Pharynx and Larynx

Overview of the Pharynx

Definition: The pharynx is a muscular tube extending from the base of the skull to around level C6, connecting the nasal cavity and mouth to the larynx and esophagus.
Function: Acts as a pathway for both the respiratory and digestive systems.

Divisions:
- Nasopharynx: Connects the nasal cavity to the pharynx.
- Oropharynx: Connects the oral cavity to the pharynx.
- Laryngopharynx: Connects larynx to the pharynx.
Clinical Relevance: Understanding areas of the pharynx is important for procedures like the insertion of a nasogastric tube for feeding when oral intake is not possible.

Trachea vs. Esophagus:
- Trachea: Transports air to and from the lungs; only air should pass through.
- Esophagus: Transports food and liquids to the stomach; only food and liquids should go down.
Mechanism to Prevent Aspiration:
- During eating, mechanisms ensure that food does not enter the trachea.

Anatomical Position:
- Anteriorly attached to the hyoid bone.
- Connects to the laryngopharynx posteriorly.
Purpose: Keeps the airway open and facilitates sound production.

Key Structures:
- Thyroid Cartilage: Recognizable "Adam's apple" at the front of the larynx.
- Cricoid Cartilage: Located below the thyroid cartilage.
- Thyrohyoid Membrane: Connects thyroid cartilage to hyoid bone.
- Cricothyroid Ligament: Important for emergency airway procedures (e.g., Cricothyrotomy).

Function: A cartilage flap that covers the larynx during swallowing, preventing food from entering the airway.
Clinical Importance: Helps prevent choking when swallowing. If food mistakenly enters the trachea, it triggers a cough reflex to expel it.

Structure: Vocal cords (ligaments) are attached to arytenoid cartilages and thyroid cartilage.
Function: Vibrate to produce sound when air passes from the trachea through them.
- Sound Variation: Pitch and volume can change based on tension and airflow:
  - Higher tension = higher pitch.
  - Lower tension = lower pitch.
  - Loudness increases with higher pressure air.
Types:
- True Vocal Cords: Responsible for sound production.
- False Vocal Cords (Vestibular folds): Assist with the protection of the larynx and help regulate sound production.

Understanding the anatomy and functions of the pharynx, larynx, and associated structures is crucial for both clinical practices and the basic physiological processes of breathing and swallowing.