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Respiratory System. Page 956. Air moves through the nose and nasal cavity where it is filtered (hairs) and warmed. Enters the pharynx (throat), a tube at the back of the mouth. The pharynx serves as a passageway for both air and food.
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Respiratory System Page 956
Air moves through the nose and nasal cavity where it is filtered (hairs) and warmed. • Enters the pharynx (throat), a tube at the back of the mouth. The pharynx serves as a passageway for both air and food.
Enters the trachea (windpipe) which is made up of fibrous and elastic tissues and smooth muscle with about twenty rings of cartilage, which help keep the trachea open. It is lined with cilia and cells that secrete mucus. The mucus traps tiny particles of debris, and the beating of the cilia moves the mucus up and out of the respiratory tract, keeping the lungs and air passages free.
Air moves over or through the larynx (voice box) depending on whether you are speaking or not. • Into two large passageways in the thoracic cavity called the bronchi (singular = bronchus), each leading into a lung. 6. Into smaller passageways called the bronchioles.
Both the bronchi and bronchioles are surrounded by smooth muscle that helps support them and enables the nervous system to regulate their diameter.
The air then enters the alveoli (alveolus) which are at the ends of each of the bronchioles. They are grouped in clusters (like grapes). Capillaries surround each alveolus. • There are about 150 million alveoli in each lung.
Gas exchange • Oxygen dissolves in the moisture on the inner surface of the alveoli and then diffuses across the one cell layer-walled capillaries into the blood. • Carbon dioxide diffuses from the capillaries into the alveoli and is exhaled. *Remember diffusion
Breathing • Breathing is the movement of air into and out of the lungs. • There are no muscles connected to the lungs. • It all works with air pressure.
The diaphragm is a large, flat muscle which separates the thoracic and abdominal cavities. • When it contracts, the rib cage rises which expands the chest cavity. Remember diffusion and the movement of gases from areas of higher concentration to areas of lower concentration. Air rushes in. When the concentration is higher in the lungs, air moves out.
The system works because our lungs are sealed; each in a sac called a pleural membrane.