Gratisexam.com-USMLE.Braindumps.Step1.v2015-03-20.by.Lavada.849q.pdf

  • No School
  • AA 1
  • CountUniverse3941
  • 437
  • 100% (1) 1 out of 1 people found this document helpful

This preview shows page 1 out of 437 pages.

You've reached the end of your free preview.

Want to read all 437 pages?

Unformatted text preview: Braindumps.USMLE.Step1 849 questions Number: USMLE Passing Score: 800 Time Limit: 120 min File Version: 4.0 USMLE Step 1 United State Medical Licensing Examination (Step 1) I only used these questions and got 80% marks with this. Perfect Show. Start your career with this assistance and you will never regret investing in its amazing study tools that are for you and your training in any kind of certification exam preparation. Still valid, Hurry up guys study and pass this one. It gave me the real atmosphere of the exam and also the questions of the same were of good standard . It was one and only which took me towards the biggest success without finding too much issues or worries in any way. Sections 1. Anatomy 2. Physiology 3. Biochemistry 4. Microbiology/Immunology 5. Pathology and Path physiology 6. Pharmacology 7. Behavioral Science and Biostatics step 1 QUESTION 1 A 2-year-old male patient develops progressive generalized weakness and muscle atrophy. The impairment first began with the muscles of the hips, and then progressed to the pelvic area, thigh, and shoulder muscles. The patient is diagnosed with Duchenne's muscular dystrophy, a congenital disorder where the protein dystrophin is deficient. Which of the following describes the role of dystrophin in muscle tissue? A. B. C. D. E. anchors actin to the sarcolemma endows the myosin filaments with elastic recoil properties extends from Z disk to Zdisk, forming a supportive network inhibits the binding of myosin to actin protects desmin filaments from stressinduced damage Correct Answer: A Section: Anatomy Explanation Explanation/Reference: Explanation: Dystrophin anchors actin to the sarcolemma, reinforcing and stabilizing the latter during muscle contraction. Titin is a large protein which associates with myosin filaments and endows them with elastic recoil properties (choice B). Desmin filaments form a supportive network extending from Z disk to Zdisk (choice C). Troponin I inhibits the binding of myosin to actin (choice D). AlphaB-crystallin protects desmin filaments from stress-induced damage (choice E). QUESTION 2 The third week of development is characterized by the appearance of the branchial apparatus, the embryonic primordium from which head and neck structures will be derived. The apparatus consists of five branchial arches, numbered 1, 2, 3, 4 and 6. Second arch anomalies represent 95% of all branchial anomalies and are classified into four types with types IIII being the most common. The anomalies manifest as cysts or fistulae in the lateral neck, located anterior and deep to the sternocleidomastoid muscle. Which of the following structures develop from the second branchial arch? A. B. C. D. E. anterior digastric muscle posterior cricoarytenoideus muscle posterior digastric muscle stylopharyngeus muscle superior constrictor muscle Correct Answer: C Section: Anatomy Explanation Explanation/Reference: Explanation: The posterior digastric muscle is derived from the second branchial arch and thus is innervated by its nerve, the facial (Seventh cranial) nerve. The anterior digastric muscle (choice A) is derived from the first branchial arch and is innervated by its nerve, the mandibular division of the trigeminal (fifth cranial) nerve. The posterior cricoarytenoideus muscle (choice B) and the superior constrictor muscle (choice E), derived from a combination of the fourth and sixth branchial arches, are innervated by the vagus (tenth cranial) nerve. The stylopharyngeus (choice D) is derived from the third branchial arch and is the only voluntary muscle innervated by the glossopharyngeal (ninth cranial) nerve. QUESTION 3 A 10-year boy is examined because his parents noticed that "his eyes never seem to look in the right direction." On examination, the left eye of the child is unable to move laterally (abduction) and when asked to look toward the nose (adduction), the eyeball retracts into the socket and the eye opening narrows. Sometimes, the eye also moves superiorly. The child is diagnosed with Duane syndrome, a congenital ocular motility disorder characterized by limited abduction of the affected eye. This is due to absence of the abducens (fifth cranial) nerve with aberrant innervation by the oculomotor (third cranial) nerve. Which of the following muscles is normally innervated by the abducens nerve? A. B. C. D. E. inferior oblique lateral rectus medial rectus superior oblique superior rectus Correct Answer: B Section: Anatomy Explanation Explanation/Reference: Explanation: The abducens (sixth cranial) nerve normally innervates the lateral rectus muscle. The inferior oblique (choice A), medial rectus (choice C), and superior rectus (choice E) are all innervated by the oculomotor (third cranial) nerve. The superior oblique (choice D) is innervated by the