nishi's qb - pathophys

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    * pathophys

    #128672nishi - 10/15/06 19:37

    Which of the following cells play a crucial role in thepathogenesis of alveolar-capillary damage in adultrespiratory distress syndrome (ARDS)?

    A. CD4-positive lymphocytes

    B. CD8-positive lymphocytes

    C. Eosinophils

    D. Mast cells

    E. Neutrophils

    Explanation:

    The correct answer is E. ARDS, pathologically referredto as diffuse alveolar damage, is a clinical syndrome ofacute respiratory failure resulting from diffuse injuryto the alveolar/capillary barrier. Such injury may becausedby a great variety of initiating insults, the mostfrequent of which are shock, severe trauma, sepsis,and gastricaspiration. All these different forms of injury result inrecruitment of neutrophils within the alveolar

    capillaries.Neutrophils release chemokines that attracthistiocytes and produce oxygen radicals,prostaglandins, andproteases that damage alveolar epithelium. Formationof hyaline membranes is due to a combination ofplasmafluid extravasation and alveolar cell necrosis.

    CD4+ (helper) lymphocytes (choice A), CD8+(cytotoxic) lymphocytes (choice B), eosinophils(choice C), andmast cells (choice D) have been implicated in anumber of pulmonary diseases, but not in diffusealveolardamage.

    An animal is made diabetic by injection of a drug thatdestroys pancreatic cells. Removal of which of thefollowing organs would most likely produce a decreasein blood glucose concentration in this animal?

    A. Anterior pituitary

    B. Colon

    C. Gonads

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    D. Kidney

    E. Pancreas

    Explanation:

    The correct answer is A. Two of the secretions of theanterior pituitary affect the sensitivity of peripheraltissues

    to the action of insulin. Growth hormone has a directeffect on liver and muscle to decrease insulinsensitivity.This may be partly through a growth hormone-induceddecline in insul in receptors or to unknownpost-receptordefects. In excess, growth hormone is "diabetogenic,"and about 25% of patients with acromegaly havediabetes. ACTH indirectly has anti-insulin effects byvirtue of the cortisol secretion it evokes. Like growthhormone, cortisol also decreases insulin sensitivity inperipheral tissues. A third anterior pituitary hormone,TSH, also tends to increase blood glucose levels. Inthis case, the effect is probably mediated mostlythrough

    increased glucose absorption by the gut. Patients withhyperthyroidism can sometimes exhibit a postprandialglucosuria because of excessive intestinal glucoseabsorption. In diabetic animals, the removal of theanteriorpituitary may lower blood glucose by increasing tissuesensitivity to whatever insulin remains.

    Removal of the colon (choice B) should have littleeffect on blood glucose since dietary glucose isabsorbed inthe small intestine.

    Sex steroids secreted by the gonads (choice C) havelittle effect on blood glucose concentration.

    The kidney (choice D) plays an important role inreabsorbing filtered glucose. In diabetes, the tubularreabsorption maximum is exceeded and glucose spillsover into the urine. The loss of glucose in the urinehelpsto reduce the severity of the plasma hyperglycemia.Removal of the kidneys would, if anything, make thehyperglycemia worse.

    Pancreatectomy (choice E) would make thehyperglycemia worse by removing the source of anyremaininginsulin.

    A 33-year-old woman gives birth to a baby girl. The

    next day, she begins to bleed from her vagina andfromvenipuncture sites. Laboratory studies demonstratedecreased platelets, prolonged prothrombin time (PT)andpartial thromboplastin time (PTT), and increased fibrinsplit products. These features are most consistent withwhich of the following?

    A. Disseminated intravascular coagulation

    B. Hemophilia A

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    C. Severe liver disease

    D. Vitamin K deficiency

    E. Von Willebrand's disease

    Explanation:

    The correct answer is A. The patient is experiencingdisseminated intravascular coagulation (DIC), a

    feared,and often life-threatening complication of many otherdisorders, including amniotic fluid embolism,infections(particularly gram-negative sepsis), malignancy, andmajor trauma. The diagnosis is suspected when both adecrease in platelets and a prolongation of PT and PTTtimes are observed. The observed hematologicabnormalities are due to consumption of platelets andclotting factors, caused by extensive microclotformationwith accompanying fibrinolysis (reflected by theincreased fibrin split products). The D-dimer assaymeasurescross-linked fibrin derivatives, and is a specific test for

    fibrin degradation products.Hemophilia (choice B) will alter the PTT withoutaffecting the other indices.

