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USMLE Step 1 > Gastrointestinal System > Flashcards

Gastrointestinal System Flashcards

1
Q

What is the embryological derivation of the pancreas?

A

Foregut endoderm

Ventral bud –> pancreatic head, main duct, uncinate process

Dorsal bud –> pancreas body, tail, isthmus, accessory pancreatic duct

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2
Q

What is the embryological derivation of the spleen?

A

Mesoderm

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3
Q

What structures are retroperitoneal?

A

Adrenal glands

Kidneys

Ureters

Aorta and IVC

Duodenum (2nd thru 4th parts)

Pancreas (except tail)

Colon (descending and ascending)

Esophagus (lower 2/3)

Rectum (partially)

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4
Q

What is contained within the portal triad?

A

Proper hepatic artery

Portal vein

Common bile duct

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5
Q

Meissner vs. Auerbach plexus

A

Meissner plexus located in the submucosa

Auerbach/myenteric plexus located in the muscularis externa

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6
Q

Describes the hepatocyte zones

A

Blood flows from the portal vein and hepatic artery to the central vein

Zone 1 = periportal zone → affected first by viral hepatitis and ingested toxins

Zone 2 = intermediate zone

Zone 3 = pericentral/centrilobular zone → affected first by ischemia, contains P-450s, most sensitive to metabolic toxins, affected first by alcoholic hepatitis

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7
Q

Above vs. below pectinate/dentate line

A
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8
Q

Describe the different kinds of hernias

A

Umbilical hernia → defect at linea alba

Sliding hiatal hernia → GE junction is displaced superiorly forming “hourglass” stomach

Paraesophageal hernia → normal GE junction but fundus protrudes into thorax

Indirect inguinal hernia → enters deep inguinal ring lateral to inferior epigastric arteries 2/2 failure of obliteration of process vaginalis

Direct inguinal hernia → protrudes through Hesselbach’s triangle through a weakness in the transversalis fascia medial to the inferior epigastric arteries

Femoral hernia → protrudes below the inguinal ligament through the femoral canal lateral to pubic tubercle (more common in females)

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9
Q

Salivary tumors

A

Benign

Pleomorphic adenoma → chondromyxoid stroma and epithelium; often recurs after resection

Warthin tumor → cystic, germinal centers

Maliganant

Mucoepidermoid carcinoma → mucinous and squamous cells

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10
Q

Triad of Plummer-Vinson Syndrome

A

Dysphagia from esophageal webs

Iron deficiency anemia

Glossitis

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11
Q

Intestinal type gastric adenocarcinoma

A

A/w H. pylori infection, smoking, nitrosamines (smoked foods)

Ulcer with raised margins on the lesser curvature

May metastasize to Virchow node (left supraclavicular) or Sister Mary Joseph nodule (subcutaneous periumbilical)

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12
Q

Diffuse type gastric adenocarcinoma

A

NOT associated with H. pylori infection

Signet ring cells, thickeninc of stomach wall → linitis plastica

a/w metastasis to bilateral ovaries (Krunkenberg tumor)

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13
Q

What are the fat soluble vitamins?

A

Vitamins A, D, E, K

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14
Q

Gardner Syndrome

A

Familial adenomatous polyposis (AD mutation of APC) + osseous and soft tissue tumors, congenital hypertrophy of retinal pigment epithelium

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15
Q

Turcot Syndrome

A

Familiarl adenomatous polyposis (AD mutation of APC) + malignant CNS tumors

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16
Q

Hereditary nonpolyposis colorectal cancer (Lynch syndrome)

A

Autosomal dominant mutation in DNA mismatch repair genes a.k.a 3’ → 5’ exonucelases (microsatellite instability)

Always involved proximal colon

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17
Q

Adenoma-carcinoma sequence

A
  1. APC mutation increases risk for formation of polyp via decreased intercellular adhesion and increased proliferation
  2. K-ras mutation leads to formation of polyp via unregulated intracellular signal transduction
  3. p53 mutation and increased expression of COX allows for progression to carcinoma; reduced risk with aspirin
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18
Q

Histology of alcoholic liver disease

A

Steatosis (reversible) → lipid droplets in hepatocytes

Hepatitis → swelling and necrosis of hepatocytes with neutrophilic infiltration and Mallory bodies (intracytoplasmic eosinophilic inclusions)

Cirrhosis (irreversible) → sclerosis around central vein, regenerative nodules surrounded by fibrous septa

19
Q

Liver disease associated with exposure to arsenic or vinyl chloride

A

Liver angiosarcoma, malignant tumor of endothelial cells

20
Q

Liver disease associated with exposure to OCPs or anabolic steroids

A

Hepatic adenoma, benign tumor of hepatocytes

21
Q

Wilson disease

A

Autosomal recessive defect in ATP7B gene (chromosome 13) → ↓ hepatic copper excretion and failure of copper to enter circulation as ceruloplamin

May manifest with hemolytic anemia, parkinsonian symptoms, asterixis, dementia, chorea, cirrhosis, hepatocellular carcinoma, Kayser-Fleischer rings (copper deposits in the cornea → visible on slit lamp exam), cystic degeneration of putamen and basal ganglia

Dx: ↓ ceruloplasmin

Tx: D-penicillamine, trientine (copper chelators)

