Uworld16 Flashcards
Where does antidiuretic hormone act in the nephron?
ADH acts primarily on the collecting ducts, increasing their permeability to water.
In the absence of ADH, the tubular fluid is most concentrated at the junction between the descending and ascending limbs of the loop of Henle and most dilute in the collecting ducts
What is thyroid dysgenesis (ie, hypoplasia, aplasia, ectopy)?
the most common cause of primary congenital hypothyroidism.
In this condition, TSH is elevated and thyroxine (T4) is low
How does cholinesterase inhibitors (eg, donepezil, galantamine) work in Alzheimer disease?
Cholinesterase inhibitors (eg donepezil, galantamine) may provide modest symptomatic improvement of cognitive symptoms and temporarily improve functioning in patients with Alzheimer disease. However, these meds do not alter the inevitable disease progression.
What is concentric left ventricular hypertrophy?
Involves thickening of the ventricular walls and reduction in the ventricular cavity size.
It occurs via the addition of myocardial contractile fibers in parallel in response to chronic pressure overlead.
Aortic stenosis and prolonged systemic hypertension are common causes of concentric left ventricular hypertrophy
What is a cohort study?
A cohort study is used to compare incidence of disease between exposed and nonexposed individuals. A common measure of association in cohort studies is the relative risk.
Piperacillin-tazobactam is effective against?
a combination of extended-spectrum penicillin with B-lactamase inhibitor.
It is effective against most gram-negative enteric rods (including Pseudomonas aeruginosa) and against Bacteroides fragilis
What forms the fibrous cap of a mature atheroma?
Medial smooth muscle cells are responsible for synthesizing the extracellular matrix proteins (eg, collagen, proteoglycans) that form the fibrous cap of a mature atheroma.
Progressive atheroma enlargement increases the likelihood of plaque rupture with resulting luminal thrombosis.
What is minimal change disease?
the most common cause of nephrotic syndrome in kids.
It is often idiopathic but may be triggered by drugs, immunization or malignancy.
Light microscopy shows normal glomeruli, with no immunoglobin or complement deposits on immunofluorescent staining.
However, electron microscopy shows diffuse podocyte foot process effacement and fusion.
what is a psoas abscess
The psoas muscle originates from the anterior surface of the transverse processes and lateral surface on the vertebral bodies and functions primarily as a hip flexor.
Psoas abscess may form due to direct spread of infection from adjacent structure (eg, vertebral bodies, appendix, hip joint) or from hematogenous seeding from a distant site
Atopic dermatitis increases the risk for allergic rhinitis, asthma, and food allergies, likely because?
of an immune response that favors IgE production.
In addition, skin barrier dysfunction facilitates food allergen penetration and sensitization, increasing the risk for food allergies.
What are the 5 major causes of hypoxemia (low arterial pressure of oxygen (PaO2)?
- alverolar hypoventilation
- low partial pressure of inspired oxygen
- ventilation-perfusion mismatch
- diffusion impairmentnt
- right to left shunting
The A-a gradient is normal with alveolar hypoventilation and low partial pressure of inspired oxygen, which heps distinguish these causes from other causes of hypoxemia.
What is seen in autologous hematopoietic stem cell transplantation?
Autologous hematopoietic stem cell transplantation reinfuses host cells from the patient’s peripheral blood or banked cord blood to reconstitute the bone marrow.
Because the reinfused cells are genetically identical to the host’s, there is no risk of graft rejection or graft versus host diease.
Although there is also no risk for transferring a new bloodborne pathogen, chronic or latent infections (eg, Epstein Barr virus, cytomegalovirus, varicella-zoster virus) may worsen due to the transient immunosuppression induced by myeloablative chemotherapy
Impaired intestinal blood flow (eg, acute mesenteric ischemia) creates an anaerobic environment that leads to?
an elevate NADH/NAD+ ratio.
