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Free STEP1 Exam Braindumps (page: 16)

Page 15 of 213
PDF with 845 Questions

A 24-year-old student is brought to the emergency room after being found in a ditch where he had lain overnight after being hit by a car. He complains of severe pain in the left arm and examination reveals a broken humerus. Neurological examination reveals that the patient can extend the elbow but displays inability to supinate the elbow when it is extended. The patient also has wrist drop and very weak hand grasp. The neurological lesion is likely localized at which of the following locations? In the above patient, when the elbow is partially flexed, the patient can supinate the left forearm. This is due to the function of which of the following?

  1. biceps brachii
  2. brachialis muscle
  3. brachioradialis
  4. pronator teres
  5. anconeus

Answer(s): A

Explanation:

The biceps brachii is a strong supinator of the forearm through its attachment to the radial tuberosity, but it can only function when the elbow is partially flexed. The supinator by itself is a weaker supinator muscle:
prove it to yourself by using a screwdriver with your right elbow flexed (biceps brachii and supinator) and your right elbow extended (supinator only). The brachialis (choice B) and brachioradialis (choice C) muscles are flexors of the forearm. The pronator teres (choice D), as its name indicates, pronates the forearm. The anconeus (choice E) helps in extension of the elbow.



Hormone-secreting chromophils in the pars distalis of the adenohypophysis are classified into acidophils and basophils. Which of the following hormones is secreted by the acidophils?

  1. adrenocorticotropin
  2. follicle-stimulating hormone
  3. luteinizing hormone
  4. prolactin
  5. thryrotropin (thyroid-stimulating hormone)

Answer(s): D

Explanation:

Prolactin is secreted by one of the two types of hormone-secreting acidophils, the mammotrophs. The other types of acidophils are the somatotrophs, which secrete growth hormone (somatotropin). The hormones listed in all the other choices are secreted by the basophils. Adrenocorticotropin (choice A) is secreted by the corticotrophs. The gonadotrophs secrete either follicle-stimulating hormone (choice B) or luteinizing hormone (choice C). Thyrotropin (choice E) is secreted by thyrotrophs.



Production of specific granules occurs mainly during which stage of granulocyte development?

  1. granulocyte colony-forming unit
  2. metamyelocyte
  3. myeloblast
  4. myelocyte
  5. promyelocyte

Answer(s): D

Explanation:

Generation of specific granules occurs during the myelocyte stage. Development of all three types of granulocytes follows a similar sequence of stages. The granulocyte colonyforming unit (choice A) is an undifferentiated progenitor cell of the granulocyte line. Buildup of the protein synthesis machinery occurs during the myeloblast (choice C) and promyelocyte (choice E) stages. The promyelocyte stage is also characterized by production of primary (nonspecific) granules. After the myelocyte stage, further condensation and reshaping of the nucleus occurs during the metamyelocyte stage (choice B).



A 1-year-old infant presents with cardiomegaly and congestive heart failure. She has increased intracranial pressure with hydrocephaly and cranial bruit. A vein of Galen aneurysm, revealed by MRI, is shown to compress the aqueduct of Sylvius, the posterior part of the third ventricle, and the splenium of the corpus callosum. Normally, the cerebral vein of Galen joins with which dural venous sinus?

  1. inferior sagittal sinus
  2. sigmoid sinus
  3. superior petrosal sinus
  4. superior sagittal sinus
  5. transverse sinus

Answer(s): A

Explanation:

The great cerebral vein of Galen joins with the inferior sagittal sinus to form the straight sinus. The latter drains into the transverse sinus (choice E). The superior sagittal sinus (choice D) drains posteriorly into the transverse sinus. The transverse sinus which runs bilaterally on the posterior wall of the posterior cranial fossa becomes the sigmoid sinus (choice B) which flows into the internal jugular vein. The superior petrosal sinus (choice C) extends from the cavernous sinus to the beginning of the sigmoid sinus.






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