Digestion and Absorption. Digestion Breaks down Carbohydrates (starch and sugar) → single sugar...
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Transcript of Digestion and Absorption. Digestion Breaks down Carbohydrates (starch and sugar) → single sugar...
Digestion and
Absorption
Digestion
Breaks down
Carbohydrates (starch and sugar) → single sugar molecules
Proteins → amino acids
Fats → fatty acids, glycerol
Enzymes
Proteins that break bonds
The Digestive System
Is a long tube from the mouth to the anus
Digestive System
Mouth to anusEpithelium lines the lumenBarrier to invadersSubmucosal layerMuscularis
Taste and smell
Peristalsis
Muscular contractions that move food along throughout GI tract
The Mouth
Mastication: chewing
SalivaEnzymes to help breakdown simple sugarsMucus to lubricate the food for easier
swallowingLysozyme to kill bacteria
TongueTaste receptors: sweet, sour, salty,
bitter, savoryEnzymes to help break down fatty acids
SwallowingBolus is the food swallowed at one time
Epiglottis blocks windpipe, prevents choking
The Esophagus
Long tube
Connects pharynx to the stomach
Peristalsis, muscle contraction
Lower esophageal sphincter
Heartburn
The Stomach
Lower esophageal sphincter and pyloric sphincterStorage capacity of ~4 cupsSecretion of acid, enzymes, and intrinsic factorHolds food for 2-4 hoursFormation of chymeMucus layer protects stomach from digestionVery little absorption of nutrients
Physiology of the Stomach
Stomach Acid
Activates digestive enzymes
Partially digests dietary protein
Assists in calcium absorption
Makes dietary minerals soluble for absorption
The Small Intestine
Most digestion and absorption happens hereAbout 10 feet longDuodenum (10 inches)Jejunum (4 feet) Ileum (5 feet)
Folded walls with villi projectionsAbsorptive cells are located on the villiIncreases intestinal surface area 600x Rapid cell turnover
The Small Intestine
Nutrient AbsorptionPassive diffusion: driven by concentration; fats, water, some minerals
Active absorption: uses energy; glucose and amino acids
Phagocytosis and pinocytosis: absorptive cells engulf compounds, generally larger molecules, as in immune substances in breast milk
Nutrient Absorption
Site of Absorption
Absorption
Digestion → small particles
End products of digestion:
Carbohydrates → monosaccharides
Proteins → amino acids
Fats → glycerol, fatty acids
Absorption
Through small intestine walls
Absorbed into
Blood – water soluble nutrients
Lymph – fat soluble nutrients
Blood → liver → general circulationLiver detoxifies and repackages
The Large Intestine
~3 1/2 feet in lengthNo villi or enzymes presentLittle digestion occursIndigestible food stuff Absorption of water, some minerals, vitaminsContains bacteria which break down fiber; produce Vitamin KFormation of feces for elimination
Rectum
Stool remains
Stimulates elimination
Muscle contraction
Anal sphinctersVoluntary controlOpens for elimination
Accessory Organs
Salivary glands
Pancreas
Gallbladder
Liver
Salivary Glands
Saliva
Works in mouth
Moistens
Salivary amylase Digests starch
The Pancreas
Produces glucagon and insulin (endocrine)
Manufactures digestive enzymes→ small intestine
Secretes pancreatic juices
Bicarbonate needed to neutralize chyme when it enters small intestine
The Liver
Produces bile (fat digestion)
Enterohepatic circulation
The Gallbladder
Stores bile
Concentrates it
Releases to small intestine when needed
The Urinary System
Kidneys
Ureter
Bladder
Urethra
Removes waste products
Regulates blood acid-base balance
Proper function determined by cardiovascular system, fluid intake, and drug use
Exchange of Nutrients
Insert Fig. 3-4
Nutrient Storage Capabilities
System of maintaining reserves
Adipose tissue
Glucose
Amino acids in the blood
Vitamins and minerals in the liver
Calcium in bones
UlcersHelicobacter pylori Excessive use of aspirinExcessive acid production StressStomach loses its mucus protectionS/S: pain in ~2 hrs after eatingRx: Antibiotics, antacid, refrain from smoking, limit use of aspirin and aspirin like meds.
Heartburn
S/S: Gnawing pain in the upper chest
Movement of acid from the stomach into the esophagus
Gastroesophageal reflux disease (GERD)
Rx: smaller, more frequent meals, low fat, wait 2 hours before lying down, refrain from smoking, low excess weight, limit spicy foods, medication
Constipation
Difficult or infrequent bowel movement
Caused by slow motility, medication, &/or supplements of calcium/iron
Feces stay in the large intestine longer
Ignore normal urges to defecate
Rx: Eat plenty of dietary fiber, drink more fluids, regular physical activity
Laxatives
Irritate the intestinal nerve to stimulate peristaltic muscles or
Draws water into the intestine
Regular use can decrease muscle action in the large intestine
GI tract becomes dependent on laxatives
Hemorrhoids
Swollen veins of the rectum and anus
Intense pressure and straining
S/S: pain, itching, bleeding
Rx: eat plenty of fiber and fluid
Irritable Bowel Syndrome
S/S: Cramps, gassiness, bloating, irregular bowel functionPossibly caused by altered intestinal peristalsis and decreased pain thresholdRx: individualized, elimination diet, moderate caffeine, low fat, small meals, stress reduction
Diarrhea
Increased fluidity, frequency, or amount of bowel movement
Usually caused by an infection in the intestine
Bacteria and viruses cause the intestinal cells to secrete fluid
Rx: plenty of fluid