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The angle formed by the two ventral flexures, the cephalic flexure and the cervical flexure together, is a right angle in the ventral direction between the axis of the body and the axis of the brain. The pontine flexure is located between these two flexures. Isthmic organizer at the midbrain-hindbrain boundary.
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).
Humans (and other primates, to some degree) make this complicated by standing up and walking on two legs. The anterior–posterior dimension of the neuraxis overlays the superior–inferior dimension of the body. However, there is a major curve between the brain stem and forebrain, which is called the cephalic flexure.
The axis of the CNS is often wrongly assumed to be more or less straight, but it actually shows always two ventral flexures (cervical and cephalic flexures) and a dorsal flexure (pontine flexure), all due to differential growth during embryogenesis. The pairs of terms used most commonly in neuroanatomy are:
In a later stage of development the superior part of the neural tube flexes at the level of the future midbrain—the mesencephalon, at the mesencephalic flexure or cephalic flexure. Above the mesencephalon is the prosencephalon (future forebrain) and beneath it is the rhombencephalon (future hindbrain).
Beginning in the future neck region, the neural folds of this groove close to create the neural tube. The formation of the neural tube from the ectoderm is called neurulation. The ventral part of the neural tube is called the basal plate; the dorsal part is called the alar plate. The hollow interior is called the neural canal. By the end of the ...
It's flu season right now, and the U.S. is in the midst of a wave that's straining hospitals.But not all influenza is the same. There are some notable differences between flu A and flu B strains.
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.