USMLE Exam 1 — Questions and Answers

Question 1: Choose the correct answer

Brachial artery (Correct answer)
Ulnar nerve
Musculocutaneous nerve
Profunda brachii artery
Radial nerve

Correct answer: Brachial artery

The brachial artery is the main artery of the upper arm, a continuation of the axillary artery. It is a crucial anatomical landmark for various medical procedures, including blood pressure measurement and arterial access. Its significant role in supplying blood to the forearm and hand makes it a frequently tested structure in anatomy and clinical contexts.

Question 2: Choose the correct answer

Complete androgen resistance
5α-reductase deficiency (Correct answer)
17α-hydroxylase deficiency
Sertoli-only syndrome
Testicular dysgenesis

Correct answer: 5α-reductase deficiency

5α-reductase deficiency is a disorder of sex development where testosterone cannot be converted to dihydrotestosterone (DHT). DHT is essential for the development of external male genitalia in utero. Individuals with this XY genetic makeup may present with ambiguous genitalia at birth, often virilizing at puberty due to increased testosterone.

Question 3: Choose the correct answer

Diphyllobothrium latum
Entamoeba histolytica
Giardia lamblia
Isospora belli (Correct answer)
Microsporidia

Correct answer: Isospora belli

Isospora belli (now Cystoisospora belli) is an intestinal parasite known to cause isosporiasis, a diarrheal illness. It is particularly associated with chronic, watery diarrhea in immunocompromised individuals, such as those with HIV/AIDS. Diagnosis involves identifying oocysts in stool, and treatment typically uses trimethoprim-sulfamethoxazole.

Question 4: Choose the correct answer

Creatinine clearance (Correct answer)
Renal excretion of creatinine
Creatinine production
Daily excretion of sodium
Plasma creatinine concentration

Correct answer: Creatinine clearance

Creatinine clearance is the most commonly used clinical measure to estimate the glomerular filtration rate (GFR), which reflects overall kidney function. It quantifies the volume of blood plasma cleared of creatinine per unit time. This provides a practical and relatively accurate assessment of how well the kidneys are filtering waste products from the blood.

Question 5: Choose the correct answer

Alpha-fetoprotein
Bombesin
CA-125 (Correct answer)
PSA
S-100

Correct answer: CA-125

CA-125 (Cancer Antigen 125) is a tumor marker primarily used in the management of ovarian cancer. Elevated levels are often found in women with epithelial ovarian cancer, and it is utilized for monitoring treatment response and detecting recurrence. While not specific enough for definitive diagnosis alone, it is a valuable tool in conjunction with imaging and clinical evaluation.

Question 6: Choose the correct answer

Esophageal body distal to the diaphragm
Esophageal body proximal to the diaphragm
Lower esophageal sphincter (Correct answer)
Pharynx
Upper esophageal sphincter

Correct answer: Lower esophageal sphincter

The lower esophageal sphincter (LES) is a physiological sphincter, not an anatomical one, formed by the muscularis propria of the distal esophagus and the surrounding diaphragm. Its primary function is to prevent reflux of gastric contents into the esophagus. Dysfunction of the LES is a common cause of gastroesophageal reflux disease (GERD).

Question 7: Choose the correct answer

Left gastric artery and right gastric artery
Left gastroepiploic artery and right gastroepiploic artery
Proper hepatic artery and gastroduodenal artery
Right colic artery and middle colic artery
Superior pancreaticoduodenal artery and inferior pancreaticoduodenal artery (Correct answer)

Correct answer: Superior pancreaticoduodenal artery and inferior pancreaticoduodenal artery

The head of the pancreas and the duodenum receive their primary arterial supply from the superior and inferior pancreaticoduodenal arteries. The superior pancreaticoduodenal artery is a branch of the gastroduodenal artery, while the inferior pancreaticoduodenal artery branches from the superior mesenteric artery. These two arteries form an important anastomotic network, ensuring robust blood flow to this vital region.

