According to Lawrence, 4th edition, p 43, you have
      15 to 25 lobes per breast
       20 to 40 lobuli per lobe
and 10 to 100 alveoli per lobulus.

That gives you 3,000 to 10,000 alveoli per breast.

The paragraph containing this info is one of my favorites for teaching.  It
gives the sizes of everything!  I found that the diameter of the sinuses
ranges from the size of Medela's old pump tubing to the size of Medela's new
pump tubing (no endorsement intended---it's just a material I happened to have
around the house!).  The diameter of the ducts is the same as a 6d (6 penny)
nail.  The diameter of an alveolus is 0.12 mm, which is less than the
thickness of a sewing thread or a sheet of paper.  So shrink those bunches of
grapes you've been picturing, folks.  Our alveoli are like flour grains
clustered around tiny spiderweb-thin filaments.  You can imagine how busy all
those little fellas are, making their droplets of milk like Santa's elves in
the workshop or like worker bees in the honeycomb.  And you can picture what
happens when the system gets backed up with milk waiting for a chance to
flow....no place to put the milk, cells getting stretched thin around the pool
of milk in the lumen of the alveolus, like a flour grain swelling up as it
absorbs moisture in the bread dough...

Well...enough of mixed metaphors!  Can you tell that I have a weekend jam-
packed with work I OUGHT to be doing, so I'm procrastinating with Lactnet
instead?

Chris Mulford again