GI system A&P

8/9/2019 GI system A&P

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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.

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