If we take the definition of body to be a gravitational limit, this makes the skin, or boundary between internal and external, to be the finite limit delineating the regions which define "me" and "not me."
Inside this limit we see 3D organs and other structures indicative of motion in 3-dimensional space.
At the boundary condition, we have the skin, or dermis. The dermal layer is a 2D structure as evident by its planar construct. Interestingly enough, this would imply classification of skin as anything but an organ despite the assurance we are given to the contrary and in fact we are told our skin is our largest organ!
Outside this unit aggregate boundary we have hair.... 1D structure.
In summary:
- 3D: organs and body interior
- 2D: skin
- 1D: hair