The brain stem

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The brain stem

• ??????? ?????
• ???

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The brain

• Telencephalon ??
• Diencephalon??
• Cerebellum ??
• Brain stem ??

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The brain stem ??

• Consists of
• Midbrain ??
• Pons ??
• Medulla oblongata??

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Medulla oblongata??

• Ventral surface
• Pyramid?? contain pyramidal tract (corticospinal
  tract)
• Decussation of pyramid???? formed by crossing
  fibers of corticospinal tract
• Olive?? produced by underlying inferior olivary
  nucleus
• Anterolateral sulcus???? rootlets of hypoglossal
  nerve emerge from it
• Retroolivary sulcus???? rootlets of
  glossopharyngeal, vagus and accessory nerves
  emerge from it

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Medulla oblongata ??

• Dorsal surface
• Lower portion
• Gracile tubercle???? produced by underlying
  gracile nucleus
• Cuneate tubercle???? marks the site of cuneate
  nucleus
• Inferior cerebellar peduncle ????
• Obex ?
• Upper portion forms the lower half of rhomboid
  fossa

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Pons ??

• Ventral surface
• Basilar part ???
• Basilar sulcus ???
• Bulbopontine sulcus ????? from medial
  to lateral, the abducent, facial and
  vestibulocochlear nerves appear
• Middle cerebellar peduncle ????
• Trigeminal nerve ????
• Pontocerebellar trigone ?????? the junction
  of medulla, pons and cerebellum

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Pons ??

• Dorsal surface
• Superior cerebellar peduncle ????
• Superior medullary velum ???
• Trochlear nerve ????

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Midbrain ??

• Ventral surface
• Crus cerebri ????
• Interpeduncular fossa ??? oculomotor nerves
  emerge from medial of crus cerebri
• Posterior perforated substance ???

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Midbrain??

• Dorsal surface
• Superior colliculus ??constitute centers for
  visual reflexes
• Inferior colliculus ??associated with auditory
  pathway
• Brachium of superior colliculi ???
• Brachium of inferior colliculi ???

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Fourth ventricle ????
Central canal ?fourth ventricle ?mesencephalic
aqueduct?third ventricle

• Position
• Situated ventral to cerebellum, and dorsal to
  pons and cranial half of medulla

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• Boundaries
• Inferolateral gracile and cuneate tubercles,
  inferior cerebellar peduncle
• Superolateral superior cerebellar peduncle
• Lateral recess

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• Features
• Median sulcus ???
• Sulcus limitans ??
• Vestibular area??? overlies vestibular nuclei
• Acoustic tubercle???overlying dorsal cochlear
  nucleus
• Medial eminence ????
• Striae medullares ??

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• Facial colliculus???? overlies nucleus of
  abducent n. and genu of facial nerve
• Hypoglossal triangle ?????? verlying
  hypoglossal nucleus
• Vagal triangle?????? overlies dorsal nucleus of
  vagus nerve
• Funiculus separans???
• Area postrema ???
• Locus ceruleus ??

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• Roof
• Anterior part formed by superior cerebellar
  peduncle and superior medullary velum
• Posterior part formed by inferior medullary
  velum and choroid plexus of fourth ventricle
• Three apertures
• Median aperture of fourth ventricle ???????
• Two lateral apertures of fourth ventricle ???????

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Tela choroidea and choroid plexus????????
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Internal structures

• Gray matter
• Cranial nerve nuclei
• Relay nuclei

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General somatic motor nuclei ???????

• Nucleus of oculomotor n.?????
• Nucleus of trochlear n. ?????
• Nucleus of abducent n. ????
• Nucleus of hypoglossal n.?????

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General somatic motor nuclei
Nucleus Site Cranial n. Function
Nucleus of Oculomotor n. Midbrain ? Supreior, inferior,and medial recti, inf. obliquus, levator palpebrae superioris
Nucleus of trochlear n. Midbrain ? Superior obliquus
Nucleus of abducent n. Pons ? Lateral rectus
Nucleus of hypoglossal n. Medulla ? Muscles of tongue
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Special visceral motor nuclei ???????

• Motor nucleus of trigeminal n. ???????
• Nucleus of facial n. ????
• Nucleus ambiguus ??
• Accessory nucleus ????

