How does Mick Jackson use imagery in The Underground Man?

Imagery:

"Where my neck and torso come together is usually a regular network of root and vein. Of late, however, I have become uncertain whether all these wires are properly attached. Some appear to have grown quite slack; one or two have come away from their housing altogether. On a bad day I worry that somewhere inside me an essential spring might have snapped, to dangle and rattle about in me for the rest of my days."

"I reckon that I am very much like the leafless tress. Autumn scares the life right out of me. Every year I worry I will not survive it, that this may be my last."