Respiratory System

Respiratory System Overview

Chapter 22 Overview

The respiratory system is essential for gas exchange and involves four key processes:

  1. Respiratory System

    • Pulmonary Ventilation
    • External Respiration

  2. Circulatory System

    • Transport
    • Internal Respiration

Four Processes of Respiration

  1. Pulmonary Ventilation (Breathing)

    • Ventilation consists of the processes of inspiration (inhaling) and expiration (exhaling).
    • Inspiration: This process moves air into the lungs from the atmosphere.
    • Expiration: This involves moving air out of the lungs into the atmosphere.

  2. External Respiration

    • Oxygen (O₂) diffuses from the lungs into the blood.
    • Carbon Dioxide (CO₂) diffuses from the blood to the lungs.

  3. Transportation of Respiratory Gases

    • The cardiovascular system facilitates the transport of gases, with blood serving as the transporting fluid.
    • O₂ is transported from the lungs to the tissue cells of the body.
    • CO₂ is transported from the tissue cells back to the lungs.

  4. Internal Respiration

    • O₂ diffuses from blood into the tissue cells.
    • CO₂ diffuses from tissue cells into the blood.
    • Tissue cells utilize O₂ and produce CO₂ during the process of cellular respiration.

Human Respiratory System Anatomy

Lower Respiratory Tract
  • Trachea (Windpipe)
  • Bronchi
  • Lungs (Right & Left)
  • Diaphragm
Upper Respiratory Tract
  • Nasal cavity
  • Nostrils
  • Paranasal sinuses
  • Oral cavity
  • Pharynx
  • Larynx
  • Epiglottis
  • Alveoli
Lung Lobes
  • Right Lung:
    • Superior lobe
    • Middle lobe
    • Inferior lobe
    • Two fissures: Horizontal fissure and Oblique fissure
  • Left Lung:
    • Superior lobe
    • Inferior lobe
    • One fissure: Left oblique fissure

Air Passage and Gas Exchange

  • Air enters the body via the nose or mouth.
  • The mucous membrane in the nasal cavity serves essential functions:
    • Acts as a filter
    • Protects lungs from dirt, pollutants, and bacteria
    • Moistens the air for easier absorption in the alveoli
    • Mucous is produced and secreted by goblet cells.

Clinical Implications

Rhinitis
  • Definition: Inflammation of the nasal mucosa.
  • Significance: Infections can spread from the nasal cavity to the throat and chest, potentially leading to further complications.|
Enlarged Adenoids
  • Condition: Infected and swollen adenoids can block air passage in the nasopharynx.
  • Effect: This blockage necessitates mouth breathing, which prevents air from being adequately moistened, warmed, or filtered before reaching the lungs.
Smoker’s Cough
  • Explanation: Smoking inhibits and destroys cilia in the respiratory tract.
  • Consequence: Without ciliary activity, coughing becomes the only method to prevent mucous from accumulating in the lungs.
  • Recommendation: Cessation of smoking will allow for the recovery of ciliary function within weeks. Morning coughs diminish as function restores.
Pleurisy
  • Definition: Inflammation of the pleurae (the membranes surrounding the lungs).
  • Symptoms: Inflamed pleurae can become rough, causing friction and sharp pain during each breath. Excessive fluid production may also occur, leading to pressure on the lungs and hindering breathing.

Structural Features of the Larynx and Trachea

  • The Epiglottis is a moveable flap of elastic cartilage that covers the larynx opening during swallowing, preventing food from entering the airway.
Air Movement and Structures
  • Air flows from the nasal cavities to the pharynx, larynx, and subsequently through the trachea to reach the lungs.
  • The trachea is a critical pathway that leads to the lower respiratory tract. It consists of alternating tracheal cartilages and connective tissue layers.
  • The Primary bronchi branch into secondary bronchi and subsequently into tertiary bronchi, continuing into bronchioles.
  • The structure of bronchioles changes throughout branching—cartilage decreases while smooth muscle increases, allowing for variations in airway diameter.

Diaphragm

  • The diaphragm is a key muscle involved in the breathing process.
  • It is a sheet of skeletal muscle that separates the thoracic cavity from the abdominal cavity.
  • The diaphragm contracts and relaxes to facilitate the intake and expulsion of air.
  • Motor innervation for the diaphragm is provided by the phrenic nerve.

Pleura Surrounding the Lungs

  • The pleura consists of two layers that protect and house the lungs:
    • Visceral Pleura: The inner membrane that directly covers the lungs.
    • Parietal Pleura: The outer membrane that lines the thoracic cavity.
  • The intrapleural space (pleural cavity) lies between these two membranes and contains pleural fluid, reducing friction experienced during breathing.

Blood Flow and Gas Exchange Mechanism

  • Pulmonary arteries send deoxygenated blood to the lungs from the heart, allowing for gas exchange.
  • Pulmonary veins return oxygenated blood from the lungs to the heart for systemic distribution.

Summary

The respiratory system plays a vital role in gas exchange and relies on the coordinated function of several anatomical structures and physiological processes. Proper functioning is crucial for maintaining oxygen and carbon dioxide balance in the body, and various clinical conditions can significantly impact this essential system.