Digestion in the Mouth

May 27, 2024

Lecture Notes on Digestion in the Mouth

Introduction to Digestion in the Mouth

  • The mouth (oral cavity) is the first place where digestion occurs.
  • Main purpose: To receive food and convert it into a bolus (a ball of food).

Process of Chewing (Mastication)

  • Mastication: The scientific term for chewing.
  • Key components involved in chewing:
    • Teeth: Will be covered more in another video.
    • Tongue: Known scientifically as lingua.

Tongue Muscles

  • External muscles: Allow movements such as lifting or lowering the tip of the tongue, sticking it out, and bringing it back.
  • Internal muscles: Change the size of the tongue by contracting. They can shorten/lengthen and widen/narrow the tongue.
  • Muscle directions:
    • Anterior (A) to Posterior (P)
    • Right to Left (Lateral)

Breakdown of Food Particles

  • Hydrolysis: Enzymatic process that breaks down macromolecules.
  • Enzymes and their sources: Salivary glands in the mouth.
    • Produced by different salivary glands contributing to the components of saliva like serous and mucinous secretions.

Types of Salivary Secretions

  • Serous secretions: Rich in enzymes and salts.
  • Mucinous secretions: Contain mucin (similar to mucus) which moistens food.
  • Purpose: Aid the formation of bolus and facilitate swallowing.

Major Salivary Glands

  1. Parotid Glands
    • Location: Sides of the mouth above the jaw.
    • Contribution: Produce around 25% of saliva, mainly serous (rich in enzymes).
  2. Submandibular Glands
    • Location: Beneath the lower jaw (mandible).
    • Contribution: Produce around 70% of saliva, both serous and mucinous.
  3. Sublingual Glands
    • Location: Under the tongue.
    • Contribution: Produce around 5% of saliva, mainly mucinous with some enzymes.
  4. Von Ebner's Glands
    • Location: Tips of the tongue.
    • Contribution: Less than 5% of saliva.
    • Special Enzyme: Lingual lipase (breaks down lipids into free fatty acids and diglycerides/monoglycerides).

Enzymes Involved in Saliva

  • Lingual Lipase: Found in Von Ebner's glands, breaks down triglycerides.
  • Alpha-Amylase
    • Found in other major salivary glands (parotid, submandibular, sublingual).
    • Breaks down carbohydrates like starch into shorter carbohydrate chains.

Significance of Saliva in Digestion and Taste

  • Saliva enzymes aid in the initial digestion but primarily enhance taste.
    • Example: Appreciating fats in burgers or sugar in soda.

pH Balance in the Mouth

  • Mouth prefers a neutral pH (around 7.0).
  • Excessive sugar can lower pH below 5.5, leading to demineralization and potential tooth decay.
  • Note: To avoid excessive sugar to maintain healthy pH in the mouth.