Dear Debipriya,
When Shree Krishn descends on this earthly planet, He assumes a "human form" and by His personal power called yoga maya we can see Him in a "human body" BUT in actuality His body (even in a "human form" ) is NEVER a mortal human body, Krishn's "human form/body" is ALWAYS Divine.
Our bodies are material/mayic/mortal , His body is Divine and eternal(even in what we perceive as a "human form"). Whatever regards God is ALWAYS Divine and eternal.
Krishn's body and soul are non-different from each other, both are Divine.
As to us, we are NOT a direct part of God but we are a part of His marginal power called Jeev Shakti (so all unlimited number of mayic and liberated souls together make this power), our souls are divine/eternal/non-changing (as a part of God's power) but our bodies are mayic/material/mortal, so we are quite different from our bodies.
God is ONE and He can be in unlimited numbers of forms( like Krishn, Ram , Shiva, etc) simultaneously. We mayic souls are countless, each as individual soul and each of us can be in only one body at one time as we are spot existent but God is omnipresent and all powerful which means He can do anything and everything within and beyond our human imagination.
So Divine Entity(Supreme Soul) in Him and His "human" body are one and the same.