UNIT 6A Respiratory System 2024-2025

Unit 6: Absorption and Excretion

Table of Contents

  • PART 1 – The Respiratory System

  • PART 2 – The Digestive System

  • PART 3 – The Urinary System

Principles of Anatomy and Physiology

  • Reference: Principles of Anatomy and Physiology (14th Edition) by Gerard J. Tortora / Bryan Derrickson

  • Focus: Chapter 23 - The Respiratory System

Unit Objectives

  • Identify and locate structures of the respiratory system.

  • Trace the path of air through the respiratory tree.

  • Describe the conducting and respiratory zones of the lungs.

  • Discuss the significance of pleural membranes.

  • Summarize physical principles controlling airflow in and out of the lungs.

  • Explain changes in intrapleural and intrapulmonary pressures during breathing.

  • Describe lung compliance, elasticity, surface tension, and pulmonary surfactant.

  • Explain exchange of oxygen and carbon dioxide in respiration.

  • Discuss blood transport of oxygen and carbon dioxide.

  • Discuss regulation of ventilation by the CNS.

Major Structures of the Respiratory System

  • Larynx: voice box.

  • Pharynx: passageway for air and food.

  • Trachea: windpipe connecting to bronchi.

  • Bronchi: main passages into the lungs.

  • Lungs: facilitate gas exchange.

Functions of the Respiratory System

  • Respiration: Involves four distinct processes:

    1. Pulmonary Ventilation: Moving air into and out of the lungs.

    2. External Respiration: Gas exchange between lungs and blood.

    3. Transport: Movement of oxygen and carbon dioxide between lungs and tissues.

    4. Internal Respiration: Gas exchange between blood vessels and tissues.

Additional Functions

  • Regulation of blood pH via carbon dioxide levels.

  • Production of voice through air movement past vocal folds.

  • Smell via airborne molecules drawn into the nasal cavity.

  • Protection against microbes via filtration and removal of foreign materials.

Organs of the Respiratory System

  • Upper Respiratory Tract: Nose, pharynx, associated structures.

  • Lower Respiratory Tract: Larynx, trachea, bronchi, lungs.

Mechanism of Breathing

  • Inhalation:

    • Active process involving diaphragm and intercostal muscles.

    • Pressure within alveoli drops below atmospheric pressure.

  • Exhalation:

    • Passive process usually; may require active muscular effort during forced breathing.

    • Pressure in lungs increases above atmospheric pressure.

Respiratory Volumes and Capacities

  • Tidal Volume (TV): Amount of air inhaled/exhaled in normal breath (~500 mL).

  • Inspiratory Reserve Volume (IRV): Additional air that can be inhaled above tidal volume.

  • Expiratory Reserve Volume (ERV): Additional air that can be exhaled beyond tidal volume.

  • Residual Volume (RV): Amount of air remaining in lungs after full exhalation.

  • Vital Capacity (VC): Total air capacity for exchange (TV + IRV + ERV).

Gas Exchange Principles

  • Dalton’s Law: Each gas in a mixture exerts its own pressure independent of others.

  • Henry’s Law: Gas solubility in liquid is proportional to its partial pressure.

Oxygen and Carbon Dioxide Transport

  • Oxygen primarily transported bound to hemoglobin (98.5%).

  • Carbon dioxide transported in three forms: dissolved in plasma (7%), bound to hemoglobin (23%), as bicarbonate ions (70%).

Regulation of Respiration

  • Neural Regulation: Respiratory centers in medulla oblongata and pons control rate and rhythm of breathing.

  • Chemical Regulation: Monitored levels of oxygen and carbon dioxide in blood influence respiratory efforts.

Breathing Patterns

  • Normal Breathing: Eupnea.

  • Other conditions include tachypnea (rapid), bradypnea (slow), hyperventilation, and hypoventilation.

Summary

  • Understanding the respiratory system's structure, function, and regulation is essential for maintaining gas exchange and overall homeostasis.