Digestion Flashcards
Mechanical Digestion
chewing, churning of the stomach, peristalsis
Chemical Digestion
saliva, enzymes, transport of nutrients to where it is needed
Movement of Digestion
mouth, pharynx, epiglottis, esophagus, esophageal sphincter, stomach, pyloric sphincter, duodenum, gallbladder and pancreas, jejunum, ileum, ileocecal valve, colon, rectum, anus
What does the mouth do?
Saliva lubricates
Amylase starts starch digestion
Chewing breaks down food
What does the pharynx do?
Epiglottis keeps food from airways
What does the Esophagus do?
Where peristalsis starts
What does the stomach do?
Food storage
Acid kills bacteria, unfolds proteins, activates pepsin
Produces chyme
What does the small intestines do?
Most digestion and absorption
Pancreatic enzymes digest food and bicarbonate neutralizes acid
Bile breaks fat
What does the large intestines do?
absorb water
Bacteria digest fiber, make vitamins
What does the rectum do?
Stores feces
what does the liver do?
manufactures bile salts to help digest fats
What does the gallbladder do?
stores bile until needed
What does the Pyloric sphincter do?
allows passage from stomach to small intestine
What does the ileocecal valve do?
allows passage from small intestine to the large intestine
What does the appendix do?
houses bacteria and lymph cells
What does the pancreas do?
manufactures enzymes to digest all energy-yielding nutrients and release bicarbonate to neutralize acidic chyme that enters the small intestine
Gastrointestinal motility
Peristalsis - muscle contractions
Segmentation - squeezing of the intestines that breaks things apart with enzymes
Digestive juices
Salivary glands (salivary amalaze breaks down starch)
Gastric glands/stomach (pepsin breaks down proteins and hydrochloric acid)
Liver (bile emulsifies fat that stores the bile in gallbladder)
Pancreas (pancreatic juices - carbs, fats, proteins)
Small intestine
Where do nutrients go?
Lymphatic system (most lipid soluble nutrients)
Bloodstream (through the liver by hepatic portal vein)
Circulatory route of blood - heart, arteries, capillaries, heptaic portal vein, liver, hepatic vein, heart
Carbohydrates info
starch, sugars, fiber
composed of monosaccharides
Carbon and water
preferred energy source
Simple carbs
Monosaccharides - glucose, galactose, fructose
Disaccharides - maltose, sucrose, lactose
Complex Carbs
Oligosaccharides (3-10 monosaccharides)
Polysaccharides
which are…
Glycogen (storage)
Starches
Fibre (soluble and insoluble)
What breaks down carbs into monosaccharides in digestion?
Salivary amalase
Carbohydrate digestion
Mouth: salivary glands secrete salivary amalase in the mouth. Starch -(salivary amalase)-> small polysaccharides, maltose
Stomach: Stomach acid and enzymes digest salivary amalases, halting starch digestion. Stomach acid hydrolyzes maltose and sucrose
Small intestine: Pancreas produces enzymes and releases them into the small intestine.
Polysaccharides -(pancreatic amalase)-> disaccharides
Enzymes on the surface of the small intestine break disaccharides into monosaccharides and cells absorb.
Monosaccharides that are absorbed after broken down in the small intestine
Maltose -(maltase)-> glucose and glucose
Sucrose -(sucrase)-> fructose and glucose
Lactose -(lactase)-> galactose and glucose
Fiber Digestion
Mouth: mechanical action of mouth breaks down fiber and saliva moistens it for swallowing
Moves through stomach and small intestine and remains unchanged
Large intestine: Some fiber -(bacterial enzymes)-> fatty acids and gas
What does fiber do for the body?
Holds water, regulates bowel activity, binds cholesterol and some minerals, carry them out as excreted
Lactose Intolerance
Amount of lactase decreases with age
If lactose is not digested by lactase and continues through the GI tract, it draws in water, creates gas in colon and causes explosive diarrhea
Glycogen (complex carb)
CHO storage in animals, mammals
Body breaks off a chain when it needs energy
Made and stored in liver and muscle
Glycogen’s role in blood glucose regulation
low blood sugar, stimulates release of glucagon, breaks down glycogen to form glucose, given to body and brain
Starch (complex carb)
CHO storage in plants
Composed of glucose
Digestible by humans
Fiber (complex carb)
CHO not well digested, not broken down for energy
Found in plant-based foods
Insoluble fiber
Does not dissolve in water (passes unchanged through colon)
Increase regularity of BM
Soluble fiber
Dissolves in water
Holds water in stool, binds to cholesterol and simple sugars, delays transit time
Fiber AI
38 g/day men
25 g/day for women
Harmful effects of excessive fiber
Pulls water into the colon
Mineral balance (pull things through without being absorbed)
Energy requirements (fiber does not give energy)
Increased fluid needs (dehydration)
Nutrients displacements (not getting the nutrients you need)
Average carbs you need for an adult per day
130 g
What does insulin do?
Pancreatic hormone that regulate blood glucose levels
What does glucagon do?
Pancreatic hormone that releases glycogen from liver
What does somatostatin do?
Hormone produced by pancreas and hypothalamus that inhibits insulin and glucagon
Glycemic index
method of classifying foods according to their potential for raising BG
Glycemic response
the extent that food raises the BG concentration and elicits an insulin response
Glycogenolysis
process converting glycogen back to glucose
Maintains blood glucose
Energy vs nutrient density
energy density = how many calories it has
more nutrients + fewer calories = high nutrient density
empty kcalorie foods
less nutrients, high calories
essential nutrients
