Transport of gases through respiratory membrane.

1. ‘RESPIRATION’

2. “TRANSPORT OF
GASES THROUGH THE
RESPIRATORY
MEMBRANE”

3. CONTENTS
 RESPIRATORY UNIT
 RESPIRATORY MEMBRANE
 FACTORS EFFECTING RATE OF GAS DIFFUSION
 DIFFUSION CAPACITY OF MEMBRANE
 TRANSPORT OF OXYGEN IN ARTERIAL BLOOD
 CONCLUSION

4. RESPIRATORY UNIT
Respiratory Unit., which is composed
of a respiratory bronchiole, alveolar
ducts, atria, and
alveoli. There are about 300 million
alveoli in the two
lungs, and each alveolus has an average
diameter of
about 0.2 millimeter.

5. RESPIRATORY UNIT

6. RESPIRATORY MEMBRANE
Gas exchange between the alveolar air and the
pulmonary blood occurs through the membranes
of all the terminal portions of the lungs, not
merely in the alveoli themselves. All these
membranes
are collectively known as the Respiratory
membrane,
also called the Pulmonary membrane.

7. CROSS SECTIONVIEWOF ALVEOLAR WALLS

8. “RESPIRATORY MEMBRANE”

9. The following different layers of the respiratory
membrane:
• A layer of fluid lining the alveolus and containing
surfactant that reduces the surface tension of the
alveolar fluid
• The alveolar epithelium composed of thin
epithelial cells
• An epithelial basement membrane
• A thin interstitial space between the alveolar
epithelium and the capillary membrane
• A capillary basement membrane that in many places
fuses with the alveolar epithelial basement membrane
• The capillary endothelial membrane

10. FACTORS AFFECTING THE RATE OF GAS
DIFFUSION
The factors that determine
how rapidly a gas will pass through the membrane
are :
 The thickness of the membrane,
 Surface area of the membrane,
 Diffusion coefficient of the gas in the substance of
the membrane, and
 Partial pressure difference of the gas between
the two sides of the membrane.

11. DIFFUSION CAPACITY
The ability of the respiratory membrane to
exchange a gas between the alveoli and the
pulmonary blood is expressed in quantitative
terms by the respiratory membrane’s
diffusing capacity, which is defined as the
volume of a gas that will diffuse through the
membrane each minute for a partial pressure
difference of 1 mmHg.
All the factors discussed earlier that affect
diffusion through the respiratory membrane
can affect diffusing capacity.

12. DIFFUSIONCAPACITYOF OXYGEN
The average young man, the diffusing capacity for
oxygen under resting conditions
averages = 21 ml/min/mm Hg.
In functional terms it means oxygen pressure
difference across the respiratory membrane during
normal, quiet breathing is about = 11 mm Hg.
Multiplication of this pressure by the diffusing
capacity (11 x 21) = 230 milliliters of oxygen
diffusingthrough the respiratory membrane each
minute;
This is equal to the rate at which the resting body
uses oxygen.

13.  98 % of the blood that enters the left atrium from the
lungs has just passed through the alveolar capillaries and has
become oxygenated up to a Po2 of about 104 mm Hg.
 Another 2 % of the blood has passed from the aorta
through the bronchial circulation, which supplies mainly the
deep tissues of the lungs and is not exposed to lung air.This
blood flow is called “shunt flow,”
 When this blood combines in the pulmonary veins with the
oxygenated blood from the alveolar capillaries, this so-called
venous admixture of blood causes the Po2 of the blood
entering the left heart and pumped into the aorta to
fall to about 95 mm Hg.
TRANSPORT OF OXYGEN IN ARTERIAL BLOOD

14. THANK
YOU..