Question 8: Choose the correct answer

Amitriptyline (Correct answer)
Propranolol
Cimetidine
Diazepam
Malathion

Correct answer: Amitriptyline

Amitriptyline is a tricyclic antidepressant (TCA) known for its potent anticholinergic, antihistaminic, and alpha-adrenergic blocking properties. It is commonly used for depression, neuropathic pain, and migraine prophylaxis. Its side effect profile includes sedation, dry mouth, constipation, and orthostatic hypotension due to these receptor interactions.

Question 9: Choose the correct answer

Apical segment of the left upper lobe
Apical segment of the right upper lobe
Medial segment of the right middle lobe
Posterior basal segment of the left lower lobe
Superior segment of the right lower lobe (Correct answer)

Correct answer: Superior segment of the right lower lobe

Aspiration pneumonia commonly affects the dependent lung segments due to gravity. In an upright or semi-recumbent position, the superior segment of the right lower lobe is the most common site for aspiration. If a patient is supine, the posterior segments of the upper lobes or the superior segments of the lower lobes are more likely to be affected.

Question 10: Choose the correct answer

Enterococcus faecalis
Staphylococcus aureus
Staphylococcus epidermidis (Correct answer)
Streptococcus agalactiae
Streptococcus pyogenes

Correct answer: Staphylococcus epidermidis

Staphylococcus epidermidis is a common component of normal skin flora and is a frequent cause of infections associated with indwelling medical devices like prosthetic joints, catheters, and heart valves. It produces a biofilm that allows it to adhere to these surfaces and resist antibiotics. Unlike S. aureus, it is coagulase-negative.

Question 11: Choose the correct answer

Gaucher disease
McArdle disease
Niemann-Pick disease
Pompe disease
Von Gierke disease (Correct answer)

Correct answer: Von Gierke disease

Von Gierke disease (Type I glycogen storage disease) is caused by a deficiency in glucose-6-phosphatase, an enzyme crucial for gluconeogenesis and glycogenolysis. This leads to severe fasting hypoglycemia, lactic acidosis, hyperlipidemia, and hepatomegaly due to glycogen accumulation. Patients often present with a "doll-like" face and growth retardation.

Question 12: Choose the correct answer

“Big boys don’t cry.”
“I left your mother, I didn’t leave you.” (Correct answer)
“I’ll see you in 2 weeks.”
“You’re the man of the house now.”
“Your mother was too hard to live with.”

Correct answer: “I left your mother, I didn’t leave you.”

When parents divorce, children often internalize the separation, feeling responsible or abandoned. Reassuring a child that the parent is not leaving them personally, but rather the other parent, helps to alleviate feelings of guilt and abandonment. This statement validates the child's feelings while clarifying the nature of the parental separation.

Question 13: Choose the correct answer

Bartonella henselae
Brucella canis
Clostridium tetani
Pasteurella multocida (Correct answer)
Toxocara canis

Correct answer: Pasteurella multocida

Pasteurella multocida is a common bacterium found in the oral flora of cats and dogs. It is a frequent cause of infection following animal bites or scratches, leading to rapidly developing cellulitis, osteomyelitis, or septic arthritis. The infection typically presents with erythema, swelling, and pain at the bite site within 24 hours.

Question 14: Choose the correct answer

Amebic colitis
Chronic appendicitis
Diverticulosis
Pseudomembranous colitis
Ulcerative colitis (Correct answer)

Correct answer: Ulcerative colitis

Ulcerative colitis is a chronic inflammatory condition affecting the colon, characterized by continuous inflammation that typically starts in the rectum and extends proximally. It involves only the mucosa and submucosa, leading to symptoms like bloody diarrhea, abdominal pain, and tenesmus. Crypt abscesses are a characteristic histological finding.

Question 15: Choose the correct answer

confined placental mosaicism
expansion of a trinucleotide repeat
a point mutation in an autosome
random inactivation of the X chromosome
uniparental disomy (Correct answer)

Correct answer: uniparental disomy

Uniparental disomy (UPD) occurs when an individual receives both copies of a chromosome, or part of a chromosome, from a single parent. If the chromosome involved carries imprinted genes, UPD can lead to genetic disorders like Prader-Willi or Angelman syndrome, even without a mutation, due to incorrect dosage of imprinted genes.

