USMLE USMLE Certifications USMLE-STEP-1 Questions & Answers

• Question 731:

  The anterior two-thirds of the tongue differ from the posterior one-third of the tongue by its special visceral afferent (SVA; taste) innervation. The perikarya of neurons providing the sensation of taste in the anterior two-thirds of the tongue are found in which of the following?

  A. geniculate ganglion

  B. otic ganglion

  C. pterygopalatine (sphenopalatine) ganglion

  D. submandibular ganglion

  E. trigeminal (gasserian) ganglion

  Correct Answer: A

  Section: Anatomy SVA (taste) fibers have their perikarya in the geniculate ganglion located in the petrous portion of the temporal bone. These neurons project their axons to the gustatory nucleus in the brainstem. The otic ganglion (choice B) receives preganglionic parasympathetic fibers originating from the inferior salivatory nucleus by way of the ninth cranial (glossopharyngeal) nerve. In turn, it projects postganglionic parasympathetic fibers to the parotid salivary gland. The pterygopalatine (sphenopalatine) ganglion (choice C) is also a parasympathetic ganglion, which receives preganglionic fibers from the superior salivatory nucleus by way of the ninth cranial (glossopharyngeal) nerve. In turn, it sends postganglionic parasympathetic fibers to the lacrimal gland and mucous glands in the nose. The submandibular ganglion (choice D) receives preganglionic parasympathetic fibers from the chorda tympani, a branch of the nervus intermedius which runs with the seventh cranial nerve. It innervates the submandibular and sublingual salivary glands. The trigeminal (gasserian) ganglion (choice E) receives sensations from the face, mucosa, cornea, teeth, gum, palate, and the anterior two- thirds of the tongue. It sends projections to the principal sensory and spinal trigeminal nuclei in the brainstem.

• Question 732:

  Sensations from the thoracic and abdominal organs are usually difficult to localize. They are conveyed by general visceral afferent (GVA) fibers, which synapse in which of the following nuclei?

  A. ambiguus nucleus

  B. dorsal motor nucleus of the vagus

  C. hypoglossal nucleus

  D. solitary nucleus

  E. spinal (descending) trigeminal nucleus

  Correct Answer: D

  Section: Anatomy GVA fibers from the thoracic and abdominal organs have their perikarya in the inferior vagal (nodose) ganglion and project to the solitary nucleus. The ambiguus nucleus (choice A) provides branchial efferent (motor) fibers to the stylopharyngeus, soft palate, pharyngeal, and laryngeal muscles. The dorsal motor nucleus of the vagus (choice B) sends parasympathetic preganglionic fibers to the thoracic and abdominal viscera. The hypoglossal nucleus (choice C) provides motor innervation for the muscles of the tongue. The spinal (descending) trigeminal nucleus (choice E) receives pain and temperature fibers from the face area.

• Question 733:

  A patient suffers from Frey's syndrome manifested by perspiration of the skin covering the left parotid gland whenever the patient eats. On inquiry, the patient reveals that he suffered deep injuries on that side of his face and neck in an automobile accident. You explain to him that his syndrome results from abnormal connections between the great auricular nerve and parasympathetic secretomotor fibers, which normally innervate only the parotid gland. This abnormal reinnervation occurred during the healing period after the accident. The parasympathetic secretomotor fibers to the parotid gland are carried by which of the following?

  A. auriculotemporal nerve

  B. buccal branch of the facial nerve

  C. buccal nerve

  D. greater petrosal nerve

  E. lesser petrosal nerve

  Correct Answer: A

  Section: Anatomy The auriculotemporal nerve is a branch of the mandibular division of the trigeminal nerve. It carries postganglionic parasympathetic fibers from the otic ganglion to the parotid gland. The buccal nerve (choice C) is a sensory branch of the mandibular division of the trigeminal nerve. It innervates the gingival adjacent to the two posterior molar teeth, the mucosa, and skin of the cheek. The buccal branch of the facial nerve (choice B) provides motor innervation to the muscles around the mouth. The greater petrosal nerve (choice D) is a branch of the facial nerve from the geniculate ganglion. It carries preganglionic parasympathetic fibers to the pterygopalatine ganglion. The lesser petrosal nerve (choice E) is a continuation of the tympanic branch of the glossopharyngeal nerve and carries preganglionic parasympathetic fibers to the otic ganglion.

