6/7 UWorld

Question 1

What structure is cut during a midline episiotomy

Answer 1

Perineal body

Midline episiotomy is a vertical incision from the posterior vaginal opening to the perineal body

Itr transects the vaginal submucosal tissue but not the external anal sphincter or the rectal mucosa

Question 2

Describe the pathogenesis of Zenker diverticulum

Answer 2

• Thought to be due to abnormal spasm or diminished relaxation of pharyngeal muscles during swallowing
• Increased oropharyngeal intraluminal pressure eventually results in herniation of the pharyngeal mucosa through a zone of muscle weakness (false diverticulum) in the posterior hypopharynx
• Pulmonary aspiration of diverticular contents may lead to recurrent pneumonia

Question 3

What causes differentiation of Th0 cells into Th1 cells

What is produced by Th1 cells

What inhibits differentation of Th1 cells

Answer 3

• Th1 cells
  
  • Differentiation caused by IL-12 (secreted by macrophages)
  • Produces IL-2 and IFN-y
  • Inhibited by IL-10

Question 4

What causes differentiation of Th0 cells into Th2 cells

What is produced by Th2 cells

What inhibits differentiation of Th2 cells

Answer 4

• Th2 cells
  
  • Differentation caused by IL-4
  • Produces IL-4, IL-5, IL-10
  • Inhibited by IFN-y

Question 5

The most common mutation of CFTR gene causes a defect in what process?

Answer 5

• Most common mutation (deltaF508) causes impaired post-translational processing of CFTR, which is detected by the ER, causing the abnormal protein to be targeted for proteasomal degradation, preventing it from reaching the cell surface

Question 6

What is the presentation of a lesion to the dominant parietal cortex

Answer 6

• Gerstmann syndrome
  
  • agraphia (inability to write)
  • acalculia (inability to calculate)
  • finger agnosia (inability to distinguish fingers)
  • left-right disorientation

Question 7

What is the treatment for organophosphate poisoning

Answer 7

Organophosphates are cholinesterase inhibitors found in pesticide = increased ACh

Treatment:

• Atropine
  
  • Competitively binds ACh receptors
• Pralidoxime
  
  • Sketchy = lid on toxic spray
  • Regenerates acetylcholine esterase

Question 8

What receptor does Clonidine work on

Answer 8

a1 agonist

Question 9

Describe the receptors that dopamine acts on

Answer 9

D-B-A order of activation

Low doses of DA = DA receptors

Medium doses = Beta receptors

High doses = Alpha receptors

Question 10

What receptors does Epinephrinw work on

Answer 10

Beta > alpha agoinst

Predominantly beta at low doses

More alpha at higher doses

Question 11

What is the drug of choice for anaphylaxis

Answer 11

Epinephrine

Question 12

What is the drug of choice for septic shock

Answer 12

Norepinephrine

Question 13

What are the 2 main clinical uses of selective alpha-1 antagonists

Answer 13

HTN

BPH

Question 14

What is the MOA of Acebutolol and Pindolol

Answer 14

Sketchy:

• Agonizing plastic bugle
• Agonizing pin

MOA: are partial beta-agonists, but funciton as beta blockers because their action on beta receptors is so low, and still prevents the binding of ligands that would strongly activate these receptors

Question 15

What are the 2 drugs that act as beta-blockers and alpha-1 antagonists

Answer 15

Carvedilol (used in chronic heart failure)

Labetolol (used in HTN in pregnancy, hypertensive emergency, acute aortic dissection)

Question 16

What is receptor does alpha-methydopa effect?

Answer 16

Alpha-2 agonist and analog of L-DOPA

Used to treat gestational HTN

Question 17

Describe the steps of catecholamine synthesis (from phenylalanine to norepinephrine), including enzymes

Answer 17

Question 18

What are the layers of the glomerular filtration barrier and which layer is responsible for size/charge?

Answer 18

• Fenestrated capillary endothelium
  
  • Size barrier
• Basement membrane
  
  • Negatively charged (contains heparin sulfate) and size barrier
• Podocyte foot process
  
  • Visceral layer of Bowman’s capsule
  • Negative charge layer

Question 19

Describe the fluid composition/compartements of the body

Answer 19

• 60-40-20 rule
• 60% of body mass is water, of that 60%:
  
  • 40% is ICF
  • 20% is ECF
    
    • Only 25% of ECF is plasma

Question 20

What substance is used to measure renal plasma flow

Answer 20

• Renal plasma flow
  
  • RPF = Blood going to the glomeruli + blood going to the tubules
  • Can be estimated with PAH (Clearance of PAH > GFR)

Question 21

When does glucose begin to appear in the urine

Answer 21

• Glucose is completely reabsorbed up until plasma glucose level ~200 mg/dL
  
  • This is when glucosuria begins (threshold)
• At ~375 mg/min, all transporters are fully saturated

Question 22

Describe the rates of absorption in the proximal tubule of:

Na+, Cl-, K+, HCO3-, Urea, Glucose, Inulin, amino acids, creatinine, and PAH

Be able to graph these on a Tubular fluid / plasma filtrate graph (specifically is HCO3- more reabsorbed or secreted?)

