A 46-year-old man comes to the emergency department due to severe anal pain. He has a history of chronic constipation and on several occasions has noticed streaks of blood on the tissue paper after wiping. He has no abdominal pain, nausea, vomiting, or weight loss and has no family history of malignancy. His temperature is 36.7 C (98 F). On examination, there are several large, purplish-blue sacs bulging into the anal canal, one of which originates below the dentate line and is extremely tender. Excision of the tender lesion under local anesthesia is planned. The anesthetic agent most likely blocks sensory impulses carried by which of the following structures?

Question

A 46-year-old man comes to the emergency department due to severe anal pain.  He has a history of chronic constipation and on several occasions has noticed streaks of blood on the tissue paper after wiping.  He has no abdominal pain, nausea, vomiting, or weight loss and has no family history of malignancy.  His temperature is 36.7 C (98 F).  On examination, there are several large, purplish-blue sacs bulging into the anal canal, one of which originates below the dentate line and is extremely tender.  Excision of the tender lesion under local anesthesia is planned.  The anesthetic agent most likely blocks sensory impulses carried by which of the following structures?

Quizplus · Accepted Answer

11ec160b_3583_2041_9249_2571f6e01051_MD0001_00 This patient has both internal and external hemorrhoids, which each have a distinct epithelial lining and innervation. Internal hemorrhoids originate above the dentate line and are covered by columnar epithelium. They have autonomic innervation from the inferior hypogastric plexus, which is only sensitive to stretch and not pain, temperature, or touch. External hemorrhoids, which originate below the dentate line, are covered by modified squamous epithelium and have cutaneous (somatic) nervous innervation from the inferior rectal nerve, a branch of the pudendal nerve. Branches of the pudendal nerve supply the perineum and external genitalia in males and females and are very sensitive to touch, temperature, and pain. External hemorrhoids are generally asymptomatic but can become exquisitely painful if they thrombose, as in this case. (Choice A) The ilioinguinal nerve is mostly sensory, derived from L1, and carries sensation from skin of the upper and medial part of the thigh, the root of the penis and upper part of the scrotum in males, and the mons pubis and labia majora in females. (Choice B) The inferior gluteal nerve, composed of branches of L5, S1, and S2, is the main nerve supplying motor functions to the gluteus maximus muscle. (Choice C) The inferior hypogastric plexus, which has both sympathetic and parasympathetic components, innervates the internal pelvic viscera but not the external perirectal area. (Choice D) The pelvic splanchnic nerves are derived from S2, S3, and S4 and provide parasympathetic innervation to the pelvic and genital organs. Educational objective: External hemorrhoids, which originate below the dentate line, are covered by modified squamous epithelium and have cutaneous (somatic) nervous innervation from the inferior rectal nerve, a branch of the pudendal nerve. __________ References: Hemorrhoids. (http://www.ncbi.nlm.nih.gov/pubmed/22379400) Hemorrhoids. (http://www.ncbi.nlm.nih.gov/pubmed/21766771)

A 46-Year-Old Man Comes to the Emergency Department Due to Severe