BHSC 204
Systems Anatomy & Physiology
The Respiratory System
Basic Health Sciences (BHSC) Program
Academic Year 2024–2025
, 1. Overview
The respiratory system supplies oxygen to the blood and removes carbon dioxide from
it. It also plays roles in acid-base balance, vocalization, and olfaction.
2. Anatomy of the Respiratory System
2.1 Upper Respiratory Tract
• Nose and nasal cavity: filters, warms, and humidifies air
• Paranasal sinuses: resonance and reduce skull weight
• Pharynx (throat): shared pathway for food and air
• Larynx: contains vocal cords; epiglottis prevents aspiration during swallowing
2.2 Lower Respiratory Tract
• Trachea: cartilaginous rings prevent collapse; lined with pseudostratified ciliated
epithelium
• Primary bronchi: right and left; right is wider and more vertical (more common
site of foreign body aspiration)
• Secondary (lobar) bronchi: one per lung lobe (3 right, 2 left)
• Tertiary (segmental) bronchi → bronchioles → terminal bronchioles
• Respiratory bronchioles → alveolar ducts → alveolar sacs → alveoli
2.3 The Alveoli
• 300 million alveoli; enormous surface area (~70 m²)
• Type I pneumocytes: thin cells forming the alveolar wall; site of gas exchange
• Type II pneumocytes: produce surfactant to reduce surface tension and prevent
collapse
• Alveolar macrophages: remove debris and pathogens
2.4 The Lungs
• Right lung: 3 lobes (upper, middle, lower); larger
• Left lung: 2 lobes (upper, lower); cardiac notch accommodates the heart
Systems Anatomy & Physiology
The Respiratory System
Basic Health Sciences (BHSC) Program
Academic Year 2024–2025
, 1. Overview
The respiratory system supplies oxygen to the blood and removes carbon dioxide from
it. It also plays roles in acid-base balance, vocalization, and olfaction.
2. Anatomy of the Respiratory System
2.1 Upper Respiratory Tract
• Nose and nasal cavity: filters, warms, and humidifies air
• Paranasal sinuses: resonance and reduce skull weight
• Pharynx (throat): shared pathway for food and air
• Larynx: contains vocal cords; epiglottis prevents aspiration during swallowing
2.2 Lower Respiratory Tract
• Trachea: cartilaginous rings prevent collapse; lined with pseudostratified ciliated
epithelium
• Primary bronchi: right and left; right is wider and more vertical (more common
site of foreign body aspiration)
• Secondary (lobar) bronchi: one per lung lobe (3 right, 2 left)
• Tertiary (segmental) bronchi → bronchioles → terminal bronchioles
• Respiratory bronchioles → alveolar ducts → alveolar sacs → alveoli
2.3 The Alveoli
• 300 million alveoli; enormous surface area (~70 m²)
• Type I pneumocytes: thin cells forming the alveolar wall; site of gas exchange
• Type II pneumocytes: produce surfactant to reduce surface tension and prevent
collapse
• Alveolar macrophages: remove debris and pathogens
2.4 The Lungs
• Right lung: 3 lobes (upper, middle, lower); larger
• Left lung: 2 lobes (upper, lower); cardiac notch accommodates the heart
