UWORLD ROUND 1

Question 1

by what week of gestation do neural crest cells reach the proximal colon and rectum?

Answer 1

8th week-proximal colon

12th week - rectum

Question 2

The arrest of migration of neural crest cells during gestation causes which disease?

Answer 2

Hirschsprung disease (rectum is always involved)

Question 3

Sx of Hirschsprung disease?

Answer 3

• failure to pass meconium within 48 hrs of birth
• sx of intestinal obstruction (bilious vomiting & abd. distention)
• bowel is filled with stool but the rectum is empty
• anal sphincter tone increased
• rectal biopsy reveals an anganglionic segment of bowel

Question 4

poststreptococcal glomerulonephritis is caused by what type of hypersensitivity?

Answer 4

nephritic syndrome
type III (immune-complex-mediated) hypersensitivity
-deposition of antibody-antigen complexes (IgG, IgM, C3)

Question 5

pleiotropy

Answer 5

multiple phenotypic manifestations result from a single genetic mutation

Question 6

local heterogeneity

Answer 6

ability of one disease or trait to be caused mutations in multiple different genes. Ex: familial hypercholesteremia, which can be caused by different mutations affecting cholesterol metabolism (LDL receptor, apo B-100)

Question 7

alpha 1 receptor:
target organ
effect of stimulation
examples

Answer 7

target organ: peripheral vasculature, bladder, eye

effect: inc. BP (esp. systolic), contraction of internal urethral sphincter, mydriasis (contraction of pupillary dilator muscle)

Ex: Epi, NE, phenylephrine

Question 8

beta 1 receptor:
target organ
effect of stimulation
examples

Answer 8

target organ: heart

effect: inc. HR, contractility & conductance

Ex: Epi, Dopamine, Dobutamine, Isoproterenol

Question 9

Beta 2 receptor:
target organ
effect of stimulation
examples

Answer 9

target: peripheral vasculature (smooth muscle), bronchi, uterus
effect: vasodilation, dec. BP (esp. diastolic), bronchodilation, uterus relaxation (tocolysis)

Ex: Isoproterenol, Terbutaline

Question 10

nonselective beta agonist MOA

Answer 10

inc. myocardial contractility and dec. systemic vascular resistance

Ex: isoproterenol

Question 11

virulence factor of strep. pneumo

Answer 11

polysaccharide capsule that inhibits opsonization and phagocytosis

Question 12

MOA of fluorouracil

Answer 12

inhibits thymidylate synthase

Question 13

clostridium perfringens alpha toxin affects cells and facilitates the spread of gas gangrene via what MOA

Answer 13

splitting lecithin to phosphorylcholine and diglyceride

Question 14

surface ectoderm derivatives

Answer 14

• anterior pituitary (rathke pouch)
• lens & cornea
• inner ear sensory organs, olfactory epithelium
• nasal & oral epithelial linings, salivary glands
• epidermis, sweat and mammary glands

Question 15

neural tube (from ectoderm) derivatives

Answer 15

• brain & spinal cord
• post. pituitary, pineal gland
• retina

Question 16

neural crest (from ectoderm) derivatives

Answer 16

• neural ganglia, adrenal medulla
• schwann cells; pia & arachnoid mater
• aorticopulmonary septum & endocardial cushions
• branchial arches (bones & cartilage)
• skull bones
• melanocytes

Question 17

mesoderm derivatives

Answer 17

• Muscles (skeletal, cardiac, smooth)
• CT, bone, cartilage
• Serosal linings (peritoneum)
• Cardiovascular & lymphtic system
• Spleen & hemopoietic cells
• Kidney & ureters, internal genitalia
• Adrenal cortex

Question 18

Endoderm derivatives

Answer 18

• GI tract, liver, pancreas
• Lungs
• Thymus, parathyroid, thyroid follicular cells
• Middle ear epithelium
• Bladder & urethra
• Parafollicular (C) cells

Question 19

gap junction proteins

Answer 19

proteins: connexins

upregulated by estrogen immediately prior to delivery

Question 20

tight junction proteins

Answer 20

claudins, occludin

Question 21

adherens junction proteins

Answer 21

cadherins

Question 22

desmosome proteins

Answer 22

cadherins (desmogleins, desmoplakin)

