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
[{'content': 'All are mesodermal in origin except \nSelect and explain. \nA. Dilator pupillae, B. Chroid, C. Iris, D. Ciliary body', 'role': 'user'}, {'content': 'Answer: A \nExplanation: EMBRYOLOGY OF EYE Surface ectoderm: S-Skin of eyelids/appendages L-Lens L-Lacrimal gland E-Epithelium of cornea/conjunctiva Neuroectoderm: R-Retina O-Optic stalk/optic nerve M-Muscles of iris(sphincter and dilator pupillae) E-Epithelium of iris/ciliary body secondary/teiary vitreous Neural crest: Neural- optic nerve coverings myelin sheath(by oligodendrocytes) ciliary ganglion melanocytes Mesenchymal- cornea (except epithelium of cornea) sclera (except temporal sclera) orbital bones Trabecular meshwork Schlemms canal Ciliary body muscles Iris/ciliary body stroma Mesoderm; Temporal sclera Blood vessels Extraocular muscles Primary vitreous Ref: Human Embryology, Inderbir Singh, 10th edition, page no: 113', 'role': 'assistant'}]