Physiology: external respiration Flashcards
what is internal respiration
refers to intracellular mechanisms that consumes O2 and produces CO2
what is external respiration
refers to sequence of events that leads to exchange of O2 and CO2 between the external environment and the cells of the body
what are the 4 steps of external respiration
ventilation
gas exchange between alveoli and blood
gas transport in blood
gas exchange between blood and tissue
what is boyles law
at any constant temperature the pressure of a gas varies inversely with the volume of the gas
(e.g. as volume increases, pressure exerted decreases)
explain the movement of gases down a pressure gradient following boyles law
gas will move from area of high pressure to low pressure
what are the major inspiratory muscles
the diaphragm and the external intercostal muscles
briefly describe the inspiration stage of ventilation
lungs expand due to inspiratory muscles, lung volume increases therefore intra-alveolar pressure decreases and air enters lung( due to boyles law)
briefly describe the expiration stage of ventilation
lungs recoil due to elastic properties(muscles relaxed) and volume decreases, intra-alveolar pressure increases and air therefore exits lung(boyles law)
what 2 forces hold the lungs and thorax in close together
the intrapleural fluid cohesiveness and the negative intrapleural pressure
what is intrapleural fluid cohesiveness
water molecules in intrapleural fluid are attached to each other and resist pulling apart, hence pleural membranes stick together
what is the negative intrapleural pressure
gas in intrapleural space is sub-atmospheric, therfore creates a transmural pressure gradient across the lung wall and across chest wall
what effect does the negative intrapleural pressure have on the lungs and chest wall
the lungs are forced to expand outwards and the chest wall is forced to squeeze inwards
what are the accessory muscles of inspiration(contract only in forceful inspiration)
sternocleidomastoid, scalenus and pectoral
what are the muscles of active expiration
abdominal muscles and internal intercostal muscles
