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GASTROINTESTINAL SYSTEM
ANATOMY AND PHYSIOLOGY
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PYRAMID POINTSy The order of anatomical structures of the
gastrointestinal (GI) tract
y Digestion and gastrointestinal enzymesy Location and function of the structures responsible for
various gastrointestinal disorders
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FUNCTIONS OF THE GI SYSTEM
y Process food substances
yAbsorb the products of digestion into the blood
y Excrete unabsorbed materialsy Provide an environment for microorganisms to
synthesize nutrients such as vitamin K
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GASTROINTESTINAL SYSTEM
From Black, Hawks, & Keene (2001), Medical-Surgical Nursing (6th ed),
W.B. Saunders.
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MOUTH
From Phipps WJ, Sands, J, Marek JF: Medical-surgical nursing: concepts and clinical practice, ed.6, St. Louis, 1999, Mosby.
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ESOPHAGUS
yA collapsible muscular tube, about 10 inches long
y Carries food from the pharynx to the stomach
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ESOPHAGUS
From Beare PG, Myers JL (1998), Adult Health Nursing, ed. 3 St. Louis: Mosby.
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STOMACHy Consists of the cardia, fundus, the body, and the
pylorus
y
Mucous Glandsy Located in mucosa
y Prevent autodigestion by providing an alkalineprotective covering
y Lower Esophageal (Cardiac) Sphinctery Prevents reflux of gastric contents into the esophagus
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STOMACHy Pyloric Sphincter
y Regulates the rate of stomach emptying into the small
intestiney Hydrochloric Acid
y Kills microorganisms, breaks food into small particles,and provides a chemical environment that is required bythe gastric enzymes
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STOMACHy Pepsin
y The chief coenzyme of gastric juice, which converts
proteins into proteases and peptonesy Intrinsic factor
y Necessary for the absorption of vitamin B12
y Gastrin
y Controls gastric acidity
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STOMACH
From Ignatavicius, D. & Workman, M. (2002). Medical-surgical nursing: Critical thinking for collaborative care,ed 4, Philadelphia: W.B. Saunders.
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SMALL INTESTINEy Duodenum
y Contains the openings of the bile and pancreatic ducts
yJejunumy Approximately 8 feet long
y Ileum
y Approximately 12 feet long
y The small intestine terminates into the cecum
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SMALL INTESTINE
From Mosbys Medical, Nursing, and Allied Health Dictionary, ed 6, (2002). St Louis: Mosby.
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PANCREATIC INTESTINAL JUICE
ENZYMES
yAmylase digests starch to maltose
y Maltase reduces maltose to monosaccharide glucose
y Lactase splits lactose into galactose and glucosey Sucrase reduces sucrose to fructose and glucose
y Nucleoses split nucleic acids to nucleotides
y Enterokinase activates trypsinogen to trypsin
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LARGE INTESTINEyApproximately 5 feet long
yAbsorbs water and eliminates wastes
y Manufacture of vitamins, including some B vitaminsand vitamin K
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LARGE INTESTINE
yAscending
y Transverse
y Descendingy Sigmoid
y Rectum
y Ileocecal valve: Prevents contents of large intestine
from entering ileumyAnal sphincters: Guard the anal canal
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LARGE INTESTINE
From Mosbys Medical, Nursing, and Allied Health Dictionary, ed 6, (2002). St Louis: Mosby.
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PERITONEUM
y Lines the abdominal cavity
y Forms the mesentery that supports the intestines and
blood supply
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LIVER
y The largest gland in the body, weighing 3 to 4 pounds
y Contains Kupffers cells, which remove bacteria in the
portal venous bloody Removes excess glucose and amino acids from the
portal blood
y Synthesizes glucose, amino acids, and fats
yAids in the digestion of fats, carbohydrates, andproteins
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LIVERy Stores and filters blood (200 to 400 ml of blood
stored)
yStores vitamin A, D, B12, and iron
y Secretes bile to emulsify fats (500 to 1000 ml of bile aday)
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HEPATIC DUCTSy Deliver bile to the gallbladder via the cystic duct
y Deliver bile to the duodenum via the common bile
ducty The common bile duct opens into the duodenum, with
the pancreatic duct at the ampulla of Vater
y The sphincter prevents the reflux of intestinal
contents into the common bile duct and pancreaticduct
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GALLBLADDERy Stores and concentrates bile
y Contracts to force bile into the duodenum during the
digestion of fatsy The cystic duct joins the hepatic duct to form the
common bile duct
y The sphincter of Oddi guards the entrance into theduodenum
y The presence of fatty materials in the duodenumstimulates the liberation of cholecystokinin, whichcauses contraction of the gallbladder and relaxation ofthe sphincter of Oddi
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PANCREAS, LIVER, AND
GALLBLADDER
From Ignatavicius, D. & Workman, M. (2002). Medical-surgical nursing: Critical thinking for
collaborative care, ed 4, Philadelphia: W.B. Saunders.
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PANCREAS
y ENDOCRINE FUNCTIONS
y Insulin secretion is produced by the islets of Langerhans
y Insulin is secreted into the bloodstream and isimportant for carbohydrate metabolism
y Secretes glucagon to raise blood glucose levels
y Secretes somatostatin to exert a hypoglycemic effect
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PANCREAS
From Beare, P. & Myers, J. (1998). Adult health nursing, ed 3, St Louis: Mosby.