Kids Research Express

. The flow of air in and out of the lungs is controlled by the nervous system , which ensures that humans breathe in a regular pattern and at a regular rate. Breathing is carried out day and night by an unconscious process. It begins with a cluster of nerve cells in the brain stem called the respiratory center. These cells send simultaneous signals to the diaphragm and rib muscles, the muscles involved in inhalation. The diaphragm is a large, dome-shaped muscle that lies just under the lungs. When the diaphragm is stimulated by a nervous impulse, it flattens. The downward movement of the diaphragm expands the volume of the cavity that contains the lungs, the thoracic cavity. When the rib muscles are stimulated, they also contract, pulling the rib cage up and out like the handle of a pail. This movement also expands the thoracic cavity. The increased volume of the thoracic cavity causes air to rush into the lungs. The nervous stimulation is brief, and when it ceases, the diaphragm and r

. The organs of the respiratory system extend from the nose to the lungs and are divided into the upper and lower respiratory tracts. The upper respiratory tract consists of the nose and the pharynx , or throat. The lower respiratory tract includes the larynx , or voice box; the trachea , or windpipe, which splits into two main branches called bronchi; tiny branches of the bronchi called bronchioles; and the lungs , a pair of saclike, spongy organs. The nose, pharynx, larynx, trachea, bronchi, and bronchioles conduct air to and from the lungs. The lungs interact with the circulatory system to deliver oxygen and remove carbon dioxide. A Nasal Passages B Pharynx C Larynx D Trachea, Bronchi, and Bronchioles E Alveoli

. Respiratory System, in anatomy and physiology, organs that deliver oxygen to the circulatory system for transport to all body cells. Oxygen is essential for cells, which use this vital substance to liberate the energy needed for cellular activities. In addition to supplying oxygen, the respiratory system aids in removing of carbon dioxide, preventing the lethal buildup of this waste product in body tissues. Day-in and day-out, without the prompt of conscious thought, the respiratory system carries out its life-sustaining activities. If the respiratory system’s tasks are interrupted for more than a few minutes, serious, irreversible damage to tissues occurs, followed by the failure of all body systems, and ultimately, death. While the intake of oxygen and removal of carbon dioxide are the primary functions of the respiratory system, it plays other important roles in the body. The respiratory system helps regulate the balance of acid and base in tissues, a process crucial for the norma