General Physiology_Nohe_Date_052010

General Physiology_Nohe_Date_052010 - Chapter 13 Study...

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Chapter 13 Study Guide Functions of the Respiratory System 1. Provides Oxygen 2. Eliminates CO 2 3. Regulates blood’s pH in coordination with the kidneys 4. forms speech sounds (phonation) 5. defends against microbes 6. influences arterial concentrations of chemical messengers by removing some from pulmonary capillary blood and producing and adding others to this blood 7. traps and dissolves blood clots arising from systemic veins Airways and Blood Vessels Pharynx → larynx (vocal cords) →trachea →bronchi (one in each lung) Nose, mouth pharynx and larynx are considered the upper airway Walls of the trachea and bronchi contain cartilage the bronchioles do not. Ventilation and Lung Mechanics Atmospheric pressure is 760 mmHg F = (P alv -P atm )/R Transpulmonary pressure (P tp )- difference in pressure between the inside and outside of the lungs. Inside the lungs is the pressure of the alveoli (P alv ) and outside is the intrapleural fluid (P ip ) o P tp =P alv -P ip The pressure acting on the chest wall is P ip -P atm The muscles on the chest wall and diaphragm contract and cause the chest wall to expand. P ip decreases and P tp becomes more positive causing the lungs to expand. P alv then decrease as they get bigger and air moves in for inspiration. Inspiration Thorax expands, P ip becomes subatmsopheric and transpulmonary pressure increases allowing lungs to expand P alv becomes subatmospheric and air flows into the alveoli Expiration Chest wall recoils inward, Pip moves back toward preinspiration value, transpulmonary pressure move back toward pre inspiration value and lungs recoil Air in the alveoli becomes compressed P alv becomes greater than P atm and air flows out of the lungs Lung Compliance The degree of lung expansion at any instant is proportional to the transpulmonary pressure (Palv-Pip) but how much the lungs expand is due to the stretch ability or compliance of the lungs o C L = V L / P tp the greater the lung compliance, the easier it is to expand the lungs Determinants of Lung compliance There are two major determinants of lung compliance
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o Stretchability of lung tissues A thickening of lung tissues decreases lung compliance o Surface tension at the air water interfaces within the alveoli Surfactant reduces the cohesive surface tension Surfactant stabilizes alveoli of different sizes by altering surface tension depending on the surface area. The reduction in surface tension helps to maintain a pressure in smaller alveoli equal to that in larger ones so the smaller ones don’t collapse Lung Volumes and Capacities Tidal volume (Vt)- volume of air entering the lungs during a single inspiration Inspiratory reserve volume (IRV)- max amount of air that can be increased about this value during deepest inspiration Functional residual capacity (FRC)- amount of air left in the lungs at the resting position
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This note was uploaded on 08/30/2010 for the course BISC 306 taught by Professor Stephens during the Spring '08 term at University of Delaware.

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General Physiology_Nohe_Date_052010 - Chapter 13 Study...

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