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Human Respiratory System – • Diaphragm – sheet of muscle • Pharynx – where digestive and respiratory systems meet • Larynx – voice box – We produce sounds by exhaling, air moves over vocal cords • Trachea – windpipe • Bronchi – lead to each lung • Bronchioles – smaller branches structure and function • Alveoli – clusters of air sacs – Where gas is exchanged with blood vessels – Increase surface area to allow for more gas exchange Scanning electron micrographs of alveoli Take A Breath • Alternation of inhalation and exhalation… • When the diaphragm contracts air is “pulled” into the lungs due to increase in volume and decrease in pressure (negative pressure breathing) • When diaphragm relaxes air is “pushed” out of the lungs due to decrease in volume and increase in pressure • Automatic control centers in the brain regulate breathing • Nerves tell the diaphragm when to contract (between contractions the diaphragm relaxes) • Respiratory rate ~ 10-14 inhalations per minute • This rate will change depending on the level of CO2 in the blood – The more CO2 in the blood the faster the respiration rate • Hyperventilation – purges the blood of so much CO2 that the brain stops sending messages to the diaphragm – So breathing into a paper bag will increase the amount of CO2 taken into the body and restore What controls our breathing? Importance of Hemoglobin • Oxygen does not readily dissolve in blood • O2 will be carried through the blood by hemoglobin molecules in red blood cells • Hemoglobin consists of 4 polypeptide chains, heme (chemical group) and iron • Every iron atom can only bind to 1 O2molecule; therefore, each hemoglobin can carry up to 4 O2 molecules • O2 rich blood is bright red / O2 poor blood is dark red (blue) Problems with hemoglobin… • Iron deficiency causes anemia • Hemoglobin can also bind to CO (carbon monoxide) • CO interferes with the delivery of O2 to the body cells and cellular respiration; therefore, causes death – CO is also found in cigarette smoke Effects of smoking • Air pollutants can cause respiratory problems – CO, SO2, O3 • Tobacco smoke is one of the worst forms of air pollution • It can contain > 4000 chemicals (many of which are deadly) • Epithelial tissues are very delicate. • Chemicals damage the mucus and cilia making it difficult to remove foreign particles