出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/04/04 04:02:16」(JST)
| Brain: Pons | |
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Diagram showing the positions of the three principal subarachnoid cisternæ (pons visible at center)
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Anteroinferior view of the medulla oblongata and pons
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| Gray's | p.785 |
| Part of | Brain stem |
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Artery
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pontine arteries |
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Vein
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transverse and lateral pontine veins |
| NeuroNames | hier-538 |
| MeSH | Pons |
| NeuroLex ID | birnlex_733 |
The pons /ˈpɒnz/ is part of the brainstem that links the medulla oblongata and the thalamus.[1] It is also called the pons Varolii ("bridge of Varoli"), after the Italian anatomist and surgeon Costanzo Varolio (1543–75).[2] It is cranial to the medulla oblongata, caudal to the midbrain, and ventral to the cerebellum. In humans and other bipeds, this means it is above the medulla, below the midbrain, and anterior to the cerebellum. This white matter includes tracts that conduct signals from the cerebrum down to the cerebellum and medulla, and tracts that carry the sensory signals up into the thalamus.[3]
The pons in humans measures about 2.5 cm or 1 inch in length. Most of it appears as a broad anterior bulge rostral to the medulla. Posteriorly, it consists mainly of two pairs of thick stalks called cerebellar peduncles. They connect the cerebellum to the pons and midbrain.[3]
The pons contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.[3]
Within the pons is the pneumotaxic center, a nucleus that regulates the change from inhalation to exhalation.[3]
The pons is implicated in sleep paralysis, and also plays a role in generating dreams.[citation needed]
During embryonic development, the embryonic metencephalon develops from the rhombencephalon and gives rise to two structures: the pons and the cerebellum.[3] The alar plate produces sensory neuroblasts, which will give rise to the solitary nucleus and its special visceral afferent (SVA) column; the cochlear and vestibular nuclei, which form the special somatic afferent (SSA) fibers of the vestibulocochlear nerve, the spinal and principal trigeminal nerve nuclei, which form the general somatic afferent column (GSA) of the trigeminal nerve, and the pontine nuclei which relays to the cerebellum.
Basal plate neuroblasts give rise to the abducens nucleus,which forms the general somatic efferent fibers (GSE); the facial and motor trigeminal nuclei, which form the special visceral efferent (SVE) column, and the superior salivatory nucleus, which forms the general visceral efferent fibers of the facial nerve.
A number of cranial nerve nuclei are present in the pons:
The functions of these four nerves include sensory roles in hearing, equilibrium, and taste, and in facial sensations such as touch and pain, as well as motor roles in eye movement, facial expressions, chewing, swallowing, and the secretion of saliva and tears.[3]
The pons first evolved as an offshoot of the medullary reticular formation.[4] Since lampreys possess a pons, it has been argued that it must have evolved as a region distinct from the medulla by the time the first agnathans appeared, 505 million years ago.[5]
Location and topography of Pons(Animation)
Scheme showing the connections of the several parts of the brain
Superficial dissection of brainstem, lateral view
Superficial dissection of brainstem, ventral view
Axial section of the pons, at its upper part
Dissection showing the projection fibers of the cerebellum
Sagittal section through right cerebellar hemisphere: The right olive has also been cut sagitally.
Scheme of roof of fourth ventricle: The arrow is in the foramen of Majendie.
Mesal aspect of a brain sectioned in the median sagittal plane
Coronal section of brain immediately in front of pons
Hind- and mid-brains; posterolateral view
Median sagittal section of brain
Dissection showing the course of the cerebrospinal fibers
Terminal nuclei of the cochlear nerve, with their upper connections
Terminal nuclei of the vestibular nerve, with their upper connections
The hypophysis cerebri in position, shown in sagittal section
Pituitary and pineal glands
Axial section of the brainstem (pons) at the level of the facial colliculus
Human cerebrum lateral view
Human brain frontal (coronal) section
Human brainstem anterior view
Nuclei of the pons and brainstem
Cerebrum. Deep dissection. Inferior dissection.
Saladin Kenneth S.(2007) Anatomy & physiology the unity of form and function. Dubuque, IA: McGraw-Hill
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| リンク元 | 「ヴァロリオ橋」 |