trochlear (fourth cranial) nerve. In Duane syndrome, the absence of lateral rectus innervations by the abducens (sixth cranial) nerve is replaced by an aberrant innervation of the oculomotor (third cranial) nerve. Thus when the patient is asked to adduct the affected eye, there is cocontraction of the lateral and medial recti with globe retraction. QUESTION 4 Retinitis pigmentosa is a hereditary disorder, which affects the photoreceptors (the rods and the cones) in the retina. These photoreceptors are located in which of the numbered layers in Figure below A. B. C. D. E. 1 2 3 4 5 Correct Answer: E Section: Anatomy Explanation Explanation/Reference: Explanation: The retina contains three layers of cells. They are, from top to bottom, the ganglion cells (choice A), the bipolar cells (choice C), and the photoreceptor cells (rods and cones, choice E). The internal plexiform layer (choice B) contains the synapses between the bipolar cells and the ganglion cells. The external plexiform layer (choice D) contains the synapses between the photoreceptors and the bipolar cells. Remember that light enters from the top and traverses all the layers to reach the photoreceptors in the bottom layer. QUESTION 5 The structure indicated by arrow 1 in Fig. 1-2 is which of the following vessels? A. B. C. D. E. brachiocephalic artery left brachiocephalic vein left common carotid artery right brachiocephalic vein superior vena cava Correct Answer: D Section: Anatomy Explanation Explanation/Reference: Explanation: Remember that in viewing axial or transverse CT scans through the body, the right side of the patient is to your left and the left side to your right. In other words, the feet of the patient are toward you and the head away from you. The back of the patient is at the bottom of the image and the front of the patient toward the top. Directional terms are always in reference to the patient. The insert at the bottom right indicates the level of the section. Arrow 1 indicates the right brachiocephalic vein. The left brachiocephalic vein (choice B) is seen as the elongated structure immediately posterior to the manubrium of the sternum and to the left of the right brachiocephalic vein. Immediately posterior to the left brachiocephalic vein is the brachiocephalic artery (choice A, arrow 2). To the left of the latter are the left common carotid artery (choice C) and the left subclavian artery (arrow 3). The superior vena cava (choice E) is not seen at this level because the right and left brachiocephalic veins are still separate. QUESTION 6 A 4-month-old male infant is brought to the clinic because of excessive noisy respiration. On examination, the infant is within the normal range of growth, appears healthy, and does not show respiratory distress. Phonation is normal, along with head and neck examination findings. However, the child displays stridor (highpitched breathing sound) on inspiration, accentuated in the supine position. The parents report that the same stridor is heard during feeding or when the child is agitated. The attending physician places the child in the prone position and the stridor is relieved. To confirm, she holds the child in a neck extended position, which also relieves the stridor. An endoscopic laryngeal examination reveals bulky arytenoids cartilages and the diagnosis of laryngomalacia is established. During development, the arytenoids cartilages arise from which of the following? A. B. C. D. E. first pharyngeal arch second pharyngeal arch third pharyngeal arch fifth pharyngeal arch sixth pharyngeal arch Correct Answer: E Section: Anatomy Explanation Explanation/Reference: Explanation: The arytenoid cartilages arise as swellings from the sixth pharyngeal (branchial) arch at 32 days of gestation. They are located between the caudal end of the hypobranchial eminence and the cranial end of the laryngotracheal tube. The swellings will grow cranially to form the arytenoids and corniculate cartilages along with the primitive aryepiglottic folds. In laryngomalacia, the bulky arytenoids cartilages prolapsed anteromedially on inspiration, resulting in stridor. The first (choice A), second (choice B), and third (choice C) pharyngeal arches do not participate in the development of laryngeal cartilages. The fifth (choice D) pharyngeal arch remains rudimentary and does not give rise to any adult structure. QUESTION 7 A newborn infant suffers from cyanotic heart disease caused by transposition of the great arteries (TGA). In this situation, the aorta arises from which of the following structures? A. B. C. D. E. ductus arteriosus left atrium left ventricle right atrium right ventricle Correct Answer: E Section: Anatomy Explanation Explanation/Reference: Explanation: In TGA, the aorta arises from the right ventricle and the pulmonary trunk arises from the left ventricle (choice C). This is the reverse of the normal situation and gives rise to the cyanotic condition in the newborn. The large arteries arise from the truncus arteriosus in the developing heart and thus could not develop from the atria (choices B and D), which are formed from the sinus