Chapter 21 of Carol Porth’s Pathophysiology presents an introduction to respiratory anatomy and physiology. The following two chapters present pathologies that affect the system. I’ve outlined here the basics of lung A&P as notes from my reading of the chapter and I thought I would present that here as a guide for any of my students. I have yet to outline the second and third chapters, but there is a skeleton of conditions that we will cover. It is also worth noting that I expect my students to be able to recognize and identify the structural components of the respiratory system even though I did not include these elements in my outline …

Pulmonology Outline

1. Structures and Functions (Chapter 21)
   1. Structures
      1. Upper Respiratory System
      2. Lower Respiratory System

• Tissue and Cell types
  1. Ciliated columnar epithelial cells
  2. Goblet cells

1. Alveoli – terminal air spaces in the lung & site of gas exchange
   1. Type I Alveolar Cells – this squamous cells making up ~95% of the alveolus
   2. Type II Alveolar Cells – secretory cells that produce surfactant, also serve as progenitors of Type I cells
   3. Alveolar Macrophages – responsible for removing organisms and debris that penetrated the lungs
2. Pleura – a double layer of membrane lining the inner thoracic cavity and covering the lungs.

1. Functions
   1. Conducting Airways
      1. Purpose: To deliver warm, moistened, cleaned air to Respiratory Tissue
   2. Respiratory Tissue: To perform gas exchange (O₂ and CO₂)

• Gas Exchange
  1. Ventilation – Inspiration and Expiration
     1. Mechanically, ventilation depends upon the structure of chest cavity – i.e. it is entirely closed with the only opening to the exterior being the trachea
     2. Inspiration occurs as the diaphragm pulls down and opens the
  2. Perfusion – flow of blood through the alveolar capillary bed

Ventilation and Perfusion must be matched in order to optimally oxygenate blood in the lungs.

3. Gas exchange (described by the Fick Law of Diffusion)
   1. V = [SA x K_D (P₁-P₂)] / T
   2. Both O₂ and CO₂ are transported by blood
4. Hb Dissociation Curve
5. Partial Pressure – the pressure of some component of a gas. By definition, all partial pressures add up to the total pressure of a gas. (i.e. if a gas is comprised of O₂ and CO₂, then the partial pressures of O₂ and CO₂ must add up to the total pressure of the gas)
6. The O₂ / Hb dissociation Curve
   1. Measures the amount of O₂ bound to Hb at any specific PO₂
7. Lung Volumes & Capacities (summarized in Table 21-1)
   1. Tidal Volume – volume of air going in and out of the lungs with each resting breath
   2. Total Lung Capacity (TLC) = tidal + inspiratory reserve + expiratory reserve + residual volumes
   3. Vital Capacity = tidal + inspiratory + expiratory reserve volumes
   4. Dead Air Space – Air in the lungs that does NOT participate in respiration

Questions

1. Why is arterial (rather than venous) blood used to measure blood gases?
   1. What would venous blood gases measure?
2. Using an O₂ / Hb dissociation curve, show how Hb effectively carries O2 from the lung to the muscles, where it is released to myoglobin for use in respiration.

Pathologies

1. General Issues
   1. Pleura effusions– are accumulations of fluid in the space between the pleural membranes around the lungs
   2. Infant Respiratory Distress Syndrome – alveolar collapse in young infants (esp prematures) due to lack of surfactant
   3. Dyspnea – general term for difficulty breathing. Can occur due to primary lung disease, heart disease, or neuromuscular disorders affecting the respiratory muscles
2. Infections
   1. Pneumonia
   2. Influenza
   3. Fungal Infections
   4. Tuberculosis
3. Congenital Problems
   1. CF
4. Acquired Problems
   1. COPD
   2. Pulmonary Hypertension – causes and outcomes
5. Respiratory Distress Syndrome
6. Respiratory Failure