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USMLE Step 1 > GI > Flashcards

GI Flashcards

1
Q

Foregut

A

Pharynx to duodenum

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2
Q

Midgut

A

duodenum to transverse colon

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3
Q

Hindgut

A

Distal transverse colon to rectum

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4
Q

Failure of rostral fold closure

A

Sternal defects

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5
Q

Failure of lateral fold closure

A

Omphalocele, Gastroschisis

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6
Q

Gastroschisis

A

Extrusion of abdominal contents through abdominal folds; NOT covered by peritoneum

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7
Q

Omphalocele

A

Persistence of herniation of abdominal contents into umbilical cord, COVERED BY PERITONEUM

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8
Q

Failure of caudal fold closure

A

Bladder extrosphy

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9
Q

Penile abnormality associted with bladder extrosphy

A

Epispadas

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10
Q

Duodenal atresia

A

failure to recanalize

* seen in trisomy 21

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11
Q

Jejunal, ileal, colonic atresia

A

due to vascular accident (apple peel atresia)

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12
Q

Midgut development

A

6th week - midgut herniates through umbilical ring

10th week - returns to abdominal cavity + rotates around SMA

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13
Q

Pathology of GI development

A

Malrotation of midgut, omphalocele, intestinal atresia or stenosis, volvulus

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14
Q

Most common tracheoesophageal anomaly

A

Esophageal atresia with distal tracheoesophageal fistula (TEF)

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15
Q

Sx of esophageal atresia w/ TEF

A

Newborn baby with drooling, choking, vomiting on first feeding. TEF allows air to ender stomach (visible on CXR). Cyanosis is secondary to laryngospasm (to avoid reflux-related aspiration)

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16
Q

Clinical test of esophageal atresia w/ TEF

A

Failure to pass NG tube into stomach

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17
Q

CXR of gasless abdomen

A

Pure atresia (isolated) esophageal atresia

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18
Q

Congenital pyloric stenosis

A

hypertrophy of pylorus causes obstruction. Palpable “olive” mass in epigastric region and nonbilious projectile vomiting at 2 weeks of age. Treatment is myoectomy. Usually in first born males.

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19
Q

Embryo origin of pancreas

A

derived from foregut.

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20
Q

Ventral pancreatic buds contribute what?

A

Pancreatic head and main pancreatic duct. Uncitate project

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21
Q

Dorsal pancreatic buds form what?

A

Pancreatic body, tail, isthmus, and accessory pancreatic duct

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22
Q

Annular pancreas

A

ventral pancreatic bud abnormally encircles 2nd part of duodenum; forms a ring of pancreatic tissue that causes duodenal narrowing

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23
Q

Pancreas divisim

A

ventral and dorsal root fail to fuse at 8 weeks

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24
Q

Embryo origin of spleen

A

Arises from mesentery of stomach (hence is mesodermal) but is supplied by foregut (celiac artery)

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25
Q

Retroperitoneal structures

A

Include GI structures that lack a mesentary and non-GI structures

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26
Q

Result of injury to retroperitoneal structures

A

Cause blood or gas accumulation in retroperitoneal space

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27
Q

Name retroperioneal structures

A 
"SAD PUCKER"
S-uprarenal (adrenal) gland
A-orta and IVC
D-uodenum (2nd and 3rd parts)
P-ancreas (EXCEPT TAIL)
U-reters
C-olon (decending and ascending)
K-idneys
E-sophageus (lower 2/3)
R-ectum (lower 2/3)
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28
Q

Falciform ligaments

A

connects liver to anterior abdominal wall
contains ligamentum teres hepatis (derivative of fetal umbilical vein)
- derivative of ventral mesentary

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29
Q

Hepatoduodenal ligament

A

connects liver to duodenum

contains: Portal triad (hepatic artery, portal vein, common bile duct)
- can do Pringle maneuver
- connects greater and lesser sacs

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30
Q

Pringle maneuver

A

Hepatoduodenal ligament may be compressed between thumb and index finger placed in omental foramen to control bleeding.