This decreases activity of pyruvate dehydrogenase (converts pyruvate –> acetyl coA) while stimulating lactate dehydrogenase (converts pyruvate –> lactate), shunting the metabolic fate of pyruvate toward lactate production,
Patients with significant tissue ischemia are therefore at risk of lactic acidosis.
What is the primary goal of medical therapy for acute aortic dissection?
to reduce aortic wall shear stress by minimizing the change in aortic blood pressure per time.
Esmolol, a selective beta-1 blocker, decreases left ventricular contraction velocity and heart rate to reduce aortic blood pressure per time.
What is borderline personality disorder?
persistant pattern of unstable relationships, mood lability, and impulsivity.
Individuals with this disorder may exhibit suicidal ideation or behavior in the context of an interpersonal crisis in which they feel rejected or abandoned.
What is Lambert-Eaton myasthentic syndrome?
characterized by antibodies against presynaptic voltage gated calcium. Patients develop progressive proximal muscle weakness with reduced/absent flexes that predominantly involves the lower extremities.
The syndrome is often associated with malignancy, particularly small cell lung cancer.
Digoxin is cleared by what organ?
Digoxin is a cardiac glycoside that is predominantly cleared by the kidneys.
Elderly patients typically exhibit age-related renal insufficiency, even in the presence of normal creatinine levels.
The dose of digoxin must be reduced in these patients to prevent toxicity.
What is capitation?
an arrangement in which a payor pays a fixed, predetermined fee to provide all the services required by a patient.
Payors may negotiate a capitated contract with an insurance company that then pays the providers, or a large medical group may negotiate directly with the payor
Lead poisoning can cause what?
neurologic, gastrointestinal, renal, and hematologic complications.
Although symptoms can be vague, lead poisoning should be suspected if these symptoms arise while residing in a home built before 1978.
Diagnosis is made by measuring the patient’s blood lead level.
Ascites in cirrhosis develops from hemodynamic changes related to?
portal hypertension.
Splanchnic vasodilation decreases the systemic vascular resistance, which causes activation of the renin-angiotensin-aldosterone system and promotes vasoconstriction and sodium and water retention.
Spironolactone, an aldosterone antagonist, is used to induce natriuresis and resolve ascites without blocking the critical vasoconstrictive effects of angiotensin.
What is mucormycosis?
an opportunistic infection caused by Rhizopus, Mucor, and Absidia species.
The classic clinical picture is paranasal sinus involvement in a diabetic or immunosuppressed patient.
The fungi form broad nonseptate hyphae that branch at right angles
Dizygotic twins occur due to?
fertilization of 2 oocytes by 2 different sperm, can be different sexes, and almost always have 2 chorions and 2 amnions (eg, dichorionic/diamniotic)
Monozygotic twins arise from the fertilization of?
a single oocytes, are the same sex, and can be dichorionic/diamniotic (days 0-4), monochorionic/diamniotic (days 4-8), monochorionic/monoamniotic (days 8-12), or monochorionic/monoamniotic conjoined twins (>13 days)
What is inclusion cell disease?
a lysosomal storage disorder in which a defect in protein targeting prevents the phosphorylation of mannose residues required to tag acid hydrolases for transport to lysosomes.
Without these lysosomal proteins, cellular debris cannot be degraded and therefore accumulates within lysosomes, forming inclusion bodies characteristic of the disease.
What is positive predictive value?
the probability that an individual has a disease given a positive test.
It is calculated as: true positives / (true positive + false positives)
What is Li-Fraumeni syndrome?
caused by an autosomal dominant mutation in the tumor suppressor gene TP53.
Leukemia, sarcomas, and tumors of the breast, brain, and adrenal cortex are most common.
What is the process of DNA synthesis?
DNA synthesis occurs is the 5’-3’ direction only.
During DNA replication, one daughter strand is synthesized continuously toward the replication fork (leading strand), whereas the other daughter strand is synthesized discontinuously away from the replication fork (lagging strand).
