The model has a single mesh with bevel and subdivision
modifiers unapplied. The product files :- blend file (procedural mesh as well
as image texture mesh), obj file,mtl, stl, texture files. The formats 3mf, ply, obj, fbx, USDZ,GLTZ & GLB with applied uv mapped textures have also been included in the downloads along with stl.

The ducts and glands are divided into two broad categories
based on there microscopic architecture :- Alveolar (acinar) and tubular ducts.
Each of these categories are further subdivided into simple and Compound ducts.
The simple ducts include the branched ducts also.

The model can be interpretated in this way :-

DUCTS

1.     
Alveolar (Acinar) ducts

a.     
Simple Alveolar (SA)

b.     
Branched Alveolar (BA) ducts

c.     
Compound Alveolar (CA) ducts

2.     
Tubular ducts

a.     
Simple Tubular (TA), Simple Coiled Tubular (SCT)

b.     
Branched Tubular (BT) ducts

c.     
Compound Tubular (CT) ducts

3.     
Compound Tubular-alveolar (CTA) ducts