Respiratory Anatomy and Physiology Overview

Introduction

• Presenter: Julie Wilkins, Wrexham University

• Content focuses on anatomy and physiology of the respiratory system, revisiting key concepts in Level 5 with clinical applications.

Session Objectives

Learning Goals

At the end of the session, students will be able to:

• Describe the function of the respiratory system.

• Understand the anatomy of the respiratory system.

• Explain the movement of the thoracic cage.

• Discuss the physiology of inspiration and expiration.

• Analyze gas exchange physiology.

• Recognize nerve supply related to respiration.

• Identify lung volumes.

• Note: Clinical applications will be covered in Level 5.

Key Concepts Introduced

Important Topics

• Pump and bucket handle movement.

• Compliance of lung tissue.

• Effect of volume change on pressure and airflow.

• Concept of closing volume.

Functions of the Respiratory System

Upper Respiratory Tract

• Warms, filters, and humidifies the air.

• Serves as a defense against pathogens.

• Functions as a passage for air transport.

Lower Respiratory Tract

• Responsible for speech and sound production.

• Facilitates gas exchange.

• Maintains homeostasis, particularly pH balance.

Gross Anatomy of the Respiratory System

Major Structures

• Nose: Passageway for air; filters, warms, and moistens.

• Mouth: Passage for air and food.

• Pharynx: Common passageway for air, food, and liquids.

• Epiglottis: Covers the larynx during swallowing.

• Larynx: Produces sound.

• Trachea (Windpipe): Main airway to the lungs.

• Bronchi: Branching airways that lead to lungs.

• Lungs: Organs of gas exchange with alveoli.

• Pleural Membranes: Cover the lungs and line the chest cavity.

• Intercostal Muscles: Aid in the movement of ribs during respiration.

• Diaphragm: Main skeletal muscle involved in respiration.

Detailed Lung Anatomy

Structure and Function

• Right Lung: Larger and has 3 lobes.

• Left Lung: Smaller (due to cardiac notch) with 2 lobes.

• Bronchial Tree: Includes trachea, bronchi, bronchioles, and alveolar ducts.

Airways and Resistance

Airway Resistance

• Airway resistance inversely related to airway size: smaller airways = greater resistance.

• Larger airways provide decreased resistance due to numerous parallel small airways.

• Healthier lungs show reduced resistance as lung volume increases, allowing airway distension.

Lung Compliance

Definition and Clinical Relevance

• Compliance: Measure of the stretchability of lungs; healthy lungs require minimal pressure changes for significant volume changes.

• Pulmonary surfactant reduces surface tension, enhancing compliance (critical in premature infants).

Ventilation and Perfusion

Matching (V/Q Ratio)

• Ventilation (V): Amount of air reaching the alveoli.

• Perfusion (Q): Amount of blood reaching the alveoli.

• Ideal scenario involves matching V to Q for efficient gas exchange (V/Q ratio of 1).

Mechanics of Breathing

Diaphragm and Intercostal Muscles

• Diaphragm: Main muscle for inspiration; contraction increases thoracic volume.

• Intercostal Muscles: Assist in elevating ribs during inhalation; external for inspiration and internal for forced expiration.

Air Movement Dynamics

• During inspiration, the diaphragm contracts, reducing internal pressure and drawing air in.

• Quiet expiration is passive; during exercise, internal intercostals and abdominal muscles engage for forceful expiration.

Gas Exchange Processes

External and Internal Respiration

• External Respiration: Exchange of gases between blood and alveoli via diffusion.

• Internal Respiration: Gas exchange at the cellular level between blood and body tissues.

Lung Volumes and Capacities

Key Volumes

• Tidal Volume (TV): Air in and out during normal breathing.

• Inspiratory Reserve Volume (IRV): Additional air that can be inhaled after normal inspiration.

• Expiratory Reserve Volume (ERV): Air that can be forcibly exhaled after normal expiration.

• Residual Volume (RV): Air remaining after forced exhalation.

• Total Lung Capacity (TLC): Sum of all lung volumes.

Clinical Importance of Respiratory Anatomy

Key Applications

• Understanding how air moves in spontaneously ventilating patients.

• Importance of V/Q matching and lung compliance.

• Knowledge of surface anatomy and its relevance to diagnostics.