The nervous system
Frank J. Dye in Human Life Before Birth, 2019
Some of the better-known structures of the brain have their origins in these vesicles. The retinas and optic nerves of the eyes are really extensions of the brain wall and arise as paired outgrowths (optic vesicles) of the walls of the diencephalon. Glands are also derived from the vesicles. The pineal gland arises as an outgrowth from the roof of the diencephalon, and a portion of the pituitary gland (neurohypophysis) arises as an outgrowth (infundibulum) of the floor of the diencephalon. The roof of the metencephalon gives rise to the cerebellum, and its floor gives rise to the pons. The medulla of the brain arises from the myelencephalon.
ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
The medulla oblongata or MYELENCEPHALON is the most caudal part of the BRAINSTEM. It merges with the PONS rostrally and the SPINAL CORD caudally and contains sensory and motor nuclei that contribute to the fifth, seventh, eighth, ninth, tenth, eleventh and twelfth CRANIAL NERVES. The RETICULAR FORMATION forms the core of the medulla. Its neurons receive diverse inputs and, in turn, send ascending, descending and propriobulbar (intramedullary) connections that provide the anatomical substrates for coordinated activity of cranial nerve nuclei and AUTONOMIC integration. The sensory and motor decussations of the MEDIAL LEMNISCUS and PYRAMIDAL TRACT (see DECUSSATION) are located in the caudal medulla oblongata.
Discussions (D)
Terence R. Anthoney in Neuroanatomy and the Neurologic Exam, 2017
The term “diencephalon” describes one of the five secondary brain vesicles formed at an early stage of embryological development, the other four being the telencephalon, mesencephalon, metencephalon. and myelencephalon (e.g., B&K, p. 4–5). Elsewhere, I have described problems which arise from using these same terms to describe regions of the mature brain, as if the constituents of the embryologic and mature regions are the same (see D: Embryological names).Nevertheless, this practice is widespread among the recent textbooks of basic neuroanatomy consulted for this discussion (e.g., B&K, p. 5 [Table 1–1]; C&S, p. 74–81; W&W, p. 164–170).
Two Case Reports of Neuropsychological Functioning in Congenital Insensitivity to Pain with Anhidrosis (CIPA)
Published in Developmental Neuropsychology, 2020
Yanin Santoya-Montes, Karol Gutiérrez-Ruiz, Rodrigo Zequeira Cotes, Pedro Puentes Rozo
CIPA is caused by loss‐of‐function mutations in the NTRK1 gene‐encoding TrkA (tropomyosin‐related kinase A), a receptor tyrosine kinase for Nerve growth factor (NGF). The NTRK1 gene is located on chromosome 1q21‐22. According to Indo (2012), NGF is a neurotrophic factor essential for the survival and maintenance of various types of neurons, including primary afferent neurons, autonomic sympathetic postganglionic neurons, and several types of neurons in the brain. Indo (2014) found that the basal forebrain, the striatum, the hypothalamus, the cerebellar nuclei, the basal part of the pons, the pontine tegmentum, and the myelencephalon are brain regions which show a high expression of TrkA.
Microsurgical techniques for achieving gross total resection of ependymomas of the fourth ventricle
Published in Acta Chirurgica Belgica, 2020
Michael G. Z. Ghali
The prominences, contours, and curves of the fourth ventricular floor provide several useful landmarks delineating surface and deep structural anatomy [48,52]. The floor is diamond shaped and formed by the dorsal surfaces of the metencephalon and myelencephalon. Midline and paramedian sulci, ridges, and impressions in the fourth ventricular floor provide a series of natural landmarks corresponding with underlying pontomedullary zones. The immediately parasagittal median eminence is interposed between the median sulcus and the bilaterally flanking sulci limitans, with respect to which the vestibular area is laterally located, overlies the abducens nucleus and ascending portion of the facial nerve genual fibers. These axons originate ventromedial with respect to the abducens nucleus and course medioposteriorly across the ventral surface of the abducens nucleus then lateroanteriorly around its dorsal surface in the fourth ventricular floor immediately above the pontomedullary junction. Impressions of the sulci limitans form dimples comprised of the metencephalic superior fovea (marking the location of the motor trigeminal nucleus) and the myelencephalic inferior fovea, medial to which are the fibers comprising the hypoglossal rootlets. An area exhibiting bluish gray hue reflecting intraneuronal lipofuscin pigment may be found at the rostral sulcus limitans and effectively marks the location of the locus coeruleus. A series of V-shaped impressions near the caudal end of the median sulcus are comprised rostrocaudally of the hypoglossal trigone, vagal trigone, and area postrema [48,52]. A dark triangular shaped area interposed between the hypoglossal trigone medially and the vestibular area laterally, termed the triangular area by Rhoton [48] and ala cinerea by other authors, specifically corresponds with, and overlies, the myelencephalic extent of the nucleus tractus solitarius and the dorsal motor nucleus of the vagus and is crossed caudally by the funiculus separans. The ala cinerea may thus be found between the hypoglossal trigone, corresponding with the hypoglossal motor nuclei, adjacent paired neuronal clusters located in the dorsal medulla, and the vagal trigone, corresponding with the nucleus tractus solitarii and dorsal motor nuclei of the vagus. The area postrema is a bilaterally paired circumventricular organ lacking a blood brain barrier located immediately caudal to the vagal trigone, flanked by the funiculus separans bilaterally, and bridged caudomedially by the interfunicular commissure. The caudal contoured edge of the interfunicular commissure and rostral contoured edge of the ligula represent the medullary attachment of the tectoria membrana and may be conceptualized to delineate the obex. Vasopressin and angiotensin acting upon the area postrema effectively desensitize the baroreflex mechanism and permit sharp rises of the arterial pressure and heart rate occurring in the setting of the defense reaction. The laterally oriented acoustic striae overlie the course of the dorsal pontocerebellar fibers and provide a natural landmark readily orienting the astute neurosurgeon to the beauty and elegance of the microsurgical ventricular anatomy.