venosus. The truncus arteriosus and the sinus venosus are at opposite ends of the heart. The ductus arteriosus (choice A) is the vessel that shunts oxygenated blood from the pulmonary trunk to the arch of the aorta in the fetus. It does not give rise to the aorta. QUESTION 8 About 75% of the blood supply of the spinal cord is derived from the anterior spinal artery. This artery arises from which of the following? A. B. C. D. E. artery of Adamkiewicz basilar artery internal carotid artery posterior inferior cerebellar artery vertebral artery Correct Answer: E Section: Anatomy Explanation Explanation/Reference: Explanation: At the level of the foramen magnum, the bilateral vertebral arteries supply a medial branch each and they combine to form the anterior spinal artery. As the anterior spinal artery continues caudally, it is supplied by radicular arteries arising from the aorta and its branches. The artery of Adamkiewicz (choice A) is the largest radicular artery (arteria radicularis magna), frequently arising from a segmental branch of the thoracic aorta at the level of T10. The basilar artery (choice B) is formed by the joining of the vertebral arteries superior to the foramen magnum and thus does not provide blood supply to the spinal cord. Its branches supply the brainstem. The internal carotid artery (choice C) supplies the orbit via its ophthalmic branch and the brain by its anterior and middle cerebral branches. The posterior inferior cerebellar artery (choice D) is a branch of the vertebral artery, providing vascular supply to the medulla oblongata and the inferior aspect of the cerebellum. QUESTION 9 Clinical edema results when lymphatic vessels are blocked or when the volume of extracellular fluid exceeds the drainage capacity of the lymphatic vessels. Which of the following numbered structures in following figure is a lymphatic vessel? A. B. C. D. E. 1 2 3 4 5 Correct Answer: C Section: Anatomy Explanation Explanation/Reference: Explanation: An irregular outline, a thin wall, and the lack of erythrocytes in the lumen characterize lymphatic vessel. Arterioles (choices A and B) have thicker walls and contain erythrocytes. Venules (choice D) are thin-walled but they contain erythrocytes. Capillaries (choice E) are small in diameter and they contain erythrocytes. QUESTION 10 The histological structure marked by the asterisk in Fig. 1-4 is which of the following structures from the integumentary system? A. B. C. D. E. aprocrine sweat gland dermal papilla eccrine sweat gland hair follicle sebaceous gland Correct Answer: C Section: Anatomy Explanation Explanation/Reference: Explanation: This is the secretory portion of the eccrine sweat gland, recognizable by its three cell types. The apical dark cells (arrow 1) are closest to the lumen. The clear or basal cells (arrow 2) and the myoepithelial cells (arrow 3) are located against the basal lamina. Characteristically, these cells are large and the lumen is small. The apocrine sweat gland (choice A) is lined with simple cuboidal epithelium and thus has a large lumen. The dermal papilla (choice B) is formed by fibroblasts, not epithelia. The hair follicle (choice D) is formed by three concentric zones of keratinized cells and does not have a lumen. The sebaceous glands (choice E) are appendages of the hair follicle and their lumen is lined by stratified squamous epithelium. QUESTION 11 Occlusion of which of the following vessels affects the entire dorsolateral part of the rostral medulla (level of the restiform body) and produces the lateral medullary (Wallenberg) syndrome? A. B. C. D. E. anterior inferior cerebellar artery anterior spinal artery posterior inferior cerebellar artery posterior spinal artery superior cerebellar artery Correct Answer: C Section: Anatomy Explanation Explanation/Reference: Explanation: The posterior inferior cerebellar artery supplies the rostral, dorsolateral medulla. The posterior spinal (choice D) and anterior spinal (choice B) arteries supply dorsal and ventral portions, respectively, of the caudal medulla. The anterior inferior cerebellar (choice A) and superior cerebellar (choice E) arteries supply portions of the pons and mesencephalon. QUESTION 12 The chief or peptic (zymogenic) cells of the gastric glands secrete pepsinogen. The latter is converted to pepsin, a 35-kilodalton (kDa) proteolytic enzyme, when the pH in the stomach falls below 5.0. In Following figure, which of the following arrows point to the location of chief or peptic (zymogenic) cells? A. B. C. D. E. 1 2 3 4 5 Correct Answer: B Section: Anatomy Explanation Explanation/Reference: Explanation: Arrow 2 points to the base of the gastric glands where chief or peptic (zymogenic) cells tend to be clustered. Arrow 1 points to the luminal surface of the stomach where mucus-secreting cells are found. Arrow 3 points to the muscularis mucosae. Arrow 4 points to the middle of the gastric glands where parietal or oxyntic cells tend to be most numerous. Arrow 5 point to the side of a gastric pit where mucus-secreting cells are also found. QUESTION 13 A 62-year-old patient diagnosed with prostate carcinoma