captured and passed on to a series of reactions called the electron transport chain. As a result of these reactions, carbon dioxide and water are formed and released. A great deal of energy is stored as ATP also. That’s where perspiration is formed and the higher the activity, the faster the cells have to work to breath faster so there is more perspiration.
To help our respiratory system we have all the muscles in our body that enable us to breathe in oxygen and breathe out carbon dioxide. Muscles near the lungs help expand and contract (tighten) the lungs to allow breathing. There are four main muscles that help with breathing. There is the Diaphragm and its job is to help pump the carbon dioxide out of the lungs and pull the oxygen into the lungs. It lies across the bottom of the chest cavity. As the diaphragm contracts and relaxes, breathing takes place. When the diaphragm contracts, oxygen is pulled into the lungs. When the diaphragm relaxes, carbon dioxide is pumped out of the lungs. Next there is the intercostals muscles which are located between your ribs. They also play a major role in helping you breathe. Beneath your diaphragm are abdominal muscles. These help you breathe out when you’re breathing fast (for example, during physical activity). Muscles in your neck and collarbone area help you breathe in when other muscles involved in breathing don’t work properly, or when lung disease impairs your breathing. To control all of this breathing process, we have a name called the respiratory center. The respiratory center is groups of nerve cells in the brain stem. Every few seconds, these cells send bursts of impulses to the muscles involved in respiration. These signals determine the rate and depth of breathing. Another group of cells, called chemoreceptors, sense the oxygen and carbon dioxide levels in the blood and the acidity of cerebrospinal fluid surrounding the brain. Slight increases or decreases in carbon dioxide cause changes in the acidity of body fluids. Chemoreceptors send signals to the respiratory center to adjust the rate and depth of breathing. During exercise, muscles in the chest wall can be stimulated to speed up expiration. In this way, the respiratory center maintains normal levels of oxygen and acidity in the body.
