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To do this, distinct ends of an organism are chosen, and the axis is named according to those directions. An organism that is symmetrical on both sides has three main axes that intersect at right angles. [3] An organism that is round or not symmetrical may have different axes. [3] Example axes are: The anteroposterior axis [8] The cephalocaudal ...
The zone of polarizing activity (ZPA) is an area of mesenchyme that contains signals which instruct the developing limb bud to form along the anterior/posterior axis. Limb bud is undifferentiated mesenchyme enclosed by an ectoderm covering. Eventually, the limb bud develops into bones, tendons, muscles and joints.
The latter flexure mainly appears in mammals and sauropsids (reptiles and birds), whereas the other two, and principally the cephalic flexure, appear in all vertebrates (the sum of the cervical and cephalic ventral flexures is the cause of the 90-degree angle mentioned above in humans between body axis and brain axis).
The floor plate is a structure integral to the developing nervous system of vertebrate organisms. Located on the ventral midline of the embryonic neural tube, the floor plate is a specialized glial structure that spans the anteroposterior axis from the midbrain to the tail regions.
The zeugopod consists of two parallel elements along the anteroposterior axis and the autopod contains three to five (in most cases) elements along the same axis. The digits also have a quasi-periodic arrangement along the proximodistal axis, consisting of tandem chains of skeletal elements.
The cytoplasm in the vegetal pole specifies this axis and removing this cytoplasm leads to a loss of axis information. The yellow cytoplasm specifies the anterior/posterior axis. When the yellow cytoplasm moves to the posterior of the egg to become posterior vegetal cytoplasm (PVC), the anterior/posterior axis is specified.
An example of this process is where the anteroposterior axis (the axis drawn between the head and tail end of an embryo) becomes longer as the lateral tissues (those that make up the left and right sides of the embryo) move in towards the dorsal midline (the middle of the back of the animal). [1]
In early embryo development, the formation of the primary body axes is a crucial step in establishing the organism's overall body plan. The axes include the anteroposterior axis, dorsoventral axis, and right-left axis. Wnt signaling is implicated in the formation of the anteroposterior and dorsoventral (DV) axes.