Respiratory System Notes

Function of the Respiratory System

• The primary function is to transport air into the lungs.
• Oxygen is diffused into the bloodstream.
• Carbon dioxide is moved out of the bloodstream.

Upper and Lower Respiratory Tracts

• The respiratory system is divided into the upper and lower respiratory tracts.

Upper Respiratory Tract

• Air enters through the mouth or nose and proceeds to the nasal cavity.
• In the nasal cavity, the air is:
  • Filtered
  • Warmed
  • Moistened
• The air then passes into the pharynx.
• From the pharynx, it enters the larynx, also known as the voice box.

Lower Respiratory Tract

• From the larynx, air moves down into the trachea, or windpipe.
• The inner membrane of the trachea contains cilia, which are tiny hair cells.
  • Cilia catch particles of dust.
  • These particles are removed through coughing.
• The trachea is protected and kept open by 15 to 20 C-shaped rings of cartilage located at the front and side.

Bronchial Tree

• The trachea divides into two smaller tubes called Bronchi.
• Inside the lung, the bronchi split into tertiary bronchi.
• Tertiary bronchi continue to divide, forming bronchioles.
  • Bronchioles are narrow tubes less than one millimeter in diameter.
• Finally, air enters alveolar sacs and alveoli.
  • Gaseous exchange occurs in the alveoli.