Pensieve Header: Drawing a wen!

{r0, r1, r2, r3} = {5, 1, 2, 3}; (* the radii of the bends, the narrow, the connect, and the wide *)
p[u_,v_] := Which[
v<0, (* the narrow tube *)
  {-r0+r0*Cos[v], 0, -r0*Sin[v]}+(r1-(r2-r1)2v/Pi)*(-Cos[u]*{-Cos[v],0,Sin[v]}+{0,Sin[u],0}),
v<Pi, (* the bend *)
  {((r1+r3)-(r3-r1)*Cos[v])*Cos[u], ((r1+r3)-(r3-r1)*Cos[v])*Sin[u], -(r1+r3)*Sin[v]}/2,
v<3Pi/2, (* the wide tube *)
  {r0+r0*Cos[v], 0, -r0*Sin[v]}+(r3-2(r3-r2)(v-Pi)/Pi)*(Cos[u]*{-Cos[v],0,Sin[v]}+{0,Sin[u],0})
];
ParametricPlot3D[
p[u,v],
{u, 0, 2Pi}, {v,-Pi/2, 3Pi/2},
 PlotStyle->Opacity[0.75], Axes -> None, Boxed -> False
]