complains of a right-sided headache worsening over 4 days and displays a drooping right upper eyelid. Examination reveals a right third nerve palsy. An MRI reveals a single metastasis of the prostatic carcinoma in the right side of the midbrain, causing Benedikt's syndrome. Which of the following signs would also be seen in this patient? A. B. C. D. E. complete paralysis of facial expression musculature on the left side deviation of the tongue to the right intention tremor in the left upper and lower extremity ipsilateral hemiplegia vertical gaze palsy Correct Answer: C Section: Anatomy Explanation Explanation/Reference: Explanation: Benedikt's syndrome results from a lesion situated in the tegmentum of the midbrain, at the level of the third cranial nerve (oculomotor) nucleus and its associated tracts, as exemplified by ptosis and third nerve palsy in this patient. The red nucleus is also affected at this level giving rise to motor impairment displayed by the intention tremor. Since the rubrospinal tract crosses at the level of the midbrain to project to the opposite side of the body, the tremor will manifest itself contralateral to the side to the lesion. The seventh cranial nerve (facial) nucleus is located in the pons, and the facial musculature (choice A) in this patient would not be affected. Likewise, the twelfth cranial nerve (hypoglossal) nucleus is located in the medulla, and the innervation of the tongue (choice B) would be spared in this patient. A lesion causing a pure Benedikt's syndrome would be confined to the midbrain tegmentum and not affect the corticospinal tract. Ipsilateral hemiplegia (choice D) would not be present in this patient. Finally, vertical gaze palsy (choice E) results from a lesion or compression of the midbrain tectum and not of the tegmentum. QUESTION 14 During a routine physical examination, you notice that your patient, a 35-year-old avid surfer, has spots of abnormal pigmentation on two of her fingers. You explain to your patient that long-term exposure to the sun increases the risk of neoplastic changes and that you would like to perform biopsies to verify the nature of the abnormal pigmentation. Referring to following figure, cells from which layer of the epidermis are most vulnerable to neoplastic changes due to long-term exposure to the sun? A. B. C. D. E. 1 2 3 4 5 Correct Answer: D Section: Anatomy Explanation Explanation/Reference: Explanation: Long-term exposure to the sun increases the risk of alteration of the DNA structure by cleavage, ionizing radiation, or recombination of DNA with highly reactive free radicals. These changes can result in neoplastic changes or death in skin cells. In the skin, mitosis occurs only in the malpighian layer formed by the stratum basale and the stratum spinosum of the epidermis. The DNA of dividing cells is more vulnerable to the harmful effects of the sun, and neoplastic changes are usually observed in the Malpighian layer. They are not seen in the stratum corneum (choice A), stratum lucidum (choice B), or stratum granulosum (choice C). Choice E represents the dermis located below the epidermis, which is the only skin layer considered in this question. QUESTION 15 A female 44-year-old patient suffers from acute bacterial sinusitis localized to the frontal sinus. The patient displays a mucopurulent greenish discharge from the nose bilaterally, with associated fever and malaise. The patient also complains of pain over the forehead with headache. Which of the following innervates the frontal sinus? A. B. C. D. E. anterior ethmoidal nerve lacrimal nerve nasociliary nerve posterior ethmoidal nerve supraorbital nerve Correct Answer: E Section: Anatomy Explanation Explanation/Reference: Explanation: The frontal sinus is innervated by the supraorbital and supratrochlear branches of the frontal nerve. All nerves mentioned in this question are branches of ophthalmic division (V1) of the trigeminal (fifth cranial) nerve. The anterior (choice A) and the posterior (choice D) ethmoidal nerves arise from the nasociliary nerve (choice C). They innervate the ethmoid and sphenopalatine sinuses. The lacrimal nerve (choice B) carries in its terminal segment the parasympathetic innervations to the lacrimal gland and provides sensory innervation to the upper eyelid. QUESTION 16 In a medial medullary syndrome that involves a left-sided branch of the anterior spinal artery, which of the following deficits is seen? A. deviation of the tongue to the left, hemiplegia of arm and leg on the left B. deviation of the tongue to the right, hemiplegia of arm and leg on the right C. loss of conscious proprioception and precise tactile discrimination over the right side of the body exclusive of the face D. only deviation of the tongue to the left E. only hemiplegia on the right Correct Answer: C Section: Anatomy Explanation Explanation/Reference: Explanation: A vascular lesio...
View Full Document

  • Fall '19
  • Test, Internal carotid artery, Common carotid artery, Internal iliac artery, Arteries of the head and neck, Internal jugular vein

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture