NCERT Solution for Class 10 Science Chapter 6
Life Processes
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Intext Questions
Page No-105
Questions No-4
How are the lungs designed in human beings to maximise the area for exchange of gases?
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The exchange of gases takes place between the blood capillaries that surround the alveoli and the gases present in the alveoli. Thus, alveoli are the site for exchange of gases. The lungs get filled up with air during the process of inhalation as ribs are lifted up and diaphragm is flattened. The air that is rushed inside the lungs fills the numerous alveoli present in the lungs. Each lung contains 300-350 million alveoli. These numerous alveoli increase the surface area for gaseous exchange making the process of respiration more efficient.
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The bronchioles in lungs are finely branched and end up in air sacs. The structure of air sac increases the surface area inside lungs. This helps in making a larger area for exchange of gases.
In lungs, the bronchioles terminate in balloon-like structures called alveoli. The alveoli provide extensive surface where the exchange of gases can take place. The thin, moist, permeable walls of alveoli facilitate quick diffusion and exchange of gases. Moreover it is richly supplied with blood capillaries. ( the alveolar area, if spread out, covers about 80 m2 which is more than our body surface area).
The structure of the lungs in human beings is designed to maximize the surface area available for the exchange of gases, specifically oxygen and carbon dioxide. The key structural features that contribute to this efficient gas exchange include:
1. Alveoli:
» The alveoli are small, thin-walled air sacs located at the ends of the bronchioles in the lungs.
» The walls of the alveoli are extremely thin, allowing for efficient diffusion of gases through them.
» The large number of alveoli provides a substantial surface area for gas exchange.
2. Alveolar Surface Area:
» The total surface area of all the alveoli in the lungs is extensive, estimated to be around 70 square meters in an adult human.
» This large surface area allows for a significant amount of gas exchange to occur simultaneously.
3. Capillary Network:
» Capillaries surround the alveoli, forming a dense network of tiny blood vessels.
» The close proximity of the capillaries to the alveoli walls facilitates the rapid exchange of gases between the air in the alveoli and the blood in the capillaries.
4. Thin Respiratory Membrane:
» The respiratory membrane is the barrier between the air in the alveoli and the blood in the capillaries.
» It consists of the alveolar epithelium, capillary endothelium, and their shared basement membrane. This membrane is extremely thin (only about 0.5 micrometers), allowing for efficient gas diffusion.
5. Ventilation and Perfusion Matching:
» Ventilation refers to the movement of air in and out of the lungs, while perfusion is the blood flow through the capillaries.
» Ventilation and perfusion are matched to ensure that blood flows to areas of the lungs where oxygen levels are high and carbon dioxide levels are low, optimizing gas exchange.
6. Respiratory Bronchioles and Terminal Bronchioles:
» The respiratory bronchioles and terminal bronchioles, leading to the alveoli, have smaller branches that increase the surface area available for gas exchange.
7. Surfactant Production:
» Surfactant is a substance produced by type II alveolar cells that reduces the surface tension of the alveolar fluid.
» This helps prevent the collapse of alveoli during exhalation, maintaining a stable and expanded surface area for gas exchange.
The combination of these features ensures that the lungs are well-suited for efficient gas exchange, allowing for the uptake of oxygen from inhaled air and the removal of carbon dioxide produced by cellular metabolism. The intricate structure of the lungs reflects the importance of maximizing the surface area for effective respiratory function.