    Severe liver disease (choice C) produces alterationscomparable to those in vitamin K deficiency, andplateletscan also be decreased secondary to a generalizedmetabolic marrow dysfunction, but fibrin splitproducts wouldnot be increased.

    Vitamin K deficiency (choice D) is associated withalterations in both PT and PTT, but platelets will not bedecreased, nor will fibrin split products be increased.

    Von Willebrand's disease (choice E) produces impairedplatelet adhesion and increases the bleeding time aswell as the PTT, but will not produce the other featuresdescribed.

    A 54-year-old woman presents with a pansystolicmurmur along the lower left sternal border radiatingrightward tothe midclavicular line. The murmur is mediumpitched, has a blowing quality, and increases slightlyon inspiration.An S3 is audib le along the lower left sternal border.

    Jugular venous pressure is elevated, and a prominent"v"wave is visible. Which of the following is the mostlikely etiology of the S3?

    A. Aortic stenosis

    B. Mitral regurgitation

    C. Pulmonic stenosis

    D. Tricuspid regurgitation

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    E. Volume overloaded left ventricle

    F. Volume overloaded right ventricle

    Explanation:

    The correct answer is F. The origin and radiation of thepansystolic murmur suggest tricuspid valveincompetence. This is further supported by its pitchand quality, and by the fact that it increases on

    inspirationwhen cardiac volume increases. The regurgitant bloodflow from the ventricle during systole increases

    jugularvenous blood pressure and atrial v wave amplitude.The origin of the S3 sound, which occurs during earlyrapidfilling, is the filling of a volume-overloaded rightventricle. The right ventricle overload is caused by thecombination of systemic venous return and the returnof the regurgitated blood volume into the rightventricle.Right ventricular failure and dilatation, withenlargement of the tricuspid valve orifice, is the mostcommon cause

    of tricuspid regurgitation and is often secondary topulmonary hypertension or left ventricular failure.

    Aortic stenosis (choice A) causes a harsh, shrill,midsystolic, crescendo-decrescendo murmur andwould notnecessarily elevate right heart (and so jugular venous)pressures. It is often associated with an S4 (late rapidfilling) rather than an S3.

    Mitral regurgitation (choice B) causes a soft, blowing,pansystolic murmur and is associated with an S3. Itwouldelevate left atrial pressures, not right atrial (and so

    jugular venous) pressures.

    Pulmonic stenosis (choice C) would also cause acrescendo-decrescendo murmur, not an S3.

    Tricuspid regurgitation (choice D) is the source of themurmur but not the source of the S3 sound.

    A volume-overloaded left ventricle (choice E) couldcause an S3, but tricuspid regurgitation will not causeavolume overload in the left ventricle.

    A routine physical examination demonstrates

    hypercalcemia in a 40-year-old man. Circulatory levelsofparathyroid hormone are also elevated. Exploratorysurgery of the neck reveals diffuse hyperplasia of allfourparathyroid glands. Which of the following screeningstudies would most likely be helpful in confirming thediagnosis of multiple endocrine neoplasia, type I (MENI)?

    A. Pentagastrin-simulated calcitonin secretion

    B. Serum epinephrine

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    C. Serum gastrin

    D. Serum norepinephrine

    E. Urinary adrenaline:noradrenaline ratio

    Explanation:

    The correct answer is C. In multiple endocrine

    neoplasia, type I (MEN I), parathyroid hyperplasiaand/oradenomata are associated with pancreatic andduodenal endocrine tumors and endocrine hyperplasia.Themost common secretory product of the pancreatic andduodenal endocrine lesions is gastrin. Pituitaryadenomata may also occur in MEN I.

    Pentagastrin-stimulated calcitonin secretion (choice A)is a marker for medullary carcinoma of the thyroid,whichis a component of MEN II.

    Epinephrine (adrenaline) is produced by

    pheochromocytomas that occur as part of MEN II;serum epinephrinelevels (choice B) and urinary adrenaline:noradrenalineratios (choice E) may be used for screening forpheochromocytomas.

    Serum norepinephrine (choice D) is usually not helpfulin the diagnosis of pheochromocytoma, since serumcatecholamines can be increased by hypoglycemia,strenuous exertion,