22
Q

Hemochromatosis

A

Excess body iron leading to deposition of hemosiderin in tissues and organ damage caused by HFE gene mutation or chronic transfusion therapy

Symptoms include cirrhosis, secondary diabetes mellitus, bronze skin, dilated cardiomyopathy → CHF, cardiac arrhythmias, testicular atrophy

Dx: ↑ ferritin, ↑ iron, ↓ TIBC → ↑ transferrin saturation

Tx: phlebotomy or chelation (deferasirox, deferoxamine)

23
Q

Embryological formation of teeth

A

Ameloblasts from ectoderm produce enamel

Odontoblasts from neural crest produce dentin

24
Q

Types of tongue papillae

A

Filiform (most common)

Fungiform

Circumvallate

Foliate (lateral aspects)

25
Q

How are taste sensations transmitted?

A

Sour and salt → interact with ion channels to depolarize membrane → activated calcium channels → influx of calcium → release of neurotransmitters

Bitter, sweet, and umami → GPCR → activates phospholipase C → influx of calcium → release of neurotransmitters

26
Q

How does flow rate affect the ionic composition of saliva?

A

Low flow → more sodium and chloride, isotonic

High flow → less sodium and chloride, hypotonic

27
Q

Where are iron, folate, vitamin B12, and bile acids absorbed?

A

Iron → Fe2+ in duodenum

Folate → jejunum and ileum

Vitamin B12 → terminal ileum (requires intrinsic factor)

Bile acids → terminal ileum

28
Q

Cholecystokinin (CCK)

A

Secreted by I cells (duodenum, jejunum) in response to fatty acids and amino acids:

↑ pancreatic secretions

↑ gallbladder contraction

↑ sphincter of Oddi relaxation

↓ gastric emptying

29
Q

Gastrin

A

Secreted by G cells (antrum) in response to stomach distention, alkalinization, amino acids (phenylalanine, tryptophan), peptides, vagal stimulation:

↑ gastric H+ secretion

↑ growth of gastric mucosa

↑ gastric motiligy

30
Q

Somatostatin

A

Secreted by D cells in the pancreatic islets and GI mucosa in response to acid:

↓ gastric acid and pepsinogen secretion

↓ pancreatic and small intestine fluid secretion

↓ gallbladder contraction

↓ insulin and glucagon release

31
Q

Secretin

A

Secreted by S cells (duodenum) in response to increases in acid and fatty acids in the duodenum:

↑ pancreatic HCO3- secretion

↓ gastric acid secretion

↑ bile secretion

32
Q

How does flow rate affect the ionic composition of pancreatic secretions?

A

As flow rate increases:

Na+ and K+ stay the same

HCO3 - ↑

Cl- ↓

33
Q

Symptoms of riboflavin deficiency (vitamin B2)

A

Angular stomatitis, chelitis, glossitis, seborrheic dermatitis, eye changes (keratitis, corneal neovascularization), anemia

May be seen in malnourished, alcoholics

Riboflavin incorporated into coenzymes FMN and FAD required with succinate dehydrogenase

34
Q

Symptoms of vitamin E deficiency

A

Vitamin E deficiency predisoses cell membranes to oxidative injury, especially vulnerable cells like neurons and erythrocytes → neuromuscular disease, hemolytic anemia

35
Q

Symptoms of vitamin A deficiency and overdose

A

Deficiency: night blindness, dry eyes (xerophthalmia), corneal sofening (keratomalacia)

Acute overdose: nausea, vomiting, blurred vision, vertigo

Chronic overdose: alopecia, dry skin, hyperlipidemia, hepatotoxicity, hepatosplenomegaly, visulal difficulties

Teratogenic effects: microcephaly, cardiac anomalies, fetal death

36
Q

Symptoms of vitamin C overdose

A

Nausea, abdominal pain, diarrhea

37
Q

What pathology is associated with hepatic microvesicular steatosis?

A

Alcoholic hepatosteatosis

Non-alcoholic hepatosteatosis

Reye syndrome (viral febrile illness treated with aspirin in children)

38
Q

What pathology is associated with hepatic apoptosis, acinar necrosis, and periportal mononuclear inflammatory infiltration?

A

Viral hepatitis

39
Q

What pathology is associated with hepatic centrilobular congestion?

A

Right-sided heart failure

Budd-Chiari syndrome (obstruction of hepatic veins or IVC)

40
Q

What pathology is associated with hepatic bile duct destruction, periductal graulomatous inflammation, and bile duct proliferation?

A

Primary sclerosing cholangitis

41
Q

Treatment for H. pylori infection

A

H. pylori is associated with duodenal (usually benign) > gastric (can be benign or malignant) ulcers

Treated with triple therapy: 2 antibiotics (amoxicillin and clarithromycin) + PPI

42
Q

What is the embryological derivation of the salivary glands?

A

Surface ectoderm

43
Q

Symptoms of vitamin C deficiency

A

Scurvy

Bleeding gums, ecchymoses and petechiae, impaired wound healing, perifollicular hemorrhages and coiled (corkscrew) hairs

Vitmain C is a co-factor for enzymes that hydroxylate proline and lysine residues in collagen in the RER

USMLE Step 1 (20 decks)

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