Chapter 21 The Respiratory System

Amerman Learning Objectives - Chapter 21 The Respiratory System

Objective Overview

Upon completion of the chapter, the student will demonstrate mastery of the following objectives along with the related vocabulary.

Organ Identification and Description

  • List the Organs of the Respiratory System
    • Upper respiratory tract: Composed of the nasal cavity, pharynx, and larynx.
    • Lower respiratory tract: Composed of the trachea, bronchi, bronchioles, and alveoli.

Conducting and Respiratory Zones

  • Upper and Lower Tracts: Differentiate between these two segments in the respiratory system, emphasizing their structural and functional roles.
  • Conducting Zone: Includes all structures that serve as passageways for air to move into the lungs, e.g., nasal cavity, trachea, bronchi.
  • Respiratory Zone: Where gas exchange occurs, e.g., alveoli and respiratory bronchioles.

Major Functions of the Respiratory System

  • Respiratory Processes:
    1. Pulmonary Ventilation: Movement of air into and out of the lungs.
    2. Pulmonary Gas Exchange: The exchange of gases (O2 and CO2) between the lungs and the blood.
    3. Gas Transport: The transport of oxygen and carbon dioxide via the blood.
    4. Tissue Gas Exchange: Exchange of gases between the blood and the cells of the body.

Nose and Nasal Cavity Functions

  • Functions: Warming, filtering, and humidifying air; olfactory sensation; and resonance for speech.
  • Meatuses: Groove-like passages that enhance airflow and increase the surface area for filtering and humidifying air.
  • Sinuses: Air-filled cavities that reduce skull weight and resonate sounds.
  • Histology of the Nasal Cavity:
    • Lined with pseudostratified ciliated columnar epithelium containing goblet cells which produce mucus.

Pharynx Histology and Functions

  • Regions of the Pharynx:
    1. Nasopharynx: Air passage, lined with respiratory epithelium.
    2. Oropharynx: Passage for food and air, lined with stratified squamous epithelium.
    3. Laryngopharynx: Last segment before the esophagus and larynx, also lined with stratified squamous epithelium.

Larynx and Trachea Histology and Functions

  • Larynx:
    • Functions include voice production, airway protection, and routing of air and food.
    • Composed of several cartilaginous structures, lined with ciliated columnar epithelium.
  • Trachea:
    • Structure includes C-shaped cartilaginous rings to maintain open airway, lined with ciliated columnar epithelium and mucus-producing goblet cells.

Bronchial Tree and Histology

  • Bronchial Tree Structure: The branching network of airways leading to the lungs, starting with the main bronchi, branching into secondary bronchi, and further into bronchioles.
  • Histology of the Bronchial Tree:
    • Lined with ciliated epithelium, with smooth muscle increasing as branching progresses, and less cartilage in smaller bronchi.
  • Air Passage during Inspiration: Air moves through the nasal cavity --> pharynx --> larynx --> trachea --> bronchi --> bronchioles --> alveoli.

Alveoli Cellular Structure

  • Types of Cells Present in Alveoli:
    1. Type I alveolar cells: Simple squamous epithelial cells for gas exchange.
    2. Type II alveolar cells: Secrete surfactant to reduce surface tension and prevent alveolar collapse.
    3. Macrophages: Immune cells that remove debris and pathogens.

Lung Structure and Pleural Cavity Functions

  • General Structure of the Lungs:
    • Composed of lobes (right lung has three lobes, left has two), alveoli, and connective tissue.
  • Pleural Cavity: Space between the pleurae (visceral and parietal) and functions in reducing friction during lung expansion and contraction, and creating pressure gradient necessary for inhalation.

Phases of Pulmonary Ventilation

  • Two Phases:
    1. Inspiration: Active process where air is drawn into the lungs.
    2. Expiration: Typically a passive process where air is pushed out of the lungs.
  • Boyle's Law:
    • States that at constant temperature, the pressure of a gas is inversely proportional to its volume: P imes V = k , where P is pressure, V is volume, and k is a constant.
  • Relation to Pulmonary Ventilation:
    • During inspiration, lung volume increases, pressure decreases, causing air to flow in. During expiration, lung volume decreases, pressure increases, causing air to flow out.

Pressure Changes During Breathing

  • Atmospheric Pressure: The pressure exerted by the weight of air in the atmosphere.
  • Intrapulmonary Pressure: The pressure within the lung alveoli that changes with breathing.
  • Intrapleural Pressure: The pressure within the pleural cavity; remains negative throughout the breathing cycle.
  • Pressure Changes with Inspiration and Expiration:
    • Inspiration:
    • Intrapulmonary pressure decreases below atmospheric pressure, causing air to flow in.
    • Expiration:
    • Intrapulmonary pressure increases above atmospheric pressure, causing air to flow out.

Factors Affecting Pulmonary Ventilation

  • Airway Resistance: Resistance to airflow within the airways; increased resistance can hinder ventilation.
  • Alveolar Surface Tension: The surface tension of fluid lining the alveoli that can cause collapse; surfactant reduces this tension.
  • Pulmonary Compliance: The ability of the lungs to stretch and expand; decreased compliance can impair breathing.

Definition of Gas Exchange Processes

  • Pulmonary Gas Exchange: The exchange of oxygen and carbon dioxide between the alveoli and blood in the lungs.
  • Tissue Gas Exchange: The exchange of gases between the blood and the tissues of the body.

Definitions

  • External Respiration: Refers to all processes involved in the exchange of gases between the lungs and the blood.
  • Factors Affecting Pulmonary Gas Exchange: Solubility of gases, partial pressure gradients, and surface area of alveoli.
  • Internal Respiration: The exchange of gases between the blood and the tissues, involving diffusion.
  • Factors Affecting Tissue Gas Exchange: Tissue perfusion, metabolic rate, and interstitial fluid conditions.

Oxygen and Carbon Dioxide Transport

  • Oxygen Transport in Blood:
    • Approximately 98.5% transported bound to hemoglobin in red blood cells; the rest is dissolved in plasma.
  • Carbon Dioxide Transport in Blood:
    1. Dissolved in Plasma: About 7%.
    2. Bound to Hemoglobin: About 23% as carbaminohemoglobin.
    3. Converted to Bicarbonate: About 70%; this process involves the carbonic anhydrase enzyme which catalyzes the reaction: CO2 + H2O
      ightleftharpoons H2CO3
      ightleftharpoons HCO_3^- + H^+ .
  • Chloride Shift: The exchange of chloride ions into red blood cells as bicarbonate ions move out; helps maintain electrical neutrality.

Stimulants for Ventilation

  • Brain Centers: Medulla oblongata and pons regulate respiration based on carbon dioxide, oxygen, and pH levels.
  • Receptors Involved: Chemoreceptors that detect changes in blood gases and initiate ventilation adjustments.

Eupnea Definition and Control

  • Eupnea: Refers to normal, unlabored breathing.
  • Control Mechanism: Regulated by neural centers in the brain (medullary and pontine centers) that adjust the rate and depth of breathing according to metabolic needs.