Chapter 26 Digestive System Part 2, Stomach, Intestines, Rectum

Fig (a) Stomach regions, anterior view Stomach Body Muscularis Longitudinal layer Circular layer Oblique layer Fundus Gastric folds Pyloric antrum Pylorus Pyloric canal Duodenum Pyloric orifice Pyloric sphincter Esophagus Cardia Entryway to stomach is cardia Opening between esophagus and cardia is cardiac orifice Fundus is lateral and superior to cardiac orifice

Fig (a) Stomach regions, anterior view Stomach Body Muscularis Longitudinal layer Circular layer Oblique layer Fundus Gastric folds Pyloric antrum Pylorus Pyloric canal Duodenum Pyloric orifice Pyloric sphincter Esophagus Cardia Largest part of stomach is body Pyloris is funnel-shaped pouch Pyloric antrum is near body of stomach Pyloric canal attaches to duodenum opening to duodenum called pyloric orifice, ringed by pyloric sphincter

Fig Gastric folds (AKA rugae) stretch to accommodate meal increase surface area for digestion Stomach Esophagus Cardiac orifice Gastric folds Diaphragm Gastric folds Liver (cut) Lesser curvature Body of stomach Pylorus of stomach Greater curvature (c) Gross anatomy of stomach (cut open)

Fig Lining is simple columnar epithelium little absorption in stomach Mucous cells secrete mucin Gastric pits are indentations in lining Stomach LM 50x Simple columnar epithelium Stratified squamous epithelium Esophageal- stomach border Gastric pits (b) Esophageal-stomach border

Fig Muscularis has 3 muscle layers inner oblique layer middle circular outer longitudinal Ensures plenty of churning Stomach Mucosa (a) Stomach wall, sectional view Myenteric nerve plexus Submucosal nerve plexus Vein Artery Serosa Muscularis Submucosa Muscularis mucosae Oblique layer Circular layer Longitudinal layer Lamina propria Simple columnar epithelium Gastric pit Stomach lumen Blood vessel Lymph vessel

Fig At base of gastric pits are gastric glands release gastric juices 5 types of gastric gland cells Stomach LM 60x (b) Stomach mucosa Stomach lumen Gastric pit Gastric glands

Fig Surface mucous cell (secretes alkaline fluid containing mucin) (c) Gastric pit and gland Simple columnar epithelium Gastric pit Gastric gland Mucin prevents ulceration of lining of stomach Other cells in gastric gland produce acid, enzymes, etc. to aid digestion

Page 794 Mucosa Submucosa Muscularis Serosa (b) Perforated gastric ulcer (a) Common locations of gastric and duodenal ulcers Duodenum Duodenal ulcer Gastric ulcers Ulcers most often caused by bacterium Helicobacter pylori However, H. pylori probably protects against reflux

Fig About 6m (20ft) in unembalmed cadaver Extends from pyloris of stomach to cecum of large intestine Small intestine Accessory organs Duodenojejunal flexure Small intestine Ileum Jejunum Duodenum Large intestine Ileocecal valve Cecum Liver Gallbladder Pancreas

Fig Duodenum is first segment; 25cm long Curves around pancreas Joins jejunum at duodenojejunal flexure Mostly retroperitoneal Small intestine Duodenojejunal flexure Small intestine Ileum Jejunum Duodenum

Fig Jejunum is 2.5 m long (2/5 total length of small intestine) Primary site of absorption and chemical digestion Intraperitoneal; suspended by mesentery proper Small intestine Duodenojejunal flexure Small intestine Ileum Jejunum Duodenum

Fig Ileum is 3.6 m long (3/5 total length of small intestine) Ends at ileocecal valve Intraperitoneal; suspended by mesentery proper Small intestine Duodenojejunal flexure Small intestine Ileum Jejunum Duodenum Ileocecal valve Cecum

Fig Serosa Outer longitudinal layer Inner circular layer Submucosa Mucosa (a) Small intestine tunics Serosa Outer longitudinal layer Muscularis Submucosa Mucosa Small intestine (b) Section of small intestine Circular folds Intestinal villi Inner circular layer Circular fold Muscularis Circular folds inside small intestine add surface area act as “speed bumps” to slow movement of chyme more numerous in duodenum and jejunum than in ileum

Fig (c) Intestinal villus Villi are microscopic, fingerlike projections on circular folds further increase surface area

Fig Simple columnar epithelial cells Mucosa (c) Intestinal villus Epithelium Goblet cells Lacteal Lymphatic nodule Capillary network Lamina propria Submucosa Arteriole Lymph vessel Venule Muscularis mucosae Each villus contains capillary bed and lacteal Submucosa has lymph vessels, arterioles and venules

