TAILIEUCHUNG - Lecture Human anatomy and physiology - Chapter 23: The digestive system (part b)

Chapter 23 - The digestive system (part b) presents the following content: Pharynx, esophagus, digestive processes: mouth, deglutition, stomach: gross anatomy, stomach: microscopic anatomy, gastric gland secretions, regulation of gastric secretion,. | 23 The Digestive System: Part B Pharynx Oropharynx and laryngopharynx Allow passage of food, fluids, and air Stratified squamous epithelium lining Skeletal muscle layers: inner longitudinal, outer pharyngeal constrictors Esophagus Flat muscular tube from laryngopharynx to stomach Pierces diaphragm at esophageal hiatus Joins stomach at the cardiac orifice Esophagus Esophageal mucosa contains stratified squamous epithelium Changes to simple columnar at the stomach Esophageal glands in submucosa secrete mucus to aid in bolus movement Muscularis: skeletal superiorly; smooth inferiorly Adventitia instead of serosa Figure Mucosa (contains a stratified squamous epithelium) Submucosa (areolar connective tissue) Lumen Muscularis externa Adventitia (fibrous connective tissue) (a) • Circular layer • Longitudinal layer Figure Mucosa (contains a stratified squamous epithelium) (b) Digestive Processes: Mouth Ingestion Mechanical digestion Mastication is partly voluntary, partly reflexive Chemical digestion (salivary amylase and lingual lipase) Propulsion Deglutition (swallowing) Deglutition Involves the tongue, soft palate, pharynx, esophagus, and 22 muscle groups Buccal phase Voluntary contraction of the tongue Pharyngeal-esophageal phase Involuntary Control center in the medulla and lower pons Figure Tongue Trachea Pharynx Epiglottis Glottis Bolus of food Epiglottis Esophagus Uvula Bolus Bolus Relaxed muscles Circular muscles contract Bolus of food Longitudinal muscles contract Stomach Relaxed muscles Gastroesophageal sphincter opens Gastroesophageal sphincter closed Upper esophageal sphincter is contracted. During the buccal phase, the tongue presses against the hard palate, forcing the food bolus into the oropharynx where the involuntary phase begins. Food is moved through the esophagus to the stomach by peristalsis. The gastroesophageal sphincter opens, and food enters the stomach. The uvula and larynx rise to prevent food from entering respiratory .

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