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Special visceral motor nuclei
Nucleus Site Cranial n. Function
Motor nucleus of trigeminal n. Pons ? Masticatory muscles
Nucleus of facial n. Pons ? Facial m., platysma, posterior belly of digastric, stylohyoid, stapedius
Nucleus ambiguus Medulla ?,?.? Skeletal m. of pharynx, larynx and upper part of esophagus
Accessory nucleus Medulla-cervical cord ? Sternocleidomastoid, trapezius
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General visceral motor nuclei ???????

• Accessory oculomotor nucleus ??????
• Superior salivatory nucleus ????
• Inferior salivertory nucleus ????
• Dorsal nucleus of vagus n. ??????

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General visceral motor nuclei
Nucleus Site Cranial n. Function
Accessory oculomotor nucleus Midbrain ? Sphincter pupillae and ciliary m.
Superior salivatory nucleus Pons ? Submandibular, sublingual and lacrimal glands
Inferior salivertory nucleus Medulla ? Parotid gland
Dorsal nucleus of vagus n. medulla ? Many cervical, thoracic and abdominal viscera
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Visceral sensory nuclei ( general and special )

• Nucleus of solitary tract ???

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Visceral sensory nuclei ( general and special )
Nucleus Site Cranial n. Function
Nucleus of solitary tract Medulla ?,?,? Taste and visceral sensation
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General somatic sensory nuclei

• Mesencephalic nucleus of trigeminal n. ???????
• Pontine nucleus of trigeminal n.
  ???????
• Spinal nucleus of trigeminal n.
  ???????

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General somatic sensory nuclei
Nucleus Site Cranial n. Function
Mesencephalic nucleus of trigeminal n. Midbrain ? Proprioception of head
Pontine nucleus of trigeminal n. Pons ? Tactile sensation of head
Spinal nucleus of trigeminal n. Medulla ? Pain and temperature sense of head
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Special somatic sensory nuclei

• Cochlear nuclei ????
• Vestibular nuclei ?????

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Special somatic sensory nuclei
Nucleus Site Cranial n. Function
Cochlear nuclei Pons and medulla ? Sense of hearing
Vestibular nuclei Pons and medulla ? Sense of equilibrium
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Relay nuclei ?????

• Gracile nucleus ???
• Cuneate nucleus ???
• Inferior olivary nucleus ????
• Superior olivery nucleus ????
• Pontine nucleus ???
• Nucleus of inferior colliculus???
• Gray matter layers of superior colliculus
  ?????
• Red nucleus ??
• Substantia nigra ??
• Pretectal area ????

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Non-cranial nerve nuclei
Nucleus Site
Gracile nucleus Medulla (underneath gracile tubercle)
Cuneate nucleus Medulla (underneath cuneate tubercle)
Superior olivery nucleus Pons
Pontine nucleus pons
Nucleus of inferior colliculus Midbrain
Gray matter layers of superior colliculus Midbrain
Red nucleus Midbrain
Substantia nigra Midbrain
Pretectal area Midbrain
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White matter

• Ascending tracts
• Medial lemniscus ????
• Spinal lemniscus????
• Trigeminal lemniscus ????
• Lateral lemniscus????

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Medial lemniscus ????
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• Spinal lemniscus
• ????

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• Trigeminal lemniscus
• ????

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Descending tracts

• Corticospinal tract ?????
• Rubrospinal tract ?????
• Tectospinal tract ?????
• Vestibulospinal tract ?????
• Reticulospinal tract ?????

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• Lateral lemniscus
• ????

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Reticular formation of brain stem

• Ascending reticular activating system (ARAS)
  ????????
• Motor central and vital centres
• Reticulospinal tract
• Cardiovascular center and respiratory center
• Serotonergic rapheal nuclei

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The characters of internal structure of brain stem
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Medulla oblongata

• Lower part (closed part)
• Two decussations
• Decussations of medial lemniscus
• Decussations of pyramid

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Medulla oblongata

• Upper part (open part)
• Appearance of inferior olivary nuculeus and
  inferior cerebellar peduncle
• Enlargement of central canal to form the fourth
  ventricle floor

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Pons

• Tegmentum of pons ????directed upward
  continuation of medulla oblongata
• Basilar part ???
• contain both longitudinal and transverse
  fibers intermixed with pontine nuclei

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Midbrain

• Rectum of midbrain???? includes superior and
  inferior colliculi
• Cerebral peduncle ???
• Tegmentum ??
• contain ascending tracts, central gray
  matter, recticular formation and so on
• Substentia nigra ??
• Crus cerebri ????
• Pyramidal tract???- middle three-fifths of the
  crus
• Frontopontine tract??? medial one-fifth
• pariatotempopontine tract ????lateral one-fifth

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