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31
Q

Gastrohepatic ligament

A

connects liver to lesser curvature of stomach

  • contains gastric arteries
  • separates greater and lesser sacs on RIGHT
  • may be cut during surgery to access lesser sac
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32
Q

Gastrocolic

A

connects greater curvature to transverse colon

  • structures contain gastroepiploic artery
  • part of greater omentum
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33
Q

Gastrosplenic

A

connects greature curvature and spleen

  • contains short gastrics, LEFT gastroepiploic vessels
  • seperate greater and lesser sacs on LEFT
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34
Q

Splenorenal

A

connect spleen to posterior abdominal wall

- contains splenic artery and vein, tail of pancreas

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35
Q

Layers of gut wall (inside to outside)

A 
"MSMS" - inside to outside
M-ucosa 
S-ubmucosa
M-uscularis externa
S-erosa
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36
Q

Musosa of gut

A
  • epithelium (absorption)
  • lamina propria (support)
  • muscularis mucosa (motility)
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37
Q

Submucosa of gut

A
  • submucosal nerve plexus (Meissner’s) - controls secretory activity
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38
Q

Muscularis externa of gut

A

include Myenteric nerve plexus (Auerbach’s)

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39
Q

Serosa of gut

A
  • serosa when intraperitoneal

- adventitia when retroperitoneal

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40
Q

Ulcers of gut are found in which gut layers?

A

Can extend into submucosa, inner or out muscular layer

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41
Q

Erosions are found in which gut layers

A

Only in mucosa

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42
Q

Frequencies of basal electric rhythm

A

Stomach - 3 waves/min
Duodenum - 12 waves/min
Ileum - 8-9 waves/min

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43
Q

Esophagus: Histology

A

Nonkeratinized stratified squamous epithelium

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44
Q

Stomach: Histology

A

Gastric glands

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45
Q

Duodenum: Histology

A

Villi and microvilli for increased absorptive surface

Brunner’s glands (submucosa) and crypts of Lieberkuhn

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46
Q

Jejunum: Histology

A

Plicae circulares and crypts of Liberkuhn

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47
Q

Ileum: Histology

A

Peyer’s patches (lamina propria, submucosa), plicae circularis (proximal ilum) and crypts of Liberkuhm

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48
Q

Colon: Histology

A

has crypts but no villi, numerous goblet cells

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49
Q

Four sites of portosystemic anastomoses

A
  1. Esophagus
  2. Umbilicus
  3. Rectum
  4. TIPS (artificial transjugular intrahepatic portosystemic shunt - used for tx of portal hypertension)
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50
Q

Esophagus anastomosis

A

Clinical sign: esophageal varices

Connects left gastric to esophageal

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51
Q

Umbilical anastomosis

A

Clinical sign: caput medusae
Below umbilicus: connects paraumbilical to superficial and inferior epigatric
Above umbilicus: connects paraumbilic to superior epigastric and lateral thoracic

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52
Q

Rectum

A

Clinical sign: internal hemorrhoids

Connects superior rectal to middle and inferior rectal

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53
Q

Common sx of portal hypertension

A

Varices of gut, butt, and caput (medusae)

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54
Q

Tx of portal hypertension

A

TIPS - transjugular intrahepatic porosystemic shunt between portal vein and hepatic vein percutaneously relieves portal hypertension by shunting blood to systemic circulation

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55
Q

Pectinate (dentate) line

A

where endoderm (hindgut) meets ectoderm

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56
Q

Pathology ABOVE pectinate line

A

Internal hemorrhoids, Adenocarcinoma
Receives arterial supply from superior rectal artery (branch of IMA)
Venous drainage is superior to rectal vein –> inferior mesenteric vein –> portal vein

57
Q

Pathology BELOW pectinate line

A

External hemorrhoids, squamous cell carcinoma
Arterial supply: Inferior rectal artery (branch of internal pudendal artery)
Venous drainage to inferior rectal vein –> internal illiac ven –> IVC

58
Q

Internal hemorrhoids (painful or not painful?

