This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
Which of the following does not develop from mesoderm? 
Select and explain. 
A. Muscles of bladder, B. Iris muscle, C. Deltoid muscle, D. LPS
B: Iris muscle
Answer: B: Iris muscle 
Explanation: The musculature of the iris is of ectodermal origin, but the ciliary muscle is of mesodermal origin.