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DEMS Unit 1 > Small Intestine > Flashcards

Small Intestine Flashcards

1
Q

Chronic Intestinal Pseudo-Obstruction (CIPO)

A
  • characterized by dilation of bowel on imaging
  • major manifestation of small intestinal dysmotility
  • bacterial overgrowth a complication
  • sx: N/V, abd pain, distention, constipation, diarrhea
  • causes: PD, autoimmune, chagas, diabetes, scleroderma, congenital in children
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2
Q

Duodenum Basic Electrical Rhythm (BER)

A

-12 cycles per minute

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3
Q

Key Hormones

A
  • CCK
  • secretin
  • GIP
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4
Q

Types of Motility in Small Intestine

A
  • peristaltic
  • segmentation
  • this alternates aspect of chime exposed to brush border
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5
Q

Gastroileal Reflex

A

-stomach activity stimulates movement of chyme through ileocecal sphincter

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6
Q

Gastrocolic Reflex

A

-food in stomach stimulates mass movement in colon

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7
Q

Ileocecal Valve

A
  • normally closed to prevent reflux of bacteria from colon into ileum
  • opened by distension of end of ileum (local reflex)
  • closed by distension of proximal colon (local reflex)
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8
Q

Digestion

A
  • some occurs in mouth and stomach

- most occurs in intestinal lumen or at surface or the absorptive enterocytes

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9
Q

Dietary Carbohydrates

A
  • plant starch amylopectin is largest source of carbs in our diet
  • amylase is major enzyme in saliva and pancreatic secretions
  • only simple monomeric sugars can be absorbed
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10
Q

Isomaltase

A

-converts alpha-limit dextrins to glucose

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11
Q

Maltase

A

-converts maltose and maltotriose to glucose

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12
Q

Lactase

A

-converts lactose to glucose and galactose

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13
Q

Sucrase

A

-converts sucrose to gluvose and fructose

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14
Q

Trehalase

A
  • converts trehalose to glucose

- shrimp

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15
Q

Lactose Intolerance

A
  • missing brush border enzyme lactase
  • causes gas and diarrhea due to colonic bacterial digestion of lactose
  • areas where dairy is not part of the staple have higher prevalence
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16
Q

SGLT1 Transporter

A
  • requires Na as a co transporter
  • transports glucose and galactose across the apical membrane of the enterocyte
  • can operate in the setting of secretory diarrhea (inc. cAMP/cholera) so is important for oral rehydration
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17
Q

GLUT5 Transporter

A

-fructose transport across the apical surface via GLUT5 is Na independent

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18
Q

GLUT2

A
  • not Na dependent

- glucose and galactose use the same transporter as fructose on the basolateral surface

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19
Q

Regulation of Carbohydrate Absorption

A
  • inc. carb consumption upregulates transporters and inc. the uptake of simple sugars-> obesity
  • and vice versa
20
Q

Protein Digestion

A

-pancreatic proteases like trypsin, chymotrypsin, carboxypeptidase & and elastase break down proteins to oligopeptides, di/tri-peptides and amino acids

21
Q

Brush Border

A

-peptidases break down oligopeptides into amino acids, dipeptides, tripeptides

22
Q

Protein Uptake Pathways

A
  • Na dependent co-transporters that utilize the Na+/K+ ATPase gradient are major route for the different classes amino acids
  • water follows
  • Na independent transporters of amino acids
  • specific carriers for small peptides
23
Q

Pinocytosis

A

-infants

24
Q

Dietary Fat

A
  • fats provide 30-40% of caloric intake
  • essential fatty acids: linoleic acid-> arachidonic acid, and alpha-linolenic acid
  • triglycerides are the most abundant fat in our diet
  • GI tract is water based so there are challenges to fat absorption
25
Q

Bile Acids

A
  • primary bile acids are produced in liver from cholesterol
  • secondary bile acids are formed by bacteria in the intestines and colon
  • bile acids are complexed with glycine or taurine to make bile salts
  • bile is recycled during a meal by update in the distal ileum- enterohepatic circulation
26
Q

Vitamin Absorption

A
  • fate soluble vitamins (A, D, E, K) are absorbed along the length of the small intestines and are carried in micelles and form chylomicrons similar to dietary lipids
  • water soluble vitamins either enter the enterocyte by simple diffusions of via spefic transporters
27
Q

Secretion and Absorption of Fluids

A
  • There is a net fluid secretion from cells in the intestinal crypts and a net fluid absorption from enterocytes on the villi
  • Villi surface area > crypt surface area
  • paracellular water permeability dec. from proximal to distal in the small intestines
  • the colon has the lowest paracellular permeability to water bc it’s trying to solidify waste and it needs to link water movement to transcellular ion movement
28
Q

