Mesencephalon

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32 Terms

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mesencephalon

part of: brainstem

consists of:

- lamina tecti (posterior part)

- pedunculi cerebri (anterior part)

aqueductus mesencephali s. cerebri

- passen through mesencephalon

- between lamina tecti and pedunculi cerebri

- connects fourth ventricle with third ventricle

- length: 1.5 - 2 cm

<p><span style="text-decoration:underline">part of:</span> brainstem</p><p></p><p><span style="text-decoration:underline">consists of:</span></p><p>- lamina tecti (posterior part)</p><p>- pedunculi cerebri (anterior part)</p><p></p><p><strong>aqueductus mesencephali s. cerebri</strong></p><p>- passen through mesencephalon</p><p>- between lamina tecti and pedunculi cerebri</p><p>- connects fourth ventricle with third ventricle </p><p>- length: 1.5 - 2 cm</p>
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Lamina tecti

extends:

- from velum medullare superius

- to corpus pineale

contains: four rounded elevations

colliculi superiores

- upper elevations

- subcortical visual centers

colliculi inferiores

- lower elevations

- subcortical centers of hearing

brachium colliculi superioris + inferioris

below colliculi:

nervus trochlearis (IV)

- contains motor fibres

- only nerve which appears on dorsal surface of brainstem

<p><span style="text-decoration:underline">extends:</span></p><p>- from velum medullare superius </p><p>- to corpus pineale</p><p></p><p><span style="text-decoration:underline">contains:</span> four rounded elevations</p><p></p><p><strong>colliculi superiores</strong></p><p>- upper elevations </p><p>- <span class="bgP">subcortical visual centers</span></p><p></p><p><strong>colliculi inferiores</strong></p><p>- lower elevations</p><p>- <span class="bgP">subcortical centers of hearing</span> </p><p></p><p><strong>brachium colliculi superioris + inferioris</strong></p><p></p><p><strong>below colliculi:</strong> </p><p><span class="bgY">nervus trochlearis</span> (IV)</p><p>- contains motor fibres</p><p>- only nerve which appears on dorsal surface of brainstem</p>
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Lamina tecti - brachium colliculi superioris

arise: from each colliculus superior forward and laterally

extends to: corpus geniculatum laterale

carries: fibres of visual pathway

<p><span style="text-decoration:underline">arise:</span> from each colliculus superior forward and laterally </p><p></p><p><span style="text-decoration:underline">extends to:</span> corpus geniculatum laterale</p><p></p><p><span style="text-decoration:underline">carries:</span> fibres of <span class="bgP">visual pathway</span></p>
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Lamina tecti - brachium colliculi inferioris

arise: from each colliculus inferior forward and laterally

extends to: corpus geniculatum mediale

carries: fibres of auditory pathway

<p><span style="text-decoration:underline">arise:</span> from each colliculus inferior forward and laterally</p><p></p><p><span style="text-decoration:underline">extends to:</span> corpus geniculatum mediale</p><p></p><p><span style="text-decoration:underline">carries:</span> fibres of <span class="bgP">auditory pathway</span></p>
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pedunculi cerebri

emerge: upward and laterally from pons

enter: lower parts of cerebral hemisphere

fossa interpeduncularis

- depressed area

- between pedunculi cerebri

substantia perforata posterior

- at bottom of interpeduncular fossa

- layer of gray matter

<p><span style="text-decoration:underline">emerge:</span> upward and laterally from pons</p><p></p><p><span style="text-decoration:underline">enter:</span> lower parts of cerebral hemisphere</p><p></p><p><strong>fossa interpeduncularis</strong></p><p>- depressed area</p><p>- between pedunculi cerebri</p><p></p><p><strong>substantia perforata posterior</strong></p><p>- at bottom of interpeduncular fossa</p><p>- layer of gray matter</p>
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substantia perforata posterior - picture

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pedunculi cerebri - further structures

sulcus lateralis mesencephali

- on lateral surface of pedunculi cerebri

trigonum lemnisci laterlis

- laterally to sulcus lateralis mesencephali

sulcus n. occulomotorii

- on medial surface of pedunculi cerebri

- on it emerges nervus occulomotorius (III) containing motor and parasympathetic fibres