A

NOT PAINFUL, because receives visceral innervation. Lymphatic drainage to deep nodes

59
Q

External hemorrhoids

A

PAINFUL. Receive somatic innervation (inferior rectal branch of pudendal nerve)
Lymphatic drainage to superficial inguinal nodes

60
Q

Apical surface of hepatocytes

A

face bile canaliculi

61
Q

Basolateral surface of hepatocytes

A

face sinusoids

62
Q

Zone I of liver

A

Periportal zone - affected first by viral hepatitis. Areas in which branch of portal vein/ hepatic artery are located)

63
Q

Zone II of liver

A

Intermediate zone

64
Q

Zone III - Pericentral vein (Centrilobular zone)

A

affected 1st by ischemia - farthest away from hepatic artery

  • contains P-450 system
  • most sensitive to toxic injury
  • site of alcoholic hepatitis
65
Q

Result of gallstone blocking ampulla of Vater

A

blocks bile and pancreatic ducts

66
Q

Result of tumor arising in head of pancreas (near duodenum)

A

Can cause obstruction of common bile duct

67
Q

Femoral region organization

A 
Lateral to medial: "NAVEL"
N-erve
A-rtery
V-ein
E-mpty pace
L-ymphatics
68
Q

Femoral triangle

A

contains femoral vein, artery, nerve

69
Q

Femoral sheath

A

Fascial tube 3-4 cm BELOW inguinal ligamen. Contains femoral vein, artery, and canal (deep inguinal lymph nodes) BUT NOT FEMORAL NERVE

70
Q

Hernia

A

protrusion of peritoneum through an opening- usually a site of weakness

71
Q

Diaphragmatic hernia

A

abdominal structures enter thorax

- may occur infants due to defective pleuroperitoneal membrane

72
Q

Hiatal hernia

A

common hernia in which stomach herniates upward through esophageal hiatus of diaphragm

73
Q

Sliding hiatal hernia

A

most common. GE junction displaced upwards. “Hourglas stomach”

74
Q

Paraesophageal hernia

A

GE juction is normal. FUNDUS protrudes into thorax

75
Q

Indirect hernia

A

goes through INTERNAL inguinal ring, external inguinal ring, and INTO scrotum.
- Enters internal inguinal ring LATERAL to inferior epigastric artery

76
Q

Cause of indirect inguinal hernia in infants

A

Due to failure of processus vaginalis to close (can form hydrocele). Much more common in males

77
Q

Direct inguinal hernia

A

protrudes through inguinal (Hasselbach’s triangle. Bulges directly rhough abdominal wall MEDIAL to inferior epigastric artery. Goes through ONLY the external (superficial) inguinal canal.
- Covered by external spermatic fascia. Usually in oldern man

78
Q

Mneumonic for Indirect/Direct Inguinal Hernias

A

MDs don’t LIe

  • Medial to inferior epigatric - Direct
  • Lateral to inferior epigastric -Indirect
79
Q

Femoral hernia

A

protrudes BELOW inguinal ligament through femoral canal and lateral to pubic tubercle. More common in women.

80
Q

Most common cause of bowel incarceration

A

Femoral hernia

81
Q

Hasselbach’s Triangle

A

Inguinal Triangle

  • Inferior epigatric vessels
  • Lateral border of rectus abdominus
  • Inguinal ligament
82
Q

Gastrin

A
  • found in G cells (antrum of stomach)
  • increases gastric H+ secretion
  • increases growth of gastric mucosa
  • increases gastric motility
83
Q

Gastrin regulation

A
  • INCREASED by stomach distention/alkanization, amino acids, peptides, vagal stimulation
  • DECREASED by stomach pH < 1.5
84
Q

Associations w/ gastrin

A

HIGHLY elevated in Zollinger-Ellision syndrome

  • Increased by chronic PPI use
  • Phenylalanine and tryptophan are potent stimulators
85
Q

Cholecystokinin

A
  • made by I cells (duodenum, jejunum)
  • increase pancreatic secretion
  • increase gall bladder contraction
  • DECREASES gastric emptying
  • DECREASE sphincter of Oddi relaxation
86
Q

Cholecystokinin regulation

A
  • increased by fatty acids, amino acids
87
Q

Cholecystokinin Notes

A

Cholecystokinin acts on neuronal muscarininc pathways to cause pancreatic secretions

88
Q

Secretin

A

S cells (duodenum)

