TOPICS: Hypertrophic pyloric stenosis, gastric outlet, inner circular layer, peristaltic waves, olive-shaped mass, hypokalemic hypochloremic metabolic alkalosis, midgut, foregut, hindgut, layers of the intestinal wall, Brunner’s glands, serosa (adventitia, myenteric plexus, submucosal plexus, Peyer’s patches, lamina propria, muscularis mucosae, submucosa, inner muscular layer, outer muscular layer, muscularis propria, projectile vomiting, principal cell, alpha-intercalated cell, hypertrophic pyloric stenosis risk factors, Azithromycin, Erythromycin, pancreas development, dorsal pancreatic bud, ventral pancreatic bud, ventral mesentery, uncinate process, normal pancreatic rotation, pancreas abnormalities, annular pancreas, spleen development, pancreas divisum, duodenum, pancreatitis, foregut vasculature, spleen, celiac trunk, splenic artery, mesoderm, hematopoiesis, Hirschsprung disease, neuroblasts, neural crest cells, meconium