Chapter 18 gas exchange in transport

Human Physiology: Chapter 18 - Gas Exchange and Transport

18.1 Gas Exchange in the Lungs and Tissues

• The body requires oxygen (O₂) for metabolic processes and must remove carbon dioxide (CO₂) to maintain homeostasis.

  • Hypoxia: Occurs when there is insufficient O₂ to maintain homeostasis.

  • Causes include:

    • Low O₂ in the air (e.g., high altitude).

    • Insufficient hemoglobin in red blood cells.

    • Blocked blood flow to tissues.

    • Toxins disrupting cellular respiration.

  • Hypercapnia: Occurs when CO₂ concentrations are too high, negatively affecting homeostasis.

  • Hypoxia and hypercapnia often occur simultaneously.

Pulmonary Gas Exchange and Transport

• To manage gas exchange, the respiratory system takes in O₂ and expels CO₂.

  • Gases are transported through the blood between the lungs and tissues.

  • O₂ diffuses into the blood in the lungs and diffuses out in the tissues, while CO₂ does the opposite.

18.1 Gas Exchange in the Lungs

• Gases move based on pressure gradients (high to low pressure) and concentration gradients (high to low concentration).

• Example of Gas Exchange:

  • In the lungs, the partial pressure of oxygen (PO₂) in the alveoli is higher than in the blood, promoting O₂ diffusion into the bloodstream.

  • Conversely, in tissues, the PO₂ is lower than in blood, encouraging O₂ to move into cells.

Summary on Gas Solubility

• The solubility of a gas in a liquid greatly influences how much gas can dissolve in the liquid,

• Hemoglobin: A protein in red blood cells that increases O₂ transport capacity

Oxygen Transport Overview

• Oxygen saturation (%) is the percentage of binding sites filled with O₂:

• ~70% converted to bicarbonate (HCO₃⁻) via carbonic anhydrase (CA) reaction: