Pharynx and Larynx: Structure and Function in the Respiratory System

Pharynx and Larynx in the Respiratory System

Pharynx: Structure and Epithelium

The pharynx is a muscular tube that serves as a passageway for both air and food, connecting the nasal and oral cavities to the larynx and esophagus. It is divided into three regions, each with distinct epithelial linings and functions.

• Oropharynx: Lined by stratified squamous epithelium, which provides protection against abrasion from food particles.

• Laryngopharynx: Also lined by stratified squamous epithelium, suitable for its role in both respiratory and digestive pathways.

Tonsils in the Oropharynx:

• Palatine tonsils and lingual tonsils are located in the oropharynx, playing a role in immune defense.

Passageways:

• Nasopharynx: Passageway for air only.

• Oropharynx and Laryngopharynx: Passageways for both air and food.

Air Flow: Inhaled air passes from the laryngopharynx into the larynx.

Larynx: Cartilages and Structure

The larynx is a cartilaginous structure that connects the pharynx to the trachea and is essential for voice production and airway protection. It is composed of nine cartilages:

• Single cartilages:

  • Thyroid cartilage

  • Cricoid cartilage

  • Epiglottis

• Paired cartilages:

  • Arytenoid cartilages

  • Corniculate cartilages

  • Cuneiform cartilages

Epiglottis: Structure and Function

The epiglottis is a leaf-shaped flap of elastic cartilage covered with mucous membrane. It acts as a switch between the trachea and the esophagus to permit air to enter the airway and food to enter the digestive tract.

• Tissues: The epiglottis consists of elastic cartilage and is covered by stratified squamous epithelium on its upper surface.

• Mechanism: During swallowing, the epiglottis closes over the glottis to prevent food from entering the airway. When not swallowing, it remains open to allow air passage.

Glottis: The glottis is the space between the vocal cords, covered by the epiglottis during swallowing.

Vocal Cords: Structure and Function

The larynx contains two sets of folds: the false vocal cords (vestibular folds) and the true vocal cords (vocal folds).

• False vocal cords (vestibular folds):

  • Located superior to the true vocal cords.

  • Function: Help close the glottis during swallowing, but do not produce sound.

• True vocal cords (vocal folds):

  • Attached anteriorly to the thyroid cartilage and posteriorly to the arytenoid cartilages.

  • Composed of elastic fibers covered by stratified squamous epithelium.

  • Function: Produce sound by vibrating as air passes through them.

Sound Production: Sound is generated by pushing air through the vibrating true vocal cords. The pitch and volume depend on the tension and length of the vocal folds.

Summary Table: Pharynx and Larynx Features

Region	Epithelium Type	Function	Associated Structures
Oropharynx	Stratified squamous	Air & food passage	Palatine & lingual tonsils
Laryngopharynx	Stratified squamous	Air & food passage	Connects to larynx & esophagus
Larynx	Pseudostratified ciliated columnar (except epiglottis & vocal cords)	Air passage, sound production	Thyroid, cricoid, epiglottis, arytenoid cartilages
Epiglottis	Stratified squamous (upper surface)	Prevents food entry into airway	Elastic cartilage
True vocal cords	Stratified squamous	Sound production	Thyroid & arytenoid cartilages

Additional info:

• The larynx is essential for phonation, airway protection, and breathing regulation.

• Damage to the laryngeal cartilages or vocal cords can result in voice changes or airway obstruction.