Tissue Development, Repair, and Remodeling - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 672

Table 11.2. Organogenesis (Source: Wikipedia). Cells that migrate inward along the archenteron
form the inner layer of the gastrula, which develops into the endoderm. Mesoderm gives
rise to: (1) chordamesoderm (axial mesoderm) along the central axis under the neural tube;
(2) paraxial mesoderm on both sides of the neural tube that generates somites (origin of vertebral
column, dermis, and skeletal muscles) and branchial arches (facial muscle and cartilage, etc.);
(3) intermediate mesoderm between the paraxial mesoderm that forms the urogenital system; and
(4) the lateral plate (or hypomere) at the periphery of the embryo that splits into 2 layers, the
somatic (body wall) and splanchnic layer (circulatory system and gut wall). The ectoderm that
emerges first and forms from the outermost of the germ layers, has 3 parts: external ectoderm
(surface ectoderm), neural crest, and neural tube (neuroectoderm).

Germ layer Organ products

Endoderm Respiratory tract

Endocrine organs
Gastrointestinal tract

Mesoderm Circulatory apparatus

Mesenchyme (blood and lymph vessels, blood cells,
bone, cartilage, and connective tissues)
Mesothelia (pericardium, pleura, and peritoneum
Muscles
Digestive tract
Reproductive apparatus
Urinary tract

Ectoderm Nervous system

Skin
Nose and mouth epithelia
Eye

influences organ morphogenesis. Epithelial wrapping controls mesenchymal shape
change and sorting of enclosed mesenchymal cells [ 1382 ].
Measurements of cell adhesiveness and cortical tension in the 3 germ layers
of zebrafish embryos using atomic force microscopy show that the strength of
homotypic adhesion decays from mesoderm, then endoderm, to ectoderm [ 1383 ].
The magnitude of measured cortical tension diminishes from ectoderm, then
mesoderm, to endoderm.
Differential actomyosin-dependent cell-cortex tension regulated by Nodal-
TGF

signaling directs progenitor sorting. Ecto- and endoderm cells occupy the
cell aggregate center and periphery, respectively. However, in vivo configuration is
defined by outer ectoderm and innermost endoderm, with mesoderm in the middle.
Strong interactions of germ-layer cells with enveloping layer cells can invert in
vitro sorting to that attained in vivo. Furthermore, groups of cells do not behave like
organized sheets of cells.

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