<p><strong>sulcus lateralis mesencephali</strong></p><p>- on lateral surface of pedunculi cerebri </p><p></p><p><strong>trigonum lemnisci laterlis</strong></p><p>- laterally to sulcus lateralis mesencephali</p><p></p><p><strong>sulcus n. occulomotorii</strong></p><p>- on medial surface of pedunculi cerebri </p><p>- on it emerges nervus occulomotorius (III) containing motor and parasympathetic fibres</p>
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sulcus n. occulomotorii - picture

knowt flashcard image
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internal features of mesencephalon

three parts on transverse section

substantia nigra:

- seperates crus cerebri <--> tegmentum mesencephali

tectum mesencephali:

- lies posteriorly

= tectal plate

substantia grisea

substantia alba

<p><strong>three parts on transverse section</strong></p><p></p><p><span class="bgB">substantia nigra:</span></p><p>- seperates <span class="bgY">crus cerebri</span> &lt;--&gt; <span class="bgY">tegmentum mesencephali</span></p><p></p><p><span style="text-decoration:underline">tectum mesencephali:</span></p><p>- lies posteriorly </p><p>= tectal plate</p><p></p><p><strong>substantia grisea </strong></p><p><strong>substantia alba</strong></p>
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mesencephalon - substantia grisea

4 groups:

1. nuclei of extrapyramidal system
2. subcortical centers for visual and auditory pathways
3. nuclei of cranial nerves
4. structures of grey matter

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mesencephalon - substantia grisea - nuclei of extrapyramidal system

nucleus ruber

- in tegmentum mesencephali

- extends into subthalamic region

- contains pigment with iron

- axons of nucleus form tractus rubrospinalis

substantia nigra

- between crus cerebri <--> tegmentum mesencephali

<p><strong>nucleus ruber</strong></p><p>- in tegmentum mesencephali </p><p>- extends into subthalamic region</p><p>- contains pigment with iron</p><p>- axons of nucleus form <span class="bgY">tractus rubrospinalis</span></p><p></p><p><strong>substantia nigra</strong></p><p>- between <span class="bgY">crus cerebri</span> &lt;--&gt; <span class="bgY">tegmentum mesencephali</span> </p>
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mesencephalon - substantia grisea - subcortical centers for visual and auditory pathways

location: tectum of midbrain

nuclei of colliculus superior

- subcortical visual center

nuclei of colliculi inferioris

- subcortical center of hearing

<p><span style="text-decoration:underline">location:</span> tectum of midbrain</p><p></p><p><strong>nuclei of colliculus superior</strong></p><p>- subcortical visual center</p><p></p><p><strong>nuclei of colliculi inferioris</strong></p><p>- subcortical center of hearing </p>
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mesencephalon - substantia grisea - nuclei of cranial nerves

location: tegmentum of midbrain

- nuclei of IIIrd cranial nerve

- nuclei of IVth cranial nerve

- nucleus of Vth cranial nerve

<p><span style="text-decoration:underline">location:</span> tegmentum of midbrain</p><p></p><p>- nuclei of<strong> III</strong>rd cranial nerve</p><p>- nuclei of<strong> IV</strong>th cranial nerve</p><p>- nucleus of <strong>V</strong>th cranial nerve</p><p></p>
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nuclei of IIIrd cranial nerve

1. nuclei n. occulomotorii (motor)

--> in tegmentum mesencephali

--> at level of colliculi superiores

2. nuclei accessorii n. occulomotorii (parasympathetic)

<p>1. <span class="bgP">nuclei n. occulomotorii</span> (motor)</p><p>--&gt; in tegmentum mesencephali</p><p>--&gt; at level of colliculi superiores</p><p></p><p>2. <span class="bgY">nuclei accessorii n. occulomotorii</span> (parasympathetic)</p>
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nuclei of IVth cranial nerve

1. nucleus n. trochlearis (motor)

--> in tegmentum mesencephali

--> at level of colliculi inferiores

<p>1. <span class="bgP">nucleus n. trochlearis</span> (motor)</p><p>--&gt; in tegmentum mesencephali</p><p>--&gt; at level of colliculi inferiores</p>
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nucleus of Vth cranial nerve

1. nucleus mesencephalicus n. trigemini (sensory)