Sodium Absorption

A
  • absorbed along intestine with most absorbed in jejunum
  • dependent on gradient established by Na+/K+ ATPase
  • water absorption is critically linked to Na absorption
  • mechanism is via Na+/glucose and galactose or Na+/amino acide cotransport, NaCl cotransport, Na+/H+ exchange or passive diffusion
29
Q

Chloride Absorption

A
  • passive in proximal intestines (due to loose TJs), offests Na+ charge in the intracellular space
  • in the distal ileum and colon, with less leaky TJs, Cl- is exchanged for HCO3 that is offsetting the acids produced by bacteria
30
Q

Potassium Absorption

A
  • passive process
  • paracellular movement in jejunum but transcellular in colon
  • K+ normally high in cells due to Na+/K+ ATPase
  • severe diarrhea can cause significant loss of K+
31
Q

Calcium and Magnesium Absorption

A
  • Ca++ and Mg++ compete for uptake by the cells
  • Ca++ enters enterocyte passively down is electrochemical gradient in proximal intestines
  • uptake of Ca++ in intracellular calcium stores maintains the gradient
  • Ca++ ATPase pumps calcium out to the blood
  • vitD stimluates uptake of Ca++ by inc. Ca++ binding proteins and Ca++ ATPase molecules
32
Q

Iron Absorption

A
  • transported across apical membrane as either heme or Fe++ (receptor mediated
  • two possible fates: binds to apoferritin to form ferritin that stays in the cell and is lost when the cell dies or binds transferrin and enter the blood
33
Q

Parietal Cells

A
  • located in stomach
  • secrete intrinsic factor and H+
  • destruction of parietal cells -> chronic gastritis and pernicious anemia
34
Q

Intrinsic Factor

A
  • secreted by parietal cells in stomach

- action: vitamin B12 binding protein (required for B12 uptake in terminal ileum)

35
Q

Goblet Cell

A
  • column-shaped cell which secretes the main component of mucus
  • located in small intestine
  • ileum has largest number of goblet cells in small intestine
  • secrete HCO3
36
Q

Paneth Cells

A
  • located in small intestine
  • reside at the bottom of the intestinal crypts
  • key effectors of innate mucosal defense
  • produce large amounts of α-defensins and other antimicrobial peptides, such as lysozymes and secretory phospholipase A2
37
Q

Cholecystokinin

A
  • peptide hormone responsible for stimulating the digestion of fat and protein
  • synthesized by I-cells in the mucosal epithelium of the small intestine and secreted by duodenum
  • release stimulated by monitor peptide released from cells in duodenum
  • causes release of digestive enzymes and bile from the pancreas and gallbladder
38
Q

Bruner Gland

A
  • characteristic of duodenum

- produce mucous rich alkaline secretion to protect duodenum from stomach acid

39
Q

Meckel Diverticulum

A

-connects intestine to umbilicus

40
Q

Enterokinasae

A

-secreted by enterocytes (in small intestine)

41
Q

Enterocytes

A

-only in small intestine
-5 functions
1- activating zymogens from pancreas
2- reclaims bile salts
3- release of IgA
4- uptakes disacharrides and converts to monosacharrides
5- uptake glucose

42
Q

Celiac Disease

A
  • a gliadin peptide complexes with TTG-> autoantibody formation
  • Class 2 HLA-DQ2 or HLA-DQ8
  • associated with other autoimmune disease
  • features: fatty diarrhea, gas, weight loss, anemia, dental enamel defects, arthritis, villous blunting, inc. intraepithelial lymphocytes
  • dermatitis herpetiformis
  • scalloping of mucosa
43
Q

Campylobacter

A
  • bacterial enterocolitis
  • causes diarrhea
  • most common stool isolate is US
  • poultry, water, dairy
44
Q

Shigella

A
  • bacterial enterocolitis
  • severe watery/bloody diarrhea
  • contaminated water
  • highest infectivity rate
45
Q

Salmonella

A
  • bacterial enterocolitis

- typhoid (bad diarrhea + risk of perforation) vs non-typhoid (mild, self-limiting)

46
Q

Pseudomembranous Colitis

A

-most often caused by C. diff

47
Q

Ischemic Colitis

A
  • features: older pts, long distance runners, women on OCs, people with hernias or volvulus
  • lack of blood flow to bowel -> acute transmural infarction

DEMS Unit 1 (8 decks)

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