Overview
This lecture covers the anatomy and key functions of the mouth and associated structures in the gastrointestinal (GI) tract, focusing on digestion's initial stages.
Structures of the Mouth
- The lips have many sensory receptors to detect temperature, texture, and potential harm in food.
- Hard palate (part of the maxilla) forms the front of the mouth roof; the soft palate and uvula form the rear.
- The uvula helps close off the nasal cavity during swallowing to prevent food from entering the nose.
- The tongue is a strong, fast-healing muscle; it mixes food with saliva and pushes it to the pharynx.
- The lingual frenulum anchors the tongue to the mouth floor; "tongue-tied" refers to a frenulum that restricts tongue movement.
- Taste buds (on papillae) detect flavors and regenerate quickly.
Tonsils and Oral Protection
- Tonsils (palatine, adenoids/pharyngeal, lingual) are lymphatic tissue protecting against microbes in food and air.
- Enlarged tonsils can interfere with swallowing and breathing.
Teeth and Mastication
- Humans have two sets of teeth: 20 deciduous (baby) teeth and 32 permanent (adult) teeth.
- Incisors cut food, canines (cuspids) pierce/tear, and premolars/molars grind food.
- Tooth anatomy: enamel (hard, white outer layer), dentin (yellow, beneath enamel), pulp (nerve and blood supply).
- Mastication (chewing) increases food surface area for better enzyme action in digestion.
Salivary Glands and Saliva Functions
- Three major salivary glands: parotid (near the ear), sublingual (under tongue), submandibular (below the jaw).
- Saliva moistens food, binds particles into a bolus, and contains the enzyme amylase to start starch digestion.
- Amylase in saliva breaks starch into sugars, making long-chewed starchy foods taste sweet.
- Saliva also cleanses the mouth and helps regulate oral pH.
Passageways to the Stomach
- The pharynx (throat) is divided into nasopharynx (nasal), oropharynx (oral), and laryngopharynx (behind vocal cords).
- The esophagus carries food from the pharynx to the stomach.
- The cardiac sphincter at the end of the esophagus prevents stomach acid from entering the esophagus; weakness causes heartburn.
Key Terms & Definitions
- Mastication — the process of chewing food to increase its surface area.
- Bolus — a moistened, chewed lump of food ready to be swallowed.
- Amylase — an enzyme in saliva that starts breaking down starch into sugar.
- Enamel — the hardest substance in the body, covering the tooth's surface.
- Cardiac sphincter — circular muscle at the esophagus-stomach junction that prevents acid reflux.
Action Items / Next Steps
- Review oral cavity diagrams to identify anatomical structures discussed.
- Read textbook section on the mouth and pharynx for further detail.
- Prepare for lab practical by memorizing the functions of teeth and salivary glands.