The Respiratory System
The respiratory system's job is to breath in oxygen and to breath out carbon dioxide(CO2). The oxygen enters the nose or mouth, but it's better to breath though the nose for several reasons. The first reason is because the mucus in your nose blocks off dust and other bad things. It's also good to breath in the nose because when the body inhales and exhales through the mouth, the CO2 comes out too quickly so the oxygen can't get fully delivered to the alveries. After the oxygen enters the nose, it goes through a short, hollow tube called the larynx, also known as the voice box. It contains the epiglottis, glottis, vocal chords, supraglottis, and subglottis. The larynx connects to the trachea, a long tube that splits into two and goes down to the lungs. The lungs have many different organs in them. The trachea continues into the lungs, but it's known as the bronchus. The bronchus branch off into bronchi, basically smaller versions of the bronchus.
After going down into the alveoli, red blood cells carry the oxygen by attaching it to the oxygen and they bring the oxygen into the arteries. The veins carry CO2 back into the alveoli and out the lungs. Then it goes up the trachea and, when you exhale, it comes out. There is also an organ known as the nasal cavity. It's above the nostril and stops blood from coming out. Without it, you would have a nonstop nosebleed! Nosebleeds happen when the nasal cavity dries up. The reason why the chest goes up when someone inhales is because of the diaphragm. It expands and pushes the rib cage up when someone inhales and relaxes when the body exhales. It allows you to breathe, sneeze, cough, etc. It is a musclular tissue at the bottom of the lungs.