Respiratory_20Basics_20-SDL

Respiratory System Basics and Terminology

• Overview of the respiratory system, including its primary functions and anatomical components.

Key Anatomical Structures

• Nasal Cavity: Pathway for air, filters and humidifies incoming air.

• Oral Cavity: Secondary pathway for air; less effective than nasal cavity in filtration.

• Tongue: Plays a role in swallowing and airway protection.

• Trachea: Main airway that conducts air from larynx to bronchi.

• Pleura: Membrane surrounding the lungs, facilitating movement during respiration.

• Pharynx: Throat region for air passage and food.

• Epiglottis: Flap that covers the trachea during swallowing to prevent food entry.

• Larynx: Voice box that contains vocal cords.

• Bronchus: Branch from trachea leading into lungs.

• Right Lung and Left Lung: Main organs of respiration.

• Diaphragm: Major muscle involved in breathing.

The Lungs

• Apex: Tip of each lung, located slightly above the first rib.

• Lobes:

  • Right lung: Contains superior, middle, and inferior lobes.

  • Left lung: Contains superior lobe and inferior lobe, with a lingula (a projection).

• Fissures:

  • Right lung has horizontal and oblique fissures separating lobes.

  • Left lung only has an oblique fissure.

• Cardiac Notch: Indentation in the left lung for the heart.

Control of Breathing

• Influences on breathing regulation:

  • Higher brain centers (cerebral cortex) for voluntary control.

  • Hypothalamus responding to pain and emotions.

  • Chemoreceptors detecting CO₂ levels (central and peripheral) influence respiratory rate.

  • Receptors in muscles and joints provide feedback on body position and movement.

  • Respiratory centers in medulla and pons coordinate rhythm of breathing.

• Stretch Receptors: Detect lung inflation and help regulate breathing rate.

• Irritant Receptors: Respond to harmful substances.

Muscles Involved in Normal Respiration

• Inspiratory Muscles:

  • Sternocleidomastoid (SCM)

  • Scalenes

  • External intercostals

• Expiratory Muscles:

  • Internal intercostals

  • Abdominals

  • Diaphragm (primary muscle for inspiration)

Phases of Breathing

• Inspiration:

  • Involves contraction of inspiratory muscles.

  • Thoracic cavity enlarges, volume increases, pressure drops, allowing air to flow into lungs.

• Expiration:

  • Primarily passive due to lung recoil.

  • Active muscles engaged during forced expiration.

Gaseous Exchange

• Occurs across alveolar-capillary membrane.

• Oxygen: Diffuses from alveoli into bloodstream, binds with hemoglobin.

• Carbon Dioxide: Exchanged from blood to alveoli for expiration.

Respiratory Mechanics

• Pressures:

  • Atmospheric pressure: Pressure outside the body.

  • Alveolar pressure: Pressure inside the lungs.

  • Intrapleural pressure: Pressure in the pleural cavity, generally negative.

• Balance: Functional residual capacity represents a balance between lung recoil and chest wall expansion.

Resistance to Airflow

• Factors influencing resistance:

  • Type of airflow (turbulent vs. laminar).

  • Viscosity of gas.

  • Dimension of airways; most resistance occurs in larger conducting airways.

Compliance of Lungs

• Definition: Measure of lung's ability to stretch and expand.

• Static Compliance: Measured without airflow (end of inspiration).

• Dynamic Compliance: Measured during breathing.

• Implication: Lower compliance indicates stiffer lungs, which may hinder function.

Ventilation

• Definition: Movement of gases into and out of the lungs.

• Alveolar Ventilation: Gas reaching alveoli for gas exchange.

• Dead Space: Gas movement not involved in exchange.

• Minute Ventilation: Calculated as tidal volume multiplied by respiratory rate.

V/Q Matching (Ventilation/Perfusion Ratio)

• Critical for assessing lung efficiency.

• Ideal Ratio: 1, indicating proper matching of ventilation to perfusion.

• Issues:

  • Low ratios indicate poor ventilation with adequate perfusion.

  • High ratios indicate good ventilation but poor perfusion.

Lung Volumes and Capacities

• Key definitions:

  • Tidal Volume (VT): Volume of air moved during normal breathing.

  • Inspiratory Reserve Volume (IRV): Max volume inhaled after a normal breath.

  • Expiratory Reserve Volume (ERV): Max volume exhaled after a normal breath.

  • Residual Volume (RV): Volume remaining post-exhalation.

  • Total Lung Capacity (TLC): Total volume of gas in the lungs after max inhalation.

  • Vital Capacity (VC): Max volume exhaled after full inspiration.

Defenses of the Respiratory System

• Upper Respiratory Tract: Filters and humidifies air, protects from potential pathogens.

• Mucociliary Escalator: Lined with cilia, propelling mucus upwards to clear excess secretions.

• Cough Reflex: Clears blockages; includes deep inspiration and sudden glottic opening to propel air.

Self Study Topics

• Effects of aging, obesity, smoking, pregnancy, exercise, immobility, sleeping, and stress on the respiratory system.

References

• Hough A. Physiotherapy for Respiratory and Cardiac Care.

• Pryor, J. & Prasad, A. Physiotherapy for Respiratory Issues.

• Wilkins, R. et al. Fundamentals of Respiratory Care.

Glossary of Terms

• Atelectasis: Collapse of lung area.

• Bradycardia: Low heart rate.

• Forced Vital Capacity (FVC): Amount exhaled after full inspiration.

• Pneumothorax: Presence of air in pleural space.

• Respiratory Distress Syndrome (RDS): Insufficient surfactant in prem infants.

• Tachypnea: High rate of respiration.

Final Note

• "Oh, you are studying the respiratory system? What an inspiration!"