UWSA

Question 1

What is the underlying pathophysiology of ARDS?

Answer 1

• ARDS: acute onset lung dsfxn, pulmonary edema, normal LA pressure, PaO2/FIO2 < 200.
• Pathophys: damage to the endothelial cells lining the pulmonary capillaries –> leakage of fluid into alveoli (exudative stage). Primary cause of injury = inflammatory cytokines and neutrophils (DAD = diffuse alveolar damage).
• Causes: trauma, pulmonary contusions, infection/sepsis, fat embolism.

Question 2

Rank the cardiac tissue conduction velocity from fastest to slowest.

Answer 2

1. Purkinje
2. Atrial
3. Ventricular
4. AV node

Mnemonic: Park At Venture Avenue

• Impulses begin at SA node (RA wall near SVC): 1.1 m/s
• Internodal tracts carry AP to AV node(interatrial septum near tricuspid orifice): 0.05 m/s (slowest)
• AP enters bundle of His/right and left bundle brances (interventricular septum): 2.2 m/s (fastest)
• AP trasmitted through ventricular myocardium: 0.3 m/s

Question 3

Patient presents with “lump in throat” but exam shows no abnl and barium swallow is unrevealing. What is the dx?

Answer 3

Globus hystericus: the sensation of a lump in the throat without accompanying physical, endoscopic, or radiologic findings of esophageal obstruction.

Question 4

How does vitamin A ingestion manifest in fetal growth?

Answer 4

• Microcephaly
• Cardiac anomalies
• Early epiphyseal closure
• Growth retardation
• Spontaneous abortion

Question 5

The appearance of DNA fragments in multiples of 180 base pairs on gel electrophoresis is known as what?

Answer 5

DNA laddering: a lab phenomenon used to identify apoptotic cells and distinguish them from necrotic cells. During karyorrhexis, endonucleases degrade DNA into fragments that are multiples of 180 base pairs.

Question 6

Confusion, blurred vision, dry mucous membranes, and intense thirst are associated with _____ toxicity?

Answer 6

Anticholinergic toxicity (atropine).

• Hot as a hare: fever
• Dry as a bone: dry skin and mucous membranes
• Red as a beet: flushing
• Blind as a bat: mydriasis, cycloplegia
• Mad as a hatter: confusion, excitation, disorientation, delirium, psychosis

Question 7

Two children have osteogenesis imperfecta but parents are unremarkable family hx. What is responsible for the d/o?

Answer 7

• Germline mosaicism (2+ genetically different gamete cell lines) should be considered when a genetic mutation is IDed in offspring but not in parents.
• Pleitropy: single gene with multiple phenotypes
• Penetrances: extent to which gene is expressed.

Question 8

What sturcutre is likely to be injured in a posterior displacement of the tibia?

Answer 8

Popliteal artery is the main concern with both anterior and posterior dislocations of knee joint. This vessel is rigidly fixed proximal and distal to the knee joint by the adductor magnus and soleus muscles, respectively.

Question 9

What are the risk factors of endometritis and which bacteria is the most commonly isolated?

Answer 9

• RF: premature and prolonged rupture of the membranes, use of devices (scalp electrodes, intrauterine pressure catheters).
• S/S: fever, uterine tenderness, foul smelling discharge, leukocytosis
• Culture: bacteroides and other mixed aerobic/anaerobic flora

Question 10

How does a heminephrectomy affect GFR immediately after surgery and six weeks after surgery?

Answer 10

50% –> 80% (not 100%)

Question 11

What do the 4 heart sounds and mid-systolic click represent?

Answer 11

• S1: closure of AV valves at beginning of systole.
• S2: closure of semilunar (aortic and pulmonic valves) at end of systole. After this sound is isovolumetric relxation of ventricle before opening of AV valves.
• S3: blood turbulence within ventricle during period of rapid diastolic filling. In adults, it occurs most commonly in setting of cardiac failure (systolic or diastolic). It’s normal in children.
• S4: pathologic. Result of forceful atrial contraction pushing blood into overfilled or stiffened ventricle.
• Midsystolic click: mitral valve prolapse

Question 12

Splenectomy can be performed on patient with hereditary spherocytosis to prevent what complication?

Answer 12

Splenectomy would improve anemia, decrease hemolysis and juandice, and reduce bilirubin gallstone formation.

