<prompt> Which one of the following is an Ectodermal Derivative?Muscles of the RectumMuscles of the Blood vesselsMuscles of the LarynxMuscles of the Iris  <response>: D Muscles of the Iris IBS7 - 346; Grays40 - 701; Grays39 - 722EctodermMesodermEndodermNeuroectodermNeural crestEpidermis, hair, nailsMuscle smooth, cardiac, skeletalEpithelial lining of Gastrointestinal tractAll neurons within brain and spinal cordGanglia: dorsal root, cranial, autonomicCochlear duct, semicircular ductsExtraocular muscles preotic somitesMuscles of the tongue occipital somitesTrachea, bronchi, lungsRetinaSchwann cellsEnamel of teethConnective tissue, dermis of skinBiliary apparatusNeurohypophysisPia and arachnoidAdenohypophysisBone, cartilageUrinary bladder, urethraAstrocytes, oligoden- drocytesAdrenal medullaLens of the eyeBlood and lymph vesselsVagina Parafollicular cells calcitoninParotid glandHeartAuditory tubeAorticopulmonary septumMammary glandsAdrenal cortexMiddle ear cavityDilator and sphincter pupillae muscle.Epithelial lining of lower anal canalSpleenParenchyma of LiverCiliary muscleKidneyPancreasDura materTestes, ovariesSubmandibular glandSublingual gland ThyroidParathyroid Muscles of Iris arc ectodermal in origin: All other muscular smooth, cardiac and skeletal muscles are mesodermal in origin. Only the muscles of Iris are exception in origin ectodermal, whereas all other visceral muscles are derived from mesoderm. The musculature of the iris Sphincter and dilator pupillae is of ectodermal origin optic cup but the ciliary muscle is mesodermal. 