Question 16: Choose the correct answer

Anti-glomerular basement membrane disease (Correct answer)
Minimal change disease
Diabetic nephropathy
Hypertensive nephropathy
Lupus nephritis

Correct answer: Anti-glomerular basement membrane disease

Anti-glomerular basement membrane (GBM) disease, also known as Goodpasture syndrome, is an autoimmune disorder characterized by antibodies targeting type IV collagen in the glomerular and often alveolar basement membranes. This leads to rapidly progressive glomerulonephritis and pulmonary hemorrhage, presenting as hemoptysis and acute kidney injury.

Question 17: Choose the correct answer

Endolymphatic stromal myosis
Endometrial carcinoma
Endometrial stromal sarcoma
Leiomyosarcoma
Malignant mixed mullerian tumor (Correct answer)

Correct answer: Malignant mixed mullerian tumor

Malignant mixed mullerian tumor (MMMT), also known as carcinosarcoma, is a highly aggressive uterine malignancy containing both malignant epithelial (carcinomatous) and malignant mesenchymal (sarcomatous) components. It typically presents in postmenopausal women with abnormal uterine bleeding and has a poor prognosis due to its aggressive nature and high recurrence rate.

Question 18: Choose the correct answer

Ectoderm
Endoderm
Neural crest (Correct answer)
Neural ectoderm
Splanchnic mesoderm

Correct answer: Neural crest

Neural crest cells are multipotent migratory cells that originate from the neural folds during embryonic development. They contribute to a wide array of tissues and cell types throughout the body, including the peripheral nervous system, melanocytes, adrenal medulla, and many craniofacial structures. Their extensive migratory capacity makes them crucial for diverse developmental processes.

Question 19: Choose the correct answer

Blood flow in the lower body
Blood flow in the upper body
Blood pressure in the upper body
Vascular resistance in the upper body
Vascular resistance in the lower body (Correct answer)

Correct answer: Vascular resistance in the lower body

Coarctation of the aorta is a congenital narrowing of the aorta, typically distal to the left subclavian artery. This narrowing significantly increases the vascular resistance in the lower body, leading to decreased blood flow and pressure in the lower extremities while increasing blood pressure in the upper extremities. The body compensates by developing collateral circulation.

Question 20: Choose the correct answer

Prostatic acid phosphatase
Prostate-specific antigen
Serum alkaline phosphatase (Correct answer)
Tartrate-resistant acid phosphatase
Urinary hydroxyproline

Correct answer: Serum alkaline phosphatase

Serum alkaline phosphatase (ALP) is an enzyme found in various tissues, including bone, liver, and placenta. Elevated ALP levels, particularly the bone isoenzyme, are a sensitive indicator of increased osteoblastic activity. This makes it a useful marker for conditions involving increased bone turnover, such as metastatic bone disease, Paget's disease, and osteomalacia.

Question 21: Choose the correct answer

Astrocytoma
Ependymoma
Glioblastoma multiforme
Meningioma
Metastatic carcinoma (Correct answer)

Correct answer: Metastatic carcinoma

Metastatic carcinoma is the most common malignant brain tumor in adults, often presenting as multiple lesions at the gray-white matter junction. The primary tumors frequently originate from the lung, breast, kidney, colon, or melanoma. These lesions typically have a well-demarcated appearance with surrounding edema on imaging.

Question 22: Choose the correct answer

Congenital heart disease
Illicit drug use (Correct answer)
Rheumatic fever
Rheumatoid arthritis
Systemic lupus erythematosus

Correct answer: Illicit drug use

Illicit intravenous drug use is a significant risk factor for infective endocarditis, particularly affecting the tricuspid valve. Contaminated needles introduce bacteria, commonly Staphylococcus aureus, into the bloodstream, which then colonize the heart valves. This can lead to vegetation formation, valve damage, and septic emboli.

Question 23: Choose the correct answer

Adherent thin, whitish patch on gingiva
Cold sores on the lips
Curdy white material overlying an erythematous base on the oral mucosa
Large shallow ulcers on the oral mucosa
Multiple small white spots on the buccal mucosa (Correct answer)

Correct answer: Multiple small white spots on the buccal mucosa

Multiple small white spots on the buccal mucosa, known as Koplik spots, are a pathognomonic sign of measles (rubeola). These spots typically appear 1-2 days before the characteristic maculopapular rash and are transient, disappearing as the rash progresses. They are considered an early diagnostic indicator of measles infection.