Answer 22

• Anything that falls below the horizontal line (1.0) – more of that soluble is being absorbed relative to water
• Anything that falls below the horizontal line – less of that solute is being absorbed relative to water
  
  • The reason that Creatinine and Inulin levels within the tubule are rising is because they are not reabsorbed, but water is, so their relative levels go up
  • PAH is not being reabsorbed and is also being secreted into the tubules
• Interpretation of graph:
  
  • PAH is freely filtered and secreted
  • Creatinine is also freely filtered but not secreted as much as PAH
  • Inulin is freely filtered but not secreted or reabsorbed
    
    • Clearance of Inulin = GFR
  • Urea is freely filtered and poorly reabsorbed
  • Na+ and K+ are reabsorbed at the same rate of water so their concentrations remain constant
  • HCO3- is actively reabsorbed due to carbonic anhydrase
  • Glucose and amino acids are almost 100% reabsorbed in the proximal tubule

Question 23

What part of the nephron are divalent cations (Mg2+ and Ca2+) reabsorbed and how?

Answer 23

Thick ascending loop

• Indirectly induces reabsorption of Mg2+ and Ca2+
  
  • K+ enters the cell from the lumen via NKCC but then leaks back into the lumen, giving the lumen a slight positive charge
  • Cations flow from lumen into cell down the electric gradient

Question 24

Describe how you get euvolemic hyponatremia in SIADH

Answer 24

Increased ADH leads to excessive water retention

Body responds to water retention with decreased renin and aldosterone, increased ANP and BNP

Causes increase urinary Na+ secretion - Euvolemic hyponatremia

Question 25

Describe the defect in type 1 renal tubular acidosis, hyper/hypokalemia, urine pH

Answer 25

* Distal renal tubular acidosis à defect in collecting tubule * Alpha-intercalated cells are unable to secrete H+ à acidosis * Hypokalemia * Urine pH will be \> 5.5 (because no H+ in urine) * THINK: * Type 1 = impaired H+ excretion = H is 1 letter

Question 26

Describe the defect in type 2 renal tubular acidosis, hyper/hypokalemia, urine pH

Answer 26

* Proximal renal tubular acidosis à defect in proximal tubule * Impaired HCO3- reabsorption à acidosis * Hypokalemia and hypophosphatemia * Urine pH \< 5.5

Question 27

Describe the defect in type 4 renal tubular acidosis, hyper/hypokalemia, urine pH

Answer 27

* Hyperkalemic renal tubular acidosis * Due to hypoaldosteronism à decreased K+ secretion à hyperkalemia * Hyperkalemia prevents collecting tubules from generating NH4+ à impaired ammonium excretion * Urine pH \< 5.5. * THINK: * Type 4 = impaired NH4 excretion due to aldosterone (aldo) = 4 = NH4 and Aldo is 4 letters

Question 29

What is the normal value for filtration fraction (FF)

Answer 29

FF = GFR/RPF Normal = 20%

Question 30

Causes of metabolic acidosis

Answer 30

* Anion gap = Adding acid to the blood * MUDPILES: * M – Methanol * U – Uremia (renal failure) * D – Diabetic ketoacidosis * P – Propylene glycol/Paraldehyde * I – Isoniazid/Iron * L – Lactic acidosis * E – Ethylene glycol (antifreeze) * S – Salicylates (aspirin) * Non-anion gap = Losing excessive HCO3- * Diarrhea, Renal tubular acidosis, Spironolactone, Acetazolamide

Question 31

Causes of metabolic akalosis

Answer 31

* Losing H+ = excessive vomiting, diuretics, hyperaldosteronism

Question 32

What is Winter's fomula and what does it do?

Answer 32

* Predicted respiratory compensation for metabolic acidosis * If measured pCO2 \> predicted pCO2 – concomitant respiratory acidosis * If measure pCO2 \< predicted pCO2 – concomitant respiratory alkalosis * pCO2 = 1.5(HCO3-) + 8 +/- 2

Question 33

Which renal tubular acidoses are associated with hypokalemia and which with hyperkalemia

Answer 33

Type 1 = hypokalemia Type 2 = hypokalemia Type 4 = hyperkalemia

Question 34

Which renal tubular acidoses are associated with urine pH \> 5.5 vs \< 5.5

Answer 34

Type 1 = \> 5.5 (a-intercalated cells unable to secrete H+) Type 2 = \< 5.5 (urine is acidified by a-intercalated cells in collecting tubule) Type 4 = \< 5.5

Question 35

What is the formula for anion gap?

Answer 35

Na - (Cl + HCO3) \> 12 = anion gap 8-12 = non-anion gap

Question 36

Disease associated with anti-mitochondrial antibody

Answer 36

Primary biliary cholangitis * Autoimmune destruction of intra-hepatic bile ducts * Associated with other autoimmune conditions * Lymphocytic infiltrate + granulomas

Question 37

What is the cause of fixed splitting int the heart

Answer 37

ASD (L to R shunt)

Question 38

Differentiate malingering from factitious disorder

Answer 38

* Malingering = conscious production of symptoms with conscious drive * Patient consciously fakes symptoms in order to obtain secondary (external) gain * Factitious disorder = conscious production of symptoms with unconscious drive * Patient consciously fakes symptoms in order to obtain primary gain (sick role) * Subtypes: * Munchausen = chronic factitious disorder with predominantly physical signs and symptoms * Munchausen by proxy = Illness fabricated by caregiver

Question 39

Cause of flushing in response to Niacin

Answer 39

Prostaglandins

Question 40

MOA of toxin involved in EHEC

Answer 40

Shiga-like toxin (same MOA as Shiga toxin) * Inactivates 60S ribosome by removing adenine from rRNA

Question 41

What do HOX genes encode for?

Answer 41

o Codes for transcription factors that will alter the expression of genes involved in the segmental organization of the embryo in craniocaudal direction o Hox mutation = appendages in wrong location

Question 42

MOA of alpha-toxin of C. perfringens

Answer 42

Toxin is a lecithinase - degrades lecithine, a component of phospholipid membranes, leading to cell death and necrosis