The lagging strand is formed from short stretches of newly synthesized DNA separated by RNA primers (Okazaki fragments)
What is ovarian vein thrombosis (infected ovarian vein thrombus)?
is a rare complication associated with the postpartum period and is typically right sided.
Because ovarian venous drainage is asymmetric, a thrombus in the right ovarian vein can extend into the inferior vena cava. In contrast, a left ovarian vein thrombosis would extend first to the left renal vein.
Shiga toxin-producing Escherichia coli O157:H7 elaborates Shiga toxin, which inactivates 60S ribosomal subunits in colonic mucosal cells, leading to the inhibition of?
protein synthesis and apoptosis; clinical manifestations include bloody diarrhea.
Hematogenous spread of Shiga toxin to renal endothelial cells can also lead to hemolytic uremic syndrome
What is idiopathic intracranial hypertension (pseudotumor cerebri)?
presents in young obese women with daily headache (which worsens during the Valsalva maneuver), bilaterally symmetric papilledema, and transient visual disturbances.
Increased intracranial pressure compresses the optic nerves, resulting in impaired axoplasmic flow and optic disc edema.
Side effects of dopamine receptor blockers (eg, metoclopramide, prochlorperazine)
Dopamine receptor blockers (eg, metoclopramide, prochlorperazine) act as antiemetics and pain relievers for severe migraine headache associated with nausea and vomiting.
However, dopamine blockade can also result in excess cholinergic activity (eg, acute dystonic reactions); diphenhydramine can be co-administered with dopamine receptor blockers to prevent these reactions due to its anticholinergic activity.
What is the most common risk factor for calcium (calcium oxalate and calcium phosphate) kidney stones in adults?
Hypercalciuria; contributing factors may include increased gastrointestinal absorption, increased mobilization of calcium from bone, or decreased renal tubular calcium reabsorption.
However, most patients remain normocalcemic due to regulation of plasma calcium levels by vitamin D and parathyroid hormone
What is anorexia nervosa?
low body weight (BMI<18.5), fear of becoming fat, and distorted body image.
Unlike other patterns of restrictive eating, (eg, bulimia nervosa), patients with anorexia nervosa experience complications of progressive clinical starvation, such as bradycardia, osteoporosis, and amenorrhea
What is TSH resistance?
due to a mutation in the TSH receptor gene presents with congenital hypothyroidism, which is characterized by increased TSH and low thyroxine.
The thyroid gland is normal in size and location.
How can the anterior cruciate ligament (ACL) can be damaged?
by sudden changes in direction or awkward landings (eg, excessive internal rotation or valgus stress) during sports activity.
ACL tears are typically associated with rapid-onset hemarthrosis.
PE shows anterior laxity of the tibia relative to the femur (eg, Lachman test, anterior drawer test)
What is epiglottitis?
causes rapidly progressive airway obstruction and classically presents with fever, dysphagia, drooling, stridor, and tripod positioning.
Individuals with incomplete immunization against Haemophilis influenzae type b are at greatest risk
A painless, solid scrotal mass should be considered?
testicular cancer until proven otherwise.
Examination generally reveals a solid, firm, or fixed nodule in the tunica albuginea that is ovoid in shape and painless to palpation.
Testicular tumors do not transilluminate
What is Wolff-Parkinson-white pattern?
characterized by a shortened PR interval, slurred initial upstroke of the QRS complex (delta wave), and widening of the QRS complex.
It is caused by an accessory pathway that bypasses the atrioventricular node, leading to ventricular preexcitation.
Some patients develop paroxysmal tachyarrhythmias (eg, atrioventricular reentrant tachycardia) due to reentry of electrical impulses through the accessory conduction pathway (ie, WPW syndrome)
Acid base for severe vomitting
hypokalemic, hypochloremic metabolic alkalosis.