Fig Inferior mesenteric artery Descending abdominal aorta Tenia coli Omental appendices Transverse mesocolon Sigmoid colon Descending colon Sigmoid mesocolon Anal canal (a) Large intestine, anterior view Rectum Vermiform appendix Ileum Cecum Ileocecal valve Superior mesenteric artery Haustrum Right colic flexure Cecum Ascending colon Transverse colon Left colic flexure Large intestine Total length 1.5m Diameter 6.5cm Receives about 1L of 3-4L that entered small intestine

Fig Sigmoid colon Descending colon Cecum Ascending colon Transverse colon Large intestine Cecum is first region extends inferiorly from ileocecal valve Vermiform appendix (AKA appendix) Ileocecal valve Vermiform appendix

Mesentery for appendix Inflamed appendix Copyright © McGraw-Hill Education. Permission required for reproduction or display. © Medicimage/Phototake Inflamed appendix Appendicitis Inflammation of the appendix, usually because fecal matter obstructs appendix If appendix bursts, contents causes infection called peritonitis Spasms of smooth muscle in appendix cause pain, often referred to T10 dermatome around umbilicus More advanced appendicitis felt in lower right quadrant of torso

Fig Sigmoid colon Descending colon Cecum Ascending colon Transverse colon Large intestine Colon begins at ileocecal valve 4 segments of colon ascending (retroperitoneal) transverse (intraperitoneal) descending (retroperitoneal) sigmoid (intraperitoneal) Ileocecal valve Vermiform appendix

Fig Inferior mesenteric artery Descending abdominal aorta Transverse mesocolon (a) Large intestine, anterior view Ileum Superior mesenteric artery Right colic flexure Left colic flexure Ascending colon becomes transverse colon at right colic flexure Transverse colon ends at left colic flexure Transverse colon is held to posterior abdominal wall by mesentery called transverse mesocolon

Fig Inferior mesenteric artery Descending abdominal aorta Transverse mesocolon Sigmoid mesocolon (a) Large intestine, anterior view Superior mesenteric artery Right colic flexure Left colic flexure Descending colon becomes sigmoid colon at sigmoid flexure Sigmoid colon is held in place by mesentery called sigmoid mesocolon Sigmoid flexure

Fig Teniae coli (a) Large intestine, anterior view Longitudinal muscles of colon form 3 thin bundles called teniae coli cause colon to bunch into haustra Haustra

Page 799 Diverticula are out- pockets of intestinal wall most common in sigmoid colon likely caused by low-fiber diet causing strain on colon presence of diverticula called diverticulosis inflammation called diverticulitis (b)(a) Diverticula Diverticulosis (a) An external view of the sigmoid colon showing diverticula. (b) An endoscopic view of diverticula. Copyright © McGraw-Hill Education. Permission required for reproduction or display. b: Photo courtesy Interactive Atlas of Gastrointestinal Endoscopy by Edgar Jaramillo, available free of charge at

Fig Anal canal (a) Large intestine, anterior view Rectum Rectum is retroperitoneal Muscular tube that stretches to accommodate fecal matter

Fig Anus External anal sphincter Internal anal sphincter Veins Anal canal Rectal valve Levator ani muscle Anal sinuses Anal columns Rectum (b) Anal canal Rectal valves ensure fecal matter stays put during farts Fecal matter leaves body through anal canal Anal canal has internal and external anal sphincters

Fig Mucosa Submucosa Muscularis Outer longitudinal layer of muscularis (tenia coli) (a) Large intestine tunics Serosa (or adventitia) Nerves Inner circular layer of muscularis Muscularis mucosae Lymphatic nodule Lamina propria Intestinal gland Simple columnar epithelium Opening to intestinal gland Goblet cells Venule Arteriole Mucosa of colon is simple columnar epithelium (absorb nutrients) and goblet cells (secrete mucin) No villi Numerous glands

Fig Mucosa LM 80x Submucosa (b) Large intestine mucosa and submucosa Muscularis mucosae Intestinal gland Simple columnar epithelium Goblet cells Opening to intestinal gland

Page 800 Colorectal cancer most common in descending colon Arises from polyps, outgrowths of colon mucosa most polyps never become cancerous Linked to low-fiber diets Often without symptoms; sometimes rectal bleeding, constipation, abdominal pain, unexplained weight loss Copyright © McGraw-Hill Education. Permission required for reproduction or display. Colorectal cancer Polyp Large intestine, frontal section Polyps Polyps in the large intestine sometimes lead to colorectal cancer.

