Skip to main content
Back

Chapter 23 Part 2

Control buttons has been changed to "navigation" mode.
1/26
  • Pharynx divisions
    The pharynx consists of nasopharynx, oropharynx, and laryngopharynx. Only the oropharynx and laryngopharynx are part of the alimentary canal.
  • Primary function of the pharynx
    The pharynx primarily functions in propulsion by swallowing, moving the bolus from the oral cavity to the esophagus.
  • Epithelium lining the pharynx and oral cavity
    Both are lined with stratified squamous epithelium to protect against abrasion from food.
  • Tonsils in the oropharynx
    The oropharynx contains palatine tonsils and lingual tonsils, which perform defensive immune functions.
  • Esophagus location and function
    The esophagus is a muscular tube posterior to the trachea that transports the bolus from the pharynx to the stomach.
  • Esophageal mucosa type
    The esophageal mucosa is lined with stratified squamous nonkeratinized epithelium.
  • Muscle composition of the esophagus
    Superior third is skeletal muscle, middle third is mixed skeletal and smooth muscle, and inferior third is smooth muscle.
  • Function of esophageal sphincters
    The esophageal sphincter controls bolus entry into the esophagus; the gastroesophageal sphincter regulates bolus entry into the stomach and prevents reflux.
  • Phases of swallowing (deglutition)
    Swallowing has two phases: buccal (voluntary) where the tongue pushes bolus back, and pharyngeal (involuntary) where the bolus moves through the pharynx.
  • Role of the epiglottis during swallowing
    The epiglottis seals off the larynx to prevent food from entering the airway during swallowing.
  • Stomach location and curvatures
    The stomach is in the left upper quadrant below the diaphragm, with a convex greater curvature on the left and a concave lesser curvature on the right.
  • Four anatomical regions of the stomach
    Cardia, fundus, body, and pyloric antrum (which contains the pyloric sphincter).
  • Unique muscular layer of the stomach
    The stomach has a third oblique layer of smooth muscle in addition to the usual circular and longitudinal layers, aiding in churning.
  • Function of stomach rugae
    Rugae are folds in the stomach lining that allow it to expand considerably when filled.
  • Primary functions of the stomach
    Mechanical breakdown, propulsion, chemical digestion, and absorption (notably aspirin and alcohol).
  • Cell type lining the stomach and its function
    Simple columnar cells secrete alkaline mucus to protect the stomach lining from acidic secretions.
  • Gastric gland cell types and secretions
    Mucous neck cells produce acidic mucus; parietal cells secrete HCl and intrinsic factor; chief cells secrete pepsinogen; enteroendocrine cells release hormones and paracrines.
  • Role of parietal cells
    Parietal cells secrete hydrochloric acid (HCl) to maintain stomach pH ~2 and intrinsic factor necessary for vitamin B12 absorption.
  • Function of chief cells
    Chief cells secrete inactive pepsinogen, which is converted to pepsin to digest proteins.
  • Enteroendocrine cells secretions
    They release paracrine signals like histamine and serotonin, and hormones such as somatostatin and gastrin.
  • Control of gastric secretions
    Gastric secretions are regulated by the parasympathetic nervous system (vagus nerve), short reflexes, and the hormone gastrin.
  • Phases of gastric secretion
    Cephalic phase (triggered by sight, smell, thought of food), gastric phase (stimulated by food in stomach), and intestinal phase (triggered by chyme in duodenum).
  • Mechanism of hydrogen ion secretion in stomach
    Hydrogen ions are pumped into the stomach lumen via the H+/K+ ATPase pump, stimulated by ACh, gastrin, and histamine.
  • Gastric phase acid secretion stimuli
    Distension of stomach wall and presence of partially digested proteins stimulate acid secretion via ENS neurons and gastrin release.
  • Intestinal phase effect on gastric secretion
    Partially digested proteins in duodenum trigger intestinal gastrin release, briefly stimulating acid secretion; acidic or fatty chyme inhibits gastric secretions.
  • Gastric motility and churning
    Gastric pacemaker cells in the myenteric plexus produce peristaltic contractions (~3/min) stimulated by serotonin and intestinal gastrin to churn food.