The metabolic alkalosis is initiated by loss of gastric H+ from the body, worsened by hypovolemia-induced activation of the renin-angiotensin-aldosterone system, and perpetuated by profround gastric and renal losses of Cl- that lead to hypochloremia and impaired renal HCO3- excretion.
Hypokalemia primarily results from aldosterone-mediated renal K+ losses
What is Vernet syndrome?
Lesions of the jugular foramen can result in jugular foramen (Vernet) syndrome, which is characterized by the dysfunction of cranial nerves IX, X, and XI.
Symptoms include dysphagia, hoarseness, loss of gag reflex on the ipsilateral side, and deviation of the uvula toward the normal side.
What is mesothelioma?
a neoplasm arising from mesothelial cells and is strongly associated with asbestos exposure.
In early mesothelioma, multiple nodules form on the parietal pleura and gradually encase the lung parenchyma.
Immunohistochemistry is important for diagnosis; nearly all mesotheliomas strain positive for cytokeratins and many also stain positive for calretinin
What is atopic dermatitis?
epidermal barrier dysfunction due to loss of function mutations in filaggrin, a key epidermal component.
Increased transepidermal water loss, skin permeability, and inflammation result in erythematous dry skin and pruritus, with chronic disease presenting as lichenification from repeated scratching.
Lithium toxicity can be caused by drug interactions with?
NSAIDs, thiazide diuretics, ACE inhibitors, tetracyclines, and metronidazole.
Signs of lithium toxicity include confusion, ataxia, and tremor
What are auer rods?
deformed azurophilic granules found in the cytoplasm of myeloblasts that stain positively for myeloperoidase.
Auer rods are found in abundance in AML M3 (acute promyelocytic leukemia)
Injury to the radial nerve at the supinator muscle may occur due to?
repetitive pronation/supination of the forearm, direct trauma, or subluxation of the radius.
Patients typically have weakness during finger and thumb extension (ie, finger drop) without wrist drop or sensory deficits.
What is relative risk?
the ratio of the probability of an event (eg, disease outcome) occurring in the exposed group (eg, treatment group) versus the probability of the even occurring in the unexposed group (eg, control group)
What is primary hypothyroidism?
decreased T4 levels and increased TSH.
T3 is primarily produced by conversion from T4 in peripheral tissues; serum levels widely fluctuate due to its short half life, and can often be within the normal range in patients with hypothyroidism.
First line therapy for organophosphate toxicity
atropine, a competitive inhibitors of acetylcholine at the muscarinic receptor.
Organophosphates are acetylcholinesterase inhibitors that are commonly used as agrocultural pesticides.
Toxicity is characterized by signs of cholinergic excess (mg, miosis, bronchospasm, muscle fasicilations/weakness, diarrhea, vomitting, lacrimation)
What is multiple myeloma?
plasma cell malignancy associated with purely radiolucent (osteolytic) bone lesions due to the stimulation of osteoclasts and the inhibition of osteoblasts.
Myeloma cells stimulate osteoclast development by secreting RANK-ligand and destroying osteoprotegerin, which increases RANK activity and results in osteoclast differentiation
What is the treatment of Giardia?
Giardia lamblia is the most common enteric parasite in the United States and Canada and is a common cause of diarrhea in campers/hikers.
Iodine-stained stool smear classically shows pear-shaped, flagellated trophozoites or ellipsoidal cysts with smooth, well defined walls and 2+ nuclei.
Txt: metronidazole
Parvovirus is highly tropic for which cells?
highly tropic for erythroid precursor cells and replicates predominantly in the bone marrow.
Erythema infectiosum (fifth disease) is causes by parvo B19 and presents with a nonspecific prodrome (eg, malaise, fever, congestion) followed by a classic slapped cheek facial rash and a lacy, reticular body rash.
What is Klinefelter syndrome (47, XXY)?
the most common cause of male primary hypogonadism and is caused by meiotic nondisjunction of chromosome X.
