from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A layer of embryonic cells formed in vertebrates by association of part of the mesoderm with the endoderm and developing into the wall of the viscera.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A layer of embryonic cells formed from the mesoderm and endoderm that develops into the wall of the viscera
from the GNU version of the Collaborative International Dictionary of English
- n. The inner, or visceral, one of the two lamellæ into which the vertebrate blastoderm divides on either side of the notochord, and from which the walls of the enteric canal and the umbilical vesicle are developed. See somatopleure.
from The Century Dictionary and Cyclopedia
- n. The inner or visceral layer of mesoderm, formed by the splitting of the mesoblast, separated from the somatopleure by the perivisceral space, cœlomatic cavity, or cœloma.
The lateral mesoderm splits into two layers, an outer or somatic, which becomes applied to the inner surface of the ectoderm, and with it forms the somatopleure; and an inner or splanchnic, which adheres to the entoderm, and with it forms the splanchnopleure (Fig. 16).
By the forward growth and flexure of the head the pericardial area and the anterior portions of the primitive aortæ are folded backward on the ventral aspect of the fore-gut, and the original relation of the somatopleure and splanchnopleure layers of the pericardial area is reversed.
The first rudiment of the heart appears as a pair of tubular vessels which are developed in the splanchnopleure of the pericardial area (Fig. 457).
The path along which they travel into the embryo is a very definite one, viz., from the yolk sac upward between the splanchnopleure and gut in the hinder portion of the embryo.