Question 24: Choose the correct answer

Amiodarone
Disopyramide
Lidocaine
Propranolol (Correct answer)
Verapamil

Correct answer: Propranolol

Propranolol is a non-selective beta-blocker (Class II antiarrhythmic) that reduces heart rate and contractility, thereby decreasing myocardial oxygen demand. It is used to treat various arrhythmias, including supraventricular tachycardias, and to prevent recurrent myocardial infarction. Its effects are mediated by blocking beta-adrenergic receptors in the heart.

Question 25: Choose the correct answer

Cricothyroid (Correct answer)
Vocalis
Lateral cricoarytenoid
Posterior cricoarytenoid
Thyroarytenoid

Correct answer: Cricothyroid

The cricothyroid muscle is the primary tensor of the vocal cords, responsible for increasing their tension and thus raising the pitch of the voice. It is innervated by the external branch of the superior laryngeal nerve. Damage to this nerve or muscle can result in a monotone or hoarse voice.

Question 26: Choose the correct answer

Bronchogenic cysts
Congenital pulmonary cysts
Posterior deviation of the tracheoesophageal septum (Correct answer)
Pulmonary immaturity
Pulmonary sequestration

Correct answer: Posterior deviation of the tracheoesophageal septum

Esophageal atresia with tracheoesophageal fistula (TEF) is a congenital anomaly resulting from incomplete separation of the foregut into the esophagus and trachea during embryonic development. This occurs due to abnormal posterior deviation of the tracheoesophageal septum, leading to a blind-ending esophagus and an abnormal connection between the trachea and esophagus.

Question 27: Choose the correct answer

Cavernous sinus (Correct answer)
Superior petrosal sinus
Occipital sinus
Sigmoid sinus
Straight sinus

Correct answer: Cavernous sinus

The cavernous sinus is a dural venous sinus located on either side of the sella turcica. It is clinically significant due to its close proximity to several cranial nerves (III, IV, V1, V2, VI) and the internal carotid artery. Infections or thromboses in this sinus can lead to severe neurological deficits, including ophthalmoplegia and facial sensory loss.

Question 28: Choose the correct answer

Bacillus cereus (Correct answer)
Staphylococcus aureus
Clostridium botulinum
Clostridium perfringens
EHEC (Enterohemorrhagic Escherichia coli)
Vibrio cholerae

Correct answer: Bacillus cereus

Bacillus cereus causes two types of food poisoning: an emetic form and a diarrheal form. The emetic form is typically associated with reheated rice and is caused by a preformed heat-stable toxin, leading to rapid onset (1-5 hours) of nausea and vomiting. The diarrheal form is associated with meat and vegetables and involves a heat-labile toxin.

Question 29: Choose the correct answer

AIDS
C1 esterase inhibitor deficiency
DiGeorge syndrome
Selective IgA deficiency (Correct answer)
Wiskott-Aldrich syndrome

Correct answer: Selective IgA deficiency

Selective IgA deficiency is the most common primary immunodeficiency, characterized by low or absent serum IgA levels with normal levels of other immunoglobulins. Patients are often asymptomatic but may experience recurrent sinopulmonary and gastrointestinal infections, as IgA is crucial for mucosal immunity. Anaphylactic reactions to IgA-containing blood products can also occur.

Question 30: Choose the correct answer

azoospermia
germinal cell aplasia
immotile sperm (Correct answer)
isolated gonadotropin deficiency
varicocele

Correct answer: immotile sperm

Immotile sperm, or asthenozoospermia, is a cause of male infertility where sperm are unable to move effectively, hindering their ability to reach and fertilize an egg. This can be due to structural defects in the sperm flagella (e.g., primary ciliary dyskinesia), metabolic deficiencies, or other genetic factors affecting sperm motility. Diagnosis involves semen analysis.

USMLE Exam 1

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