Which germ layer gives rise to iris muscles?

Which germ layer gives rise to iris muscles?

• A. Neural ectoderm
• B. Mesoderm
• C. Neuroectoderm
• D. Ectoderm

Answer: (C)

Iris muscles come from neuroectoderm, the neural tissue that forms the optic cup. During eye development, the optic cup—a structure derived from neuroectoderm—gives rise to the neural retina and also the intrinsic iris muscles (the sphincter and dilator). Other iris components, like the stroma and vasculature, primarily come from neural crest cells, which migrate into the iris, and the broader surrounding tissues can involve mesoderm for other ocular muscles. So, the direct germ layer for iris muscles is neuroectoderm.

Iris muscles come from neuroectoderm, the neural tissue that forms the optic cup. During eye development, the optic cup—a structure derived from neuroectoderm—gives rise to the neural retina and also the intrinsic iris muscles (the sphincter and dilator). Other iris components, like the stroma and vasculature, primarily come from neural crest cells, which migrate into the iris, and the broader surrounding tissues can involve mesoderm for other ocular muscles. So, the direct germ layer for iris muscles is neuroectoderm.