Mesoderm
Mesoderm , noun
[Meso- + Greek de`rma skin.]
(a)
(Biology) The layer of the blastoderm, between the ectoderm and endoderm; mesoblast. See Illust. of Blastoderm and Ectoderm.
(b)
(Biology) The middle body layer in some invertebrates.
(c)
(Biology) The middle layer of tissue in some vegetable structures.