Digestive Processes Occurring in the Mouth, Pharynx, Esophagus

1. Composition of Saliva & Control of Salivation
1. major components of saliva:
• water (97-99.5%)
• electrolytes: Na+, K+, Cl-, PO4-
• mucin - protein that forms thick, slimy mucus
• IgA antibodies - immune defense
• lysozyme - antibacterial enzyme
• salivary amylase - starts breakdown of carbo's
2. control of salivation:
• ingestion of foodstuffs -----> activate chemoreceptors and pressoreceptors -----> salivatory nuclei (pons & medulla) ----->
• PARASYMPATHETIC nerve activation -----> Facial (VII) and Glassopharyngeal (IX) nerves -----> secretion by salivary glands
• SYMPATHETIC nerve activation -> decreased salivation
2. Mechanical Processes
1. mastication (chewing) - cheeks, tongue, and teeth involved in both voluntary and involuntary grinding, ripping, and tearing of foodstuffs
2. deglutition (swallowing) - moving "bolus" on its way
• tongue compacts ground food into a "bolus"
• buccal phase (voluntary): tongue against hard palate -----> tongue contraction -----> bolus forced into oropharynx
• pharyngeal-esophageal phase (involuntary):
• tongue blocks off mouth
• soft palate blocks off nasopharyx
• epiglottis blocks off trachea ------> peristaltic waves moves food to stomach

Category: Physiology Notes