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University of Toronto St. George
Doug Mac Kay

PSL302-Lecture 36- Respiratory System Overview: What are the functions of the respiratory system? Structures that make up the respiratory system? How is blood transported to and from the lungs? What protects the respiratory system from pathogensforeign particles? How is lung function measured? Asthma attacks- treated by steroids inhalers or lung dilators What lung structures are affected during an asthma attack? If he were to undergo a lung function test during an asthma attack, what would you expect to observe? The respiratory system functions to Pulmonary ventilation Exchange gases between air and blood, take in oxygen for cellular respiration and put out CO2 (made through metabolism) Regulate blood pH this is due to the CO2 levels Acid-base balance Gas transport Defense from inhaled pathogensforeign particles Vocalization - specifically the larynx the air moves across the vocal chords along with the movement of the tongue and the teethetc Cellular respiration = chemical processes inside the cell Structures in the respiratory system: The nasal cavity and the mouth are part of the respiratory system Common passage way called the pharynx, both air and food can pass the food goes into the esophagus towards the digestive system and the air goes to the trachea At the top of the trachea we have the larynx When you swallow food, the epiglottis covers the common area so it goes to the esophagus not the trachea There has to be a shuttling mechanism so food goes to the esophagus not the lungs Air is going through the larynx and trachea, and the trachea branches to form the right and left bronchus, which branch further to get all the way down to microscopic sacs called the alveoli Starting at the trachea, it is the lower respiratory tract Respiratory muscles change the volume of the cavity in which lungs are found o Muscles of inspiration o Muscles of expiration Both types of muscles are found on both sides, even though they are put each on a side on the diagram. To bring air into the lungs, it requires that the diaphragm contracts and pushes down so that it expands the thoracic cavity o While in forced breathing in, the external intercostals will contract and raise up the rib cage and expand In the case of expiration, it can be completely passive that when you stop breathing in there is elastic recoil that will cause air to move out of the lungs esp when the diaphragm is relaxed, but if you want to forcefully expire air, you rely on the internal intercostals to contract which draw the rib cage inward to make the thoracic cavity smaller and the abdominal muscles, which contract and push up on the diaphragm, and decrease the volume of the thoracic cavity. You need these muscles to breathe in and for forced expiration to breathe out
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