Digestion and Gut Health Flashcards
Digestion and Gut Health 2015
Mouth
The journey begins with MASTICATION - teeth grind and
crush food into small pieces (_____ _________)
1 • Saliva moistens food exposing it to salivary enzymes
(chemical digestion begins):
–AMYLASE (carbohydrate hydrolyzing) aka. ptyalin
A– Amylase begins the digestion of _______
B– small amounts of lypase (lipid hydrolyzing)
– Lipase in the mouth only contributes minimally to digestion of FATS
C—Saliva also contains _____, a secretion that causes food particles to stick together and lubricate the mass (BOLUS) for swallowing…
mechanical digestion
starches
mucus,
Digestion and Gut Health 2015
Esophagus
• Tongue moves bolus of food into esophagus
• Esophagus pushes it down into stomach with ________ wave like contractions
• Food is prevented from regurgitation by upper and lower esophageal sphincters
• Lower Esophageal Sphincter (LES) Valve at the lower end of esophagus. Allows food to pass into stomach.
Closes after food passes - prevents _________ movement of partially digested food
peristaltic
retrograde
Digestion and Gut Health 2015
Clinical Consideration
If LES is NOT working properly, will allow acid mixed
food to seep back into the esophagus = “__________”
GERD (Gastroesophageal Reflux Disease):
Esophageal barrier is NOT effective - acid contents of the
stomach escape into the esophagus
heartburn
Digestion and Gut Health 2015
Stomach
Once the bite of food (bolus) enters Stomach…
1–Undergoes _______&_________ hydrolysis
2–The stomach holds it, prepares it and mixes it
3–Reduces the bacterial load through ____ _______
chemical and enzymatic
acid secretion
Digestion and Gut Health 2015
Gastric Secretions Include:
• HCl
- Destroys microorganisms
- Activates ________ to pepsin
- Activates ______ ________
- Denatures macromolecules
• Pepsin
- -a _________ first secreted in an inactive form as pepsinogen then converted by HCl to active form
- -Proteolytic enzyme - degrades proteins into peptides
• Gastric Lipase
- -Secreted by _____ _______, less active than pancreatic lipase
- -Contributes to breaks down of triglycerides
pepsinogen
intrinsic factor
protease
chief cells
Digestion and Gut Health 2015
Gastric Secretions Include:
A • Mucus
- -Contains glycoprotiens and bicarbonate
- -Protects the gastric mucosa from ____ ______ and autodigestion
B • Intrinsic Factor
–Glycoprotein that facilitates B12 absorption in the ileum
C • GASTRIN
—GI Hormone that stimulates ______ _______ and motility
• Stimulates secretion of HCl and pepsinogen from gastric parietal and chief cells
• Simulates gastric peristalsis
• Maintains the proliferation of gastric parietal cells
• INCREASING acidity of the lumen ______ gastrin secretion
acid damage
gastric secretions
inhibits
Digestion and Gut Health 2015
Clinical Consideration
Low stomach acid =__________________
Common, especially in elderly
1—As we age, we make LESS stomach acid
2—As the pH rises consequences include for example, the decrease pepsin activity
A variety of factors can _________ sufficient stomach
acid production including:
1–Helicobacter pylori
2– frequent use of antacids
hypochlorhydria
inhibit
***Recall
The microbial flora is: SPARSE in the stomach and
upper/small intestine
– HCl, pepsin and bile act as germicidal agents
——Abundant in the large intestine!!
Digestion and Gut Health 2015
Clinical Consideration
A–Decreased gastric secretions may allow increased survival of microbes
1 • INCREASES the risk of inflammation of mucosa (gastritis)
2 • _______ ________ - an acid tolerant bacteria known
to infect the stomach -leads to gastritis and ulceration
3 • Increases risk of _____ _____ ______ ________
(SIBO) 1
— Associated with mucosal inflammation and nutrient
malabsorption
— Symptoms include: bloating, diarrhea, dyspepsia, in severe cases weight loss
Helicobacter Pylori
Small intestinal bacterial overgrowth
Digestion and Gut Health 2015
Still in the Stomach….