Question 23

hemidesmosome proteins

Answer 23

integrins

Question 24

what is the diagnostic feature of infectious mononucleosis

Answer 24

reactive lymphocytes:
large, scalloped and have abundant cytoplasm.
They contain cytotoxic granules composed of perforins (create holes in the infected cell’s membrane) and granzymes (enter the cytoplasm of infected cells and trigger cell death), which are released in response to foreign antigens on the surface of MHC I receptors (cytotoxic T cells) of infected host cells

Question 25

ventral pancreatic bud contributes to which structures?

Answer 25

main pancreatic duct and uncinate process

Question 26

the dorsal pancreatic bud contributes to which structures?

Answer 26

body, tail, isthmus and accessory pancreatic duct

Question 27

what embryonic structure composes the pancreatic head?

Answer 27

both ventral and dorsal pancreatic buds

Question 28

chromaffin cells: | location & function

Answer 28

modified neuroendocrine cells derived from the neural crest and located in the adrenal medulla -they are stimulated by acetylcholine released by sympathetic preganglionic neurons and secrete catecholamines (80% Epi, 20% NE) directly into the bloodstream to amplify SNS activity

Question 29

role of cortisol in catecholamine synthesis?

Answer 29

cortisol produced in response to ACTH increases the activity of the adrenal medullary enzyme phenylethanolamine N-methyltransferase, which catalyzes the conversion of NE to Epi

Question 30

site of thoracentesis

Answer 30

- below 6th rib midclavicular - below 8th rib midaxillary - below 10th rib paraverterbrally **insertion of needle below the 9th rib increases the risk of penetrating abdominal structures

Question 31

GPCR receptors on pancreatic beta cells:

Answer 31

* M3 - Gq - inc. insulin secretion * Glucagon - Gs/Gq - inc. insulin secretion * beta 2 adrenergic & Glucagon like peptide 1- Gs - inc. insulin secretion **alpha 2 adrenergic, somatostatin 2 - Gi - decrease insulin secretion

Question 32

sympathetic stimulation's effect on insulin secretion

Answer 32

pancreatic beta cells contain both alpha 2 and beta 2 receptors, which exert opposite effects. However, alpha 2 mediated inhibitory effect is predominant, causing SNS to lead to overall inhibition of insulin secretion

Question 33

thayer martin medium

Answer 33

used to identify pathogenic Neisseria organisms: chocolate sheep blood agar infused with vanocmyocin to inhibit gram positive bacteria, colistin and trimethoprim to inhibit gram negative bacteria and nystatin to inhibit yeast

Question 34

function of glucagon like peptide 1 (GLP-1)

Answer 34

regulates glucose by slowing gastric emptying, suppressing glucagon secretion and increasing glucose-dependent insulin release

Question 35

which drugs decrease breakdown of GLP-1?

Answer 35

Dipeptidyl peptidase-4 inhibitors (sitagliptin, saxagliptin) decrease breakdown of GLP-1 and improve glycemic control in patients with type II diabetes *low risk of hypoglycemia

Question 36

mechanism of penicillin resistance:

Answer 36

- beta lactamase, ESBL - mutated penicillin binding proteins - mutated porin protein

Question 37

mechanism of vancomycin resistance:

Answer 37

- mutated peptidoglycan cell wall | - impaired influx/increased efflux

Question 38

mechanisms of quinolone resistance:

Answer 38

- mutated DNA gyrase | - impaired influx/increased efflux

Question 39

mechanism of aminoglycosides resistance:

Answer 39

- aminoglycoside-modifying enzymes - mutated ribosomal subunit protein - mutated porin protein

Question 40

mechanism of tetracycline resistance:

Answer 40

- impaired influx/increased efflux | - inactivated enzyme

Question 41

mechanism of rifamycin resistance:

Answer 41

-mutated RNA polymerase

Question 42

A stepmother treats a child she resents with excessive nurturing and overprotection

Answer 42

reaction formation - replacing a warded-off idea or feeling with an emphasis on its opposite