GI 3 Flashcards by Michael McMahan

What 4 things are secreted in duodenum?

CCK
Secretin
Gip,
HCO3

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What is secreted by jejunum?

Nothing

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What i2 things are secreted by ileum?

PYY

HCO3-

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What is the main product absorbed in duodenum?

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What is the main products absorbed in ileum?

Bile acids

Vitamin B12

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What are the 3 mechanisms of motility of small intestine?

MMC
Segmentation
Peristalsis

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Where does digestion and absorption occur in the small intestine?

All along (highest in duodenum)

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Motilin
Sweep intestines of undigested material
One every 90 minutes

Migrating Motility Complex

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Is the MMC part of the fasting or feeding pattern?

Fasting

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Interstitial Cells of Cajal
3-12 waves/min
Controlled 1⁰ by ENS

BER Slow waves in small intestine

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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

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What 4 hormones stimulate the BER slow waves in small intestine?

CCK
Gastrin
Insulin
Serotonin

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What 2 hormones inhibit the BER slow waves in small intestine?

Secretin

Glucagon

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Mixing

chyme with digestive enzymes
emulsifies fats
adjusts pH
exposes mucosa to chyme.

Segmentation

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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

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______ reflex: short feedback loop from stomach to small intestine

Gastroenteric reflex

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The duration of feeding pattern depends on what 2 things?

Caloric content of meal

Nutrient composition of meal

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An increase in the caloric intake will _____ the time of feeding pattern

Increase

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The Net rate of movement of any substance across the intestinal epithelium is influenced by what 2 things?

Surface area

Motility

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The north-south vector of movement from mouth to anus is influenced by ______

motility

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The east west vector of the rate of movement across intestinal epithelium is influenced by ______

surface area

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_______: – carbohydrate, protein, fat–Require “digestion”

Macronutrients

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What are the 6 things presented for digestion and/or absorption?

Macronutrients 
Electrolytes
Water
Bile Salts
Vitamins
Drugs

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The following factors influence \_\_\_\_\_\_:
Motility
Large surface area
Appropriate pH
Hydrolytic enzymes
  –carbohydrates, protein, fat
Emulsifying factors
  –Fat

digestion

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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

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?

In _____ Proteases digest R-binding protein B12 binds to intrinsic factor (pH neutral)

Duodenum

Does intrinsic factor bind to B12 in duodenum?

Yes

In IleumIntrinsic factor binds to ____ and taken into cells via receptor-mediated endocytosis

IFCR

In IleumIntrinsic factor binds to IFCR and taken into cells via ___________

receptor-mediated endocytosis

Inside cellsIntrinsic 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

2. 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

GI 3 Flashcards

(117 cards)