Merge Surface to obtain a Solid

I’m working on a modeling of the lung lobe for an internship.
I want ot make a solid from the different surfaces that I’ve got but there always a problem with the last surface.
If someone can help me it will be awesome.

right_lobe_upper.3dm (10.2 MB)

I selected the surfaces, and used Join. The surfaces joined into a single closed polysurface which is a solid in Rhino.

What problem are you having?

By the way, your surfaces have an extremely large number of control points.

As David mentioned, Join works to make a solid but if you were looking for a single surface instead, that is also closed, Join the curves in this direction and then use NetworkSrf…