A 32-year-old construction worker sustains an amputation of the long finger of the dominant right hand through the mid portion of the nail plate. Which of the following structures is most likely injured? 

A 22-year-old man comes to the emergency department after he sustained a machete laceration of the left cheek extending from the tragus through the midpoint of the upper lip. The wound is full thickness along the central third. Examination shows left upper lip droop and flattening of the associated nasolabial fold. Which of the following structures were most likely injured? 

The metacarpophalangeal (MCP) joint of the thumb is which of the following types of joint? 

A 42-year-old woman is brought to the emergency department after sustaining traumatic fractures of the right orbit and zygoma in a motor vehicle collision. Physical examination shows localized edema. Which of the following indications is most likely for immediate ophthalmologic consultation? 

A 21-year-old man is brought to the emergency department 6 hours after he reportedly fell asleep on his right arm after ingesting a large amount of narcotics and alcohol. On examination, the arm is warm, swollen, and tense to palpation. Physical examination shows no sensation or movement of the fingers, wrist, or forearm. After initiating resuscitation, which of the following is the most appropriate next step in management?