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Function of the Lungs. Primary - to provide a means of gas exchange between environment and body Secondary - maintenance of acid-base balance and as a resevoir for blood. Ventilation vs. Diffusion. Ventilation - moving air into and out of the lungs
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Function of the Lungs • Primary - to provide a means of gas exchange between environment and body • Secondary - maintenance of acid-base balance and as a resevoir for blood
Ventilation vs. Diffusion • Ventilation - moving air into and out of the lungs • oxygen is moved into the lungs and CO2 is moved out during ventilation • Diffusion - random movement of molecules from area of high concentration to low concentration • because O2 concentration is high in the lungs, and low in the blood, O2 diffuses into the blood from the lungs (converse for CO2)
Structure • Conductive zone - area where no gas exchange occurs, air is simply moved through (eg. trachea, bronchii) • Respiratory zone - area where gas exchange does occur (eg. alveoli)
Mechanics of Breathing • Bulk Flow • movement of air from the environment to the lungs • occurs due to pressure differences at end of system
Cont’d • Inspiration • major muscle involved is the diaphragm • (diaphragm only skeletal muscle in body considered essential for life) • intrapulmonary pressure reduced below atmospheric • during exercise • external intercostals, pectoralis minor, scalene, sternomastoids increase volume of thorax
More • Expiration • intrapulmonary pressure exceeds atmospheric • passive at rest • during exercise • rectus abdominus, internal obliques involved
Mechanics of Inspiration and Expiration • Pulmonary - ventilation (breathing) and gas exchange in the lungs • Cellular - O2 utilization and CO2 production in the tissues