Food becomes semi liquid, acid-food mix =_________
Approx 50% water
• Peristaltic contractions of distal stomach propels food
towards _______ ________
Travels from the pyloric opening (valve) into proximal
small intestine but NOT all particles can enter this next
stage…
1–Only small particles get through (
chyme
gastric pylorus
Digestion and Gut Health 2015
Clinical Consideration
Rate of stomach emptying depends on _______ and
TYPE of food.
Carbohydrates leave most rapidly, followed by protein,
fat, then fibrous food
—Liquid meals empty over 1-2 hour (on avg)
—Solid meals empty over 2-3 hours (on avg)
Important clinical consideration when counseling
patients with nausea or vomiting or for satiety during
weight loss
volume
Digestion and Gut Health 2015
The Small Intestine
Major site of _____ ________ and nutrient
absorption
• Acid chyme from stomach enters the duodenum
– Mixed with duodenal juices and secretions from
pancreas and biliary duct
– Alkaline secretions neutralizes the ___
• Entry of the partially digested food stimulates release
of hormones that in turn, secrete enzymes and fluids
that affect GI motility and satiety
chemical digestion
PH
Digestion and Gut Health 2015
The small intestine along with the pancreas, liver and gall
bladder supply secretary materials to meet the needs of
________ digestion
—Secrete _______ specific for digestion of carbs, proteins, and fats
chemical
enzymes
Digestion and Gut Health 2015
Digestion in the Small Intestine
Pancreatic Enzymes:
1 • Pancreatic Lipase and Colipase = FAT
– Primary lipid digesting enzymes from the pancreas
– Digest fats into free fatty acids and B-monoglycerides (these combine with bile salts to form ______)
2 • Trypsin and Chemotrypsin = PROTEIN
–________ enzymes
• Split proteins into SMALLER peptides then into single amino acids
– Secreted in inactive form and activated by ENTEROKINASE which is secreted when chyme contacts the intestinal mucosa
3 • Pancreatic Amylase = CARBS
– __________ large starch molecules into smaller sugars – maltose and sucrose
micelles
Proteolytic
Hydrolyze
Digestion and Gut Health 2015
Digestion in the Small Intestine
2 Intestinal Enzymes:
1— __________ – Activates tripsinogen to trypsin (for protein digestion)
2— ___________- (ie. Matase, lactase, and sucrase)
– Convert respective disaccharides (maltose, lactose,
sucrose) into monosaccharides (glucose, fructose,
galactose)
Enterokinase
Disaccharidases
Digestion and Gut Health 2015
Clinical Consideration
__________________ is most common enzyme
deficiency affecting about ½ of all adults worldwide
—Lactase required to digest lactose
—Generally only infant mammals ingest milk thus the gene that encodes for lactase is active in infancy, then deactivated
*** Preservation of lactase production is a genetic mutation
Lactose intolerant adults– can often tolerate __ g of
lactose at a time (approx. 100 mL / 3.4 oz of milk)
***Cannot tolerate milk products unless in “predigested” form or processed with enzymes or contain lactic acid bacteria in food help digest the lactose (eg. Yogurt, buttermilk, aged cheeses (Parmesan, old goudas etc.) lactase treated milk)
Lactase deficiency
5
Digestion and Gut Health 2015
Digestion in the Small Intestine
Hormones:
1–_______
– control acidity and secretion of pancreatic enzymes
2– ___________
– secreted when fat is present
– triggers release of bile to emulsify fat
________:
– Produced in liver, stored in gallbladder
– Facilitate digestion and absorption of lipids
Secretin
Cholecystokinin
Bile:
Digestion and Gut Health 2015
Absorption in Small Intestine
Food now is changed into simple end products and
ready for use by cell
1– Vitamins and minerals are also liberated
2– 100% of nutrients are NOT absorbed due to varying
degrees of _________. Degree of bioavailability is a factor in setting dietary intake standards.
