GI 3 Flashcards
What 4 things are secreted in duodenum?
CCK
Secretin
Gip,
HCO3
What is secreted by jejunum?
Nothing
What i2 things are secreted by ileum?
PYY
HCO3-
What is the main product absorbed in duodenum?
Fe
What is the main products absorbed in ileum?
Bile acids
Vitamin B12
What are the 3 mechanisms of motility of small intestine?
MMC
Segmentation
Peristalsis
Where does digestion and absorption occur in the small intestine?
All along (highest in duodenum)
Motilin
Sweep intestines of undigested material
One every 90 minutes
Migrating Motility Complex
Is the MMC part of the fasting or feeding pattern?
Fasting
Interstitial Cells of Cajal
3-12 waves/min
Controlled 1⁰ by ENS
BER Slow waves in small intestine
What are the 4 stimuli of the BER slow waves in small intestine?
- Distention of duodenum
- Nutrient content of chyme
- Gastroenteric Reflex – short feedback loop from stomach to small intestine
- Hormones
What 4 hormones stimulate the BER slow waves in small intestine?
CCK
Gastrin
Insulin
Serotonin
What 2 hormones inhibit the BER slow waves in small intestine?
Secretin
Glucagon
Mixing
- chyme with digestive enzymes
- emulsifies fats
- adjusts pH
- exposes mucosa to chyme.
Segmentation
Propel chyme through small intestine at a velocity of 1 cm/min.
Spread chyme across mucosal surface as it enters from stomach
Can begin anywhere in the small intestine
Normally weak and die out after traveling only 3 – 5 cm
3 - 5 hours from pyloric valve to ileocecal valve
Peristalsis
______ reflex: short feedback loop from stomach to small intestine
Gastroenteric reflex
The duration of feeding pattern depends on what 2 things?
Caloric content of meal
Nutrient composition of meal
An increase in the caloric intake will _____ the time of feeding pattern
Increase
The Net rate of movement of any substance across the intestinal epithelium is influenced by what 2 things?
Surface area
Motility
The north-south vector of movement from mouth to anus is influenced by ______
motility
The east west vector of the rate of movement across intestinal epithelium is influenced by ______
surface area
_______: – carbohydrate, protein, fat–Require “digestion”
Macronutrients
What are the 6 things presented for digestion and/or absorption?
Macronutrients Electrolytes Water Bile Salts Vitamins Drugs
The following factors influence \_\_\_\_\_\_: Motility Large surface area Appropriate pH Hydrolytic enzymes –carbohydrates, protein, fat Emulsifying factors –Fat
digestion
What are the 5 factors influencing digestion?
Motility Large surface area Appropriate pH Hydrolytic enzymes –carbohydrates, protein, fat Emulsifying factors –Fat
What are the 5 factors influencing absorption?
Large surface area Specialized cells Specific transport mechanisms – carriers, pumps, pores Energy Blood or lymph flow
The following factors influence \_\_\_\_\_\_: Large surface area Specialized cells Specific transport mechanisms – carriers, pumps, pores Energy Blood or lymph flow
absorption
Most substances completely digested and absorbed in ______ (~25%) small intestine.
proximal small intestine
What percentage of the total substances are absorbed in the proximal small intestine?
25%
What substance is not absorbed mostly in the proximal small intestine?
Dietary fat
In the proximal small intestine, Increased intake produces increased absorption that may increase ____ and ______
Storage and obesity
Diversion of chyme to _____ is one treatment for obesity
distal gut
Digestive enzymes in small intestine require a _____ pH to function
neutral
What is used to decrease the acidity of the chyme in the small intestine?
Bicarb
Pancreatic HCO3–Maximal stimulus of pancreas produces pancreatic juice with [HCO3- ] of _____ mEq/L
145 mEq/L
_____ digestion:
(Stage I – pancreatic hydrolases):
yields di- and tripeptides, amino acids, maltose, maltotriose, α-limit dextrins, glucose;
Fat digestion completed in lumen.
Intraluminal
_____ digestion:
(Stage II – brush border hydrolases):
End products: amino acids and di- and tripeptides, glucose, galactose, fructose.
