How Important Is Internal Communication In Any Orgnisation ?

Hi All
Would like to have some expert opinions here on importance and need of internal communication in an organisation . How vital it is to the success of the organisation and some instructions on how one can go about implementing this communication programme.
Thanks.

Internal communication helps to promote and protect the organization's mission and vision. Internal communications help staff to keep focus and carry on their duties without complications.

Dear Krishnau,
Internal communication is as important as blood circulation in the body. What will happen if the blood circulation stops or slows down? The reply will speak in itself.
Thanks,
Dinesh Divekar