Digestion Flashcards
What is the most satiating macronutrient?
Protein
What have low satiety value?
Carbs and fat
Digestion in the mouth
- cephalic phase – sight, smell or thought of food initiates the digestive
process with the salivary and gastric responses - Mechanical digestion = chewing
-Chemical digestion = saliva
How many salivary glands are there?
3
What does saliva contain?
- water
- bicarbonate (pH maintenance)
- mucus (lubrication)
- antibodies (protection)
- enzymes e.g. salivary amylase which
initiates the digestion of starch
What is the gastroesophageal sphincter?
separates the esophagus from the stomach; the bolus
(the portion of food shallowed at one time)
cannot slip back, from the stomach to esophagus
Digestion in the stomach includes..?
-Mechanical digestion to mix food with gastric juices
-Chemical digestion via gastric juices
What is gastric juices?
Digestive secreation containing water, HCL, and enzymes (pepsin)
What is chyme?
semi-solid product of mechanical and chemical digestion in the
stomach; partially digested food mixed with water and gastric juices; expelled
by the stomach into the duodenum (the top portion of the small intestine).
What does the liver produce?
Bile
What does the gallbladder store?
Bile
What is bile?
– secreted into duodenum when needed, whenever fat arrives there
– it is an emulsifier: disperses the fat in the water forming an emulsion
What is the purpose of the pancreas?
– produces pancreatic juice which flows from the pancreas into the small
intestine through the pancreatic duct
What is pancreatic juice?
i) enzymes that act on all 3 macronutrients (amylase for carbohydrates,
protease for proteins, and lipase for fats)
ii) sodium bicarbonate to neutralize acidic chyme as it enters the small intestine
What os the major site of digestion?
Small intestine
What is the final stage of digestion?
Small intestine
What is peristalsis?
-successive waves of involuntary muscular contractions passing along the walls of the GI
tract that push the contents along
- circular and longitudinal muscles contract
-Enhances the absorption along the intestine
What is segmentation?
-circular muscles contract, creating segments of chyme within the intestine
What is in the small intestine that facilitates absorption?
-Villi
-Microvilli
What is Villi?
finger-like projections made up of cells
that found on the folds of the small intestine and
they are in close contact with nutrient
molecules; absorb nutrients and shuttle them
into the bloodstream so they can travel where
thy are needed.
What is microvilli?
-Microscopic hair-like projections
-Primary site of absorption of most nutrients
What is simple/passive diffusion?
-Pass through the membrane freely
-move along concentration gradient
-High to low
- Lipids and water
What is facilitated diffusion?
-Only soluble in water
-requires a carrier protein
-requires concentration gradient (high to low)
-Does not require expenditure of cellular energy
- Water-soluble vitamins, fructose
What is active transport?
-Concentration is higher inside than outside
-Requires carrier protein
-requires energy
-glucose and amino acids
What is endocytosis?
- small amount of intestinal content engulfed by cell membrane
Where does undigested food move through?
In the sphincter called ileocecal valve in the large instestine
How long is material stored prior to elimination?
12-24 hours
How many live bacteria is needed in a probiotic?
1-10 billion live bacteria
What is the use of prebiotics
-Promotes growth of good bacteria within the large intestine
What are synbiotics?
-Combination of pro and pre
What are postbiotics?
bioactive
compounds (e.g. short chain fatty
acids, Vitamins B and K, amino
acids, etc) that are produced
when probiotic bacteria consume
prebiotic fiber in your colon.
- Boosts immune system, reduce digestive symptoms
What is the vascular system?
- Transport of water soluble nutrients through the blood
What is the reason for the lymphatic system?
-Lymph = transports of lipids
-transports fat-soluble nutrients
-returns fluid to the blood
-part of the immune system
What is the Hepatic portal system?
portal vein (receives first
absorbed water-soluble nutrients)
- ensures liver is first to receive materials absorbed from GI tract
(“gatekeeper”)
What is the major metabolic organ?
Liver = prepares absorbed nutrients for use by rest of body
What is homeostasis?
maintain important variables in the face of large environmental changes
What is negative feedback?
response to a stimulus in order to reverse or cause the opposite effect of
the original stimulus
What is CNS?
-Central nervous system
-main processing area
-Brain and spinal cord
What is PNS?
-Peripheral nervous system
-nerves outside CNS
-GI tract component called enteric nervous system
What is gastrin?
Hormone produced by G cells in the stomach
-Triggered by entry of food into the stomach
-Promotes the release of HCL from the stomach
-Controls release of pepsin from the stomach
What is secretin?
Hormones released from the duodenum when stomach acid contents come to duodenum (when pH is below 4.5)
-Inhibits gastric motility and gastrin
-stimulates bicarbonate secretion from pancrease to neutralize chyme
What is CCK?
Cholecystokinin
-Hormone produced by the duodenum due to lipid rich chyme
-Stimulates the release of digestive enzymes from the pancrease and of bile from the gallbladder
What is GIP?
Gastric-inhibitory peptide
-hormone produced by duodenum
-inhibits gastric motility and secretion of acid
-stimulates the release of insulin from pancreas in response to glucose infusions
