What does "fluid ground substance" mean? Does it mean that the substance was ground to fluid or the substance was ground by the fluid? Here it is in context.
In this case the matrix is the fluid ground substance called plasma.
What does "fluid ground substance" mean? Does it mean that the substance was ground to fluid or the substance was ground by the fluid? Here it is in context.
In this case the matrix is the fluid ground substance called plasma.
OP's cited example contains a somewhat quirky sequence of some highly domain-specific terms combined in an unusual way. But I did find these related usages Google Books...
1: Whole blood is often divided into a matrix, or liquid fraction, called plasma and formed elements, or blood cells. Anatomy & Physiology (2015)
...and...
2: ...the granule-containing alveoli probably move through the fluid ground substance The Journal of Experimental Zoology (1911)
...and...
3: The structural strength of the ground substance is also provided by various kinds of fibers Applied Kinesiology (2002)
From that it should be clear that a "ground substance" means the basic material that something's made of. Metaphorically, it's at the "base. bottom, ground-level", before you start "building it up" with additives.
It just looks a bit odd to someone like me when preceded by another adjective such as fluid (or even the gelatinous ground substance), because I'm more likely to associate ground with earth, soil (or reduced to particles in a grinder).