Deck XI Flashcards Preview

USMLE World Missed Questions > Deck XI > Flashcards

Flashcards in Deck XI Deck (30):
1

The bacterial lac operon is an example of which type of mRNA?

Polycistronic mRNA- it codes for several proteins. Transcription and translation is regulated by a single gene promoter, operator, and set of regulatory elements.

2

What is the function of 7a-hydroxylase?

It induces conversion of cholesterol into bile acids which decreases cholesterol concentration in bile.

3

How do cholesterol levels induce gallstones?

When the gallbladder is hypomotile or there is more cholesterol than can be dissolved by bile salts then cholesterol precipitates into insoluble crystals that lead to gallstones.

4

How does estrogen contribute to gallstone formation?

By increasing hepatic HMG-CoA reductase activity, thereby facilitating cholesterol biosynthesis.

5

Describe the mechanism of colonic diverticula.

Formed by pulsion (increased pressure due to straining to defecate)

6

What is the difference between a true and false diverticulum?

False diverticula do not have all organ layers; true diverticula do (ex. Meckel diverticulum)

7

What layers compose a colonic diverticula?

Mucosa and submucosa.

8

Where is the most common site for colonic diverticula to occur?

The sigmoid colon.

9

How does shigella gain access to the intestinal mucosa?

It exhibits specificity for the M cells that lie in the base of mucosal villi within a Peyer's patch region of the ileal mucosa. At the base of M cells, macrophages and lymphocytes lie, waiting to mount an immune response; Shigella penetrates mucosal membranes of the gut by passing through M cells first.

10

What are M cells of the ileal mucosa?

Antigen sampling cells designed to sample the contents of the gut lumen and transfer antigens to their basal lamina within endosomes.

11

What is the most common etiological agent of shigellosis in the US?

S. Sonnei.

12

What symptoms are characteristic of left sided colon cancers?

Infiltration of intestinal walls and encircling of the lumen, causing symptoms of partial intestinal obstruction- changes in stool caliber, constipation, cramping abdominal pain, distention, nausea, vomiting.

13

What symptoms are characteristic of a right sided colon cancers?

Exophytic masses that do not cause intestinal obstruction but rather cause iron deficiency anemia (fatigue and pallor) due to blood loss. Anorexia, malaise, and weight loss also occur.

14

In what condition is the liver typically seen as black?

Dubin- Johnson syndrome

15

What is the pathophysiology associated with Dubin- Johnson syndrome?

A defect in hepatic excretion of billirubin glucuronidases across the canalicular membrane

16

What symptoms characterize Dubin Johnson syndrome?

Conjugated chronic hyperbilirubinemia that is not associated with hemolysis

17

In Dubin Johnson syndrome, the pigment in hepatocytes is composed of what compounds?

Epinephrine metabolites within lysosomes

18

Name the three main causes of HIV- associated esophagitis?

Candida, Cytomegalovirus, Herpes virus.

19

Esophagitis associated with cytomegalovirus presents with what microscopic and endoscopic findings?

Endoscopic findings include linear ulceration; microscopic findings include intranuclear and cytoplasmic inclusions.

20

Name four conditions associated with vitelline duct abnormalities.

A persistent vitelline duct, Meckel diverticulum, vitelline sinus, vitelline duct cyst.

21

What is the mechanism of ribavirin in treatment of hepatitis C?

A nucleoside antimetabolite drug that interferes with duplication of viral genetic material. It causes a defective 5' cap to form on viral mRNA transcripts and mediates a more effective immune response.

22

What two conditions is ribavirin used to treat?

Hepatitis C and RSV.

23

Where do most duodenal ulcers occur?

In the duodenal bulb (the first portion of the duodenum)

24

What condition is suggested by an ulcer located in the distal duodenum or other location in the duodenum besides the duodenal bulb?

Zollinger- Ellison syndrome (caused by gastrinomas)

25

What acid-base status changes are present in a patient with DKA?

Anion Gap metabolic acidosis- decreased bicarb with compensatory respiratory alkalosis (low PaCO2). Arterial pH less than 7.3

26

What sound is commonly heard in patients in left ventricular systolic failure?

S3 heart sound

27

Where is the S3 heart sound best heard?

With the bell of the stethoscope at the ventricular apex in L. lateral decubitus position. It is heard loudest by listening at end expiration as this decreases lung volume and brings the heart closet to the chest wall.

28

Which types of murmurs become more audible when decreasing venous return to the heart (i.e. valsalva, standing up)?

Murmurs associated with mitral valve prolapse and hypertrophic cardiomyopathy become more audible

29

Which types of murmurs become less audible when decreasing venous return to the heart (i.e. valsalva, standing up)?

Murmurs associated with aortic stenosis (these increase with increased venous return, ie valsalva release or laying supine)

30

In physiologic conditions, which ions flow out of a cell after opening of their ion channels?

Potassium only.