The outermost portion of the wood is known as bark.
Pith (medulla) - It is the innermost central portion or core of the tree.
Heartwood - These are the outer annular rings surrounding the pith.
Sapwood - These are the outer annular rings in between the heartwood and cambium layer.
Cambium - It is a thin layer of sap in between the sapwood and inner bark.
Medullary rays - These are the thin radial fibres, extending from the pith up to the cambium layer holding the annular rings of the heartwood and sapwood in position.
Bark - The outermost portion of the wood is known as bark. It is the outer protective layer around the cambium layer.