Factors that affect bioavailability include:
- __________ of nutrient in GI tract
- COMPETITION b/w nutrients for common absorption sites
- FORM in which nutrient is present
bioavailability
Amount
Digestion and Gut Health 2015
Vitamins and Minerals
Vitamins and minerals are varied in structure and
amount within food
1–They can be in a _____ ______
2–______ _______ to a larger molecule, or
3–Tightly _______ inside a food aggregate
• Most often they are liberated during eating by the
mechanical process of grinding.
• May also be liberated during the breakdown of the
large molecules in which they are encased.
free form
Chemically bound
encased
Digestion and Gut Health 2015
Folds, _____&______ make up the inner surface of
the intestinal wall
1–Increase the inner surface area ~600 times!
2–Deliver nutrients into circulation
3–Nutrients then converted into _____or______ for later
use.
NOTE: Resistant starches and most dietary fiber escape
digestion in ________ intestine
energy or stored
small
Digestion and Gut Health 2015
Absorption Mechanisms
- _______ ________ (Simple Diffusion)
Nutrient moves down its concentration gradient - ________ __________
Transported nutrient moves down its concentration
gradient however, nutrient is attached to a lipid
soluble membrane carrier protein - ______ _________
Nutrient moves AGAINST a concentration gradient
Requires participation of a carrier protein – a
receptor – and consumes biochemical energy
provided by ATP
Passive Diffusion
Facilitated Diffusion
Active Transport
Digestion and Gut Health 2015
Clinical Consideration
A. Takes approx. ____to_____ hours for intestinal contents to travel through entire ______ intestine to ileocecal valve
–Valve limits the amount of intestinal material passed back and forth from the small intestine to the colon.
B. Damaged valve increased the chance of ________
overgrowth in the small intestine
3 to 8
small
microbial
Digestion and Gut Health 2015
Clinical Consideration
1—~___% of bile salts secreted from liver and gallbladder are reabsorbed as bile salts in the distal ileum
—-This recycling is critical – de novo syntheses of bile acids in the liver cannot keep pace with needs for adequate lipid digestion.
2—Bile Salt Insufficiency:
Clinically important in patients who have resections of the
distal small bowel and diseases affecting the _____
intestine such as Crohn’s, radiation enteritis and cystic
fibrosis.
—-Leads to __________: Vitamin D deficiency is one
consequence of major clinical importance
95%
small
malabsorption
Digestion and Gut Health 2015
LARGE Intestine - the site of:
• Absorption of remaining water and salt
• Bacterial ___________
• Synthesis of small amount of vitamins
—Absorb vitamins produced by intestinal bacteria
• Provide environment conducive to fermentation of dietary fiber
• Storage
• Excretion
—Eliminate dried residue (undigested, unabsorbed material) as feces
• Mucus
–Secreted by mucosa
–Protects wall from bacterial activity and excoriation
(tearing/abrasion of the lining)
— Helps bind feces together
fermentation
Digestion and Gut Health 2015
A. Fiber, resistant starches, remaining amino acids and
mucus are ________ in the colon.
B. Colonic bacteria continue to digest some materials that have resisted digestion until arriving at the colon.
C. • Contribute to the formation of short chain fatty acids
(SCFAs) (acetic, butyric acid* etc.) and gases (hydrogen, CO2, nitrogen etc.)
—SCFAs help maintain the _____ of the large intestine to support of growth of healthy bacteria also prevent inflammation
—BACTERIA also contribute to formation of potentially toxic substances (ammonia, indoles, amines etc.) contribute to odor of feces
• Nutrients formed by bacterial synthesis include:
Vitamin K, Biotin, B12, thiamin (B1) and riboflavin (B2)
fermented
pH
