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Encyclopedia > Mesencephalon
Brain: Mesencephalon
Inferior view mesencephalon (2), above (3)
Human brainstem mesencephalon (B)
Latin mesencephalon
Gray's subject #188 800
NeuroNames hier-445
MeSH Mesencephalon

In biological anatomy, the mesencephalon (or midbrain) is the middle of three vesicles that arise from the neural tube that forms the brain of developing animals. Caudally the mesencephalon adjoins the pons (metencephalon) and rostrally it adjoins the diencephalon (Thalamus, hypothalamus, et al). Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... For other uses, see Latin (disambiguation). ... NeuroNames is a system of nomenclature for the brain and related structures. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... In the developing vertebrate nervous system, the neural tube is the precursor of the central nervous system, which comprises the brain and spinal cord. ... The human brain In animals, the brain (enkephalos) (Greek for in the skull), is the control center of the central nervous system, responsible for behavior. ... For other uses, see Pons (disambiguation). ... The diencephalon is the region of the brain that includes the epithalamus, thalamus, and hypothalamus. ...


In mature human brains, the mesencephalon becomes the least differentiated, from both its developmental form and within its own structure, among the three vesicles. The mesencephalon is considered part of the brain stem. Its substantia nigra is closely associated with motor system pathways of the basal ganglia. The brain stem is the lower part of the brain, adjoining and structurally continuous with the spinal cord. ... The substantia nigra, (Latin for black substance, Soemering) or locus niger is a heterogeneous portion of the midbrain, separating the pes (foot) from the tegmentum (covering), and a major element of the basal ganglia system. ... Structure of a skeletal muscle Muscle is one of the four tissue types. ... The basal ganglia (or basal nuclei) are a group of nuclei in the brain interconnected with the cerebral cortex, thalamus and brainstem. ...


The human mesencephalon is archipallian in origin, meaning its general architecture is shared with the most ancient of vertebrates. Dopamine produced in the substantia nigra plays a role in motivation and habituation of species from humans to the most elementary animals such as insects. In anatomy of animals, the archipallium the oldest region of the brains pallium. ... This article does not cite any references or sources. ... For other uses, see Dopamine (disambiguation). ...

Contents

Gross Structures On The Midbrain

The mesencephalon forms the upper part of the brain stem. It carries corpora quadrigemina (also called as optic lobes or tectum) on the dorsal side and cerebral peduncles (also called as crura cerebrii) on the ventral side of the cerebral aqueduct. The brain stem is the lower part of the brain, adjoining and structurally continuous with the spinal cord. ... The tectum is the dorsal part of the midbrain, derived in embryonic development from the alar plate of the neural tube. ... The mesencephalic duct, also known as the aqueduct of Sylvius or the cerebral aqueduct, contains cerebrospinal fluid (CSF), is within the mesencephalon (or midbrain) and connects the third ventricle in the diencephalon to the fourth ventricle, which is between the pons and cerebellum. ...


Corpora Quadrigemina

It consists of four solid optic lobes on the dorsal side of cerebral aqueduct, where the anterior (front) pair called as the superior colliculus and the posterior (back) pair is called as inferior colliculus. The 4 solid optic lobes help to decussate several fibres of the optic nerve, and by their contra lateral arrangement, the optic chiasma is formed. However some fibres also show homolateral or ipsilateral arrangement i.e they run parallel on the same side without decussating. The superior colliculus is involved with saccadic eye movements; while the inferior is a synapsing point for sound information. The trochlear nerve comes out of the posterior surface of the midbrain, below the inferior colliculus. The optic chiasm is the part of the brain where the optic nerves partially cross, those parts of the right eye which see things on the right side being connected to the left side of the brain, and vice versa. ... The fourth of twelve cranial nerves, the trochlear nerve controls the function of the superior oblique muscle, which rotates the eye away from the nose and also moves the eye downward. ...


