Search results
Results from the WOW.Com Content Network
The anterior/posterior axis is specified by the sperm at the posterior side. At the two cell stage, the anterior cell is the AB cell while the posterior cell is the P1 cell. The dorsal/ventral axis of the animal is set by a random position of cells during the four cell stage of the embryo.
Communicate with the proteins that determine the anterior-posterior and dorsal-ventral axes to supply instructions concerning differentiation and cell fates. The FGFs secreted by the AER interact with the limb mesenchyme – including the ZPA – to induce further FGF and Shh expression.
Sperm entry can occur anywhere in the animal hemisphere. [2] The point of sperm entry defines the dorso-ventral axis - cells opposite the region of sperm entry will eventually form the dorsal portion of the body. [1] [3] In the frog Xenopus laevis, the animal pole is heavily pigmented while the vegetal pole remains unpigmented. [4]
If talking about the skull, the dorsal side is the top. [38] The ventral (from Latin venter 'belly') surface refers to the front, or lower side, of an organism. [38] For example, in a fish, the pectoral fins are dorsal to the anal fin, but ventral to the dorsal fin. The terms are used in other contexts; for example dorsal and ventral gun ...
The limb bud remains active throughout much of limb development as it stimulates the creation and positive feedback retention of two signaling regions: the AER and its subsequent creation of the zone of polarizing activity (ZPA) with the mesenchymal cells. [5] In addition to the dorsal-ventral axis created by the ectodermal expression of ...
When multiple clusters of cells intercalate in the dorsal-ventral axis, through junctional neighbor exchange, the outcome is an extension of germ-band in the anterior-posterior axis. In addition to the simple neighbor exchange, higher-ordered rosette formations have been observed in which five or more cells meet at a vertex.
The posterior region (including the hindgut) expands and extends towards the anterior pole along the dorsal side of the embryo. At this time, segments of the embryo become visible, creating a striped arrangement along the anterior-posterior axis. The earliest signs of segmentation appear during this phase with the formation of parasegmental ...
The primitive streak is a structure that forms in the early embryo in amniotes. [1] In amphibians, the equivalent structure is the blastopore. [2] During early embryonic development, the embryonic disc becomes oval shaped, and then pear-shaped with the broad end towards the anterior, and the narrower region projected to the posterior.