As the gills does not develop into gills, they are likely to
contribute to the development of the lower jaw of the human embryo though after
the embryonic stage, the gill slits won’t be retained or won’t be a part of a
human as they only appear during embryonic stage for the development of the
lower jaw.
The valves' main job is to keep the blood moving in one direction – back up towards the heart. When the valve is open, blood freely flows upward towards the heart and when the valves are closed, blood cannot flow back
