Define breathing. Write the mechanism of breathing.

Breathing:

Breathing is the physical process of taking in oxygen from the environment (inhalation) and expelling carbon dioxide from the body (exhalation) through the respiratory system. It is a vital function that allows for the exchange of gases necessary for cellular respiration, which produces energy for the body.

Mechanism of Breathing:

Breathing involves two main phases: inhalation (inspiration) and exhalation (expiration). The mechanism of breathing is controlled by the movement of the diaphragm and the intercostal muscles, which are the muscles between the ribs. Here’s how it works:

1. Inhalation (Inspiration):

  • Diaphragm contracts: The diaphragm, a dome-shaped muscle below the lungs, contracts and flattens, moving downwards.
  • Intercostal muscles contract: The external intercostal muscles (between the ribs) contract, pulling the ribs upwards and outward.
  • Thoracic cavity expands: The contraction of the diaphragm and the intercostal muscles causes the thoracic cavity (chest cavity) to expand.
  • Decreased pressure: As the volume of the thoracic cavity increases, the pressure inside the lungs decreases (according to Boyle’s Law, as volume increases, pressure decreases).
  • Air rushes in: Because the pressure in the lungs is now lower than the atmospheric pressure outside, air flows into the lungs to equalize the pressure.
  • Oxygen enters alveoli: The oxygen from the inhaled air reaches the alveoli (air sacs), where gas exchange occurs with the blood.

2. Exhalation (Expiration):

  • Diaphragm relaxes: The diaphragm relaxes and moves back up into its dome shape.
  • Intercostal muscles relax: The external intercostal muscles relax, and the ribs move downwards and inwards.
  • Thoracic cavity shrinks: The relaxation of the diaphragm and intercostal muscles causes the chest cavity to decrease in volume.
  • Increased pressure: As the volume of the thoracic cavity decreases, the pressure inside the lungs increases.
  • Air is pushed out: Because the pressure inside the lungs is now higher than the atmospheric pressure outside, air is forced out of the lungs.
  • Carbon dioxide is expelled: The carbon dioxide, which is a waste product of cellular respiration, is expelled from the body during exhalation.

Summary of the Breathing Process:

  • Inhalation: Diaphragm contracts, chest cavity expands, air enters the lungs.
  • Exhalation: Diaphragm relaxes, chest cavity shrinks, air is expelled from the lungs.

Breathing is an automatic process controlled by the respiratory center in the brainstem, which monitors the levels of carbon dioxide in the blood and regulates the rate and depth of breathing accordingly.

Related Questions:

  1. Differentiate between:
  2. Breathing through the nose is healthier than breathing by mouth. Why?
  3. What are the conditions necessary for efficient gaseous exchange between an organism and the environment?
  4. How are gases exchanged in a leaf?
  5. Explain the difference between respiration and photosynthesis.
  6. Describe the structure of the human respiratory system.
  7. Name the structure through which the exchange of gases can take place in plants.
  8. Why should one not sleep under a tree at night?
  9. Why would very wet soil be dangerous to plants
  10. Why do plants not need a specialized respiratory system?
  11. How does the exchange of gases take place in alveoli?
  12. What is the effect of exercise on the rate of breathing?
  13. Compare inspired air and expired air.
  14. How do viral infections like COVID-19 affect bronchi?
  15. What is the importance of breathing in fresh air?
  16. What is the importance of keeping the nasal and oral cavity clear?
  17. Describe the effects of cigarette smoking on the inner walls of the trachea of human beings.
  18. The diagram shows the percentage of gases in inspired and expired air.
  19. The figure shows a healthy lung and a diseased lung.
  20. The diagram shows the structural and functional unit of the lungs.