USMLE USMLE Certifications USMLE-STEP-1 Questions & Answers

• Question 761:

  The structure indicated by arrow 1 in following figure is innervated by which of the following?

  A. anterior ethmoidal nerve

  B. greater palatine nerve

  C. lesser palatine nerve

  D. middle superior alveolar nerve

  E. nasopalatine nerve

  Correct Answer: D

  Section: Anatomy Arrow 1 points to the maxillary sinus, which is innervated by the posterior, middle, and anterior superior alveolar nerves. The latter are branches from the infraorbital nerve arising from the maxillary division (V2) of the trigeminal (fifth cranial) nerve. The anterior ethmoidal nerve (choice A) is a branch of the nasociliary nerve from the ophthalmic division (V1) of the trigeminal nerve. The greater palatine nerve (choice B) and lesser palatine nerve (choice C) are branches of the maxillary division of the trigeminal nerve supplying the hard and soft palate, respectively. The nasopalatine nerve (choice E) is derived from the maxillary division of the trigeminal nerve and supplies the nasal septum.

• Question 762:

  Horner syndrome is sometimes seen in patients diagnosed with the lateral medullary syndrome. Which of the following is a characteristic feature of Horner syndrome?

  A. atrophy of tongue musculature

  B. mydriasis

  C. paralysis of muscles of facial expression

  D. profuse sweating

  E. red blushing of the skin in the affected area

  Correct Answer: E

  Section: Anatomy The skin in the affected area is red and dry (not moist as in choice D) due to diminished sympathetic activity. The pupil on the affected side is constricted (myosis) (not dilated as in choice B) due to unopposed activity of the sphincter pupillae muscle. Motor deficits such as atrophy of tongue musculature (choice A) or paralysis of facial expression muscles (choice C) are typically not part of Horner syndrome.

• Question 763:

  A 52-year-old male patient with a history of alcoholism is brought to the emergency room because of a sudden onset of right upper quadrant pain, nausea, blood in the vomitus, and fever. Ultrasound diagnosis reveals a portal vein obstruction caused by liver cirrhosis and accompanied by esophageal varices. Proper portal circulation must be reestablished to alleviate the esophargeal varices, and the attending surgeon decides on an end-to-side portocaval shunt. Which of the following describes the chosen procedure?

  A. anastomosis by communication between the portal vein and the inferior vena cava

  B. anastomosis by prosthetic vascular graft between the inferior vena cava and the superior mesenteric vein

  C. anastomosis by suturing the inferior end of the portal vein to the inferior vena cava

  D. anastomosis of the splenic vein to the left renal vein

  E. placement of an expandable stent between a hepatic vein and the portal vein

  Correct Answer: C

  Section: Anatomy Suturing the inferior end of the portal vein to the inferior vena cava is termed end-to-side portocaval shunt, whereas establishing a communication between the portal vein and the inferior vena cava (choice A) is a side-to-side portocaval shunt. Placing a prosthetic vascular graft between the inferior vena cava and the superior mesenteric vein (choice B) is termed a mesocaval shunt. Anastomosis of the splenic vein to the left renal vein (choice D) is a splenorenal or Warren shunt. Placement of an expandable stent between the hepatic vein and portal vein (choice E) is called a transjugular intrahepatic portosystemic shunt or TIPS.

• Question 764:

  The efferent limb of the pupillary light reflex is interrupted along with corticospinal and orticobulbar fibers in which of the following clinical entities?

  A. Broca's aphasia

  B. inferior alternating hemiplegia

  C. middle alternating hemiplegia

  D. superior alternating hemiplegia

  E. Wallenberg syndrome

  Correct Answer: D

  Section: Anatomy Compression of cranial nerve III, in combination with descending corticospinal and corticobulbar fibers, occurs as part of superior alternating hemiplegia. Patients with Broca's aphasia (choice A) typically do not exhibit involvement of the pupillary light reflexes. Inferior alternating hemiplegia (choice B) and middle alternating hemiplegia (choice C) involve cranial nerves XII and VI, respectively, in combination with corticospinal fibers. Wallenberg syndrome (lateral medullary syndrome) (choice E) typically does not include damage to the corticospinal tract.

• Question 765:

  A 17-year-old male college student is brought to the emergency room, displaying vomiting, fever, and diarrhea. The patient reports that for a period of 24 hours prior to admission, he suffered from abdominal pain first centered around the navel and then moving inferiorly to the right. As the patient talks, you realize that he is gesturing toward McBurney's point. You tentatively diagnose acute appendicits and request emergency surgery. Accurate visual identification of the appendix during surgery can be verified by using which of the following landmarks?

  A. bifurcation of the abdominal aorta

  B. epiploic appendages

  C. haustra

  D. inferior border of the right kidney

  E. taeniae coli

  Correct Answer: E

  Section: Anatomy The position of the appendix varies depending on the patient. The taeniae coli are three longitudinal bands of smooth muscle running the length of the colon. Since the appendix is part of the colon, the taeniae coli can be accurately followed to this structure. The bifurcation of the abdominal aorta (choiceA) and inferior border of the right kidney (choice D) are retroperitoneal and would not be of value in identification of the appendix. The epiploic appendages (choice B) are small pockets of fatty tissue along the length of the colon, but they are not found on the appendix. The haustra (choice C) are sacculations of the large intestine resulting from contractions of the taeniae coli.