Question 13

Androgen insensitivity syndrome

Answer 13

• 46XY Male
• X-linked disorder
• Androgen receptor defect
• Free T is aromatized to E –> breasts
• Cryptorchid testes (secretes T)
• No axillary or pubic hair
• No penis/scrotum
• No uterus/ovaries: due to MIF
• Vagina ends in blind pouch

Question 14

5-a reductase deficiency

Answer 14

• Autosomal recessive
• Ambiguous genitalia in newborns
• Testosterone cannot convert to DHT

Question 15

What is a significant cause of brain injury in premature infants? Where does it usually arise from?

Answer 15

• Intraventricular hemorrhage (IVH) is common in premature infants in the first five days of life.
• RF: birth < 32 wks, <1500g, intrapartum asphyxia, respiratory distress syndrome, prolonged resuscitation.
• Begins in germinal matrix: highly cellular and vascular in the subventricular region that generates neurons and glia during fetal development.

Question 16

Most head and neck cancers what ______ types of cancers? Where are they usually found?

Answer 16

• Squamous cell carcinoma
• HNSCCs are strongly a/w tobacco and alcohol.
• Usually ventral tongue, floor of mouth, lower lip, soft palate, gingiva

Question 17

How are G protein coupled receptors anchored to cell membranes?

Answer 17

• Via palmitoylation
• Process in which FA are covalently anchored to plasma membrane cysteine residues, increasing the hydrophobicity of a protein.

Question 18

How does nitroglycerin affect HR and end-systolic LV volume?

Answer 18

• Increases HR, decreases end-systolic LV volume
• Systemic venodilation –> myocardial oxygen consumption is decreased relative to coronary perfusion through a reduction of steady state ventricular volumes that overcome the associated reflexive increase in HR.
• Nitroglycerin relaxes vascular smooth muscles in veins more than arteries. This rapidly decreases ventricular preload (end diastolic volume), which reduces venous return to the heart, and decreases effective circulating blood volume through venous blood pooling.
• CV reflexes compensate for the drop in SV, CO, and MAP with sympathetic increases in HR and myocardial contractility.
• In the new steady state, preload, afterload, end systolic ventricular volume, and CO are somewhat reduced, while TPR is the same. Due to reduction in stroke work a/w smaller ventricular volumes, decreased ejection time, and decreased afterload during the cardiac cycle, the ratio of myocardial oxygen consumption to coronary blood flow is decreased in the new steady state.

Question 19

Liver disease + hepatomegaly, skin hyperpigmentation (sun exposed areas) and DM is a sign of what pathology?

Answer 19

Hematochromatosis. The skin hyperpigmentation results from hemosiderin deposition in the dermis.

Question 20

When protons are added to growth media, previously resistant bacteria are no longer resistant to specific abx. What is the likely mechanism?

Answer 20

Efflux pumping is an active, energy-requiring process. Most are powered by moving protons (H+) along their concentration grandeitn out of the cell, coupled with expelling the abx. When the medium is saturated with protons, the gradient is eliminated.

Question 21

A prohormone peptide molecule has a signal sequence with a hydrophobic core. A alrge deletion in the hydrophobic core would result in protein accumulation in which compartment?

Answer 21

mRNA –> protein

1. In the cytosol, mRNA binds to ribosome and initiates translation.
2. Proteins destined for ER have N-terminal peptide signaling sequences, recognized by SRPs (signal recognition particles), which halt translation and target the ribosome to protein pores in the RER.
3. Once bound to RER, the SRP dissociates and translation proceeds with the polypeptide being fed into RER through membrane pore.
4. Signal sequences: 15-20 hydrophobic AA residues.
5. Deletion of this hydrophobic signaling sequence: failure of SRP binding, failure to translocate appropriate proteins into the RER, accumulation of ER proteins int he cytosol.

Question 22

23 yo male has normal secondary sexual characteristics and normal blood T, but T in seminiferous tubules and epididymis is abnl low. Which cell is dysfxn?

Answer 22

• Sertoli cells
• Seminiferous tubules and epididymis must contain high T relative to the testoterone in circulation for spermatogenesis and sperm maturation to occur.
• Androgen-binding protein (ABP) binds T and DHT to concentrate them in the luminal fluid.
• ABP is made by sertoli cells.
• Leydig cells: make T

Question 23

Red safranin O is used to stain what?

Answer 23

• Cartilage
• Mast cell granules
• Mucin

Question 24

How does PE affect pH, PaCO2, and PaO2?

Answer 24

• High pH, low PaCO2, low PaO2
• PE is characterized by hypoxemia secondary to pulmonary ventilation-perfusion (V/Q = infinity) mismatch.
• Hypoxemia –> hyperventilation and respiratory alkalosis.
• Increase in pH and reductions in PaO2 and PaCO2

Question 25

How does chronic obstructive pulmonary disease affect pH, PaCO2, and PaO2?

Answer 25

• Slightly decreased pH, increased PaCO2, and decreased PaO2
• Hypoxia and CO2 retention due to hypoventilation.

Question 26

Which phospholipid causes severe bronchoconstriction, vasoconstriction, and platelet aggregation with microthrombus formation? What is the signaling mechanism?

Answer 26

• PAF via Inositol triphosphate-Calcium (Gq)
• Made by platelets, basophils, mast cells, neutrophils, monocytes, MO, and endothelial cells.
• Excessive PAF –> platelet aggregation with microthrombus formation and constriction of smooth muscle in the bronchi, BVs, and upper digestive tract.

Question 27

What is the pathogenesis of pulmonary hypertension?

Answer 27

1. Injury to the pulmonary endothelium secondary to idiopathic mechnism or a known medical condition (cardiac defect, collagen vascular dz, PE).
2. Narrowing of pulmonary vascular bed –> RVH
3. Accelearted vascular injury secondary to increased pulmonary artery pressure.
4. Further rise in RV afterload.
5. Dilation of RV

RVH leads to exertional dyspnea, angina, peripheral edema, increased intensity of 2nd heart sound (pulmonic component), a systolic ejection murmur, and RV heave.

*Note: COPD is a known cause of pulmonary HTN, but would be unlikely in a young female.

Question 28

What is the slope, x-intercept, and y-intercept of the line-weaver burk plot?

Answer 28

Question 29

Person exposed to hep a, b, and c with jaundice and ascites can be treated with what to improve his confusion?

Answer 29

• Lactulose: nonabsorbable disaccharide that is degraded by colonic bacteria to form lactic acid and acetic acid.
• GI tract beomes acidified and NH3 is converted to NH4+. More NH3 diffuses from blood into the gut lumen, which gets converted to NH4+.
• Osmotic effect is established in the colon –> luminal distension –> peristalsis.
• Note: when portal blood is diverted into systemic circulation, neurotoxic substances (ammonia) are allowed to accumulate and breach the BBB.

Question 30

Diabetic with cramping pain in right calf (worse with walking and at night), thinned skin over right foot and small ulcer over right toe most likely has what condition?

Answer 30

PAD (peripheral arterial disease)

• Thinning skin, calf claudication
• Prolonged venous filling time, shiny colored skin, hair loss, nail changes
• Femoral artery atherosclerosis is most likely the cause in this patient.

Question 31

What are some unmyelinated nerve fibers (group C)?

Answer 31

• Postganglionic autonomic nervous sytem axons
• Afferent neurons that conduct heat sensation
• Afferent neurons that transmit slow-onset dull, burning, or visceral pain
• First order bipolar sensory neurons of olfaction

Question 32

In MO antigen presentation to CD4+, which HLA class II components is digested by MO during antigen processing?

Answer 32

During antigen processing in MO, the invariant chain is removed from the MHC-invariant complex and replaced by an external protein. This MHC-peptide complex (with a-chain, b-chain, and external protein) is expressed at the cell surface.

Question 33

Mutations of different genes that cause similar phenotypes is called ___________.

Answer 33

Genetic heterogeneity

• Mutations of different genes with similar phenotypes
• Marfan and homocystinuria
• Muscular dystrophies: X-linked defects in dystrophin or autosomal recessive and autosomal dominant defects in other cytoskeletal gene

Question 34

Different mutations in the same genetic locus cause imilar phenotypes is called _____________.

Answer 34

Allelic heterogeneity

Question 35

Ability of a single genetic defect to produce multiple simultaneous phenotypic effects is called ____________.

Answer 35

Pleiotropy

• Marfan: single defect in fibrillin causes skeletal, cardiac, and ophthalmologic effects

Question 36

How does leuprolide work in treating prostate cancer with back pain?

Answer 36

Leuprolide causes long-term reduction of circulating T levels (medical orchiectomy) by decreasing anterior pituitary gland release of LH. The testicular Leydig cells respond to the lower LH levels by producing less T. Because 80% of newly dx prostate cancer cases are androgen dependent, leuprolide treatment is useful in prolonging survival.

Question 37

Methylated regions of DNA are rich in which nucleotides?

Answer 37

They are rich in cytosine-guanine dinucleotide repeat sequences.

Question 38

What causes high anion gap metabolic acidsois?

Anion gap = Sodium - (Chloride + Bicarb)

Answer 38

MUDPILES

• Methanol
• Uremia
• Diabetic ketoacidosis
• Propylene glycol/Paraldehyde
• Isoniazid/Iron
• Lactic acidosis
• Ethylene glycol (antifreezn)
• Salicylates (aspirin)