37 Pulmonary Ventilation

37 Pulmonary Ventilation - PSL302: Lecture 37, by Prof....

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Pulmonary Ventilation Outline - How does air get into and out of the lungs? - What respiratory muscles are needed? - How do the properties of the lungs affect ventilation? - At rest, how much air is exchanged per minute? Textbook reading: 577, 579-588 1. How does air get into lungs? - Air mvt occurs wherever a pressure gradient exists - For air to enter lungs: P lungs < P outside = 0 - Relationship btwn P & V - For air to enter lungs: V lungs = P lungs Boyle’s Law: P 1 V 1 = P 2 V 2 By changing V lung , pressure gradients develop 2. What respiratory muscles are needed? Muscles of inspiration: V thoracic - Diaphragm : main muscle of breathing - Controlled by phrenic nerve , from cervical spinal segments C3, C4 & C5 - Attached to lower ribs, which move down as it contracts - Abdominal contents forced down & fwd - Sternocleidomastoids : attached to sternum - Produces “ bucket-handle ” motion - lateral dimension of ribcage - Also caused by mvt of vertebrae - Scalenes : attached to ribs - Produces “ pump-handle ” motion - anterior-posterior dimension of ribcage - External intercostals : move ribs outwds Ai d l Lectu Respirato s Airways and lungs alveoli Mus pleura fun Pulmonary ventilation Gas excha alveoli/blo blood/tissu ± pressures lung how much? properties Respiratory contr Exercise a ure 2 ory system structures scles Pulmonary circulation nctions ange Gas Defense Vocalization nge ood ues transport Acid/base balance O 2 CO 2 + H 2 0 H + + HCO3 ± ol and High Altitude PB = 0 P = 0 PB = 0 P P Volume Volume Pressure Pressure (sterum) (first 2 ribs) PSL302: Lecture 37, by Prof. French Wednesday, Jan. 12, 2010 1 of 5
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Expiration - At rest, expiration is passive via elastic recoil of lungs (diaphragm relaxes) - Enough V so that P = air moves out - But expiratory muscles used during voluntary expiration or when BR - Internal intercostals & abdominal muscles - Contract & force rib cage down & inwd = abdominal volume But: the lungs are not fastened to thoracic wall ...How does mvt of diaphragm & rib cage expand lungs? -
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37 Pulmonary Ventilation - PSL302: Lecture 37, by Prof....

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