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