Human Anatomy Unit 2 DIGESTIVE SYSTEM Abdominopelvic Quadrants Abdominopelvic Regions Body Cavi<es Body Cavi<es Serous Membranes • A simple squamous epithelium and its underlying connec<ve ssue – Produces a serous fluid – Lubricates, prevent fric<onal damage • Pericardial cavity – Visceral pericardium – Parietal pericardium • Pleural cavity – Visceral pleura – Parietal pleura • Abdominal cavity – Visceral peritoneum – Parietal peritoneum Components of the Diges<ve System Funcons • Mo<lity – ingeson – mas<caon – degluon – peristalsis • Secreon – exocrine – endocrine • Digeson • Absorp<on Terminology • Inges<on • to take in food • Mas<caon • chewing (mechanical breakdown of food) • Degluon • swallowing • Digeson • chemical breakdown of food • Absorp<on • passage of nutrients from the gi tract lumen to the blood • Peristalsis • Waves of smooth muscle contrac<on to propel food • Defecaon • formaon and excre<on of solid waste Mucosa • Absorp<ve layer, large surface area • 3 major components – Mucosal epithelium • Columnar epithelium (stomach, intes<nes) or strafied squamous • Crypts of Leiberkuhn – folds in the mucosa of the small intes<nes, colon – source of new epithelial cells – diges<ve enzymes – Lamina propria • Loose CT of the mucosa, with capillaries that receive absorbed nutrients • lymphac <ssue: capillaries and lymphac nodules involved in absorp<on of fat • Peyer’s Patches: aggregates of lymph nodes, significant protec<on against intes<nal infec<ons – Muscularis mucosa • a thin layer of smooth muscle that keeps the folds of the mucosa folded Submucosa, Muscularis Externa, Serosa • Submucosa – <ssue: dense irregular CT – Submucosal plexus • nerve supply to the muscularis mucosa • Muscularis Externa – mainly a double layer of smooth muscle, propels and mixes diges<ve contents • circular layer: thick inner layer, muscle fibers describe a circle • longitudinal layer: thin outer layer, muscle fibers run along the length of the GI tract – Myenteric plexus: nerve supply to the muscularis externa • Serosa – loose CT + simple squamous epithelium – outer wall of the GI tract – Is the visceral peritoneum Enteric Nervous System Movement Through the Diges<ve Tube Mesentaries • Sheets of serous membrane that connect the parietal and visceral peritoneum – Suspends organs in the space – Provides a route for blood vessels, nerves, lymphacs • Lesser omentum • Greater omentum • Mesentery proper • Mesocolon • Transverse mesocolon • Sigmoidal mesocolon Mesentaries Oral Cavity The Tongue • Body • Root • Papillae • Taste buds • Frenulum Salivary Glands • Release water, lysozyme, diges<ve enzymes, mucus – Salivary amylase • Paro<d – Pure serous – Paro<d duct • Sublingual – Pure mucus – Sublingual ducts • numerous • Submandibular – Mixed serous/mucus – Submandibular ducts • numerous Teeth • Neck • Crown • Gingivae • Enamel • Denne • Pulp cavity – Apical foramen • Periodontal ligaments • Cementum Types of Teeth Pharynx • Passageway for air, water, food • Divisions – Nasopharynx – Oropharynx – Laryngeal pharynx Swallowing Esophagus • Funcon – move food to the stomach • Lining epithelium – strafied squamous • Muscle layer – 1st third • skeletal muscle – 2nd third • a mixture of skeletal and smooth muscle – 3rd third • smooth muscle Esophageal Gastric Juncture Gross Anatomy of the Stomach • Lesser curvature • Greater curvature • Cardia – Cardiac orifice • Fundus • Body • Pylorus – Pyloric sphincter • Rugae Layers of the Stomach Func<ons of the Stomach • Funcons – Food storage – Chemical diges<on • Chief cells • Parietal cells – Mechanical diges<on • Churning by 3 layers of smooth muscle – Kills bacteria – Moves food to SI – Hormonal regulaon of digeson • G cells Histology of the Stomach • Lining epithelium – simple columnar epithelium – Mucon neck cells • Gastric glands – microscopic folds, secrete gastric juice. • Gastric pits – openings from gastric glands to gastric lumen The Small Intes<ne • ~ 3 meters long • Funcon – Diges<on and absorp<on • Duodenum • Jejunum • Ileum • Support of the small intes<ne – Mesentary proper Intes<nal Surface Area • Plicae circularis – macroscopic permanent folds (permanent un<l death) – Circular pleats like conduit • Villi – fingerlike projecons • Microvilli – submicroscopic folds on apical surface of columnar cells – “brush border” Histological Organizaon of the Small Intes<ne Serosa versus Adven<<a Histology of the Small Intes<ne • Intes<nal villi • Microvilli • Goblet cells • Crypts of Lieberkühn Large Intes<ne • Cecum – Ileal papilla – Iliocecal valve – appendix • The colon – Thin wall – Larger diameter – Haustra – Taeniae coli Appendix: an extension of lymphac – Fay appendices <ssue near the ileocecal junc<on Regions of the Colon • Ascending colon – Right colic flexure • Transverse colon – Lec colic flexure • Descending colon • Sigmoid colon – Sigmoid flexure The Rectum • Last 15 cm • Anal canal • Anal columns • Internal anal sphincter • External anal sphincter Histology of The Large Intes<ne • Lacks villi • Abundant goblet cells • Intes<nal crypts – Deeper – More goblet cells • Large lymphoid nodules • Taenia coli – Reduced longitudinal muscularis layer Accessory Glandular Diges<ve Organs • Liver • Gall bladder • Pancreas Anatomy of the Liver • Lobes – Lec, right, caudate, quadrate • Ligaments – Falciform ligament • Liver to anterior body wall – Coronary ligament • Liver to diaphragm – Ligamentum teres hepas (also called the round ligament) • Falciform ligament to umbilicus • Lec, right hepac ducts Liver Lobules • Func<onal unit of the liver • Hepac triad – Hepac artery – Hepac portal vein – Bile duct • Bile canaliculi • Hepatocytes – Hepac plates (cords) • Kupffer cells – macrophages • Central vein • Sinusoids The Gall Bladder • Fundus • Body • Neck • Stores, concentrates bile • Ducts – Lec, right hepac ducts – Common hepac duct – Cys<c duct – Common bile duct • Hepatopancreac sphincter – Ampulla of Vater – Sphincter of Oddi The Pancreas • Head • Body • Tail • Pancreac duct – Sphincter of Oddi • Accessory pancreac duct – Duct of Santorini Histology of the Pancreas • Pancreac acini – Exocrine glands – Pancreac juice • Islets of Langerhans – Endocrine glands – Alpha cells • glucagon – Beta cells • insulin .