This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Parasympathetic System & Glaucoma, Subject name: Pharmacology
On the basis of the examination at her doctor's office, a patient is told that her parasympathetic nerves are damaged. Which of the following muscles would most likely be affected ? 
Select and explain. 
A. Muscles in the hair follicles, B. Muscles in blood vessels, C. Muscles that act at the elbow joint, D. Muscles in the gastrointestinal (GI) tract
D: Muscles in the gastrointestinal (GI) tract
Answer: D: Muscles in the gastrointestinal (GI) tract 
Explanation: The answer is D. Smooth muscles in the gastrointestinal tract are innervated by both parasympathetic and sympathetic nerves. Smooth muscles in the wall of the blood vessels and errector pili muscles in hair follicles are innervated only by sympathetic nerves. Muscles that act at the elbow joint and muscles enclosed by epimysium are skeletal muscles that are innervated by somatic motor (general somatic efferent ) nerves