In the
development
Development or developing may refer to:
Arts
*Development (music), the process by which thematic material is reshaped
* Photographic development
*Filmmaking, development phase, including finance and budgeting
* Development hell, when a proje ...
of
vertebrate animals, the prechordal plate is a "uniquely thickened portion" of the mesendoderm that is in contact with
ectoderm
The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from the o ...
immediately
rostral
Rostral may refer to:
Anatomy
* Rostral (anatomical term), situated toward the oral or nasal region
* Rostral bone, in ceratopsian dinosaurs
* Rostral organ, of certain fish
* Rostral scale
The rostral scale, or rostral, in snakes and other sca ...
to the cephalic tip of the
notochord
The notochord is an elastic, rod-like structure found in chordates. In vertebrates the notochord is an embryonic structure that disintegrates, as the vertebrae develop, to become the nucleus pulposus in the intervertebral discs of the verteb ...
. It is the most likely origin of the rostral cranial
mesoderm
The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical ...
.
[Seifert, R; et al. ''J Anat'' 1993 183:75-89]
STAGE 6
The prechordal plate is a thickening of the endoderm at the cranial end of the primitive streak seen in Embryo Beneke by Hill J.P., Florian J (1963)
STAGE 7
The prechordal plate is described as a median mass of cells, located at the anterior end of the notochord, which appears in early embryos as an integral part of the roof of the foregut. e.g. Embryos Bi 24 and Manchester 1285.
and Gilbert P.W., (1957)
STAGE 8
O'Rahilly R., Müller F. (1987) present a detailed discussion of the term 'prechordal plate' and its relation to the 'prochordal plate'. These essentially synonymous terms refer to the horseshoe-shaped band of thickened endoderm rostral to the notochord but not quite reaching the rostral extremity of the embryo. It reaches its maximum state of development at about this stage and contributes mesodermal type cells to the surrounding tissue. Cells derived from the prechordal plate become incorporated into the cephalic
mesenchyme
Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood, or bone. The interactions between mesenchyme and epithelium help to form nearly ever ...
( including the 'premandibular' condensation described by Gilbert P.W., (1957) and some of the foregut endoderm.
STAGE 9
The prechordal plate is continuous rostrally with the cardiac mesenchyme and it is rotated caudo-ventrally as the cranial flexure develops and the head moves ventrally.
STAGE 10
In the 10 somite embryo, Carnegie No. 5074, the prechordal plate is continuous posteriorly with the notochord, and is made up of about 35-40 cells. The prechordal mesenchyme proliferates laterally over the junction of the dorsal aorta and first aortic arch on each side. Gilbert P.W., (1957)
STAGE 11
The prechordal plate contributes largely to the premandibular condensation and the mesenchyme of the heart such that little is seen in the median plane at this stage. Müller F., O'Rahilly R., (1986)
STAGE 12
The premandibular condensation is situated bilaterally at the rostral end of the notochord, bridged in the median plane by mesenchymal cells also of prechordal origin. e.g. The 26 somite embryo, Carnegie No. 4736. Gilbert P.W., (1957)
STAGE 13
The premandibular condensation has formed from the prechordal plate mesoderm, the bilateral masses remain connected by a bridge of mesenchyme that is thought to later contribute to the meninges. Müller F., O'Rahilly R., (1986)
References
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Animal developmental biology