Digestive system

• Alimentary canal includes: mouth, pharynx, esophagus, stomach, small intestine, and large intestine
• Accessory digestive organs include: teeth, tongue, gallbladder, salivary glands, liver, and pancreas
• Peritoneum is the serous membrane of the abdominal cavity
• Visceral peritoneum covers the external surface of most digestive organs
• Parietal peritoneum lines the body wall
• Peritoneal cavity lubricates digestive organs and allows them to slide across one another
• Mesentery is a double layer of peritoneum that provides vascular and nerve supplies to the viscera and holds digestive organs in place
• Arteries and the organs they serve include: hepatic (liver), splenic (spleen), left gastric (stomach), inferior mesenteric and superior mesenteric (small and large intestines)
• Hepatic portal circulation collects nutrient-rich venous blood from the digestive viscera and delivers it to the liver for metabolic processing and storage
• Histology of the alimentary canal includes four tunics: mucosa, submucosa, muscularis externa, and serosa
• Mucosa is the innermost moist epithelial layer that lines the lumen of the alimentary canal
• Mucosa consists of lining epithelium, lamina propria, and muscularis mucosae
• Mucosa functions include secretion of mucus, absorption of end products of digestion, and protection against infectious diseases
• Submucosa is dense connective tissue containing elastic fibers, blood and lymphatic vessels, lymph nodes, and nerves
• Muscularis externa is responsible for segmentation and peristalsis
• Serosa is the protective visceral peritoneum
• The mouth is lined with stratified squamous epithelium to withstand abrasions
• Tongue functions include gripping and repositioning food, mixing food with saliva, forming the bolus, initiation of swallowing, and speech
• Salivary glands include parotid and submandibular glands
• Teeth are classified into incisors, canines, premolars, and molars based on shape and function
• Tooth structure includes crown, root, neck, dentin, pulp cavity, pulp, root canal, apical foramen, and enamel
• Esophagus is a muscular tube going from the laryngopharynx to the stomach
• Stomach functions include chemical breakdown of proteins and conversion of food to chyme
• Stomach regions include cardiac, fundus, body, and pyloric regions
• Stomach has greater and lesser curvatures, lesser and greater omentum, and rugae
• Microscopic anatomy of the stomach includes epithelial lining with goblet cells, gastric pits, and gastric glands
• Small intestine runs from pyloric sphincter to the ileocecal valve and has three subdivisions: duodenum, jejunum, and ileum
• Structural modifications of the small intestine wall increase surface area with villi and microvilli
• Pancreas structure includes head, body, tail, pancreatic duct, hepatopancreatic ampulla, and accessory duct
• Pancreas histology includes glandular epithelial cells, pancreatic islets, and acini producing pancreatic juice
• Liver is the largest gland in the body with four lobes: right, left, caudate, and quadrate
• Liver associated structures include falciform ligament, ligamentum teres, lesser omentum, hepatic blood vessels, and gallbladder
• Bile leaves the liver via bile ducts and common hepatic duct
• Gallbladder stores and concentrates bile and releases it via the cystic duct
• Large intestine is subdivided into cecum, appendix, colon, rectum, and anal canal
• Colon has distinct regions including ascending, hepatic flexure, transverse, splenic flexure, descending, and sigmoid colon
• Anus has internal and external sphincters for control
• Digestive process includes ingestion, propulsion, mechanical and chemical digestion, absorption, and defecation
• Peristalsis and segmentation aid in moving food through the gastrointestinal tract
• Mesenteries provide support and structure to digestive organs