--> extends from fossa rhomboidea

<p>1. <span class="bgB">nucleus mesencephalicus n. trigemini</span> (sensory)</p><p>--&gt; extends from fossa rhomboidea</p>
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mesencephalon - substantia grisea - structures of grey matter

formatio reticularis

- in tegmentum mesencephali

- laterally to aqueductus mesencephali

substantia grisea centralis

- surrounds aqueductus mesencephali

<p><strong>formatio reticularis</strong></p><p>- in tegmentum mesencephali</p><p>- laterally to aqueductus mesencephali</p><p></p><p><strong>substantia grisea centralis </strong></p><p>- surrounds aqueductus mesencephali</p>
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mesencephalon - substantia alba

tractus ascendentes

1. via tegmentum mesencephali

tractus descendentes

1. via basis pedunculi cerebri for voluntary movements

2. via tegmentum mesencephali

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mesencephalon - substantia alba - tractus ascendentes

via tegmentum mesencephali

1. lemniscus medialis
2. lemniscus spinalis
3. lemniscus trigeminalis
4. lemniscus lateralis

<p>via tegmentum mesencephali<br><br>1. lemniscus medialis<br>2. lemniscus spinalis<br>3. lemniscus trigeminalis<br>4. lemniscus lateralis</p>
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mesencephalon - substantia alba - lemniscus medialis

tractus ascendentes

function: pathway of epicritic sensibility

joint by: sensory fibres of IXth, Xth and n. intermedius

<p><strong>tractus ascendentes</strong></p><p></p><p><span style="text-decoration:underline">function:</span> <span class="bgP">pathway of epicritic sensibility</span></p><p></p><p><span style="text-decoration:underline">joint by:</span> sensory fibres of <span class="bgY">IXth</span>, <span class="bgY">Xth</span> and <span class="bgY">n. intermedius</span></p><p></p>
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mesencephalon - substantia alba - lemniscus spinalis

tractus ascendentes

<p><strong>tractus ascendentes</strong></p>
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mesencephalon - substantia alba - lemniscus trigeminalis

tractus ascendentes

- sensory fibres of Vth cranial nerve

<p><strong>tractus ascendentes</strong></p><p></p><p>- sensory fibres of <span class="bgY">V</span>th cranial nerve</p>
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mesencephalon - substantia alba - lemniscus lateralis

tractus ascendentes

part of: auditory pathway

<p><strong>tractus ascendentes</strong></p><p></p><p><span style="text-decoration:underline">part of:</span> <span class="bgP">auditory pathway</span></p>
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mesencephalon - substantia alba - tractus descendentes

via basis pedunculi cerebri for voluntary movements

1. tractus corticospinalis

2. tractus corticonuclearis

3. tractus corticopontinus

via tegmentum mesencephali

1. tractus tectospinalis

2. tractus rubrospinalis

3. tractus reticulospinalis

4. fasciculus longitudinalis medialis

5. tractus cerebellorubralis

<p><strong>via basis pedunculi cerebri for voluntary movements</strong></p><p>1. tractus corticospinalis</p><p>2. tractus corticonuclearis</p><p>3. tractus corticopontinus</p><p></p><p><strong>via tegmentum mesencephali</strong></p><p>1. tractus tectospinalis</p><p>2. tractus rubrospinalis</p><p>3. tractus reticulospinalis</p><p>4. fasciculus longitudinalis medialis</p><p>5. tractus cerebellorubralis</p>
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mesencephalon - substantia alba - tractus corticospinalis

tractus descendentes

formed by: axons of pyramidal cells of cortex

- part of pyramidal system

descends: to nuclei motorii cornu anterioris (spinal cord)

- via basis pedunculi cerebri

function: coordination of voluntary movements of tunk + limbs

<p><strong>tractus descendentes</strong></p><p></p><p><span style="text-decoration:underline">formed by: </span>axons of <span class="bgY">pyramidal cells of cortex</span></p><p>- part of pyramidal system</p><p></p><p><span style="text-decoration:underline">descends:</span> to <span class="bgB">nuclei motorii cornu anterioris</span> (spinal cord)</p><p>- via basis pedunculi cerebri</p><p></p><p><span style="text-decoration:underline">function:</span> <span class="bgP">coordination of voluntary movements of tunk + limbs</span></p>
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mesencephalon - substantia alba - tractus corticonuclearis

