What 3 nerves form the cervical plexus?

There are more than 3 nerves in the cervical plexus. The most important nerve here is the phrenic nerve, which supplies the diaphragm, from roots C3-5. Other deep branches include the ansa cervicalis and segmental branches; the superficial branches are the lesser occipital, great auricular, transverse cervical and supraclavicular.