USMLE Step 1 Qs (5)

50 Questions | Total Attempts: 155

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USMLE Step 1 Qs (5)

Biology and living organisms are interesting part of nature which are fascinating to study. If you are prepared to test your knowledge, this quiz will help you understand this part of nature even better, try it out.


Questions and Answers
  • 1. 
    . A 55-year-old woman presents with pain in her right hip and thigh. The pain started approximately six months ago and is a deep ache that worsens when she stands or walks. Your examination reveals increased warmth over the right thigh. The only laboratory abnormalities are alkaline phosphatase 656 IU/L (normal 23 to 110 IU/L), elevated 24-h urine hydroxyproline, and osteocalcin 13 ng/mL (normal 6 ng/mL). X-ray of hips and pelvis shows osteolytic lesions and regions with excessive osteoblastic activity. Bone scan shows significant uptake in the right proximal femur. Which of the following should you include in your differential diagnosis?
    • A. 

      Paget's disease

    • B. 

      Multiple myeloma

    • C. 

      Osteomalacia

    • D. 

      Osteoporosis

    • E. 

      Hypoparathyroidism

  • 2. 
    A 66-year-old man with no previous significant illness presents with back pain. The patient had felt well except for an increase in fatigue over the past few months. He suddenly felt severe low back pain while raising his garage door. Physical examination reveals a well-developed white male in acute pain. His pulse is 88 beats per minute and blood pressure is 150/90 mmHg. The conjunctivae are pale. There is marked tenderness to percussion over the lumbar spine. The following laboratory data are obtained: hemoglobin 11.0 g/dL (normal 13 to 16 g/dL), serum calcium 12.3 mg/dL (normal 8.5 to 11 mg/dL), abnormal serum protein electrophoresis with a monoclonal IgG spike, urine positive for Bence Jones protein, and abnormal plasma cells in bone marrow. X-rays reveal lytic lesions of the skull and pelvis and a compression fracture of lumbar vertebrae. Which of the following is the most likely diagnosis?
    • A. 

      Osteoporosis

    • B. 

      Osteomalacia

    • C. 

      Multiple myeloma

    • D. 

      Hypoparathyroidism

    • E. 

      Paget's disease

  • 3. 
    A 46-year-old woman presents with a pain in the left leg that worsens on weight-bearing. An x-ray shows demineralization and a decalcified (EDTA-treated) biopsy shows reduction in bone quantity. The patient had undergone menopause at age 45 without estrogen replacement. She reports long-standing diarrhea. In addition, laboratory tests show low levels of 25-hydroxyvitamin D, calcium, and phosphorus and elevated alkaline phosphatase. A second bone biopsy, which was not decalcified, shows uncalcified osteoid on all the bone surfaces. On the basis of these data, which of the following is the most likely diagnosis?
    • A. 

      Osteoporosis

    • B. 

      Osteomalacia

    • C. 

      Scurvy

    • D. 

      Paget's disease

    • E. 

      Hypoparathyroidism

  • 4. 
    DiGeorge syndrome is a congenital malformation in which the embryologic derivatives of the third and fourth branchial pouches fail to form. Which of the following would be expected to occur in children with this syndrome?
    • A. 

      Absence of the parafollicular cells

    • B. 

      Increased numbers of cells in the deep cortex of the lymph nodes

    • C. 

      Tetany

    • D. 

      Excess activity of osteoclasts

    • E. 

      Increased Ca2+ levels in the blood

  • 5. 
    This electron micrograph is a preparation from bone matrix in close proximity to the cellular components. Which of the following statements is true in regard to these structures?
    • A. 

      They contain type I collagen

    • B. 

      They are absent during endochondral bone formation

    • C. 

      They bud off from osteoclasts

    • D. 

      They may serve a "seed crystal" function in developing bone

    • E. 

      They contain acid phosphatase

  • 6. 
    The multinucleate arrangement of skeletal muscle during development is produced by which of the following?
    • A. 

      Duplication of DNA in myoblasts without cytokinesis

    • B. 

      Fusion of mononucleate myoblasts

    • C. 

      Cell proliferation of myotubes

    • D. 

      Hypertrophy of myoblasts

    • E. 

      Satellite cell differentiation

  • 7. 
    Observation of a histologic preparation of muscle indicates the cross-striations and peripherally located nuclei. The use of histochemistry shows a strong staining reaction for succinic dehydrogenase. The same tissue prepared for electron microscopy shows many mitochondria in rows between myofibrils and underneath the sarcolemma. Which of the following is the best description of this tissue?
    • A. 

      White muscle fibers

    • B. 

      Fibers that contract rapidly but are incapable of sustaining continuous heavy work

    • C. 

      Red muscle fibers

    • D. 

      Cardiac muscle

    • E. 

      Smooth muscle

  • 8. 
    . In muscular dystrophy, the actin-binding protein dystrophin is absent or defective. Dystrophin contains similar actin-binding domains to the spectrins (I and II) and -actinin and has a similar function. Which of the following is most likely to occur as a result of this deficiency?
    • A. 

      Deficiency in skeletal muscle actin synthesis

    • B. 

      Enhanced smooth muscle contractility

    • C. 

      Loss of binding of the I and M bands to the cell membrane

    • D. 

      Loss of organelle and vesicle transport throughout the muscle cell

    • E. 

