Gaseous Exchange in Animals

Gaseous Exchange in Animals

• Primary aim is to understand oxygen and carbon dioxide exchange mechanisms in humans, invertebrates, and vertebrates.

Human Respiratory Structure

• Main organ for respiration: lungs.
• Trachea splits into two bronchi, leading to smaller bronchioles, which terminate in alveoli (air sacs).
• Gas exchange occurs in alveoli via simple diffusion.

Breathing Mechanism in Humans

• Exhalation Process:

  • External intercostal muscles relax; internal intercostal muscles contract.
  • Rib cage lowers and moves inward.
  • Diaphragm muscles relax and curve upward.
  • Thoracic cavity volume decreases, increasing pressure and pushing air out.

• Inhalation Process:

  • External intercostal muscles contract; internal intercostal muscles relax.
  • Rib cage lifts and moves outward.
  • Diaphragm muscles contract and flatten.
  • Thoracic cavity volume increases, leading to lower pressure that draws air in.

Alveolus and Gaseous Exchange

• Alveoli have small size and high numbers to maximize surface area for gas exchange.
• Moist walls facilitate gas dissolution.
• Thin walls expedite diffusion rates.
• Rich blood capillary network enhances diffusion and gas transport.

Oxygen and Carbon Dioxide Exchange

• During inhalation:

  • Higher O₂ partial pressure in alveoli directs O₂ diffusion into blood capillaries.
  • Higher CO₂ partial pressure in capillaries leads to CO₂ diffusion into alveoli for exhalation.

• In tissues:

  • O₂ partial pressure is higher in blood capillaries, leading to O₂ release into tissues.
  • Higher CO₂ concentration in tissues causes diffusion into blood capillaries.

Transport of Oxygen

• 98% of O₂ is carried by hemoglobin as oxyhemoglobin (HbO₂).
• Remaining 2% is dissolved in plasma.

Transport of Carbon Dioxide

• 7% of CO₂ is dissolved in plasma.
• 23% binds with hemoglobin to form carbaminohemoglobin (HbCO₂), which releases CO₂ into alveoli.
• 70% diffuses into red blood cells, forming carbonic acid (H₂CO₃), which then enters plasma; dissolved CO₂ diffuses to alveolar air.

Respiratory Control System

• Controlled by the medulla oblongata, which regulates respiration by sending signals to respiratory muscles.
• The pons fine-tunes the rate of breathing.

Regulation of Breathing

• Functions as a negative feedback mechanism to maintain blood pH within the normal range.
• Chemoreceptors detect blood chemical changes and send signals to the brain.
• Increased CO₂ concentration decreases blood pH, prompting the medulla to send impulses, accelerating muscle contraction and relaxation for faster respiration.

This quiz explores the concepts of gaseous exchange in various animals, including humans and both invertebrates and vertebrates. Understand the respiratory structures involved and how they facilitate this essential biological process. Test your knowledge and learn more about the critical mechanisms of respiration.