system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 40-year-old woman comes to the physician because of a 2-week history of anal pain that occurs during defecation and lasts for several hours. She reports that she often strains during defecation and sees bright red blood on toilet paper after wiping. She typically has 3 bowel movements per week. Physical examination shows a longitudinal, perianal tear. This patient's symptoms are most likely caused by tissue injury in which of the following locations?
assistant
Posterior midline of the anal canal, distal to the pectinate line