Mesencephalon

(Redirected from Midbrain)
Jump to: navigation, search
Brain: Mesencephalon
Human brain inferior view description.JPG
Inferior view mesencephalon (2), above (3)
Human brainstem-thalamus posterior view description.JPG
Human brainstem mesencephalon (B)
Latin mesencephalon
Gray's subject #188 800
NeuroNames hier-445
MeSH Mesencephalon

WikiDoc Resources for Mesencephalon

Articles

Most recent articles on Mesencephalon

Most cited articles on Mesencephalon

Review articles on Mesencephalon

Articles on Mesencephalon in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Mesencephalon

Images of Mesencephalon

Photos of Mesencephalon

Podcasts & MP3s on Mesencephalon

Videos on Mesencephalon

Evidence Based Medicine

Cochrane Collaboration on Mesencephalon

Bandolier on Mesencephalon

TRIP on Mesencephalon

Clinical Trials

Ongoing Trials on Mesencephalon at Clinical Trials.gov

Trial results on Mesencephalon

Clinical Trials on Mesencephalon at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Mesencephalon

NICE Guidance on Mesencephalon

NHS PRODIGY Guidance

FDA on Mesencephalon

CDC on Mesencephalon

Books

Books on Mesencephalon

News

Mesencephalon in the news

Be alerted to news on Mesencephalon

News trends on Mesencephalon

Commentary

Blogs on Mesencephalon

Definitions

Definitions of Mesencephalon

Patient Resources / Community

Patient resources on Mesencephalon

Discussion groups on Mesencephalon

Patient Handouts on Mesencephalon

Directions to Hospitals Treating Mesencephalon

Risk calculators and risk factors for Mesencephalon

Healthcare Provider Resources

Symptoms of Mesencephalon

Causes & Risk Factors for Mesencephalon

Diagnostic studies for Mesencephalon

Treatment of Mesencephalon

Continuing Medical Education (CME)

CME Programs on Mesencephalon

International

Mesencephalon en Espanol

Mesencephalon en Francais

Business

Mesencephalon in the Marketplace

Patents on Mesencephalon

Experimental / Informatics

List of terms related to 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).

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 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.

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.

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.

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.

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.

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 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 cerebral aqueduct runs through the midbrain, and is the communication between the third and fourth ventricle.

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.

Organization

Additional images

See also

da:Mesencephalon de:Mittelhirn it:Mesencefalo lt:Vidurinės smegenys mk:Среден мозок nl:Mesencephalon no:Mesencephalon sk:Stredný mozog fi:Keskiaivot



Linked-in.jpg