Patients have small, firm testes; gynecomastia; and tall stature.
Learning disabilities and behavioral problems may also occur.
What happens with damage to the branches of the vagus nerve (anterior and posterior vagal trunks)?
branches of the vagus nerve (anterior and posterior vagal trunks) pass through the esophageal hiatus.
Damage to these branches, which can occur during esophageal hiatal hernia repair (eg, fundoplication), may result in delated gastric emptying and gastric hypochlorhydria
What can happen with long term use of supraphysiologic doses of glucocorticoids?
suppression of the hypothalamic-pituitary-adrenal axis, which in turn leads to bilateral adrenocortical atrophy involving the zona fasciculata and reticularis.
Sudden cessation of the exogenous corticosteroids can precipitate adrenal crisis.
ADH acts on which part of the nephron?
Dehydration stimualtes ADH secretion.
ADH acts on the collecting ducts, increasing their permeability to water. Thus, in the presence of ADH, the collecting ducts contain the most concentrated fluid in the nephron, while the distal convoluted tubule contains the most dilute fluid.
What is seen on biopsy for herpes simplex virus esophagitis?
Herpes simplex virus esophagitis is most common in those with impaired cell-mediated immunity.
Endoscopy typically reveals small vesicles and punched out ulcers. Findings on biopsy usually include multinucleated giant cells and eosinophilic intranuclear inclusions (Cowdry type A inclusion bodies).
Acyclovir is the treatment of choice.
The total oxygen content of blood (CaO2) is affected primarily by 2 variables:
hemoglobin concentration and its percentage of oxygen saturation (SaO2), which is directly affected by the arterial oxygen tension (PaO2).
Anemia is characterized by decreased hemoglobin concentration in the setting of normal SaO2 and PaO2
What is neuroleptic malignant syndrome?
severe muscular rigidity, mental status changes, autonomic dysregulation, and hyperthermia.
Dopamine antagonism, the mechanism of action of most antipsychotics, has been implicated as a primary cause of NMS.
Renal excretion of a drug is dependent on?
-glomerular filtration (reduced with low renal blood flow, kidney disease, and high drug protein binding)
-renal tubular secretion (reduced by coadministration of drugs with overlapping substrate specificity)
-tubular reabsorption (may be altered by changed in urine pH)
Damage to the left temporal hemiretina will disrupt the transmission of visual information along?
the ipsilateral optic nerve, lateral optic chiasm, optic tract, lateral geniculate body, optic radiations, and primary visual cortex
Chemotherapeutic drugs that induce DNA damage increase the risk for secondary malignancy (eg, treatment-related myeloid neoplasms). Cyclophosphamide side effects?
Cyclophosphamide is an alkylating agent that induces apoptosis in malignant cells via formation of DNA cross links.
Side effects: hemorrhagic cystitis and bladder cancer
What is congenital torticollis?
typically noted by 2 to 4 weeks of age, after which the child prefers to hold the head titled to one side.
It is most commonly the result of malposition of the head in utero or birth trauma.
Most cases resolve with conservative therapy and strethcing exercises.
What pathway does insulin act via?
Insulin is an anabolic hormone that acts via receptor tyrosine kinase signaling to increase the synthesis of glycogen, proteins, fatty acids, and nucleic acids.
Tyrosine kinase/phosphatidylinositol-3-kinase stimulation promotes glycogen synthesis by activating protein phosphatase, an enzyme that dephosphorylates (activates) glycogen synthase
What is primary amebic encephalitis?
occurs when the free-living, motile protozoan Naegleria Fowleri penetrates the olfactory mucosa and migrates in a retrograde fashion through the olfactory nerve to the brain.
This rare, deadly infection primarily occurs after exposure to warm, fresh water during recreational activitites
Elevated gastric pH stimulates?
secretion of gastrin, a polypeptide hormone that increases gastric acid production.