• Question 734:

  Your young female patient has a large bulge on the anterior thigh below the inguinal ligament. You suspect an abdominal hernia that has passed through the femoral ring into the femoral sheath and then through the saphenous hiatus into the subcutaneous layer of the upper thigh. In addition to the hernia sac, you would expect the femoral canal to contain which of the following?

  A. connective tissue and lymph nodes

  B. femoral artery

  C. femoral nerve

  D. femoral vein

  E. great saphenous vein

  Correct Answer: A

  Section: Anatomy The femoral canal, the medial compartment of the femoral sheath, contains only a slight amount of loose connective tissue and one or two lymphatic vessels and nodes. The femoral artery (choice B) is found in the lateral compartment of the femoral sheath with the genital branch of the genitofemoral nerve. The femoral nerve (choice C) is the most lateral structure in the femoral triangle, but it does not lie within the femoral sheath. The femoral vein (choice D) occupies the intermediate compartment of the femoral sheath. The saphenous vein (choice E) is a superficial vein that passes through the saphenous hiatus to end in the femoral vein. It does not lie within the femoral canal.

• Question 735:

  An opera singer, who has maintained a demanding work schedule, worries about the effect on her vocal cords. The epithelium covering the vocal cords is which of the following?

  A. pseudostratified ciliated

  B. simple columnar

  C. simple cuboidal

  D. simple squamous

  E. stratified squamous

  Correct Answer: E

  Section: Anatomy A stratified squamous epithelium covers the vocal cords or folds. This epithelium protects the underlying tissue from the mechanical stress acting on the surface of the vocal cords. A simple squamous epithelium (choice D) is not suitable for protection. The rest of the larynx is covered with a pseudostratified ciliated epithelium (ie, a respiratory epithelium [choice A]). Simple columnar (choice B) and simple cuboidal (choice C) epithelia are found more commonly in organs with secretory or absorptive functions.

• Question 736:

  Your patient reports that several days earlier he "threw his back out" when he bent from the waist and picked up a very heavy package. The pain was immediate and extended from his hip, down the back of the thigh, and into his leg and foot. As he lies on the examining table, you raise his leg by the foot keeping the knee extended and elicit intense pain over the distribution of the sciatic nerve. An MRI scan confirms your conclusion that your patient has a herniated intervertebral disk between the fourth and fifth lumbar vertebrae. Intervertebral disks may protrude or rupture in any direction, but they most commonly protrude in which direction?

  A. anteriorly

  B. anterolaterally

  C. laterally

  D. posteriorly

  E. posterolaterally

  Correct Answer: E

  Section: Anatomy Intervertebral disks may protrude or rupture in any direction but do so most commonly in a posterolateral direction, just lateral to the strong central portion of the posterior longitudinal ligament. This is usually the weakest part of the disk, because the annulus is thinner here and is not supported by other ligaments. Anteriorly (choice A) the intervertebral disks are supported by the broad and strong anterior ligament. Herniation is less common in this direction. Anterolaterally (choice B) the intervertebral disk is supported by the broad anterior longitudinal ligament. The nucleus pulposus is also situated posteriorly in the disk, making herniation here less likely. Herniation of the intervertebral disk laterally (choice C) is not particularly common. Posteriorly (choice D) the intervertebral disks are supported by the posterior longitudinal ligament. Herniation is less common in this direction.

