Given the following context:

The focal point of the scene is the "Tree-Man", whose cavernous torso is supported by what could be contorted arms or rotting tree trunks. His head supports a disk populated by demons and victims parading around a huge set of bagpipes—often used as a dual sexual symbol—reminiscent of human scrotum and penis. The tree-man's torso is formed from a broken eggshell, and the supporting trunk has thorn-like branches which pierce the fragile body. A grey figure in a hood bearing an arrow jammed between his buttocks climbs a ladder into the tree-man's central cavity, where nude men sit in a tavern-like setting. The tree-man gazes outwards beyond the viewer, his conspiratorial expression a mix of wistfulness and resignation. Belting wondered if the tree-man's face is a self-portrait, citing the figure's "expression of irony and the slightly sideways gaze [which would] then constitute the signature of an artist who claimed a bizarre pictorial world for his own personal imagination".Many elements in the panel incorporate earlier iconographical conventions depicting hell. However, Bosch is innovative in that he describes hell not as a fantastical space, but as a realistic world containing many elements from day-to-day human life.
Animals are shown punishing humans, subjecting them to nightmarish torments that may symbolise the seven deadly sins, matching the torment to the sin. Sitting on an object that may be a toilet or a throne, the panel's centerpiece is a gigantic bird-headed monster feasting on human corpses, which he excretes through a cavity below him, into the transparent chamber pot on which he sits. The monster is sometimes referred to as the "Prince of Hell", a name derived from the cauldron he wears on his head, perhaps representing a debased crown. To his feet a female has her face reflected on the buttocks of a demon. Further to the left, next to a hare-headed demon, a group of naked persons around a toppled gambling table are being massacred with swords and knives. Other brutal violence is shown by a...

answer the following question:

What has thorn-like branches which pierce the fragile body? 

Tree-Man