Proton pump inhibitors block gastric acid production by parietal cells; the resultant increase in pH leads to hypergastrinemia, which can cause rebound hypersecretion of gastric acid when the drug is withdrawn after chronic use.
What is positive predictive value?
represents the probability of truly having a disease given a positive test result.
It increases with increasing disease prevalence and decreases with decreasing disease prevalence
What are small nuclear RNA (snRNA)?
synthesized by RNA polymerase II in the nucleus and complexes with specific proteins to form small nuclear ribonucleoproteins (snRNPs)
snRNPs are an essential component of spliceosomes, which remove introns from pre-mRNA to form mature mRNA. Patients with systemic lupus erythematosus can have autoantibodies directed against snRNPs (eg, anti-Smith antibody)
Normal (bell shaped) distribution relation to standard deviations?
In a normal (bell shaped) distribution: 68% of all values are within 1 standard deviation from the mean
95% of all values are within 2 standard deviations from the mean
99.7% of all values are within 3 standard deviations from the mean
MOA of tranexamic acid (TXA)
an antifibrinolytic medication that stabilizes blood clots in hemorrhaging patients.
It inhibits plasmin formation, thereby preventing fibrin degradation and clot dissolution.
TXA used for the treatment of postpartum hemorrhage improves maternal morbidity and mortality
What can trigger acute angle-closure glaucoma?
Acute angle-closure glaucoma occurs when the space between the cornea and iris is narrowed, limiting the flow of aqueous humor out of the anterior chamber and raising pressure in the eye.
Meds that cause pupillary dilation (eg, alpha-adrenergic agonists, anticholinergics) can trigger acute angle-closure glaucoma
What is a sequence?
A sequence is a predictable series of anatomically related anomalies that develop as a consequence of a known primary anomaly (ie, cause-and effect relationship).
Oligohydramnios leads to fetal compression and the predictable cascade of findings in Potter sequence (eg, pulmonary hypoplasia, facial and limb anomalies)
MOA of proton pump inhibitors
prevent the hydrogen-potassium-ATPase pump found in parietal cells from releasing hydrochloric acid into the stomach lumen.
Chronic PPI use protects exogenously administered lipase and enhances fat absorption in patients dependent on pancreatic enzyme replacement therapy.
Postpartum depression versus postpartum blues
Postpartum depression is diagnosed using the same diagnostic criteria used for major depressive episodes that occur outside the postpartum period.
It should be differentiated from postpartum blues, which is a milder and self limited form of depression that peaks at 5 days and resolves within 2 weeks
Patients with sickle cell disease become functionally asplenic within the first few years of life due to repeated microinfarction of splenic vascular beds. This dramatically increases the risk for?
fulminant infections with encapsulated bacterial organisms, particularly Strep pneumo.
Patients with sickle cell disease ar also at increased risk for other bacterial infections, most notably salmonella osteomyelitis
Medical therapy to dissolve cholesterol gallstones is an option in patients refusing cholecystectomy or with high surgical risk. What can be given?
Hydrophilic bile acids (eg, ursodeoxycholic acid) improve cholesterol solubility by reducing the amount of cholesterol secreted into the bile and increasing biliary bile acid concentration.
Blunt lower abdominal trauma can rupture what organ?
The dome of the bladder rises into the peritoneal cavity when distended with urine.
Blunt lower abdominal trauma can abruptly increase intravesical pressure and rupture the bladder dome, spilling urine into the intraperitoneal cavity.
Acute hepatitis C is characterized by?
panlobular lymphocytic inflammation with hepatocyte injury (eg, ballooning degeneration) and cell death (eg, Councilman bodies).
What is chronic hepatitis C characterized by?
leads predominantly to portal lymphocytic infiltration, including lymphoid follicle formation, and fibrosis.
Histo findings of cirrhosis include extensive fibrosis and the formation of bridging septa that surround regenerative nodules.
