23.2 Introduction to the Lower Respiratory System

The lower respiratory system is a complex network of airways and air sacs that facilitate breathing. From the trachea to the alveoli, each structure plays a crucial role in delivering oxygen to our bodies and removing carbon dioxide.

Common conditions like asthma and COPD can disrupt this delicate system, causing breathing difficulties. Fortunately, diagnostic tools like pulmonary function tests and treatments ranging from inhalers to oxygen therapy can help manage these respiratory challenges.

Structure and Function of the Lower Respiratory System

Trachea, bronchi, bronchioles, alveoli

Top images from around the web for Trachea, bronchi, bronchioles, alveoli

• 

  Organs and Structures of the Respiratory System · Anatomy and Physiology View original

  Is this image relevant?

• 

  Organs and Structures of the Respiratory System · Anatomy and Physiology View original

  Is this image relevant?

• 

  Mechanics of Breathing | Boundless Anatomy and Physiology View original

  Is this image relevant?

• 

  Organs and Structures of the Respiratory System · Anatomy and Physiology View original

  Is this image relevant?

• 

  Organs and Structures of the Respiratory System · Anatomy and Physiology View original

  Is this image relevant?

1 of 3

Top images from around the web for Trachea, bronchi, bronchioles, alveoli

• 

  Organs and Structures of the Respiratory System · Anatomy and Physiology View original

  Is this image relevant?

• 

  Organs and Structures of the Respiratory System · Anatomy and Physiology View original

  Is this image relevant?

• 

  Mechanics of Breathing | Boundless Anatomy and Physiology View original

  Is this image relevant?

• 

  Organs and Structures of the Respiratory System · Anatomy and Physiology View original

  Is this image relevant?

• 

  Organs and Structures of the Respiratory System · Anatomy and Physiology View original

  Is this image relevant?

1 of 3

• Trachea connects larynx to bronchi lined with ciliated pseudostratified columnar epithelium contains C-shaped cartilage rings for support (windpipe)
• Bronchi
  • Primary bronchi formed by bifurcation of trachea into left and right bronchi (main airways)
  • Secondary bronchi branch from primary bronchi into lobar bronchi supply each lobe of the lung
  • Tertiary bronchi branch from secondary bronchi into segmental bronchi supply bronchopulmonary segments
• Bronchioles smaller airways that branch from tertiary bronchi
  • Terminal bronchioles smallest bronchioles lead to respiratory bronchioles (conducting zone)
  • Respiratory bronchioles contain alveoli sites of gas exchange (respiratory zone)
• Alveoli tiny air sacs at the end of respiratory bronchioles surrounded by capillaries for gas exchange (grape-like clusters)
  • Type I alveolar cells thin allow for efficient gas exchange (squamous epithelium)
  • Type II alveolar cells secrete surfactant to reduce surface tension prevent alveolar collapse (great alveolar cells)

Common Lower Respiratory Conditions

Asthma, COPD

• Asthma chronic inflammatory disorder of airways characterized by airway hyperresponsiveness and reversible airflow obstruction
  • Triggers include allergens (pollen), irritants (smoke), and exercise
  • Symptoms: wheezing, coughing, chest tightness, shortness of breath
• COPD group of progressive lung diseases includes chronic bronchitis and emphysema characterized by persistent airflow limitation and respiratory symptoms
  • Main risk factor: smoking
  • Chronic bronchitis inflammation and narrowing of bronchi increased mucus production (blue bloater)
  • Emphysema destruction of alveolar walls leading to enlarged air spaces and reduced gas exchange (pink puffer)

Diagnostic Methods and Treatment Approaches

PFTs, pharmacological interventions

• Diagnostic Methods
  • Pulmonary Function Tests (PFTs) assess lung function
    • Spirometry measures lung volumes (FVC) and airflow rates (FEV1)
    • Peak Expiratory Flow Rate (PEFR) measures maximum speed of expiration
    • Lung volume measurements assess total lung capacity (TLC) and residual volume (RV)
  • Imaging studies: chest X-ray, CT scan, or MRI visualize lung structure
  • Arterial Blood Gas (ABG) analysis evaluates oxygenation (PaO2) and ventilation (PaCO2)
• Treatment Approaches
  • Pharmacological interventions
    • Bronchodilators relax smooth muscles in airways improving airflow
      1. Short-acting beta-2 agonists (SABAs): albuterol, levalbuterol
      2. Long-acting beta-2 agonists (LABAs): salmeterol, formoterol
      3. Anticholinergics: ipratropium, tiotropium
    • Corticosteroids reduce inflammation in airways
      1. Inhaled corticosteroids (ICS): fluticasone, budesonide
      2. Oral corticosteroids: prednisone, methylprednisolone
    • Leukotriene modifiers block leukotriene-mediated inflammation (montelukast)
  • Oxygen therapy provides supplemental oxygen for hypoxemia
  • Pulmonary rehabilitation includes exercise, education, and support for COPD patients
  • Smoking cessation crucial for preventing and managing COPD