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As a result of the cephalocaudal and lateral folding of the embryo, a portion of the endoderm-lined yolk sac cavity is incorporated into the embryo to form the primitive gut. In the cephalic and caudal parts of the embryo, the primitive gut forms a tube, the foregut and hindgut, respectively.
The three vesicles need to develop further into five brain vesicles but the space at the cranial end is limited. This causes the neural tube to bend ventrally at two flexures – the first at the cephalic flexure and the second at the cervical flexure. A third flexure is oriented in the opposite dorsal direction as the pontine flexure.
The cephalic end opens into the pharynx through a slit-like aperture formed by the persistent anterior part of the groove. Initially, the cephalic end is in open communication with the foregut, but eventually it becomes separated by the indentations of the mesoderm , the tracheoesophageal folds .
The sagittal plane or lateral plane (longitudinal, anteroposterior) is a plane parallel to the sagittal suture. It divides the body into left and right. It divides the body into left and right. The coronal plane or frontal plane ( vertical ) divides the body into dorsal and ventral (back and front, or posterior and anterior) portions.
A cephalic folding defect results in an epigastric exomphalos that is positioned high up on the abdomen which can be seen in the chromosomal defect pentalogy of Cantrell. Lateral folding defects result in a typical exomphalos that is positioned in the middle of the abdomen.
As the neural plate progresses through the Hamburger-Hamilton stages, the plate thickens until about HH6-7, when the neural plate begins to fold into tube form. The apical surface area increases during neurulation, unlike amphibian embryos. [5] In mouse embryos, there is a large convex-shaped curve to each side of the middle of the plate.
Later, the lateral and middle prominences join forming the first of the three parts of the tongue. The terminal sulcus is a V-shaped line that separates the body of the tongue from the posterior part. [1] The corresponding nerve for the three prominences of the anterior tongue is the trigeminal nerve. The posterior tongue is innervated by the ...
Stages of development of the brain vesicles. Four neural tube subdivisions each eventually develop into distinct regions of the central nervous system by the division of neuroepithelial cells: the forebrain (prosencephalon), the midbrain (mesencephalon), the hindbrain (rhombencephalon) and the spinal cord.