Histopath of adenocarcinoma of the lungs
Adenocarcinoma, the most common pulmonary malignancy, is characterized histopathologically by invasive glandular cells with abundant cytoplasm and eccentrically placed nuclei; mucin production is common.
Imaging typically demonstrates a discrete mass or pneumonia-like consolidation at the periphery of the lung
What cardiovascular changes does hyperthyroidism cause?
Increased metabolic demand in the tissues and a direct vasodilatory effect of thyroid hormone lead to reduced systemic vascular resistance (and decreased diastolic blood pressure).
A direct sympathetic-like effect of thyroid hormone on the myocardium leads to increased heart rate, contractility, and cardiac output.
Increased stroke volume increases pulse pressure and systolic blood pressure
What is Kaposi sarcoma?
a vascular tumor associated with human herpesvirus 8, often arises in immunosuppressed patients (eg, HIV infection).
Involves the skin but can also affect the viscera, including the gastrointestinal tract (eg, abdominal pain) and pulmonary system (eg, cough, hemoptysis)
Biospy: spindled shaped endothelial cells forming slit like vascular spaces, extravasated red blood cells, and inflammation
What is granulomatosis with polyangiitis (wegener)?
Necrotizing vasculitis of the upper and lower respiratory tract (causing nasal ulcerations, sinusitis, hemoptysis) and rapidly progressive glomerulonephritis, producing a variable degree of renal failure.
A/W C-ANCAs, which may target neutrophil proteinase 3
REM sleep is characterized by?
dreaming and voluntary muscle paralysis, and occurs more often during the final third of the night.
Nightmares occurs during REM sleep and can be differentiated from sleep terrors, a non-REM parasomnia characterized by incomplete arousals and lack of recall of dream content.
What is the treatment of symptomatic PDA?
A patent ductus arteriosus classically presents with a continous murmur, widened pulse pressure, and bounding pulses.
Because physiologic closure of the ductus arteriosus is normally initiated by loss of placental prostaglandin E2, treatment of a symptomatic PDA includes cyclooxygenase inhibitors (indomethacin), which decrease PGE2 production.
Ionizing radiation causes cellular and DNA damage primarily through?
generation of reactive oxygen species, which can trigger progressive inflammation and tissue damage.
In the GI tract, the acute effects of radiation exposure typically occur several weeks after radiotherapy is initiated and manifest as abdominal pain and diarrhea due to mucosal denudation, inflammation, and edema
What is myasthenia gravis caused by?
an autoantibody mediated attack on the acetylcholine receptors of the postsynaptic neuromuscular junction, leading to a reduced number of acetylcholine receptors.
It is characterized by fatigable weakness of the skeletal muscles; respiratory failure can occur due to diaphragmatic weakness.
Poison ivy dermatitis is mediated by?
Poison ivy dermatitis is a form of allergic contact dermatitis, which is a type IV HSR, mediated primarily by T lymphocytes,
It manifests as intensely pruritic erythematous papules, vesicles, or bullae that often form linear patterns
The mature capsid of hepatitis B contains?
Replication of the hep B genome occurs within a newly synthesized capsid through the action of reverse transcriptase on an RNA template.
The mature capsid contains partially double stranded circular DNA and reverse transcriptase.
What is polyarteritis nodosa?
A systemic vasculitis characterized by constitutional manifesations and ischemic symptoms in the kidneys, skin, GI tract, and neurologic system.
Biopsy will show segmental, transmural arterial inflammation with fibrinoid necrosis and damage to the internal and external elastic lamina.
PAN is often associated with underlying viral hep B and C.
The third aortic arch is associated with the third pharyngeal arch, which gives rise to?
the glossopharyngeal nerve (CN IX), parts of the hyoid bone, and the stylopharyngeus muscle.
Common carotid artery and the proximal portion of the internal carotid artery are derived from which arch?
third aortic arch
What are common manifestations of Turner syndrome?
primary amenorrhea, short stature, a high arched palate, and widely spaced nipples.
