University:
Stanford University
Course:
MED 101 | Human Anatomy
Academic year:

2024
Views:

227

Pages:

1
Author:

larbi43100

‭GAS EXCHANGE THROUGH THE ALVEOLO MEMBRANE‬‭CAPPILARY.‬ ‭ as‬ ‭diffusion‬ ‭occurs‬ ‭through‬ ‭the‬ ‭alveolar-capillary‬ ‭membrane.‬ ‭This‬ G ‭membrane‬ ‭is‬ ‭found‬ ‭between‬ ‭the‬ ‭alveoli‬ ‭and‬ ‭the‬ ‭capillaries.‬ ‭We‬ ‭speak‬ ‭of‬ ‭alveolar-capillary diffusion.‬ ‭ his‬‭alveolar-capillary‬‭membrane‬‭has‬‭a‬‭very‬‭large‬‭and‬‭fine‬‭surface,‬‭which‬ T ‭allows‬ ‭O2‬ ‭to‬ ‭pass‬‭easily.‬‭Its‬‭surface‬‭increases‬‭with‬‭effort.‬‭It‬‭is‬‭around‬‭70‬ ‭m²‬‭when‬‭resting‬‭and‬‭around‬‭120‬‭m²‬‭when‬‭exercising.‬‭The‬‭O2‬‭crosses‬‭the‬ ‭alveolar-capillary‬‭membrane‬‭by‬‭a‬‭pressure‬‭gradient‬‭(that‬‭is‬‭to‬‭say‬‭from‬‭a‬ ‭high pressure zone to a low pressure zone).‬ ‭This membrane has several walls:‬ ‭⮚‬ ‭The capillary wall‬ ‭⮚‬ ‭The alveolar wall‬ ‭⮚‬ ‭The alveolar-capillary barrier‬ ‭The direction of gas diffusion is by pressure difference.‬ I‭ n‬ ‭this‬ ‭diagram‬ ‭we‬ ‭see‬ ‭the‬ ‭different‬ ‭pressures‬ ‭in‬ ‭the‬ ‭alveolus‬ ‭and‬ ‭the‬ ‭capillary.‬‭It‬‭is‬‭these‬‭pressures‬‭which‬‭organize‬‭the‬‭movement‬‭of‬‭gases‬‭(CO2‬ ‭exit and O2 entry).‬ ‭ he‬ ‭deoxygenated‬ ‭blood‬ ‭arriving‬ ‭in‬ ‭the‬ ‭capillary‬ ‭has‬ ‭a‬ ‭CO2‬ ‭pressure‬ T ‭higher‬ ‭than‬ ‭the‬ ‭alveolar‬ ‭pressure,‬ ‭which‬ ‭causes‬ ‭the‬ ‭CO2‬ ‭to‬ ‭exit,‬ ‭and‬ ‭an‬ ‭O2‬ ‭pressure‬ ‭lower‬ ‭than‬ ‭the‬ ‭alveolar‬ ‭pressure,‬ ‭which‬ ‭favors‬‭its‬‭entry‬‭into‬ ‭the‬ ‭capillary.‬ ‭It‬ ‭is‬ ‭these‬ ‭different‬ ‭pressures‬ ‭PO2,‬ ‭PCO2,‬ ‭PaO2,‬ ‭PaCO2,‬ ‭which allow alveolar-capillary exchanges.‬ ‭At the cell level.‬ ‭ xchanges‬ ‭at‬ ‭one‬‭level‬‭of‬‭tissues‬‭operate‬‭according‬‭to‬‭the‬‭same‬‭principle‬ E ‭of‬‭pressure‬‭gradient‬‭as‬‭for‬‭alveolar-capillary‬‭exchanges.‬‭This‬‭time‬‭it‬‭is‬‭the‬ ‭O2‬ ‭which‬ ‭leaves‬ ‭towards‬ ‭the‬ ‭cells‬ ‭and‬ ‭the‬ ‭CO2‬ ‭produced‬ ‭by‬ ‭the‬ ‭tissues‬ ‭which enters.‬