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Respiratory System Anatomy (Overview)
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Respiratory System Anatomy (Overview)

The Respiratory System
Key Function:
  • Provides mechanisms for the exchange of oxygen and carbon dioxide between the blood and the outside environment.
Review histology
Review embryology
Review respiratory mechanics
  • Anatomically, the respiratory system divides into upper and lower respiratory tracts
The upper respiratory tract:
  • Nose
  • Nasal cavity
  • Paranasal sinuses
  • Pharynx
The lower respiratory tract:
  • Larynx
  • Trachea
  • Bronchi
  • Bronchioles
  • Respiratory bronchioles
  • Alveolar ducts
  • Alveolar sacs
  • Alveoli
Functionally, the respiratory system divides into conducting and respiratory portions
The conducting portion
Moves (aka, conducts) air between the lungs and the outside environment.
  • Nose
  • Nasal cavity
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Bronchioles
The respiratory portion
Participates in gas exchange
  • Respiratory bronchioles
  • Alveolar ducts
  • Alveolar sacs
  • Alveoli
Anatomical Details:
Upper Respiratory Tract
  • The nose opens the respiratory system to the outside environment.
  • The nasal cavity has a mucosal lining, which "conditions" the air; specifically, it moistens, warms, and cleans it. The posterior-superior wall of the nasal cavity houses special sensory cells (olfactory cells) that detect smells.
  • The paranasal sinuses:
– Frontal sinus of the frontal bone – Ethmoid sinus (aka, ethmoidal air cells) of ethmoid bone, which lies posterior to the frontal sinus. – Sphenoidal sinus, which is located posterior to the nasal cavity. – Maxillary sinus in the maxilla on either side of the nasal cavity.
Because the paranasal sinuses are open to the nasal cavity, infection can spread to the paranasal sinuses, which results in sinus infection (aka, sinusitis).
  • The pharynx is the muscular tube that lies behind the nasal cavity, oral cavity, and larynx; it is a conduit for air and food/liquid.
Lower Respiratory Tract
  • The larynx is the cartilaginous start of the lower respiratory tract; it prevents food/liquid from entering the lower respiratory tract and is often referred to as the "voice box" because it produces and modifies sounds.
Tracheobronchial tree* = trachea and its branches.
    • The trachea (the "windpipe") descends through the neck to the thorax (it terminates posterior to the sternal angle, at the level of T2); it comprises C-shaped (vertically-stacked) cartilaginous rings.
    • Right and left primary (aka, main) bronchi arise from trachea; they enter the lungs.
    • Secondary bronchi (aka, lobar bronchi) serve specific lobes of the lungs.
    • Tertiary bronchi (aka, segmental bronchi) serve specific bronchopulmonary segments.
    • Bronchioles are histologically different.
    • Terminal bronchioles are the final branches of the conducting portion of the respiratory system.
    • Respiratory bronchioles are the start of the respiratory portion, as they can participate gas exchange.
    • Respiratory bronchioles open to alveolar ducts.
    • Alveolar ducts open to alveolar sacs.
    • Alveolar sacs comprise outpockets called alveoli.
  • Aveloli:
– Very thin walls, and are the primary sites of gas exchange. – The hundreds of millions of alveoli within give the lungs a light, spongy texture.
– Separated into lobes: – Right lung = 3 lobes – Left lung = 2 lobes – The left lung is slightly smaller to accommodate the heart
Clinical Correlations

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