NUTR 3100: CHPT. 3
64 Cards in this Set
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Hunger and thirst
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physical needs which drive how much and how often we eat
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Appetite
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Influenced by food preferences and psychological stimulation May eat without being hungry or needing nourishment
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We Develop a Taste for Certain FoodsTaste
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Five basic categories Detected by at least 10,000 taste buds mostly on tongue, but also throat and elsewhere in mouth
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Brain recognizes taste
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food dissolves in saliva, contacts the tongue surface, taste cells send nerve impulses to brain, translated into taste sensations
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Digestion
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a multi-step process of breaking down foods into absorbable components using mechanical and chemical means in the gastrointestinal (GI) tract
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Gastrointestinal tract consists of
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Mouth, Esophagus,Stomach ,Small and large intestines ,Other organs
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Main roles of the GI tract are to
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Break down food into smallest components, Absorb nutrients,Prevent microorganism or other harmful compounds in food from entering tissues of the body
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GI tract
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is about 23 feet long with extensive surface area for nutrient absorption
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Cells lining GI tract
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are replaced every three to five days
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Mechanical digestion
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chewing, grinding food to aid swallowing
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Peristalsis
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(mechanical) the forward, rhythmic muscular contraction that moves food through GI tract
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Chemical digestion
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digestive juices and enzymes break down food into absorbable nutrients
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Peristalsis
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Digestion Allows Us to Absorb Nutrients from Foods
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After digestion
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nutrients are absorbed through the walls of the intestines
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the body's two transport systems
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Circulatory system (blood), Lymph system
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Where are nutrients Sent before cells
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to the liver for processing
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GI tract is highly efficient
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92 to 97 percent of nutrients from food are digested and absorbed
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Saliva released
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contains water, electrolytes, mucus and a few enzymes,Softens, lubricates, dissolves food particles
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Bolus
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(food mass) moves into pharynx, is swallowed, and enters the esophagus
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Epiglottis
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closes off trachea during swallowing to prevent food from lodging in the windpipe
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Esophagus
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propels food into the stomach
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Bolus is pushed
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down esophagus by peristalsis
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Lower Esophageal Sphincter (LES)
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at bottom of esophagus relaxes and allows food into stomach
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LES closes
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to prevent backflow of hydrochloric acid (HCl) from stomach"Reflux" of stomach acid causes "heartburn" (irritation of esophagus lining)
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Stomach's mechanical action
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churning mixes food with digestive juices for several hours
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Stomach produces powerful digestive secretions HCl
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activates enzyme pepsin, enhances absorption of minerals, breaks down connective tissue of meat
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Mucus
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protects stomach lining from damage
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Chyme
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semi-liquid substance of partially digested food and digestive juices
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Gastrin
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stimulates digestive activities and secretion of HCl; increases gastric motility and emptying
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Pyloric sphincter
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located between the stomach and small intestine; allows about 1 tsp of chyme to enter the small intestine every 30 seconds Prevents backflow of intestinal contents
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Small intestine Three segments
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Duodenum (10 inches), Jejunum (8 feet), Ileum (12 feet)
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Peristalsis
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moves chyme through intestine
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Segmentation
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mixes chyme with chemical secretions
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Pendular
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movement enhances nutrient absorption
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Chyme moves though
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at rate of 1 centimeter per minute Total contact time 3 to 10 hours, depending on amount and type of food
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Ileocecal sphincter
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prevents backflow of fecal matter into ileum
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Large intestine has three sections
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cecum, colon, rectum, About 5 feet long, 2.5 inches in diameter, Absorbs water and electrolytes
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No digestive enzymes In large Intestine
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chemical digestion done by bacteria
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Intestinal matter passes through colon in
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12 to 70 hours depending on age, health, diet, fiber intake
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Bacteria in colon
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produce vitamin K and biotin and break down fiber and undigested carbohydrates, producing methane, carbon dioxide, hydrogen gas, and other compounds
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Stool stored in rectum Anus controlled by two sphincters
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internal and external
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Complete digestion of chyme requires
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Complete digestion of chyme requires enzymes and Hormones
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Enzymes
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break down food into absorbable nutrient components, Secreted by stomach, small intestine, pancreas, Amylases, lipases, proteases
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Hormones
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gastrin, insulin, glucagon, secretin, cholecystokinin;Control digestive secretions and regulate enzymes
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Liver
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largest gland in body Produces bile needed for fat digestion Metabolism of carbohydrates, fats, and protein
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Liver Stores nutrients
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vitamins A, D, B12, E, copper, iron, glycogen, Detoxifies alcohol
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Gallbladder
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concentrates and stores bile Released into GI tract when fat is ingested
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The Liver, Gallbladder, and Pancreas Are
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Accessory Organs
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Pancreas Produces
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hormones insulin and glucagon regulate blood glucoseSodium bicarbonate neutralizes acidic chyme, protects enzymes from inactivation by acid
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Digestive enzymes
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Amylase, Lipase, Trypsin
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Amylase
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digests carbohydrate
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Lipase
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digests fats
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Trypsin, chymotrypsin, and carboxypeptidase
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digest protein
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Nervous system stimulates your appetite
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Hormone ghrelin signals brain to eat when stomach is empty
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Circulatory system
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transports nutrients, oxygen, waste products through your blood
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Lymphatic system
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distributes fat and fat-soluble nutrients through your lymph
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Excretory system
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eliminates wastes from circulatory system via the urine
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Disorders of the mouth and esophagus
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Gingivitis and periodontal disease
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Swallowing problems
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dysphagia
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Esophageal problems
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Heartburn (acid reflux) may be caused by weak LES Certain foods, smoking, drinking alcohol, being overweight or obese, tight-fitting clothes, reclining after eating, large evening meals may worsen condition
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Disorders of the stomach
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Gastroenteritis, Peptic ulcers
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Gallbladder disease
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Gallstones
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Disorders of the intestines
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Flatulence, Constipation and diarrhea, Hemorrhoids
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More serious intestinal disorders
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Irritable Bowel Syndrome (IBS), Celiac disease, Crohn's disease, Colon cancer
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NUTR 3100: CHAPTER 1