  • increase pancreatic HCO3 secretion
  • decrease gastric acid secretion
  • increases bile secretion
89
Q

Secretin regulation

A

Increased by fatty acids in lumen of duodenum

  • Increased HCO3 neutralizes gastric acid in duodenum allowing pancreatic enzymes to function
90
Q

Somatosatin

A

secreted by D cells (pancreatic islets, GI mucosa)

  • decreases gastric acid and pepsinogen secretion
  • decreases pancreatic and small intestine fluid secretion
  • decreases gallbladder contraction
  • decreases insulin and glucagon release
91
Q

Somatostatin regulaton

A
  • increased by acid
  • decreased by vagal stimulation
  • inhibitory hormone.
  • Antigrowth hromone effects (inhibits digestion and absorption of substances needed for growth)
92
Q

Glucose-dependent insulinotropic peptide

A 
K cells (duodenum, jejunum)
Exocrine: decreases gastric H secretion
Endocrine: increases insulin release
93
Q

Glucose-dependent insulinotropic peptide: regulation

A

increased by fatty acids, amino acids, oral glucose

  • Also known as GIP
  • An oral glucose load is used more rapidly than IV due to GIP
94
Q

Vasoactive intestinal polypeptide (VIP)

A

Parasympathetic ganglia in sphincters, gallbladder, small intestine

  • Increases water and electrolyte secretion
  • Increases relaxation of intestinal smooth muscle and sphincters
95
Q

VIP Regulation

A
  • Increased y distention of vagal stimulation

- Decreased by adrenergic input

96
Q

VIPoma

A
  • non alpha, non-B islet pancreatic tumor that secretes VIP.
    Associated with WHDA syndrome -
    Watery Diarrhea, Hypokalemia, and Achlorydia
97
Q

Nitric Oxide

A

Increases smooth muscle relaxation, including lower esophageal sphincter

98
Q

NO and its implication in achalasia

A

Loss of NO secretion is implicated in lower esophageal tone in achalasia

99
Q

Motilin

A
  • found in small intestine

- produce migrating motor complexes

100
Q

Motilin regulation

A
  • increased in fasting state

- motilin receptor agonists (such as erythromycin) are used to stimulate intestinal peristalsis

101
Q

Intrinsic factor

A
  • found in parietal cells (stomach)

- Vitamin B12 - binding porein (required for B12 uptake to terminal ileum)

102
Q

Autoimmune destruction of parietal cells

A

Chronic gastritis and pernicious anemia

103
Q

Gastric acid

A
  • secreted by parietal cells (stomach)

- decrease stomach pH

104
Q

Gastric acid regulation

A
  • Increased by histamine, ACh, gastrin

- Decreased by somatostatin, GIP, prostaglandin, secretin

105
Q

Gastrinoma

A

gastrin-secreting tumor that causes continuous high levels of acid secretion

106
Q

Pepsin

A
  • found in chief cells (stomach)

- protein degestin

107
Q

Pepsin regulation

A

increased by vagal stimulation, local acid

Inactive pepsinogen –> pepsin by H+

108
Q

HCO3

A
  • made by mucosal cells (stomach, duodenum, salivary glands, pancreas) and Brunner’s glands (duodenum)
  • neutralizes aics
109
Q

HCO3 regulation

A

Increased by pancreatic and biliary secretion with secretiin

- HCO3 is trapped in mucus that covers the gatric epithelium

110
Q

Saliva

A

secretion from parotid, submandibular, and sublingual glands is stimulated by SYMPATHETIC and PARASYMPATHETIC acitivity.
Amylase digests starch, Bicarb neutralizes bacterial acids, Mucins lubricate food
Normally hypotonic because of absorption but more isotonic with higher flow rates

111
Q

Discuss atropine and parietal cells

A

Atropine blocks vagal stimulation of parietal cells. Vagal stimulation of G cells (secretes gastrin) is unaffected because uses GRP as neurotransmitter not ACh

112
Q

Gastrin increases acid secretion through its effect on which cells

A

ECL cells (which lead to histamine release) rather than through direct effect on parietal cells

113
Q

Brunner’s glands

A

located in duodenal submucosa. Secretes alkaline mucus. Hypetrophy seen in peptic ulcer disease

114
Q

Nature of pancreatic secretions

A

Isotonic fluid
low flow –> high Cl-
High flow –> High Bicarb

115
Q

Alpha-amylase

A

Pancreatic secretion. Digests starch.