      Loss of integrity of the desmosomal components of the intercalated discs of cardiac muscle

  • 9. 
    In the accompanying transmission electron micrograph of striated muscle, which of the following is true of the zone labeled "C"?
    • A. 

      The sarcomere is defined as the distance between these two structures

    • B. 

      Thin filaments are anchored to this structure

    • C. 

      This structure bisects the H band and is formed predominantly of creatine kinase

    • D. 

      No overlap of thick and thin filaments occurs in this zone

    • E. 

      This portion of the A band consists solely of the rodlike portions of myosin

  • 10. 
    . In the histogenesis of the neural tube, which zone will become the white matter of the adult CNS?
    • A. 

      Ventricular zone

    • B. 

      Marginal zone

    • C. 

      Mantle zone

    • D. 

      Ependymal zone

    • E. 

      Intermediate zone

  • 11. 
    The neurons shown in the accompanying photomicrograph of a dorsal root ganglion have which of the following functions?
    • A. 

      Transmission of autonomic information

    • B. 

      Transmission of proprioceptive information

    • C. 

      Innervation of striated muscle

    • D. 

      Transmission of dental pain

    • E. 

      Transmission of visual stimuli

  • 12. 
    . The blood-brain barrier is formed by which of the following?
    • A. 

      Fenestrations between brain capillary endothelial cells

    • B. 

      Occluding junctions between brain capillary endothelial cells

    • C. 

      Astrocytic foot processes surrounding blood vessels entering the brain parenchyma

    • D. 

      The basement membrane associated with the glia limitans

    • E. 

      Microglial activity

  • 13. 
    In the photomicrograph below of tissue taken from the central nervous system, which of the following are the predominant cells?
    • A. 

      Basket cells

    • B. 

      Granule cells

    • C. 

      Glial cells

    • D. 

      Pyramidal cells

    • E. 

      Purkinje cells

  • 14. 
    The neural crest gives rise to which of the following?
    • A. 

      Zona glomerulosa of the adrenal gland

    • B. 

      Pyramidal cells

    • C. 

      Ventral horn cells

    • D. 

      Astrocytes

    • E. 

      Sensory neurons of the cranial ganglia

  • 15. 
    Which of the following is the structure indicated by the arrow?
    • A. 

      An artery

    • B. 

      A vein

    • C. 

      A peripheral nerve

    • D. 

      A ganglion cell

    • E. 

      A serous acinar cell

  • 16. 
    The venous sinuses are located in which of the following regions?
    • A. 

      Epidural space

    • B. 

      Dura mater

    • C. 

      Subdural space

    • D. 

      Arachnoid

    • E. 

      Pia mater

  • 17. 
    Which of the following structures best represents the large endothelial pores defined in physiologic studies?
    • A. 

      Zonulae occludentes

    • B. 

      Gap junctions

    • C. 

      Pinocytotic vesicles

    • D. 

      Zonula adherens

    • E. 

      Coatomer-coated vesicles

  • 18. 
    Anionic proteins, such as insulin and transferrin, cross capillary endothelial cells primarily via which of the following?
    • A. 

      Diffusion through the membrane

    • B. 

      Intercellular space

    • C. 

      Fenestrated diaphragms

    • D. 

      Gap junctions

    • E. 

      Vesicular and channel pathways

  • 19. 
    Organs such as the brain and thymus have a more effective blood barrier because they have what type of blood capillaries?
    • A. 

      Continuous type with few vesicles

    • B. 

      Fenestrated type with diaphragms

    • C. 

      Fenestrated type without diaphragms

    • D. 

      Discontinuous type with diaphragms

    • E. 

      Discontinuous type without diaphragms

  • 20. 
    Atherosclerosis is usually initiated by which of the following?
    • A. 

      Proliferation of smooth muscle cells

    • B. 

      Formation of an intimal plaque

    • C. 

      Attraction of platelets to collagen microfibrils

    • D. 

      Adventitial proliferation

    • E. 

      Injury to the endothelium

  • 21. 
    Thrombocytopenia is a reduction in the number of circulating blood platelets. Which of the following would most likely occur in thrombocytopenia?
    • A. 

      Decreased vascular permeability

    • B. 

      Failure of initiation of the blood-clotting cascade

    • C. 

      Failure of conversion of fibrinogen to fibrin

    • D. 

      Absence of plasmin

    • E. 

      Absence of thrombin

  • 22. 
    Which of the following is the structure labeled A in the photomicrograph below?
    • A. 

      A Pacinian corpuscle

    • B. 

      Peripheral nerve

    • C. 

      Smooth muscle bundle

    • D. 

      Skeletal muscle bundle

    • E. 

      A venule

  • 23. 
    Anaphylactic shock is primarily due to the action of which of the following?
    • A. 

      Macrophages

    • B. 

      Mast cells

    • C. 

      T lymphocytes

    • D. 

      B lymphocytes

    • E. 

      Eosinophils

  • 24. 
    Expression of antigen associated with class I major histocompatibility complex (MHC) molecules is recognized primarily by which of the following?
    • A. 

      B cells

    • B. 

      CD4+ T lymphocytes

    • C. 

      CD8+ T lymphocytes

    • D. 

      Plasma cells

    • E. 

      Macrophages

  • 25. 
    Immunoglobulin switching from IgM to IgG occurs primarily in which of the following sites?
    • A. 

      Bone marrow

    • B. 

      Peripheral blood

    • C. 

      Germinal centers

    • D. 

      Thymus

    • E. 

      Splenic red pulp

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