Mucosal surface
Which of the 3 main things getting digested are digested by intraluminal digestion?
Fats, carbs, and proteins
Which of the 3 main things getting digested are digested by mucosal surface digestion?
Proteins and carbs
Typical American diet includes what range of carbs per day?
250-300 grams per day
How much of the daily caloric intake is made up of carbs?
1/2
___ can’t be digested and is lost in the feces
Fiber/cellulose
____ must be broken down into its building blocks before it can be absorbed
Carbs
____ digestion begins in mouth when food exposed to salivary amylase-Not significant-Enzyme inactivated by acidic gastric juice
Carb digestion
Carb digestion begins in mouth when food exposed to ______
- Not significant
- Enzyme inactivated by acidic gastric juice
salivary amylase
> 95% of ____ digested in small intestine
Carbs
Starch and Glycogen digestion by _______: breaks polysacs to disacs
pancreatic amylase
Brush border _____ produce the monosaccharides: breaks disacs to monosacs
hydrolases
Which monosaccharide is reabsorbed less because of the apical channel acting by facilitated diffusion?
Fructose
Typical American diet includes what range of proteins per day?
≈ 60 – 90 g/day
How much of the average daily caloric intake/day are proteins?
1/6
What starts protein digestion in the stomach?
- 10-20% of total protein digestion
- Important for collagen digestion
- Enzyme inactivated by basic pH in small intestine
Pepsin
What are the 4 intraluminal digestive enzymes that digest proteins into small peptides and aas?
Trypsin
Chymotrypsin
Carboxypolypeptidases
Elastase
What is the mucosal digestive enzyme that digest proteins and produce amino acids?
Peptidases
____ is a secondary active symporter coupled to H+ that has an extremely broad substrate availability
Peptide transporter 1 (PEPT1)
The typical american diet has what range of fats per day?
70-100 g/day
How much of the caloric intake is made up of fats?
1/3
What are the most abundant dietary fats?
Triglycerides
What are the 3 dietary fats that are less abundant than triglycerides?
cholesterol
cholesterol esters
phospholipids
Digestion of fat requires ______
emulsification
What are the 2 things necessary to emulsify fats?
–Bile Salts
–Lecithin (phospholipid)
Agitation of the fat called ______ breaks the fat globule down into smaller fragments, increasing surface area for digestion.
(Segmentation)
What digests fat in the stomcah?
Lingual lipase
How much of fats are digested in the stomach?
Less than 10%
What are the 2 intraluminal enzymes that digest fats in small intestine?
Pancreatic lipase
Colipase
Small intestine digests all triglyceride it can in less than ____ minutes
1 minute
After it digests triglyceride, what does small intestine produce?
2 fatty acids
1 monoglyceride
Digestion products solubilized in ______
- Removes TG digestion products from fat globules so fat digestion can continue
- Transports TG digestion products to brush border membrane
micelles
Digestion of Cholesterol esters is done by pancreatic _______
cholesterol ester hydrolase
Digestion of Phospholipids is done by Pancreatic _______
Phospholipase A2
Are micelle formation and breakdown in equilibrium?
Yes
FA and MG cross apical membrane via _______
simple diffusion
In smooth ER, TG is _______
resynthesized
When _____ is resynthesized,
- Keeps [FA] and [MG] low inside cell
- Maintains gradient for simple diffusion and absorption
TG
Fat-soluble vitamins (A, D, E, K), phospholipids, and cholesterol esters absorbed by ________
Simple diffusion due to TG getting resynthesized
TG and other hydrophobic substances packaged into _____ and secreted across BL membrane via _______
chylomicrons; exocytosis
Chylomicrons enter lymphatic vessels via the _____ and are transported to systemic veins and enters circulation
lacteals
Which of the main nutrients are absorbed directly into the bloodstream?
Carbs and proteins
Which of the main nutrients are absorbed by the lymphatics?