• Question 766:

  Anewborn infant suffers from a posterolateral defect on the left side of the body. His abdominal contents have herniated through the defect into the thoracic cavity, and as a result, the infant suffers from pulmonary hypoplasia. His breathing difficulty is life threatening because the herniation has inhibited lung development and inflation. This congenital defect is due to a malformation of which of the following?

  A. mesentery of the esophagus

  B. muscular ingrowth of the body wall

  C. pleuropericardial membrane

  D. pleuroperitoneal membrane

  E. septum transversum

  Correct Answer: D

  Section: Anatomy congenital defect of the pleuroperitoneal membrane results in an abnormal opening in the posterolateral aspects of the diaphragm. This defect occurs more often on the left side of the body. It is due to the failure of the pleuroperitoneal membrane to form properly and/or to fuse with the other parts of the diaphragm: the mesentery of the esophagus (choice A), the muscular ingrowth of the body wall (choice B), and the septum transversum (choice E). The pleuropericardial membranes (choice C) participate in the formation of the mediastinum and do not contribute to the formation of the diaphragm.

• Question 767:

  A female patient is diagnosed by sonogram with uterus didelphys (double uterus). The imaging study reveals a bicornuate uterus with a single vagina. During development, the uterus develops from which of the following?

  A. mesonephric ducts

  B. nephrogenic ridge

  C. paramesonephric ducts

  D. urogenital sinus

  E. yolk sac

  Correct Answer: C

  Section: Anatomy During development, the uterus develops from fusion of the caudal ends of the para-mesonephric ducts. Failure of fusion results in uterus didelphys. The mesonephric ducts (choice A) give rise to the epididymis, vas deferens, and ejaculatory duct in the male. The nephrogenic ridge (choice B) is the derivative of the urogenital ridge which will give rise to the urinary system. The urogenital sinus (choice D) gives rise to the urinary bladder, urethra, vagina, and associated glands in the female. The yolk sac (choice E) plays a role in transfer of nutrients before uteroplacental circulation is established, in blood development before the liver begins its hemopoietic activity, and is the site of formation of primordial germ cells.

• Question 768:

  The abdominal aorta provides for the major blood supply in this region and its branches are organized into paired or unpaired and visceral or parietal branches. Which of the following are paired visceral branches of the abdominal aorta?

  A. celiac trunk

  B. gonadal arteries

  C. inferior phrenic arteries

  D. lumbar arteries

  E. superior mesenteric artery

  Correct Answer: B

  Section: Anatomy The gonadal arteries are paired visceral branches of the abdominal aorta. Other branches in this category are the suprarenal and renal arteries. The celiac trunk (choice A) and superior mesenteric artery (choice E) are unpaired visceral branches. The inferior phrenic (choice C) and lumbar (choice D) arteries are paired parietal branches.

• Question 769:

  Infiltrating or invasive ductal cancer is the most common breast cancer histological type, comprising 7080% of all cases. Invasive breast cancers usually are epithelial tumors of ductal or lobular origin. Which of the following epithelia line the lactiferous ducts?

  A. pseudostratified

  B. simple squamous

  C. stratified cuboidal

  D. stratified squamous

  E. transitional

  Correct Answer: C

  Section: Anatomy The lactiferous duct is lined by a two-cell layered cuboidal epithelium. All other epithelial choices are not found in the breast tissue and are thus incorrect.

• Question 770:

  Aurologist is teaching her resident to perform a vasectomy. She explains that he has to inject the anesthetic in the skin of the scrotum, in preparation for incision of its lateral aspect. This surgical location allows for easy access to the spermatic cord. Which of the following nerves innervates the skin of the scrotum?

  A. femoral nerve

  B. iliohypogastric nerve

  C. ilioinguinal nerve

  D. obturator nerve E. subcostal nerve

  Correct Answer: C

  Section: Anatomy The anterior aspect of the scrotum is innervated by branches of the ilioinguinal nerve (L1).Other nerves innervating the scrotum are branches of the genitofemoral nerve (L1, L2), pudendal nerve (S2-S4), and posterior femoral cutaneous nerve (S2, S3). The femoral nerve (L2-L4, choice A) supplies sensory innervations to the anteromedial thigh, hip joint, and knee joint. It also innervates muscles of the anterior compartment of the thigh. The iliohypograstric nerve (L1, choice B) provides sensory innervations over the iliac crest and the hypogastric region. The obturator nerve (L2-L4, choice D) supplies motor innervation to the medial compartment of the thigh. The subcostal nerve (T12, choice E) provides motor innervation for the lower part of the external oblique muscle and sensory innervations over the hip and anterior superior iliac spine.