Respiratory System

• Respiratory system function - allows animals to move oxygen (for cellular respiration) into body tissues and remove carbon dioxide (waste of cellular respiration) from cells
• Respiration - exchange of oxygen and carbon, when you breathe in: the respiratory system sends oxygen to the blood, when you breathe out: respiratory system removes carbon dioxide
• Nasal Cavity - air enters through the nose and mouth, behind nose is a hollow space called the nasal cavity, The nasal cavity is lined with cells that secrete mucus and hairs to trap dust, bacteria and other particles, incoming air is moistened and warmed, keep the respiratory system from drying out
• Pharynx - aka the throat, air passes through the pharynx when inhaling through the nasal cavity, the epiglottis covers the air pathway to prevent food from going into your trachea when you swallow
• Larynx (voice box) - between pharynx and trachea, entrance is covered by the epiglottis when swallowing, contain vocal cords, cartilage is the Adam’s apple
• Trachea (Windpipe) - extends from the larynx to the center of the chest, cells in trachea have hair-like cilia and secrete mucus to trap pollutants and other particles, particles are swallowed or expelled by coughing them up
• Bronchi - trachea branches into smaller tubes called bronchi, in the lungs, bronchi branches into a smaller, narrower network of tubes called bronchioles, coated with cilia and mucus
• Lungs and Alveoli - each bronchiole ends in grape-like clusters of tiny air sacs called alveoli. Surrounded by capillaries, gas exchange occurs 
• Diffusion/ Gas Exchange - substances always diffuse from where they are in high concentration to areas of low concentration. Concentration of oxygen in the blood is always less than concentration of air in the alveoli. Oxygen always diffuses into the blood. Excess carbon dioxide diffuses from the cells into the blood. It is carried by the blood to the lungs and expelled to the outside
• Inhalation - when you inhale, the muscular diaphragm and muscles in the rib cage contract. Diaphragm has a dome shape when it is relaxed, lung volume increases, air rushes into the lungs, high to low pressure
• Exhalation - diaphragm and the muscles of the rib cage relax, diaphragm rises upwards and rests in the chest cavity again, lung volume decreases, air rushes out of the lungs (high to low pressure