Fats
______ cells:
- Mature intestinal epithelial cells
- Absorb Na+, Cl-, and H2O
Surface Cells
______ cells
- Found deep in the spaces between the circular folds
- Immature intestinal epithelial cells
- Produced by stem cells
- Mature and migrate to surface
- Secrete Na+, Cl-, and H2O
Crypt Cells
Fluid secreted by ____ cells flow to surface cells where reabsorbed
Provides flowing H2O for absorbing intestinal digestates
Crypt cells
Not enough secretion by the crypt cells causes _______
Cystic fibrosis
Too much secretion by the crypt cells causes ______
Infectious diarrhea
In the ____ state, 1 ion is moved passively and anions and water follow
Prandial state
In the _____ state, Na and Cl are absorbed, and H20 follows
Post Prandial state
1 ion is moved passively and anions and water follow
Electrogenic
Na and Cl are absorbed, and H20 follows
Electroneutral
How much sodium per day is secreted into the lumen of GI?
30g/day
______ and ______ infections are major cause of death in undeveloped countries.
Cholera and E. coli
Cholera and E. coli both produce enterotoxins that increase ______
cAMP
cAMP activates ___ secretion via CFTR into gut lumen leading to massive diarrhea
Cl-
cAMP activates Cl- secretion via CFTR into gut lumen leading to _______
massive diarrhea
What are the 2 things placed in an oral rehab therapy solution?
Na and Glucose
In stomach Binds to the _______ protein
Stabilizes B12 in acidic environment
Intrinsic factor secreted by gastric parietal cells cannot interact with B12 at low pH
R-binding
Does intrinsic factor bind to B12 in stomach?
No
In _____
Proteases digest R-binding protein
B12 binds to intrinsic factor (pH neutral)
Duodenum
Does intrinsic factor bind to B12 in duodenum?
Yes
In IleumIntrinsic factor binds to ____ and taken into cells via receptor-mediated endocytosis
IFCR
In IleumIntrinsic factor binds to IFCR and taken into cells via ___________
receptor-mediated endocytosis
Inside cellsIntrinsic factor ______
B12 binds to _______
Complex crosses BL via exocytosis
degraded; TCII
Absorption of Water Soluble Vitamins:
Thiamin, riboflavin, niacin, pyridoxine, pantothenate, biotin, and ascorbic acid: is done by _____ transport with _____; completed where?
Cotransport with Na+
Completed in upper small intestine.
What are other actively absorbed substances in the small intestine?
Ca++, PO4—
Mg++
Fe++
Bile salts
Pressure and chemical irritation in ileum ____ sphincter and ____ peristasis
Relaxes sphincter and excite peristalsis
Fluidity of contents in the ileum ____ emptying
Promotes emptying
Pressure or chemical irritation in cecum _____ peristalsis in ileum and ____ sphincter
Inhibits peristalsis and excites sphincter
Proximal ½
Absorption of water and electrolytes from chyme to form solid feces
≈ 1.4 L/day
Absorbing Colon
Distal ½
Storage of Fecal matter until it can be expelled
- Storage Colon
Takes ___ to ___ hours to move contents from ileocecal valve to anus
8-15 hours
______ colon movements:
Fecal material slowly dug into and rolled over
All fecal material gradually exposed to mucosal surface
Facilitates absorption of water and dissolved substances
Movement of material from cecum through ascending colon
Mixing movements “haustrations”
\_\_\_\_\_ colon movements: 1-3x each day Transverse to Sigmoid Occurs throughout colon for 10 min. Force feces into rectum Gastrocolic and Duodenocolic Reflexes Irritation can stimulate
Propulsive movements “Mass movements”
Which colon movement mirrors segmentation?
Mixing movements / haustrations
Which colon movement mirrors peristaltic contractions?
Propulsive movements / mass movements
How many different bacterial species are found in colon?
1500 species
Fast or slow motility in colon promotes growth of bacteria?
Slow
What valve keeps bacteria in the colon?
Ileocecal valve
Ferment undigested carbohydrates to short-chain fatty acids:
–Soluble and easily absorbed.
–Nutrient salvage
–Evidence obesity associated with biasing microbes to species efficient at nutrient salvage
Produce Vitamin K (vital since amount in diet not sufficient)
Increase resistance of the intestinal mucosa to colonization with pathogenic microorganism
Produce Flatus
Colon bacteria