Cerebral Peduncle

These are paired structures, present on the ventral side of cerebral aqueduct, and they further carry tegmentum on the dorsal side and cresta or pes on the ventral side, and both of them accommodate the corticospinal tract fibres, from the internal capsule (i.e ascending + descending tracts = longitudinal tract.) the middle part of cerebral peduncles carry substantia nigra (also called "Black Matter") which is a type of basal nucleus. It is the only part of the brain that carries melanin pigment. The midbrain tegmentum is part of the midbrain extending from the substantia nigra to the cerebral aqueduct. ... The corticospinal or pyramidal tract is a massive collection of axons that travel between the cerebral cortex of the brain and the spinal cord. ... The internal capsule is an area of white matter in the brain that separates the caudate nucleus and the thalamus from the lenticular nucleus. ... The substantia nigra, (Latin for black substance, Soemering) or locus niger is a heterogeneous portion of the midbrain, separating the pes (foot) from the tegmentum (covering), and a major element of the basal ganglia system. ...


Between the peduncles is the interpeduncular fossa, which is a cistern filled with cerebrospinal fluid. The occulomotor nerve comes out between the peduncles, and the trochlear nerve is visible wrapping around the outside of the peduncles. Cerebrospinal fluid (CSF), Liquor cerebrospinalis, is a clear bodily fluid that occupies the subarachnoid space in the brain (the space between the skull and the cerebral cortex—more specifically, between the arachnoid and pia layers of the meninges). ... The oculomotor nerve () is the third of twelve paired cranial nerves. ...


Cross-Section Through the Midbrain

The midbrain is usually sectioned at the level of the superior and inferior colliculi.


A cross-section through the superior colliculus shows the red nucleus, the nuclei of the oculomotor nerve (and associated Edinger-Westphal nucleus), as well as the substantia nigra. The red nucleus is a structure in the rostral midbrain involved in motor coordination. ... The oculomotor nerve () is the third of twelve paired cranial nerves. ... The Edinger-Westphal nucleus is the accessory parasympathetic nucleus of the oculomotor nerve, supplying the constricting muscles of the iris. ... The substantia nigra, (Latin for black substance, Soemering) or locus niger is a heterogeneous portion of the midbrain, separating the pes (foot) from the tegmentum (covering), and a major element of the basal ganglia system. ...


The substantia nigra is still present at inferior colliculus level. Also apparent are the trochlear nerve nucleus, and the decussation of the superior cerebellar peduncles. The fourth of twelve cranial nerves, the trochlear nerve controls the function of the superior oblique muscle, which rotates the eye away from the nose and also moves the eye downward. ...


The cerebral aqueduct runs through the midbrain, and is the communication between the third and fourth ventricle. The mesencephalic duct, also known as the aqueduct of Sylvius or the cerebral aqueduct, contains cerebrospinal fluid (CSF), is within the mesencephalon (or midbrain) and connects the third ventricle in the diencephalon to the fourth ventricle, which is between the pons and cerebellum. ... The third ventricle is one of the four connected fluid-filled cavities within the human brain. ... The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. ...


As a mnemonic the mesencephalic cross-section resembles a bear (or teddybear) upside down with the two red nuclei as the eyes and the crus cerebri as the ears. For other uses, see Mnemonic (disambiguation). ...


Organization

The tectum is the dorsal part of the midbrain, derived in embryonic development from the alar plate of the neural tube. ... The inferior colliculus is part of the brain that sits below the superior colliculus, above the trochlear nerve and at the base of the projection of the medial geniculate nucleus (MGN) and the lateral geniculate nucleus (LGN). ... The Superior collici is an area in the mesencephalon of vertebrate brains. ... The cerebral peduncle, by most classifications, is everything in the mesencephalon except the tectum. ... The midbrain tegmentum is part of the midbrain extending from the substantia nigra to the cerebral aqueduct. ... The cerebral peduncle, by most classifications, is everything in the mesencephalon except the tectum. ... The substantia nigra, (Latin for black substance, Soemering) or locus niger is a heterogeneous portion of the midbrain, separating the pes (foot) from the tegmentum (covering), and a major element of the basal ganglia system. ...

Additional images

See also

Look up Mesencephalon in
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