Respiratory System Organs and Functions

Upper and Lower Respiratory Systems

  • The respiratory system is divided into the upper and lower respiratory systems.
  • The division occurs at the level of the larynx; however, the larynx is considered part of the lower respiratory system for HPS 109.
  • The epiglottis, located at the top of the larynx, acts as a lid separating the two systems.
  • Upper respiratory system:
    • Nose
    • Nasal cavity
    • Sinuses
    • Pharynx
  • Lower respiratory system:
    • Larynx
    • Trachea (windpipe)
    • Primary bronchi (left and right)
    • Secondary and tertiary bronchi
    • Bronchioles
    • Alveoli

The Nose

  • The nose begins at the nostrils, also known as external nares.
  • The posterior aspect of the nose contains the internal or posterior nares.
  • The nose extends from the external nares (nostrils) to the internal nares.
  • Nasal Vestibule:
    • The front, wobbly part of the nose.
    • Contains hairs that filter large particles from the air.
  • Nasal Septum:
    • Divides the nose into left and right sides.
  • Conchae:
    • Shell-like structures located on the wall of the nasal septum.
    • There are three conchae.
    • Air bounces off the conchae, creating a narrow, windy path.
    • The walls of the conchae are lined with mucus and small hairs.
      • They filter the incoming air.
      • They remove particles and bacteria.
      • They are highly vascularized, warming and humidifying the air.

The Pharynx

  • The pharynx begins where the nose ends, at the posterior or internal nares.
  • The pharynx consists of three regions:
    • Nasopharynx
    • Oropharynx
    • Laryngopharynx
  • Nasopharynx:
    • The nasal part of the pharynx.
    • Located above the soft palate and behind the posterior nares.
    • Air passes through this region.
  • Oropharynx:
    • The oral (mouth) part of the pharynx.
    • Located at the back of the mouth.
    • Both air, food, and liquid pass through this region.
    • Contains stratified epithelium for protection.
  • Laryngopharynx:
    • The laryngeal (larynx) part of the pharynx.
    • A shared region where the body directs air to the trachea and food/drink to the esophagus.
    • Contains stratified epithelium for protection.
  • Stratified Epithelium:
    • Multiple layers of cells that protect against abrasion and chemical attack.
    • Found in the oropharynx and laryngopharynx.
  • Ciliated Epithelium:
    • Hairs (cilia) that filter air.
    • Found in the nasopharynx.

The Larynx

  • The larynx marks the beginning of the lower respiratory system.
  • Epiglottis:
    • A lid above the glottis (the opening into the trachea).
    • It closes over the glottis during swallowing to prevent food and drink from entering the trachea.
    • It opens during breathing to allow air to enter and exit the trachea.
  • Thyroid Cartilage:
    • Also known as the Adam's apple.
    • More prominent in men than in women.
    • It moves during swallowing and provides an attachment point for muscles that control the glottis.
  • Cricoid Cartilage:
    • A complete ring of cartilage.
    • Forms the entrance to the trachea.
    • The only complete ring of cartilage in the trachea, it helps keep the trachea open.

The Trachea and Primary Bronchi

  • Trachea (Windpipe):
    • Air passes through the trachea after entering via the epiglottis.
  • Cartilage Rings:
    • The trachea contains 15-20 incomplete, C-shaped cartilage rings.
    • The cricoid cartilage is the only complete ring.
    • Smooth muscle connects the ends of the C-shaped rings, allowing the body to regulate the diameter of the trachea.
    • Muscle contraction: Decreases the trachea's diameter.
    • Muscle relaxation: Increases the trachea's diameter.
  • Primary Bronchi:
    • The trachea divides into the right and left primary bronchi.
    • These bronchi also contain C-shaped cartilage rings.
  • Right Primary Bronchus:
    • Wider
    • Shorter
    • Steeper
    • Aspirated contents are more likely to enter the right primary bronchus due to its anatomy.
    • It branches into three secondary bronchi, corresponding to the three lobes of the right lung.
  • Left Primary Bronchus:
    • Thinner
    • Longer
    • Less steep
    • It branches into two secondary bronchi, corresponding to the two lobes of the left lung.
  • Pulmonary Lobes:
    • Right lung: three lobes
    • Left lung: two lobes