• Question 737:

  Your patient reports that several days earlier he "threw his back out" when he bent from the waist and picked up a very heavy package. The pain was immediate and extended from his hip, down the back of the thigh, and into his leg and foot. As he lies on the examining table, you raise his leg by the foot keeping the knee extended and elicit intense pain over the distribution of the sciatic nerve. An MRI scan confirms your conclusion that your patient has a herniated intervertebral disk between the fourth and fifth lumbar vertebrae. Herniation of the intervertebral disk between the fourth and fifth lumbar vertebrae most likely impinges on the roots of which spinal nerve?

  A. L3

  B. L4

  C. L5

  D. S1

  E. S2

  Correct Answer: C

  Section: Anatomy A bulging or protruded disk typically affects the traversing nerve root; that is, the nerve affected is one number greater than the number of the disk. The L3 spinal nerve (choice A) would be affected by protrusion of the L2 intervertebral disk. The L4 spinal nerve (choice B) would be affected by protrusion of the L3 intervertebral disk. The S1 spinal nerve (choice D) would be affected by protrusion of the L5 intervertebral disk. The S2 spinal nerve (choice E) exits through the foramina of the fused sacrum and, therefore, is not subject to compression by herniated intervertebral disks.

• Question 738:

  During maturation of the oocytes, which of the following structures retain almost all of the cytoplasm after the first meiotic division?

  A. first polar body

  B. ovum

  C. primary oocyte

  D. second polar body

  E. zygote

  Correct Answer: B

  Section: Anatomy The first meiotic division results in two secondary oocytes: the ovum retains almost all of the cytoplasm whereas the first polar body (choice A) does not. Primary oocytes (choice C) are the cells undergoing the first meiotic division. The second polar body (choice D) is formed after the second meiotic division. The zygote (choice E) is the fertilized ovum.

• Question 739:

  Your patient presents in your office complaining of hoarseness. During your examination, you find that one vocal fold has deviated toward the midline and does not abduct during deep inspiration or vocalization. You also observe that touch sensation in the vestibule of the larynx appears to be intact.

  You suspect that a nerve has been damaged, but which nerve is most likely involved?

  A. external laryngeal

  B. glossopharyngeal

  C. inferior laryngeal

  D. internal laryngeal

  E. superior laryngeal

  Correct Answer: C

  Section: Anatomy The inferior laryngeal nerve is motor to the intrinsic muscles of the larynx except the cricothyroid muscle, and is sensory to the larynx below the level of the vocal fold. The external laryngeal nerve (choice A) is the branch of the superior laryngeal nerve that contains the motor fibers to the cricothyroid muscle and to the cricopharyngeus muscle. The glossopharyngeal nerve (choice B) does not supply either motor or sensory fibers to the larynx. The internal laryngeal nerve (choice D) is the branch of the superior laryngeal nerve that contains the sensory fibers to the laryngeal mucosa above the vocal fold. The superior laryngeal nerve (choice E) is sensory to the laryngeal mucosa above the vocal fold and also includes motor fibers to the cricothyroid muscle.

• Question 740:

  Your patient presents in your office complaining of hoarseness. During your examination, you find that one vocal fold has deviated toward the midline and does not abduct during deep inspiration or vocalization. You also observe that touch sensation in the vestibule of the larynx appears to be intact. Which laryngeal muscle is most important in abduction of the vocal folds?

  A. cricothyroid

  B. lateral cricoarytenoid

  C. posterior cricoarytenoid

  D. thyroarytenoid

  E. transverse arytenoid

  Correct Answer: C

  Section: Anatomy The vocal folds are abducted and the rima glottidis is widened by the posterior cricoarytenoid muscles that rotate the arytenoid cartilages laterally. The cricothyroid muscles (choice A) tense and lengthen the vocal ligament by tilting the thyroid cartilage forward. The lateral cricoarytenoid muscles (choice B) adduct the vocal folds by medially rotating the arytenoid cartilages. The thyroarytenoid muscles (choice D) decrease the tension and length of the vocal ligaments by tilting the thyroid cartilages posteriorly. The transverse arytenoids muscle (choice E) adducts the vocal folds by pulling the arytenoid cartilages together.