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The gill arches have both nerves and arteries as well as entoderm and ectoderm coverings. Openings between the gut side (entoderm) and the body surface (ectoderm) occur as gill slits between the pouches and the surface. Motor nerves are related to muscles of the arches and the sensory nerves relate to the entodermal and ectodermal derived tissues of the arches and pouches. The first arch (I) forms the upper and lower jaw (with mouth cavity) and are innervated by the motor 5th nerve to the muscles for mastication. Their action is between the two jaws formed by arch 1. The pouch (oral and nasal cavity) and the external surface of the jaws are innervated by the sensory fifth nerve.
The gill arches have both nerves and arteries as well as entoderm and ectoderm coverings. Openings between the gut side (entoderm) and the body surface (ectoderm) occur as gill slits between the pouches and the surface. Motor nerves are related to muscles of the arches and the sensory nerves relate to the entodermal and ectodermal derived tissues of the arches and pouches. The first arch (I) forms the upper and lower jaw (with mouth cavity) and are innervated by the motor 5th nerve to the muscles for mastication. Their action is between the two jaws formed by arch 1. The pouch (oral and nasal cavity) and the external surface of the jaws are innervated by the sensory fifth nerve.