Liver celebrates New Year’s Eve

Fig Gallbladder Round ligament of liver Falciform ligament (a) Anterior view Left lobe Inferior vena cava Right lobe Liver Produces bile greenish fluid that breaks down fats stored in gallbladder Detoxifies drugs, metabolites, and poisons Stores excess nutrients (especially fats) and vitamins releases as needed by body Synthesizes blood plasma proteins Helps recycle old red blood cells

Fig Gallbladder Round ligament of liver Falciform ligament (a) Anterior view Left lobe Inferior vena cava Right lobe Liver 4 incompletely separated lobes right lobe and left lobe are major lobes Supported by ligaments falciform ligament separates right and left lobes and secures liver to anterior abdominal wall inferior edge is round ligament of the liver (AKA ligamentum teres) is remnant of umbilical vein

Normal, healthy liverFatty liver

Page 804 (a) Nodular cirrhosis of the liver(b) Histology of liver cirrhosis Normal hepatocytes Fibrous scar tissue LM 100x (a) This gross specimen depicts a type of nodular cirrhosis of the liver. (b) A photomicrograph shows how scar tissue infiltrates and replaces hepatocytes. Steatohepatitis image by Nephron

Fig Common bile duct Duodenum Major duodenal papilla Hepatopancreatic ampulla with hepatopancreatic sphincter Minor duodenal papilla Fundus Stored bile Gallbladder Body Neck Cystic duct Common hepatic duct Left and right hepatic ducts Gallbladder Stores and concentrates bile secreted by hepatocytes 3 regions Neck; sphincter controls flow into and out of gallbladder Body Fundus

Fig Common bile duct Duodenum Major duodenal papilla Hepatopancreatic ampulla with hepatopancreatic sphincter Minor duodenal papilla Fundus Stored bile Gallbladder Body Neck Cystic duct Common hepatic duct Left and right hepatic ducts Gallbladder Bile flows out of liver through left and right hepatic ducts, then common hepatic duct Bile flows into and out of gallbladder through cystic duct then into common bile duct to duodenum Enters duodenum at major duodenal papilla

Page 806 Photo of gallstones in a gallbladder. Copyright © McGraw-Hill Education. Permission required for reproduction or display. © Gladden Willis/Visuals Unlimited Gallstones Caused by high concentrations of certain materials More common in women, Caucasian people, and in developed countries Linked to obesity, age, female sex hormones, lack of physical activity Treatment: removal of gallbladder (cholecystectomy) liver continues to produce bile

Fig Jejunum Tail of pancreas Body of pancreas Main pancreatic duct Common bile duct Duodenum Accessory pancreatic duct Hepatopancreatic ampulla Major duodenal papilla (a) Duodenum and pancreas, anterior view Head of pancreas Pancreas Duodenojejunal flexure Sits above and behind stomach Retroperitoneal Wide head, long body, small tail touches spleen

Fig Jejunum Tail of pancreas Body of pancreas Main pancreatic duct Common bile duct Duodenum Accessory pancreatic duct Hepatopancreatic ampulla Major duodenal papilla (a) Duodenum and pancreas, anterior view Head of pancreas Pancreas Duodenojejunal flexure Endocrine function: produces insulin to help some tissues take up glucose Exocrine function: produces enzymes for digestion

Fig Jejunum Tail of pancreas Body of pancreas Main pancreatic duct Common bile duct Duodenum Accessory pancreatic duct Hepatopancreatic ampulla Major duodenal papilla (a) Duodenum and pancreas, anterior view Head of pancreas Pancreas Duodenojejunal flexure Creates pancreatic juice (digestive enzymes and bicarbonate) released into duodenum

Fig Pancreatic acini Acinar cell LM 75x Pancreatic islet LM 200x (b) Histology of pancreas Pancreatic acinus Pancreas Acinar cells are modified simple cuboidal epithelial cells organized into clusters called acini (AKA lobules) secrete mucin and digestive enzymes into pancreatic ducts Unite to form main pancreatic duct Cells lining ducts produce bicarbonate (alkaline) Pancreatic ducts Main pancreatic duct

Fig Main pancreatic duct Common bile duct Duodenum Minor duodenal papilla Hepatopancreatic ampulla Major duodenal papilla (a) Duodenum and pancreas, anterior view Pancreas Pancreatic juices and bicarbonate flow into duodenum Main pancreatic duct drains into main duodenal papilla combines with common bile duct at hepatopancreatic ampulla Accessory pancreatic duct drains into minor duodenal papilla Accessory pancreatic duct

Fig Left and right hepatic ducts merge to form a common hepatic duct. Common hepatic and cystic ducts merge to form a common bile duct. Accessory pancreatic duct Common bile duct Duodenum Major duodenal papilla Hepatopancreatic ampulla with hepatopancreatic sphincter Minor duodenal papilla Fundus Stored bile Gallbladder Body Neck Cystic duct Common hepatic duct Left and right hepatic ducts