Primary amenorrhea occurs in these patients due to in utero degeneration of the ovarian follicles (gonadal dysgenesis)
What is the pathogenesis of asthma?
An excess of Th2 cell activity relative to Th1 cell activity may underlie the pathogenesis of asthma.
In the asthma sensitization phase, inhaled antigens stimulate Th2 cells to secrete IL-4 and IL-13, which together promote B-lymphocyte class switching for IgE synthesis, leading to mast cell priming.
Th2 cells also secrete IL-5, which activates eosinophils.
Gallbladder hypo motility causes what?
The gallbladder functions to actively absorb water from bile. Gallbladder hypomotility causes the bile to become concentrated, promoting precipitation and accumulation of particulate material.
This forms a viscous biliary sludge that can cause transient bile duct obstruction (biliary colic) and promote cholesterol gallstone formation.
What is hereditary spherocytosis?
results from red cell cytoskeleton abnormalities, most commonly spectrin and ankyrin.
Hemolytic anemia, jaundice, and splenomegaly are classic manifestations.
Spherocytes are seen on peripheral blood smear
Propionic acidemia is due to?
Propionyl-CoA is derived from the metabolism of valine, isoleucine, methionine, threonine, and odd chain fatty acids.
Congenital deficiency of propionyl-CoA carboxylase, the enzyme responsible for the conversion of propionyl-CoA to methylmalonyl-CoA, leads to the development of propionic acidemia.
The condition presents with lethargy, poor feeding, vomitting, and hypotonia 1-2 weeks after birth.
Squamous cell carcinoma of the vulva can metastasize via lymphatic drainage. The vulva first drains to?
the inguinofemoral nodes of the groin, which should be the target for sentinel lymph node biopsy because they are most likely lymph nodes to have tumor involvement
Tumor necrosis factor-alpha inhibitors are associated with?
impairments to the cell-mediated immune response and increase the risk of infection with intracellular bacteria and granulomatous fungi (eg, Histoplasma capsulatum).
Histoplasma replicates within the intracellular space of macrophages and can spread from the lungs to the lymph nodes and the reticuloendothelial system (liver, spleen, bone marrow)
What values are increased in chronic obstructive pulmonary disease?
Chronic obstructive pulmonary disease involves components of chronic bronchitis and emphysema.
Bronchial airway obstruction from chronic bronchitis and decreased alveolar elasticity from emphysema result in air trapping and lung hyperinflation.
The functional residual capacity is increased, as are residual volume and total lung capacity.
In patients with hypertrophic cardiomyopathy, left ventricular outflow tract obstruction results from?
a hypertrophied interventricular septum and abnormal systolic anterior motion of the anterior leaflet of the mitral valve.
The degree of LVOT obstruction is dynamic and varies with changes in left ventricular blood volume
What is a risk factor for a ruptured ectopic pregnancy>
A ruptured ectopic pregnancy can cause abdominal pain, vaginal bleeding, and hemodynamic instability.
A common risk factor is tubal scarring from a prior upper genital tract infection (ie, pelvic inflammatory disease) due to Neisseria gonorrhoeae or Chlamydia trachomatis
What happens in the body during low blood pressure?
Low blood pressure results in decreased arterial distention and reduced firing of aortic and carotid baroreceptors.
This leads to an increase in sympathetic outflow and decrease in parasympathetic outflow, stimulating vasoconstriction and increased heart rate and contractility in order to help maintain blood pressure.
Hypovolemia reduces atrial stretch, causing decreased atrial natriuretic peptide secretion.
What are the symptoms of thoracic aortic aneurysms?
Thoracic aortic aneurysms are usually asymptomatic until they grow large enough to compress surrounding structures or cause rupture.
The most common symptomatic presentation is chest or back pain, but compression of nearby structures can cause dysphagia, hoarseness, cough, or dyspnea
