D2.2 - Breathing and Respiration

Breathing and Respiration

• Breathing is the mechanism of gas exchange
• The mechanism of breathing involves the movement of gases from an area of high pressure to an area of low pressure.
• The diaphragm and intercostal muscles are crucial in achieving this.
• In inhalation, the diaphragm contracts, lowering pressure inside the lungs, and air rushes in. Intercostal muscles lift the rib cage.
• In exhalation, the diaphragm relaxes, raising pressure inside the lungs, and air moves out. Intercostal muscles relax allowing the rib cage to return to its normal position.

The Mechanics of Breathing

• Breathing relies on the pressure difference between the chest cavity and atmosphere.
• Atmospheric pressure is constant, but lung pressure changes.
• An increase in lung volume decreases pressure, pulling air into lungs (inhalation)
• A decrease in lung volume increases pressure, pushing air out of lungs (exhalation)

Breathing Movements

• Inhalation:

  • Diaphragm contracts
  • Intercostal muscles contract
  • Lung volume increases
  • Environmental air pressure is greater than lung pressure
  • Air rushes into the lungs to equalize pressure

• Exhalation:

  • Diaphragm relaxes
  • Intercostal muscles relax
  • Lung volume decreases
  • Environmental air pressure is less than lung pressure
  • Air rushes out of the lungs to equalize pressure

Gas Exchange

• Gas exchange happens by diffusion between alveolar air and blood in capillaries.
• Blood with high CO2 diffuses into alveoli to be exhaled
• Alveoli with high O2 diffuses into the blood to be transported throughout the body.
• Factors that facilitate gas exchange include thin, moist membranes, rich blood supply, large surface areas.

Adaptations for Gas Exchange

• Small aquatic organisms diffuse gases directly between the environment and body cells.
• Larger organisms need specialized respiratory structures (e.g., lungs) with thin walls, kept moist, richly supplied with blood vessels, and having large surface areas

Measuring Respiratory Volumes

• Spirograph: A graph portraying respiratory volumes.
• Tidal volume: Normal volume of air inhaled or exhaled during breathing cycles.
• Inspiratory reserve volume: Additional air inhaled beyond tidal volume
• Expiratory reserve volume: Additional air exhaled beyond tidal volume.
• Vital capacity: Total volume of air that can be moved into and out of the lungs.
• Residual volume: Air remaining in lungs even after maximal exhalation (essential for preventing lung collapse).
• Spirometer is a device for measuring respiratory volumes.

Measuring Your Own Vital Capacity

• Instructions on how to measure individual variation in lung capacity using a balloon.
• Factors (age, sex, size) influence vital capacity.
• Vital capacity can change due to illness
• Medical professionals use vital capacity to diagnose and monitor diseases.

Summary

• Gases move from areas of higher to lower pressure.
• Partial pressure of gases in the atmosphere, blood, and tissues drives gas exchange.
• Chemical receptors detect changes in gas levels (O2 and CO2), and send a message to adjust breathing rate.

Explore the mechanisms of breathing and respiration in this quiz. Understand how pressure changes in the lungs facilitate gas exchange, and learn the roles of the diaphragm and intercostal muscles in inhalation and exhalation.