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.
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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???
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