Name: Human Respiratory System
Uploaded: 2019-07-19
Duration: 4 min 39 s
Description: Fishes need gills for respiration, while frogs have skin as one of their respiratory organs. Check out this video for details about the respiratory organs in humans.

Question

Describe the pathway taken by a molecule of oxygen as it passes from the atmosphere to the lungs.

Accepted Answer

The exchange of gases takes place inside the alveoli of lungs where the oxygen of the atmospheric air is exchanged with the carbon dioxide present in the deoxygenated blood of the lung capillaries. The gaseous exchange depends on the partial pressure of the gases.

In the alveoli of lungs, the partial pressure of oxygen is about 104 mm Hg while in the deoxygenated blood of lung capillaries it is about 40 mm Hg. Also, the partial pressure of carbon dioxide in the lung capillaries is about 45 mm Hg, while in the lung alveoli it is about 40 mm Hg. There exists a partial pressure gradient across these respiratory surfaces. Thus, the gases diffuse along their concentration gradient. i.e the oxygen enters the lung capillaries and the carbon dioxide diffuses into the alveoli.

In the tissues (muscle cell), the partial pressure of the CO2 (45 mm Hg) and that of O2 is 40 mm Hg. The PO₂ is less and PCO₂is more in the capillaries surrounding them. The oxy-haemoglobin in the tissue capillaries thus loses the O2 and combines with CO2 that diffuses out of the tissues to form carboxy-haemoglobin. It is then transported to the lung alveoli where it again releases the CO2 and forms oxy-haemoglobin. This process of gaseous exchange continues in the lungs and the body tissues. Given below is a diagram showing the exchange of gases across the respiratory surfaces:

Mary Jones, Richard Fosbery, Dennis Taylor and, Jennifer Gregory Solutions for Chapter: Gas Exchange, Exercise 3: Questions

Mary Jones Biology Solutions for Exercise - Mary Jones, Richard Fosbery, Dennis Taylor and, Jennifer Gregory Solutions for Chapter: Gas Exchange, Exercise 3: Questions

Questions from Mary Jones, Richard Fosbery, Dennis Taylor and, Jennifer Gregory Solutions for Chapter: Gas Exchange, Exercise 3: Questions with Hints & Solutions

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