*Secreted in active form

116
Q

Lipase, Phospholipase A, colipase

A

Pancreatic secretions. Aids in fat digestion.

117
Q

Pancreatic proteases

A
  • Digests proteins

- Includes trypsin, chemotrypsin, elastase, carboxypeptidases

118
Q

Trypsinogen

A

Converted to active enzyme trypsin –> activation of other pro-enzymes and creation of more trypsinogen (positive feedback loop)

119
Q

Enterokinase/ Enteropeptidase

A

converts trypsinogen to trypsin

- secreted from duodenal mucosa

120
Q

Salivary amylase

A

Starts carbohydrate digestion. Hydolyzes alpha 1,4 linkages to yield disaccarides (maltose and alpha limit dextrins)

121
Q

Pancreatic amylase

A

Highest concentration in duodenal lumen, hydrolyzes starch to oligosaccharides and disaccharides

122
Q

Oligosaccharide hydrolases

A

At intestinal brush border.

RATE LIMITING STEP in carbohydrate digesti, produce monosaccharide from oligo-disaccharides

123
Q

Monosaccharide absorption

A
  • Only monosaccharides (glucose, galactose, fructorse) are absorbed by enterocytes. All are transported to blood by GLUT-4
124
Q

Glucose and galactose absorption

A

Taken by SGLT1 (Na+ dependent)

125
Q

Fructose absorption

A

Facilitated diffusion by GLUT-5.

126
Q

D-xylose absorption test

A

Distinguishes GI mucosal damage from other causes of malasborption

127
Q

Fe absoprtion

A

absorbed as Fe2+ in DUODENUM

128
Q

Folate absorption

A

Absorped in jejunum

129
Q

B12 absorption

A

absorbed in terminal ileum, along with bile acids, requires intrinsic factor

130
Q

Peyer’s patches

A

unencapsulated lymphoid tissue found in lamina proproa and submucosa of ileum. Contains specialized M cells that take up antigen

131
Q

Discuss B cells and Peyer’s Patches

A

B cells stimulated by germinal centers of Peyer’s patches differentiate in to Ig-A secreting plasma cells, which ultimately reside in lamina propria.
IgA receives protective secretory component and is then transported across epithelium to deal with intraluminal antigen

132
Q

Bile Composition

A

composed of bile salts (bile acids conjugated to glycine/taurine, making them water soluble), phospholipids, cholesterol, bilirubin, water, and ions.

133
Q

Bile Function

A 
Digestion and absorption of lipids and fat soluble vitamins.
Cholesterol excretion (body's only means of eliminating cholesterol)
Antimicrobial activity (via membrane disruption)
134
Q

Enzyme that catalyze bile formation

A

Cholesterol 7-alpha hydroxylase catalyzes rate limiting step.

135
Q

Bilirubin

A

product of heme metabolism. Bilirubin is removed from by liver, conjugated wth glucuronate, and excreted in bile

136
Q

Direct bilrubin

A

Made in liver

- conjugated in glucuronic acid; water soluble

137
Q

Indirect bilirubin

A

Unconjugated - water insoluble

- made from breakdown of heme

138
Q

Trace Heme break down

A
  1. RBCs lyse
  2. Heme breaks down to form unconjugated bilirubin (water insoluble)
  3. Albumin- complexes w/ unconjugated bilirubin for transport to liver
  4. UDP-glucoronsyl transferase in liver conjugates bilirubin to make direct bilirubin
  5. Direct bilirubin is secreted into gut and broken down by gut bacteria to become urobillinogen
139
Q

Discuss pathway of urobillinogen

A

Product of gut bacteria breakdown of direct billirubin.

  1. 80% of urobillinogen is excreted into feces
  2. 20% of urobillinogen is absorted into gut - small fraction is excreted in kidney as urobilin (gives pee its color)
    - majority of absorbed urobillinogen is recirculated in the enterohepatic circulation

USMLE Step 1 (34 decks)

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