Gas Exchange
Types of gaseous exchange External respiration (pulmonary respiration) Gaseous exchange between the lungs and the blood. Blood gains oxygen and looses carbondioxide. Internal respiration (tissue respiration) Gaseous exchange between the blood and tissue cells. In internal respiration the blood looses oxygen and gains carbondioxide.
Airways leading to the Alveoli
Gas Exchange in the Alveoli
The exchange of Carbon Dioxide and Oxygen in the Alveoli
The Diffusion Pathway
The Diffusion Pathway A Large Surface Area A Small Diffusion Pathway A Large Difference in Concentration
The percentage of gases in inspired, expired and alveolar air Oxygen/% Carbon Dioxide/% Inspired air 21 0.04 Alveolar air 13 5 Expired air 16 4 – 4.5
Fick’s Law The rate of diffusion is proportional to: Surface area x difference in concentration Thickness of surface Using Fick’s Law, explain how the Alveoli are an ideal site for gas exchange The surface area is large and the difference in concentration is maintained by the flow of blood in the capillary network surrounding the alveoli. The surface is thin due to the epithelium of the alveoli and of the capillary being one cell thick and the red blood cell being close to the surface of the vessel.
The Breathing Mechanism Intercostal muscles shorten
The Breathing Mechanism Inspiration External Intercostal Muscles and Diaphragm contract The intercostal muscles shorten causing the rib cage to move up and out The Diaphragm flattens and pulls downward The Volume of the Thoracic Cavity ____________ This causes the air pressure to _______ As a result air is sucked into the lungs decreases fall
The Breathing Mechanism Expiration External Intercostal Muscles and Diaphragm relax The intercostal muscles lengthen causing the rib cage to move down and in The Diaphragm returns to its original dome shape The Volume of the Thoracic Cavity __ This causes the air pressure to _______ As a result air is pushed out of the lungs decreases increase
During Exercise During active exercise the Internal Intercostal muscles contract and forcibly lower the rib cage, expelling more air from the lungs, making room for a greater volume of air in each inspiration.
Control of Breathing More Messages sent down ‘Phrenic Nerve’ to Intercostal muscles Fewer messages sent down ‘Phrenic Nerve’ to Intercostal muscles