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Gastrointestinal system

Gastrointestinal system




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USMLE® Step 1 style questions USMLE

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A 6-day-old female is brought to the pediatrician by her parents for evaluation of jaundice. She was born at 36 weeks gestation to a 29-year-old, gravida 1 para 1, woman via an uncomplicated vaginal delivery. According to her parents, the patient has had difficulty latching to her mother’s breast. The patient has passed meconium and produces 3-4 wet diapers per day. In the office, she is fussy but consolable. Physical examination shows depressed anterior and posterior fontanelles. Scleral icterus and jaundice of the head and chest are observed. Cardiac, pulmonary, and abdominal exams are noncontributory. Which of the following best describes the pathophysiology of this patient’s condition?  

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jaundice with p. 402

Jaundice p. 402

alcoholic cirrhosis and p. 401

biliary tract disease p. 404

cholangitis p. 377, 404

cirrhosis p. 398

Crigler-Najjar syndrome p. 718

as drug reaction p. 250

fructose intolerance p. 78

galactosemia p. 78

graft-versus-host disease p. 117

hepatitis B p. 180

hepatocellular carcinoma p. 401

hereditary hyperbilirubinemias p. 403

leptospirosis p. 145

newborn hemolytic disease p. 416

painless p. 717

pancreatic cancer p. 404

ToRCHeS infections p. 181

transfusion reaction p. 112

yellow fever p. 165


jaundice in p. 402

Obstructive jaundice p. 407

Phototherapy for jaundice p. 402


Content Reviewers

Jaundice, which doesn’t have the most intuitive name, comes from the french jaunice, meaning yellowing.

It’s also sometimes referred to as icterus though, the origin of which is even less intuitive, coming from the thought that jaundice could once be cured by looking at a yellow bird, the more you know!

Anyways, as you’ve probably gathered, jaundice involves someone taking on yellow pigments, specifically in the skin and eyes.

The yellowing pigment is caused by a compound called bilirubin, a component of bile and the main cause of bruises being yellow, and after its metabolism, the yellow-ness of urine and brown-ness of feces.

So since bilirubin’s our main culprit of yellow-ness, it’s super important to know where it comes from.

As red blood cells near the end of their lifespan—which is about 120 days—they’re eaten up or phagocytosed by macrophages in the reticuloendothelial system, aka the macrophage system, where the spleen plays the largest part, but it’s also made of parts of the lymph nodes.

K so first the macrophage eats up the blood cell, and hemoglobin is broken up into heme and globin, the globin is further broken into amino acids.

The heme on the other hand is split into iron and protoporphyrin, protoporphyrin is then converted into unconjugated bilirubin, or UCB.

Unconjugated bilirubin is the form of bilirubin that’s lipid-soluble, meaning it’s not water-soluble, sometimes it’s also known as indirect bilirubin.

Albumin in the blood then binds to UCB and gives it a lift over to the liver where it’s taken up by hepatocytes, where it’s conjugated by an enzyme called uridine glucuronyl transferase (UGT), making it now water soluble.

At this point the conjugated bilirubin is secreted out the bile canaliculi where it drains into the bile ducts and sent to the gallbladder for storage as bile.

Now when you eat a donut or something, your gallbladder secretes the bile and CB, it moves through the common bile duct to the duodenum of the small intestine and is converted to urobilinogen, or UBG, by intestinal microbes in the gut.


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