Overview
This lecture covers the structure and function of the oral (buccal) cavity, types of teeth and salivary glands, processes of mechanical and chemical digestion, formation of the bolus, swallowing phases, and the concept of peristalsis in the digestive tract.
Structure of the Oral Cavity
- The oral (buccal) cavity is surrounded by lips (front), cheeks (sides), palate (roof), and opens into the pharynx (back).
- The palate is divided into the hard palate (front roof) and soft palate (back roof).
- The uvula is a flap at the end of the soft palate, preventing food from entering the nasal cavity during swallowing.
- Cheeks form the sides, and the tongue lies on the floor of the cavity.
- The oral cavity contains teeth and three paired salivary glands.
Teeth and Tongue
- Four types of teeth: incisors (4), canines (2), premolars (4), molars (6) per jaw; total of 32 teeth.
- Tongue surface has rough projections called papillae, which contain taste buds and aid food handling.
- Papillae provide friction for mastication and house taste buds for different tastes, including umami (savory).
Salivary Glands and Saliva
- Three pairs of salivary glands: sublingual (below tongue), submandibular/submaxillary (below jaw), and parotid (in front of ears).
- Saliva, a mix of secretions from these glands, contains digestive enzymes to begin food breakdown.
Mechanical and Chemical Digestion
- Mechanical digestion: physical breakdown of food by chewing (mastication), increasing surface area for enzymes.
- Chemical digestion: minor in the mouth; salivary enzymes begin starch and lipid digestion.
- Two main enzymes: salivary amylase (ptyalin) breaks starch into maltose/maltotriose, and lingual lipase starts lipid breakdown.
Formation of Bolus and Swallowing
- The chewed and partially digested food forms a soft oval mass, the bolus, ready to be swallowed.
- Swallowing (deglutition) has three phases: oral (voluntary, tongue pushes bolus), pharyngeal (involuntary, closes nasal cavity and windpipe), and esophageal (involuntary, peristalsis moves bolus to stomach).
Peristalsis
- Peristalsis is a wave-like muscular contraction starting in the esophagus, moving food through the digestive tract.
- Each region of the GI tract has its own unique peristaltic movement; it doesn't begin in the oral cavity.
Key Terms & Definitions
- Oral/Buccal cavity — space inside the mouth where digestion begins.
- Palate — the roof of the mouth; divided into hard and soft palate.
- Uvula — flap at the end of the soft palate, closes nasal passage during swallowing.
- Papilla (on tongue) — rough projections with taste buds.
- Salivary glands — sublingual, submandibular (submaxillary), parotid glands producing saliva.
- Saliva — fluid containing enzymes for initial digestion.
- Mastication — chewing, mechanical breakdown of food.
- Bolus — mass of chewed food ready to be swallowed.
- Peristalsis — wave-like muscular contractions moving food in the GI tract.
- Swallowing (deglutition) — process of moving bolus from mouth to stomach; oral, pharyngeal, esophageal phases.
Action Items / Next Steps
- Read about the next process after peristalsis for the upcoming lecture.
- Prepare any questions on today's oral cavity topics for the next class.