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Nutrition Ch 3

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Anatomical flow through the GI tract
Mouth, espohagus, stomach, small intestine (pancreas, gall bladder & liver dump into sm int), and large intestine
Four accessory organs to the GI tract
Salivary glands, pancreas, liver, gallbladder
Three main functions of the GI tract
Digestion, absorption, elimination
Digestion
Breakdown of lg food molecules to smaller by the means of
Physical (mechanical) and chemical
Absorption
Process of taking digested products through the intestinal wall into the intestinal cell and then releasing into the body
Elimination
Undigested portions of food and waste products are removed from the body
Chemical digestion
Breakdown of nutrients by digestive enzymes
Chemical digestion requirement
Emzymes and water for hydrolysis to breakdown the different macronutrients (bonds)
Breaks down food to create increased surface area
Chewing
Control center for the digestive process
Brain and CNS
Enzymes are....
Macronutrient specific
Lipase
Lipid enzyme
Carbohydrase (amylase)
CHO enzyme
Protease
Protein enzyme
Function of sphincters
Control the flow of food from one digestive organ to the next.
Circular muscles that close off one digestive organ from another
Peristalsis
Wave like muscular contractions that propel digesting food forward through the GI tract
Segmentation
Muscular action causing physical digestion of food by breaking down into smaller pieces
Haustra
Segmentations in the colon that contract sluggishly to move contents
Mass movement
Occurs in large intestine to move waste towards the rectum
Homeostasis
Physiological equilibrium or stability - normal body function
Regulates feelings of hunger and fullness / digestive system
Hypothalamus
Hunger
Physiological desire (need) for food - non specific (any food will do)
Appetite
Desire to consume specific foods - due to smells, stress eating, sensoral or emotional need for food
Anorexia
Need for food yet no appetite
Satiation
Sensation of fullness from eating - satisfied need for hunger and appetite
Gastrin
Hormone produced by the stomach to stimulate gastric acid production to reach a pH of 1.5
Secretin
Hormone produced by sm intestine and released into the blood in response to presence of acidic chyme
Stimulates production and secretion of pancreatic fluids
Secretin
Cholecystokinin
Hormone produced by the small intestine and released into the blood in response to fat and proteins
Stimulates the secretion of bile from the gall bladder and digestive fluids from the pancreas while slowing GI mobility
Cholecystokinin
Digestive steps that occur in the mouth
Physical - chewing & tongue mixes saliva and food
Chemical - Salivary amylase digests complex CHO (grains, veggies, beans, nuts and seeds)
Food that is chewed up, moist and ready to swallow
Bolus
Digestive steps in the stomach
Physical - Muscles churn bolus into chyme
Chemical 1 - HCL denatures protein
Chemical 2 - Pepsin digest protein into smaller chains
Food in the stomach that is digested and ready to move to the small intestine
Chyme
Protective secretion in stomach that protects against HCL
Mucus layer and production of bicarbonate
Digestive steps of small intestion
P - Segmentation
C 1 - Pancreatic bicarbonate to neutralize HCL
C 2 - Bile emulsifies (mixes) fat and water (liver & gall bladder)
C 3 - Pancreatic enzymes digest macronutrients
C 4 - Small intestinal cells produce disaccarides & peptisases
Pancreatic enzymes
Lipase, amylase and protease
Chylomicrons
Fat bus
Omentum
Fat pad around abdominal wall
What organ receives fat first
heart
Digestive steps in the large intestine
P - Stool digestion
C - Gut bacteria (digest soluble fiber)
Absorption
Process of taking molecules across a cell membrane and into cells of the body
What part of the GI tract is responsible for the greatest amount of absorption
Small intestine / duodenum - due to its structure
Small intestine folds that increase absorption and surface area
Villi
Form brush border which increases surface area more
Microvilli
Three mechanisms of absorption
Diffusion, Facilitated diffusion and Active absorption
Diffusion
Requires no energy and has no transporter - inefficient absorption of nutrients
Facilitated diffusion
Requires no energy but has a transporter - more efficient than diffusion
Active absorption
Requires ATP and has a transporter for nutrient - most effective
(glucose and amino acids)
Water soluble macronutrients
CHO and protein
Water soluble micronutrients
B Vits and Vit C
Water soluble nutrient path as leave intestine and released to body cells
Bloodstream and taken to liver via portal vein then heart
Fat soluble macronutrients
Lipids and triglycerides
Fat soluble micronutrients
Vits A, D, K, and E
Fat soluble nutrient path as leaves intestine and released to body cells
Transported through the lymph, bypasses liver and directly to heart and then ultimately the blood
Fat soluble nutrients are transported
Packaged into chylomicrons and released into the lymph
Water soluble nutrients are transported
Freely or bound to a carrier in the blood
Cells use nutrients for a....
Functional or structural purpose
Protects from HCL backflow
Gastro-esophageal sphincter
Prevents HCL from entering into the small intestive
Pyloric Sphincter
Primary systems responsible for regulating digestion and absorption
Nervous - provide sensory info - distention and muscle action
Endocrine - hormonal regulation of digestion by GI & brain (hypotha)
In brain above pituitary gland
Hypothalamus
Cephalic phase
Starts before 1st bite - hunger feeling/ body ready to receive food, thoughts of food stimulate release digestive enzymes, olfactory receptors detect aroma and trigger organs to be ready to receive food
Highest satiation value
Proteins
Enzyme that breaks down starches
Salivary amylase
Gastric juices contain
HCL (denature protein & activates pepsin), pepsin (digest protein), gastric liapase (digest fat), and intrinsic factor
Intrinsic factor
Protein to absorb vitamin B 12
Chyme
End product of stomach digestion
Produces bile
Liver
Stores bile
Gall bladder
Cholescytokinin (CCK)
Stimulates the gallbladder to release bile and the liver to produce more bile