Lecture Notes: The Pharynx and Esophagus

Overview

• Focus: Connection between oral cavity and stomach.
• Function: Passageway for food from mouth to stomach.

The Pharynx

• Regions of the Pharynx:

  • Oropharynx: Next to oral cavity.
  • Laryngopharynx: Leads into the esophagus.
  • Nasopharynx: Located above the uvula; involved in air movement, not digestion.

• Epiglottis:

  • Functions to block trachea during swallowing to prevent food and fluids from entering.

• Tissue Composition:

  • Stratified Squamous Epithelium: Similar to oral cavity.
  • Mucus-Producing Glands: Aid in the movement of materials.

• Musculature:

  • Predominantly skeletal muscle.
  • Layers:
    • Inner longitudinal layer.
    • Outer pharyngeal constrictors: Propels material into the stomach during swallowing.

The Esophagus

• Characteristics:

  • Muscular tube from laryngopharynx to stomach.
  • Does not remain open like the trachea.
  • Passes through the diaphragm at the esophageal hiatus.

• Cardiac Orifice and Sphincter:

  • Slight thickening near stomach interface forms the gastroesophageal sphincter.
  • Function: Prevents stomach acids from regurgitating into the esophagus.
  • Heartburn: Occurs if the sphincter fails; factors include overeating, obesity, pregnancy, running.

• Hiatal Hernia:

  • Structural abnormality where part of the stomach is above the esophageal hiatus.
  • Can lead to conditions like esophagitis and esophageal cancer if untreated.

• Tissue Composition:

  • Four Tunics similar to the alimentary canal.
  • Esophageal Mucosa:
    • Stratified squamous epithelium transitions to simple columnar at cardiac orifice.
  • Submucosa: Contains mucus-secreting glands for lubrication.

• Musculature:

  • Muscularis Externa:
    • Superior third: Exclusively skeletal muscle.
    • Middle third: Mixture of skeletal and smooth muscle.
    • Inferior third: Exclusively smooth muscle.

• Adventitia:

  • Replaces the serosa tunic; consists of fibrous connective tissue.

Summary

• The pharynx and esophagus are integral in the digestive process, facilitating the movement of food from the mouth to the stomach with specialized structures and tissue compositions. Proper functioning of the gastroesophageal sphincter is crucial to prevent conditions like heartburn and esophagitis.