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Distribution and Characteristics of Brain Dopamine
Published in Nira Ben-Jonathan, Dopamine, 2020
The brain stem is located between the spinal cord and the diencephalon and is divided into three major structures: the medulla oblongata (myelencephalon), the pons with the cerebellum (metencephalon), and the midbrain (mesencephalon). Although the pons and cerebellum together constitute the metencephalon, only the pons, but not the cerebellum, is considered as a part of the brainstem. The transition zone between the medulla and the spinal cord is located at the level of the foramen magnum and is also at the level of the pyramidal decussation.
The nervous system
Published in Frank J. Dye, 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.
Nervous System
Published in Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard, Toxicologic Pathology, 2018
Mark T. Butt, Alys Bradley, Robert Sills
The lateral ventricles are within the telencephalon; the third ventricle is the ventricular system of the diencephalon. The midbrain corresponds to the mesencephalon; the aqueduct is the ventricle. The metencephalon is divided between the pons and cerebellum. The myelencephalon forms the medulla oblongata. The fourth ventricle is associated with the metencephalon and myelencephalon.
Horizontal gaze palsy and progressive scoliosis—a tale of two siblings with ROBO3 mutation
Published in Ophthalmic Genetics, 2020
Poornima Narayanan Nambiar, Santha Kumar S, Ramshekhar Menon, Sruthi S Nair, GK Madhavilatha, Soumya Sundaram
This case illustrates the classical neuro-ophthalmological and radiological features described in HGPPS (2,3). The oculomotor abnormalities in this syndrome are due to the absence of midline decussation of the oculomotor pathways at the level of pons and medulla (1). ROBO3 plays a role in axonal guidance during embryogenesis, is responsible for hindbrain axon crossing (2). Hence, the mutation in ROBO3 leads to maldevelopment of dorsomedial brainstem structures and impaired decussation of the ascending sensory, descending motor, and oculomotor pathways (1,2). The structure of the pons in this condition is similar to the embryonic metencephalon between 5 and 8 weeks, where the fourth ventricle shows a ventral cleft that splits the dorsal metencephalon, before the dorsomedial nuclei and tracts begin to develop (3). The site of involvement hypothesized for the oculomotor abnormalities in HGPPS includes the paramedian pontine reticular formation (PPRF), abducens nucleus, or the medial longitudinal fasciculus (MLF) (1,3). Bilateral horizontal gaze palsy along with absent horizontal VOR argue for a localization at the level of abducens nucleus and the preserved convergence implies a relative sparing of the midbrain (4). The absence of normal contour of the facial colliculus also implies an agenesis or hypoplasia of the abducens nuclei (3).
Measurement of Fetal Mesencephalon and Pons Via Ultrasonographic Cross Sectional Imagining
Published in Fetal and Pediatric Pathology, 2018
Ruiqi Yang, Rui Li, Xuejuan Liu, Limei Fan, Jialing Zhang, Libo Wang, Hong Teng
During the fourth and fifth weeks of gestation, three primary brain vesicles complete their development: forebrain vesicle, midbrain vesicle, and metencephalon vesicle (1). Midbrain vesicle will form mesencephalon or midbrain; metencephalon vesicle will form the pons, medulla oblongata, and cerebellum (2). The mesencephalon, pons, and inferior medulla oblongata compose brainstem, the region of the brain that connects cerebrum with spinal cord. Pons, a major portion of which appears as a broad anterior bulge, participates in the transmission of signals between the cerebrum and the rest of the body and is involved in the regulation of sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture (3).
Microsurgical techniques for achieving gross total resection of ependymomas of the fourth ventricle
Published in Acta Chirurgica Belgica, 2020
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.