CompTIA
Checkpoint
ISC
HP
Dell
EC-Council
EXIN
Fortinet
ITIL®
Juniper
PMI
Microsoft
VMware
Avaya
Google
Salesforce
Amazon
Palo Alto Networks
Certiport
ISC2
All Vendors
  2. Home
  3. Exams
  4. USMLE
  5. STEP1

Free STEP1 Exam Braindumps (page: 18)

Page 18 of 213
PDF with 845 Questions

A football player was simultaneously tackled from the front above the knee and from the back below the knee. In the emergency room, he displays a positive anterior drawer test which becomes negative if the knee is internally or externally rotated. Which of the following has ruptured?

  1. anterior cruciate ligament
  2. fibula
  3. fibular (lateral) collateral ligament
  4. posterior cruciate ligament
  5. tibial (medial) collateral ligament

Answer(s): A

Explanation:

In the anterior drawer test, the patient's tibia is pulled forward and anterior tibial displacement reveals rupture of the anterior cruciate ligament. The drawer test becomes negative when the knee is internally rotated because of the tightening of the posterior cruciate ligament (choice D); in this case, the result reveals that the posterior cruciate ligament is not affected. External rotation is limited by the tibial (medial) collateral ligament (choice E) and since the drawer sign is negative with the knee in this position, this ligament is also intact. The fibula (choice B) and fibular colateral ligament (choice C) do not participate in the knee joint and have no effect on the drawer test.



In this same patient, the pectineus muscle is also badly bruised. This muscle is innervated by which of the following?

  1. genitofemoral nerve
  2. obturator nerve
  3. peroneal division of the sciatic nerve
  4. saphenous nerve
  5. tibial division of the sciatic nerve

Answer(s): B

Explanation:

The pectineus muscle is part of the adductor muscles of the thigh, which are innervated as a group by the obturator nerve. The genitofemoral nerve (choice A) provides sensory innervation for a small area of the skin in the medial superior aspect of the thigh, and motor innervation to the cremaster muscle. The peroneal division of the sciatic nerve (choice C) innervates the skin and muscles in the peroneal and anterior comparments of the leg. The saphenous nerve (choice D) is purely a sensory nerve for the medial aspect of the leg and the foot. The tibial division of the sciatic nerve (choice E) provides sensory and motor innervations to the posterior compartment of the leg and the plantar foot.



An overworked surgical resident is resecting an acinic cell carcinoma from the inferior aspect of the parotid gland when he makes a careless incision and nicks a branch of the facial (seventh cranial) nerve. Which of the following muscles may be affected by this injury?

  1. omohyoid
  2. sternohyoid
  3. sternothyroid
  4. stylohyoid
  5. thyrohyoid

Answer(s): D

Explanation:

The stylohyoid is innervated by the facial (seventh cranial) nerve. During the embryonic period, the muscles developing from the second pharyngeal arch include the stylohyoid, stapedius, posterior belly of the digastric, auricular muscles, and muscles of facial expression. The nerve supplying the second pharyngeal arch, and thus all these muscles, is the facial (seventh cranial) nerve. All the other muscles, omohyoid (choice A), sternohyoid (choice B), sternothyroid (choice C), and thyrohyoid (choice E) form the infrahyoid muscle. They are supplied as a group by branches of the ansa cervicalis derived from C1, C2, and C3.



A 35-year-old male patient suffering from pulmonary hypertension has been diagnosed with ostium secundum atrial septal defect. Abnormal development of which of the following structures is responsible for this developmental defect?

  1. aorticopulmonary septum
  2. endocardial cushion
  3. interventricular septum
  4. septum primum
  5. sinus venosus

Answer(s): D

Explanation:

Abnormal development of either the septum primum or septum secundum results in ostium secundum atrial septal defects in the area of the fossa ovalis. This common type of congenital heart defect is manifested by a patent foramen ovale between right and left atria. This is well-tolerated during childhood, but symptoms usually appear after 30 years of age. The aorticopulmonary septum (choice A) divides the truncus arteriosus of the developing heart and gives rise to the ascending aorta and pulmonary trunk. The endocardial cushions (choice B) give rise to the right and left atrioventricular canals. The interventricular septum (choice C) forms between the right and left ventricles. The sinus venosus (choice E) becomes incorporated into the atria, as well as giving rise to the openings of the pulmonary veins and the venae cavae.






Post your Comments and Discuss USMLE STEP1 exam with other Community members: