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chapter 22 final part

Overview of the Respiratory System

  • Conducting Division: Includes parts of the respiratory system that direct air to gas exchange sites.

    • Components:
    • Nose
    • Pharynx
    • Larynx
    • Trachea
    • Primary Bronchi
    • Secondary Bronchi
    • Tertiary Bronchi
    • Bronchioles
    • Terminal Bronchioles

  • Respiratory Division: Where gas exchange occurs.

    • Components:
    • Respiratory Bronchioles
    • Alveolar Ducts
    • Alveolar Sacs

Alveolar Cells and Functions

  • Squamous Alveolar Cells:

    • Main cells forming alveoli
    • Site of gas exchange through their membranes

  • Great Alveolar Cells:

    • Function: Repair squamous alveolar cells and secrete surfactant.
    • Surfactant:
    • Decreases surface tension between alveolar membranes
    • Prevents alveolar collapse by disrupting hydrogen bonds between moist membranes

  • Macrophages (Dust Cells):

    • Alveolar macrophages, involved in cleaning debris and pathogens.

Physiology of Ventilation

  • Boyle's Law:

    • Pressure of gas inversely related to its volume.
    • Lung volume increases -> gas pressure decreases, facilitating inhalation.

  • Inhalation Process:

    • Diaphragm contracts (moves down)
    • External intercostal muscles elevate the rib cage, increasing lung volume
    • Pleura: Parietal pleura adheres to the rib cage; visceral pleura adheres to the lungs, allowing lung expansion.

  • Exhalation Process:

    • Muscles relax, reducing lung volume
    • Increased pressure in lungs compared to the atmosphere pushes air out.

Gas Exchange Mechanisms

  • Diffusion: Basic process for gas exchange.

  • Systemic Gas Exchange:

    • CO2 Loading: Tissues produce CO2, diffusing into blood; catalyzed by carbonic anhydrase, forming carbonic acid and bicarbonate.
    • Chloride Shift: Exchange of bicarbonate ions for chloride ions to maintain equilibrium, promoting CO2 removal.
    • pH decrease: Increased H+ ions leading to oxygen unloading from hemoglobin.
    • Oxygen Unloading: Higher partial pressure of oxygen diffuses from blood into tissues.
    • Cellular respiration: Oxygen enables ATP production via electron transport chain.

  • Alveolar Gas Exchange:

    • Oxygen Loading: Oxygen moves from alveoli (high concentration) to blood (lower concentration).
    • Reverse Chloride Shift: Bicarbonate ions re-enter blood while chloride ions leave, reversing previous systemic exchange processes.
    • CO2 Removal: CO2 diffuses from blood into alveoli to be expelled.

Partial Pressures in Blood

  • Oxygen Rich Blood:
    • PO2 = 95 mmHg, PCO2 = 40 mmHg
  • Oxygen Poor Blood:
    • PO2 = 40 mmHg, PCO2 = 46 mmHg

Factors Influencing Gas Exchange

  • Partial Pressure of Gases: Direct influence on diffusion rates.
  • Temperature: Higher temperatures facilitate oxygen unloading, especially in active tissues.
  • Bohr Effect: Lower pH (higher CO2) enhances oxygen unloading from hemoglobin.
  • BPG Production: Increased BPG levels in actively metabolizing erythrocytes reduce hemoglobin's oxygen affinity.

Respiratory Rhythm Influences

  1. Blood pH: Most potent influence on respiratory rate.
  2. Partial Pressure of CO2: Increased levels trigger increased ventilation.
  3. Partial Pressure of Oxygen: Significant only when levels drop critically low.

Acid-Base Balance Terms

  • Acidosis: pH < 7.35 often due to high CO2 (hypercapnia).
  • Alkalosis: pH > 7.45 often due to low CO2 (hypocapnia).

Compensation Mechanisms

  • Hyperventilation: Increases CO2 expulsion, addressing hypercapnia and acidosis.
  • Hypoventilation: Increases CO2 retention, addressing hypocapnia and alkalosis.

Exercise and Respiratory Changes

  • Increased respiratory rate and rhythm due to heightened muscle activity and demand for oxygen.

Environmental Factors

  • High Elevations: Reduced oxygen availability impacts breathing and gas exchange.
  • Lung Conditions: Pneumonia and other lung diseases can impede gas exchange due to fluid buildup or tissue damage