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The Respiratory System

Jul 17, 2024

Chapter 22: The Respiratory System

The Process of Respiration

  1. Pulmonary Ventilation

    • Air is moved into and out of the lungs (inhalation and exhalation).
  2. External Respiration

    • Oxygen diffuses from the lungs to the blood.
    • Carbon dioxide diffuses from the blood to the lungs.
  3. Transport

    • Oxygen is transported from the lungs to the tissue cells.
    • Carbon dioxide is transported from the tissues to the blood.
  4. Internal Respiration

    • Oxygen diffuses from the blood to the tissues.
    • Carbon dioxide diffuses from the tissues into the blood.

Structural Components

Upper Respiratory Tract

  • Includes:
    • Nostrils
    • Nasal cavity
    • Pharynx (shared with the digestive system)

Lower Respiratory Tract

  • Includes:
    • Larynx
    • Trachea
    • Bronchi
    • Lungs
    • Alveoli

The Nose

  • Functions:
    • Humidifies air
    • Warms air
    • Filters air
    • Removes microbes and dust
  • Additional Functions:
    • Resonating chamber for speech
    • Contains olfactory receptors
  • Structure:
    • Lined with pseudostratified ciliated columnar epithelium
    • Goblet cells produce mucus containing lysozyme and antimicrobial proteins

The Pharynx

  • Muscular tube connecting nasal cavity to larynx and esophagus
  • Divided into three parts:
    1. Nasopharynx: Pseudostratified ciliated columnar epithelium
    2. Oropharynx: Stratified squamous epithelium
    3. Laryngopharynx: Stratified squamous epithelium

Functional Anatomy

Respiratory Zone

  • Site for gas exchange
  • Includes:
    • Respiratory bronchioles
    • Alveolar ducts
    • Alveoli

Conducting Zone

  • Conducts air
  • Includes:
    • Trachea
    • Primary bronchi
    • Secondary bronchi
    • Tertiary bronchi

Larynx

  • Known as the voice box
  • Connects to the trachea
  • Responsible for voice production
  • Epiglottis:
    • Made of elastic cartilage
    • Covers the glottis during swallowing

Air Passage

  • Route:
    1. Nose
    2. Pharynx
    3. Larynx
    4. Trachea
    5. Primary Bronchi
  • Branching:
    • Trachea branches into primary bronchi (right and left)
    • Primary bronchi branch into secondary bronchi (three on the right, two on the left)
    • Secondary bronchi branch into tertiary bronchi
    • Further branching leads to terminal bronchioles and respiratory bronchioles

Trachea and Bronchi

  • Trachea:
    • About 10 cm long, 2.5 cm wide
    • Has C-shaped cartilage rings that are open at the back
    • Prevents trachea from collapsing
    • Bifurcates into primary bronchi
  • Primary Bronchi:
    • Right primary bronchus is wider and more vertical
    • Branch into secondary bronchi and then into tertiary bronchi
  • Branching:
    • 23 orders of branching from trachea to respiratory bronchioles

Respiratory Zone Structure

  • Begins at terminal bronchioles
  • Branches into respiratory bronchioles, then alveolar ducts, and finally alveolar sacs
  • Alveolar sacs contain clusters of alveoli (like a bunch of grapes)
  • Alveoli:
    • About 300 million in the lungs
    • Increase surface area for gas exchange
    • Connected through alveolar pores (alternate route for gas exchange)

Respiratory Membrane

  • Includes:
    • Alveolar wall (simple squamous epithelium, Type 1 alveolar cells)
    • Capillary wall
    • Basement membrane
  • Gas Exchange:
    • Occurs by simple diffusion (oxygen and carbon dioxide)
  • Alveolar Cells:
    • Type 2 alveolar cells secrete surfactant (reduces surface tension)
    • Surfactant prevents alveoli from collapsing
    • Premature babies may lack surfactant, causing distress syndrome
  • Other Features:
    • Alveoli are covered by fine elastic fibers and pulmonary capillaries
    • Alveolar macrophages keep the surface sterile

Lung Anatomy

  • Apex: Pointed tip
  • Base: Sits on the diaphragm
  • Hilum: Indentation for entry/exit of blood vessels and bronchi
  • Left Lung:
    • Smaller, with 2 lobes (superior and inferior, separated by oblique fissure)
  • Right Lung:
    • Larger, with 3 lobes (superior, middle, inferior)
    • Horizontal fissure between superior and middle lobes
    • Oblique fissure between middle and inferior lobes