Chapter 15 The Digestive System. The Digestive System Alimentary canal or GI tract Extends from mouth to anus—9 m (29 feet) Involved in digestion, absorption.

Chapter 15The Digestive System

The Digestive System Alimentary canal or GI tract

Extends from mouth to anus—9 m (29 feet) Involved in digestion, absorption and

metabolism of nutrientsSystem includes main and accessory organs

Main organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anal canal

Accessory organs: teeth and tongue, salivary glands, liver, gallbladder, pancreas, and vermiform appendix

Mouth

Roof of the mouth consists of hard and soft palates and uvula

Floor of the mouth consists of tongue and its muscles, papillae, and taste buds

What is the function of the following?Soft palate and uvula? (they work together)

Tongue?

Salivary Glands Three pairs of glands produce about 1 liter of saliva

each day—located outside of GI tract—convey secretions via ducts into tract lumen

Parotid glandsLargest of salivary glands—located in front of ear at

angle of jawDucts open into mouth opposite second molars

People who suffer from dry mouth (or xerostomia) as a result of a medical issue or a side effect from a medication: what are their treatment options?

What is the role of the salivary glands for digestion?

Disorders of the Mouth and TeethProblems include infections, cancer and

congenital defectsSquamous cell carcinoma—most common form of mouth

cancer Dental caries

Tooth disease resulting in permanent defect called “cavity” Infection may spread to other adjacent tissues or to bloodLost or diseased teeth may be replaced by dentures or implants

Gingivitis—gum inflammation or infectionMay result from poor oral hygiene, diabetes, vitamin deficiency, or

pregnancyThrush or oral candidiasis—caused by yeast-like fungal

organismPatches of “cheesy” looking exudate form over an inflamed tongue

and oral mucosa which itches and bleeds easilyCommon in immunosuppressed individuals (AIDS) or after antibiotic

therapy

EsophagusMuscular, mucus-lined tube about 25 cm (10

inches) longConnects pharynx with stomachMuscular walls help push food toward stomachSphincters in GI tract help keep ingested

material moving in one direction down the tubeEach end of esophagus “guarded” by a

sphincter—upper esophageal sphincter (UES) and lower esophageal sphincter (LES)

Esophagus: Practical ApplicationMr. Harrison, your neighbor, has complained

of heartburn and indigestion for over 6 months. He recently went to his physician and was told he has a hiatal hernia. He asks you the following questions:1) What is a hiatal hernia?

2) My doctor told me I have gastroesophageal reflux disease. Can you explain this to me? What symptoms are usually present?

Stomach Size—expands after large meal; about size of

large sausage when emptyPylorus—lower part of stomach; pyloric

sphincter muscle closes opening of pylorus into duodenum

Wall—many smooth muscle fibers; contractions produce churning movements (peristalsis)

Lining—mucous membrane; many microscopic glands that secrete gastric juice and hydrochloric acid into stomach

Stomach: Practical ApplicationStomach cancer is associated with consumption

of alcohol or preserved food and use of chewing tobacco

Mr. Desai is a 45 year old male who had been complaining of stomach pain for several months. He’s also had unintentional weight loss. After an extensive workup, he was discovered to have a Stage 3 gastric cancer. He underwent surgery to remove two-thirds of his stomach.What are the ramifications of this in regards to:

Digestion and metabolism?Eating?Drinking?

Small Intestine Size—about 7 meters (20 feet) long but only 2

cm or so in diameterDivisions

DuodenumJejunumIleum

Wall—contains smooth muscle fibers that contract to produce peristalsis

Lining—mucous membrane; many microscopic glands secrete intestinal juice; villi contain blood and lymph capillaries

Disorders of the Small IntestineEnteritis—intestinal inflammation

What is gastroenteritis?

Malabsorption syndrome—group of symptoms resulting from failure to absorb nutrients properly

Large Intestine Divisions

CecumColon—ascending, transverse, descending, and

sigmoidRectum

Opening to exterior—anusWall—contains smooth muscle fibers that

contract to produce churning, peristalsis, and defecation

Lining—mucous membrane

Disorders of the Large IntestineOften relate to abnormal motility (rate of movement

of contents)Diarrhea results from abnormally increased intestinal

motility; may result in dehydration or convulsionsConstipation results from decreased intestinal motilityDiverticulitis (inflammation of abnormal outpouchings

called diverticula) may cause constipationColitis is the general name for any inflammatory

condition of the large intestineColorectal cancer is a common malignancy of the

colon and rectum associated with colonic polyps; advanced age; low-fiber, high-fat diets; and genetic predisposition

