Int and ext respiration

EXTERNAL AND INTERNAL RESPIRATION

1. EXTERNAL AND INTERNAL RESPIRATION BY: Mrs.Keerthi Samuel, Asst.Professor, Vijay Marie College of Nursing

2. EXTERNAL RESPIRATION EXTERNAL RESPIRATION OR PULMONARY GAS EXCHANGE -diffusion of oxygen from air in the alveoli of the lungs to the blood in pulmonary capillaries and diffusion of co2 in opposite direction. External respiration in lungs converts deoxygenated coming from the right side of the heart into oxygenated blood that returns to the left side of heart.

3. As blood flows through pulmonary capillaries it picks up oxygen from alveolar air and unloads co2 into alveolar air. Although this process is commonly called as exchange of gases. The gas diffuses independently from the area of higher partial pressure to the area of low partial pressure. EXTERNAL RESPIRATION

4. The partial pressure of oxygen in the pulmonary capillaries of a resting person is 40mmHg. And the po2 in the alveolar air is 105mmhg. Hence o2 diffuses from alveolar air into the pulmonary capillaries Diffusion continues until the Po2 of pulmonary capillaries increases to the Po2 in alveolar air that is 105mmhg. While the oxygen is diffusing from the alveolar air into deoxygenated blood,co2 is diffusing in the opposite direction. EXTERNAL RESPIRATION

5. EXTERNAL RESPIRATION The partial pressure of Co2 in deoxygenated blood is 45mmHg in a resting person whereas Pco2 of alveolar air is 40mmHg. Because of this difference in pco2 , co2 diffuses from deoxygenated blood to the alveoli until pco2 of blood decreases to 40mmHg. Exhalation keeps the alveolar pressure at 40mmHg. Oxygenated blood returning to the left side of the heart in the Pulmonary veins thus has the Pco2 of 40mmHg. EXTERNAL RESPIRATION

6. EXTERNAL RESPIRATION The number of capillaries near alveoli in the lungs is very large and blood flows slowly enough through these capillaries that it picks up a maximal amount of O2. The left ventricle pumps oxygenated blood into the aorta ----- systemic arteries--------systemic capillaries-----------tissue cells which is called as INTERNAL RESPIRATION EXTERNAL RESPIRATION

7. INTERNAL RESPIRATION As o2 leaves the blood the oxygenated blood is converted into deoxygenated blood. The Po2 of the blood in systemic capillaries is higher than the Po2 in the tissue cells(40mmHg at rest) because the cells constantly use o2 for ATP production. Due to this pressure difference , O2 diffuses out of capillaries into tissue cells and blood Po2 drops to 40mmHg by the time blood exits systemic capillaries

8. INTERNAL RESPIRATION While o2 diffuses from systemic capillaries into tissue cells ,Co2 diffuses in the opposite dimension. Because tissue cells constantly produce co2, the Pco2 of the tissue cells is higher than the systemic capillaries(40mmHg) As a result o2 diffuses from tissue cell through interstitial fluid into systemic capillaries until Pco2 of blood increases to 45mmhg. The deoxygenated blood id then returned to the heart and is pumped to the lungs for another cycle of EXTERNAL RESPIRATION. INTERNAL RESPIRATION

9. FACTORS RESPONSIBLE FOR INTERNAL AND EXTERNAL RESPIRATION

10. PARTIAL PRESSURE DIFFERENCES OF GASES For the o2 to diffuse from alveolar air into blood the alveolar po2 must be greater than blood. Rate of diffusion increases with the pressure difference. Certain drugs slow ventilation thereby decreasing the diffusion of o2 and co2. SURFACE AREA AVAILABLE FOR GAS EXCHANGE The surface area of alveoli of lungs is 70m2. In addition many capillaries surround each alveolus , so 900ml of blood is able to participate in gas exchange at any instant. Any pulmonary disease can decrease the functional surface area of resp.membrane decreasing the rate of Ext respiration FACTORS RESPONSIBLE FOR INTERNAL AND EXTERNAL RESPIRATION

11. DIFFUSION DISTANCE Respiratory membrane is very thin, so diffusion occurs quickly. Also capillaries are so narrow that the RBC s must pass through them in single file which decreases the diffusion distance from the alveolar space to Hb in the RBcs MOLECULAR WEIGHT AND SOLUBILITY OF GASES Because the O2 has low molecular weight than C02 ,it is expected to diffuse cross the respiratory membrane about 12 times faster. FACTORS RESPONSIBLE FOR INTERNAL AND EXTERNAL RESPIRATION