A deep groove encircles the body of the circumvallate papilla. Serous (von Ebner s) glands (serous) drain into the base of this groove.

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1 By Dr. Raja Ali

2 A deep groove encircles the body of the circumvallate papilla. Serous (von Ebner s) glands (serous) drain into the base of this groove. The flow of fluid from these glands serves to wash surface of the papilla and clean materials from taste buds so they are ready for new gustatory stimuli. Other serous and mucous glands in other parts of oral region serve the same sort of purpose for cleansing other types of papillae

3 Taste buds a. Oval multicellular structures b. Cells surround a cavity that communicates with the oral cavity via a small pore between the apexes of the cells. c. Dissolved substances enter the cavity through this pore and come into contact with the microvilli of gustatory cells (neuroepithelial sensory cells) of the taste bud. d. These chemical stimuli are transduced to an electrical impulse that is transmitted through afferent axons of cranial nerves 7, 9, and 10 that synapse on the basal portions of the neuro-epithelial cells. e. Action potentials travel along these axons to the portions of the brain responsible for our sense of taste.

4 f. Taste buds are composed of 3 cell types * Gustatory (taste) cells * Sustentacular (support) cells * Basal cells - stem cells for replacement of gustatory cells ** gustatory cells live for about 7-10 days g. Both gustatory and sustentacular cells have similar structure, long microvilli that extend into the lumen of the taste bud.

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7 Pharynx Passes from mouth into pharynx 3 parts -Nasopharynx:- located superior and posterior to the soft palate. -contains the PHARYNGEAL TONSILS and TUBAL TONSILS Functions only in respiration Oropharynx Digestive and respiratory functions Laryngopharynx Digestive and respiratory functions

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9 Functions of the Esophagus

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14 Note While the circular and longitudinal muscle layers are responsible for gross movements of the digestive tract The muscularis mucosae causes movements of the mucous layer that are independent of the rest of the digestive tract.

15 Specializations of esophageal tissues 1. Tubuloacinar mucus secreting glands called esophageal glands proper are present in the submucosa. Their ducts extend to the esophageal lumen. 2. Small branched mucus secreting glands are also sometimes found in the lamina propria near the stomach. These are called esophageal cardiac glands.

16 3. The muscular layer of the esophagus changes from striated muscle near mouth, to smooth muscle near stomach. Why would this be the case? 4. A serosal layer with a simple squamous epithelium as its outermost component is only found in the peritoneal cavity, below the diaphragm and near the stomach. The rest of the esophagus has an adventitia - outer layer of loose C.T. that blends with surrounding tissues.

17 Digestive Processes in the Pharynx, and Esophagus Pharyngeal processes: Deglutition = swallowing Voluntary Buccal phase Involuntary Pharyngeal-Esophageal Phase Esophageal processes: Peristalsis (rhythmic contractions, involuntary)

18 Esophagus Secretes mucous, transports food no enzymes produced, no absorption Mucosa protection against wear and tear Submucosa Muscularis divided in thirds Superior 1/3 skeletal muscle Middle 1/3 skeletal and smooth muscle Inferior 1/3 smooth muscle 2 sphincters upper esophageal sphincter (UES) regulates movement into esophagus, lower esophageal sphincter (LES) regulates movement into stomach Adventitia no serosa attaches to surroundings

19 Deglutition Act of swallowing Facilitated by secretions of saliva and mucus Involves mouth, pharynx, and esophagus 3 stages Voluntary bolus passed to oropharynx Pharyngeal involuntary passage through pharynx into esophagus Esophageal involuntary passage through esophagus to stomach Peristalsis pushes bolus forward