Liver and Gallbladder Size and location—liver is largest gland; fills

upper right section of abdominal cavity and extends over into left side

Liver secretes bileDucts

Hepatic—drains bile from liverCystic—duct by which bile enters and leaves

gallbladderCommon bile—formed by union of hepatic and

cystic ducts; drains bile from hepatic or cystic ducts into duodenum

Liver and Gallbladder

GallbladderLocation—undersurface of the liverFunction—concentrates and stores bile produced in

the liver

Disorders of the liver and gallbladderGallstones—calculi (stones) made of crystallized bile

pigments and calcium saltsCholelithiasis—condition of having gallstones (Figure

17-13)Cholecystitis—inflammation of the gallbladder; may

accompany cholelithiasisCan obstruct bile canals, causing jaundice

Liver and Gallbladder Hepatitis—liver inflammation

Characterized by liver enlargement, jaundice, anorexia, discomfort, gray–white feces, and dark urine

Caused by a variety of factors—toxins, bacteria, viruses, and parasites

Cirrhosis—degeneration of liver tissue involving replacement of normal (but damaged) tissue with fibrous and fatty tissue

Portal hypertension—high blood pressure in the hepatic portal veins caused by obstruction of blood flow in a diseased liver; may cause varicosities of surrounding systemic veins

Pancreas Location—behind stomach Functions

Pancreatic cells secrete pancreatic juice into pancreatic ducts; main duct empties into duodenum

Pancreatic islets (of Langerhans)—cells not connected with pancreatic ducts; secrete hormones glucagons and insulin into the blood

Pancreas Pancreatic disorders

Pancreatitis—inflammation of pancreas; acute pancreatitis results from blocked ducts that force pancreatic juice to backflow, digesting the gland

Cystic fibrosis—thick secretions block flow of pancreatic juice

Pancreatic cancer is very serious—fatal in the majority of cases

Appendix and AppendicitisBlind tube off cecum; no important digestive

function in humansAppendicitis—inflammation or infection of

appendix; if appendix ruptures, infectious material may spread to other organs

Energy ProductionAdenosine triphosphate (ATP)—molecule in

which energy obtained from breakdown of foods (glucose) is storedserves as a direct source of energy for

cellular work Produced in the Krebs cycle, which needs

oxygen to work (so aerobic); occurs in the mitochondria

Can produce ATP anaerobically with ATP-Phosphocreatine system or lactic acid system both of which occur in the muscles

Peritoneum Definitions—peritoneum, serous membrane lining

abdominal cavity and covering abdominal organs; parietal layer of peritoneum lines abdominal cavity; visceral layer of peritoneum covers abdominal organs; peritoneal space lies between parietal and visceral layers

Peritonitis—inflammation of peritoneum resulting from infection or other irritant; often a complication of ruptured appendix

Ascites—abnormal accumulation of fluid in peritoneal space, often causing bloating of abdomen

Chapter 16 Nutrition and Metabolism

Nutrition and MetabolismWhat do each of these terms mean to you?

Some important definitions to know:Catabolism—breaks food molecules down,

releasing their stored energy; oxygen used in catabolism

Anabolism—builds food molecules into complex substances

Carbohydrate metabolismCarbohydrates are primarily catabolized for

energy, but small amounts are anabolized by glycogenesis (a series of chemical reactions that changes glucose to glycogen—occurs mainly in liver cells where glycogen is stored)

Blood glucose (imprecisely, blood sugar)—normally stays between about 80 and 120 mg per 100 ml of blood; insulin accelerates the movement of glucose out of the blood into cells, therefore decreases blood glucose and increases glucose catabolism

Fat and Protein MetabolismFats mainly used for energy and storage

catabolized to yield energy and anabolized to form adipose tissue

Broken down into fatty acids and glycerol

Proteins primarily anabolized and secondarily catabolizedProteins can be converted to glucose if needed

through a process called gluconeogenesisCannot make protein from either fat or

carbohydrate due to a lack of Nitrogen

Vitamins and MineralsVitamins—organic molecules that are

needed in small amounts for normal metabolismAvitaminosis—deficiency of a vitamin, such

as avitaminosis C (vitamin C deficiency)Hypervitaminosis—excess of a vitamin, such

as hypervitaminosis A (excess of vitamin A)

Minerals—inorganic molecules required by the body for normal function

Metabolic ratesBasal metabolic rate (BMR)—rate of

metabolism when a person is lying down, is awake, is not digesting food, and the environment is comfortably warm

Total metabolic rate (TMR)—the total amounts of energy, expressed in calories, used by the body per day

Questions???