tractus descendentes

formed by: axons of pyramidal cells of cortex

- part of pyramidal system

descends: nuclei of cranial nerves (III + IV) --> synapsing

- via basis pedunculi cerebri

function: for coordination of voluntary movements of head and neck

<p><strong>tractus descendentes</strong></p><p></p><p><span style="text-decoration:underline">formed by:</span> axons of <span class="bgY">pyramidal cells of cortex</span></p><p>- part of pyramidal system</p><p></p><p><span style="text-decoration:underline">descends:</span> <span class="bgB">nuclei of cranial nerves</span> (III + IV) --&gt; synapsing</p><p>- via basis pedunculi cerebri </p><p></p><p><span style="text-decoration:underline">function:</span> <span class="bgP">for coordination of voluntary movements of head and neck</span></p>
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mesencephalon - substantia alba - tractus corticopontinus

tractus descendentes

descend to: nucleus pontinus

- via basis pedunculi cerebri

function: for coordination of voluntary movements

<p><strong>tractus descendentes</strong></p><p></p><p><span style="text-decoration:underline">descend to:</span> <span class="bgB">nucleus pontinus </span></p><p>- via basis pedunculi cerebri </p><p></p><p><span style="text-decoration:underline">function:</span> <span class="bgP">for coordination of voluntary movements</span></p>
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mesencephalon - substantia alba - tractus rubrospinalis

tractus descendentes

formed by: axons of nucleus ruber

descends to: nuclei motorii cornu anterioris (spinal cord)

- via tegmentum mesencephali

- fibres crossed --> decussatio tegmentalis anterior

<p><strong>tractus descendentes</strong></p><p></p><p><span style="text-decoration:underline">formed by:</span> axons of <span class="bgY">nucleus ruber</span></p><p></p><p><span style="text-decoration:underline">descends to:</span> <span class="bgB">nuclei motorii cornu anterioris</span> (spinal cord)</p><p>- via tegmentum mesencephali</p><p>- fibres crossed --&gt; <span class="bgY">decussatio tegmentalis anterior</span></p>
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mesencephalon - substantia alba - tractus tectospinalis

tractus descendentes

formed by: axons of nuclei colliculi superiores

descends: nuclei motorii cornu anterioris (spinal cord)

- via tegmentum mesencephali

- fibres crossed --> decussatio tegmentalis posterior

function: visual pathway

<p><strong>tractus descendentes</strong></p><p></p><p><span style="text-decoration:underline">formed by:</span> axons of <span class="bgY">nuclei colliculi superiores</span></p><p></p><p><span style="text-decoration:underline">descends:</span> <span class="bgB">nuclei motorii cornu anterioris</span> (spinal cord)</p><p>- via tegmentum mesencephali</p><p>- fibres crossed --&gt; <span class="bgY">decussatio tegmentalis posterior</span></p><p></p><p><span style="text-decoration:underline">function:</span> <span class="bgP">visual pathway</span></p>
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mesencephalon - substantia alba - tractus reticulospinalis

tractus descendentes

descends: via tegmentum mesencephali

<p><strong>tractus descendentes</strong></p><p></p><p><span style="text-decoration:underline">descends:</span> <span class="bgB">via tegmentum mesencephali</span></p>
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mesencephalon - substantia alba - fasciculus longitudinalis medialis

tractus descendentes

descend: via tegmentum mesencephali

<p><strong>tractus descendentes</strong></p><p></p><p><span style="text-decoration:underline">descend:</span> <span class="bgB">via tegmentum mesencephali</span></p>
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mesencephalon - substantia alba - tractus cerebellorubralis

tractus descendentes

formed by: axons of nucleus dentatus

descend to: nucleus ruber

- via tegmentum mesencephali

part of: voluntary coordination of movements

<p><strong>tractus descendentes</strong></p><p></p><p><span style="text-decoration:underline">formed by:</span> axons of <span class="bgY">nucleus dentatus</span> </p><p></p><p><span style="text-decoration:underline">descend to:</span> <span class="bgB">nucleus ruber</span></p><p>- via tegmentum mesencephali</p><p></p><p><span style="text-decoration:underline">part of:</span> <span class="bgP">voluntary coordination of movements</span></p>

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