UWorld_2.9

Question 1

Failure of fusion of urethral folds in female and male==> ?

Answer 1

• @ female = normal ==> vaginal opening
• @ male = abnormal ==> hypospadia
  
  • urtheral folds normally form ventral portion of penis
  • failure of fusion ==> urethral opening on ventral surface somewhere between perineum and just proximal to glans penis

Question 2

Epispadia presentation

Answer 2

• location of urethral opening on dorsal surface of penile shaft
• due to malpositioning of genital tubercle during 5th week of gestation

Question 3

Characteristics of kinesin and dynein

Answer 3

• microtubule-associated motor proteins fxn of rapid transport of materials/organelles in cells
• @ neurons:
  
  • kinesin = anterograde transport
  • dynein = retrograde transport
• dynein also associated w/ciliary and flaggelar movement
• energy for movement derived from ATP

Question 4

Common proto-oncogenes + gene product + associated cancer

Answer 4

• RAS = GTP-binding protein
  
  • Choliangiocarcinoma
• MYC = transcription factor
  
  • Burkitt’s Lymphoma
• ERBB-1 (EGFR) = receptor tyrosine kinase
  
  • Lung adenocarcinoma
• ERBB-2 (HER2) = receptor tyrosine kinase
  
  • Breast Cancer
• ABL = nonreceptor tyrosine kinase
  
  • chronic myelogenous leukemia
• BRAF = RAS signal transduction
  
  • Hairy cell leukemia
  • melanoma

Question 5

Common tumor-suppressor genes + gene product + associated cancer

Answer 5

• BRCA-1, BRCA-2 = DNA repair gene
  
  • Breat & Ovarian cancer
• APC/B-catenin = WNT signaling
  
  • colorectal, gastric, pancreatic cancer
  • FAP
• TP53 = genomic stability
  
  • most cancers
  • Li-Fraumeni
• Rb = inhibits G1/S transition
  
  • Retinoblastoma
  • Osteosarcoma
• WT1 = urogenital differentiation
  
  • Wilm’s tumor
• VHL = ubiquitin ligase component
  
  • von-hippel lindau

Question 6

Blood gas levels during aerobic exercise

Answer 6

• homeostatic mechanisms maintain arterial O₂/CO₂/pH
• increased O₂ consumption @ muscles + increase CO₂ production ==> decreased O₂ and increased CO₂ @ mixed venous blood

Question 7

Location of B cell VDJ recombination + post-activation location

Answer 7

• VDJ recombination ==> formation of antibodies/antigen recognition; occurs during maturation @ bone marrow
• Activated B-cells ==> germinal centers of lymph nodes
  
  • proliferation of B-cells into memory cells and antibody secreting cells
  • antibody-secreting cells undergo isotype switching

Question 8

Characteristics of horshoe kidney

Answer 8

• horshoe kidney = fusion of kidneys at upper or lower pole (90% at lower pole)
• kidneys normall ascend from sacral area ==>
• in horshoe kidney, fused pole lies anterior to great vessels
  
  • fused poles become trapped by inferior mesenteric artery and cannot ascend to normal position
• can lead to urinary tract obstruction and hydronephrosis

Question 9

Causes/location of osteomyletis in childhood

Answer 9

• s. aureus
• long bones

Question 10

Causes/location of osteomyletis in sickle cell disease

Answer 10

• salmonella
• s.aureus
• @ long bones

Question 11

Causes/location of osteomyletis in Pott disease

Answer 11

• mycobacterium tuberculosim
• @ vertebrae

Question 12

Cause/location of osteo in DM

Answer 12

• polymicrobial
• @ bones of foot (from foot ulcers)

Question 13

Causes/location of osteo @ recumbent patient

Answer 13

• polymicrobial
• @ sacrum/heels