Respiratory system.

Hello everybody, here we are in a new year. I hope you rested in Christmas holidays after all the work of the first quarter. I also assume that you had a good time with your family and friends. But we are in a new year and we must return to work. We have to keep improving our knowing about the human body. In the first quarter we finished with the digestive system. we studied its anatomy and fisiology. Now we continue with the nutrition function and we will study:
The respiratory system:
The main function of the respiratory system is to bring oxygen into the body and releases carbon dioxide into the atmosphere. The respiratory system is made up of the organs that take part in this process. These structures include your nose, mouth, larynx, pharynx, lungs, and diaphragm. These structures are shown in Figure


The nose and nasal cavity filters, warms, and moistens the inhaled air. The nose hairs and mucus produced by the cells that line the nose catch airborne particles and prevent them from reaching the lungs.
Behind the nasal cavity, air next passes through the pharynx, a tube that is shared with the digestive system. Both food and air pass through the pharynx. A flap of connective tissue called the epiglottis closes over the trachea when food is swallowed to prevent choking or inhaling food.
The larynx is found just below the point at which the pharynx splits into the trachea and the esophagus. Your voice comes from your larynx. Air from the lungs passes across thin membranes (vocal cords) in the larynx and produces sound.
The trachea, or wind pipe, is a long tube that leads down to the chest where it divides into the right and left bronchi in the lungs. The bronchi branch out into smaller bronchioles in each lung.
The bronchioles lead to the alveoli.
Alveoli are the little sacs at the end of the bronchioles. They look like little bunches of grapes at the end of the bronchioles, as shown in Figure. Gas exchange occurs in the alveoli, oxygen move across a membrane and into the blood and carbon dioxide move out of the blood. The alveoli are the tiny grape-like structures in the lungs and the sites of gas exchange.
The diaphragm is a sheet of muscle that extends across the bottom of the rib cage. It performs an important function in respiration. When the diaphragm contracts the chest volume gets larger and the lungs take in air. When the diaphragm relaxes, the chest volume gets smaller and air is pushed out of the lungs.