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The brain stem

The brain stem

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The brain stem

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  1. The brain stem SHANDONG UNIVERSITY Liu Zhiyu

  2. The brain stem Consists of • Midbrain • Pons • Medulla oblongata

  3. The brain stem Position • The brain stem occupies the posterior cranial fossa of the skull

  4. Gross Appearance of the Brain Stem

  5. Ventral Surface of the Brain Stem Medulla oblongata • Pyramid: Composed of bundles of nerve fiber, pyramidal tract • Decussation of pyramid: Formed by crossing fibers of pyramidal tract • Olive: Produced by underlying inferior olivary nucleus • Anterolateral sulcus: Emerge the roots of hypoglossal nerve • Retroolivary sulcus: Emerge the roots of glossopharyngeal, vagus and accessory nerves

  6. Ventral Surface of the Brain Stem Pons • Basilar part • Basilar sulcus • Bulbopontine sulcus: There emerge, from medial to lateral, the abducent, facial and vestibulocochlear nerves • Middle cerebellar peduncle • Trigeminal nerve Emerges from the junction of basilar part and middle cerebellar peduncles • Pontocerebellar trigone: The junction of medulla, pons and cerebellum

  7. Ventral Surface of the Brain Stem Midbrain • Crus cerebri • Interpeduncular fossa Oculomotor nerve emerges on the medial side crus cerebri • Posterior perforated substance

  8. Dorsal Surface of the Brain Stem Medulla oblongata • Lower portion • Gracile tubercle:produced by underlying gracile nucleus • Cuneate tubercle:produced by underlying cuneate nucleus • Inferior cerebellar peduncle • Obex • Upper portion:forms the lower half of rhomboid fossa

  9. Dorsal Surface of the Brain Stem Pons • Superior cerebellar peduncle • Superior medullary velum • Trochlear nerve

  10. Dorsal Surface of the Brain Stem Midbrain • Superior colliculus Constitute centers for visual reflexes • Inferior colliculus Associated with auditory pathway • Brachium of superiorcolliculus • Brachium of inferior colliculus

  11. Fourth ventricle Central canal →fourth ventricle →mesencephalic aqueduct→third ventricle Position • Situated ventral to cerebellum, and dorsal to pons and cranial half of medulla

  12. Floor of the Fourth ventricle — Rhomboid Fossa Boundaries • Inferolateral: gracile and cuneate tubercles, inferior cerebellar peduncle • Superolateral: superior cerebellar peduncle • Lateral recess

  13. Floor of the Fourth ventricle — Rhomboid Fossa Features • Median sulcus • Sulcus limitans • Vestibular area Overlies vestibular nuclei • Acoustic tubercle Overlying dorsal cochlear nucleus • Medial eminence • Striae medullares

  14. Floor of the Fourth ventricle — Rhomboid Fossa • Facial colliculus Overlies nucleus of abducent n. and genu of facial nerve • Hypoglossal triangle Overlies hypoglossal nucleus • Vagal triangle Overlies dorsal nucleus of vagus nerve • Funiculus separans • Area postrema • Locus ceruleus Bluish-gray in color, it owes its color to a group of deeply pigmented nerve cells

  15. Roof of the Fourth ventricle • 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

  16. Tela choroidea and choroid plexus

  17. Internal structure of the brain Stem

  18. Internal structure of the brain Stem General somatic motor nuclei Special visceral motor nuclei • Central canal • Gray matter • Cranial nerve nuclei • Relay nuclei • White matter • Reticular formation of brain stem General visceral motor nuclei Visceral sensory nuclei( general and special ) General somatic sensory nuclei Special visceral motor nuclei

  19. Cranial nerve nuclei

  20. General somatic motor nuclei • Nucleus of oculomotor n. • Nucleus of trochlear n. • Nucleus of abducent n. • Nucleus of hypoglossal n.

  21. General somatic motor nuclei • Nucleus of oculomotor n. • Nucleus of trochlear n. • Nucleus of abducent n. Nucleus of hypoglossal n.

  22. Generalsomatic motor nuclei

  23. Special visceral motor nuclei • Motor nucleus of trigeminal n. • Nucleus of facial n. • Nucleus ambiguus • Accessory nucleus

  24. Special visceral motor nuclei • Motor nucleus of trigeminal n. • Nucleus of facial n. • Nucleus ambiguus • Accessory nucleus

  25. Special visceral motor nuclei

  26. General visceral motor nuclei • Accessory oculomotor nucleus • Superior salivatory nucleus • Inferior salivertory nucleus • Dorsal nucleus of vagus n.

  27. General visceral motor nuclei

  28. Visceral sensory nuclei ( general and special ) • Nucleus of solitary tract

  29. Visceral sensory nuclei ( general and special )

  30. General somatic sensory nuclei • Mesencephalic nucleus of trigeminal n. • Pontine nucleus of trigeminal n. • Spinal nucleus of trigeminal n.

  31. General somatic sensory nuclei

  32. Special somatic sensory nuclei • Cochlear nuclei • Vestibular nuclei

  33. Special somatic sensory nuclei

  34. Relay nuclei • Superior colliculus • Nucleus of inferior colliculus • Red nucleus • Substantia nigra • Pretectal area • Superior olivery nucleus • Pontine nucleus • Nucleus ceruleus • Gracile nucleus • Cuneate nucleus • Inferior olivary nucleus

  35. Non-cranial nerve nuclei

  36. White matter Ascending tracts • Medial lemniscus • Spinothalamic tract(Spinal lemniscus ) • Trigeminothalamic tract(Trigeminal lemniscus ) • Lateral lemniscus

  37. Ascending tracts Central thalamic radiation Medial lemniscus VPL 3°neurons Medial lemniscus Gracile and cuneate nuclei 2°neuron Decussation of medial lemniscus Fasciculus cuneatus T4 Fasciculus gracilis Spinal ganglion 1°neuron

  38. Ascending tracts Central thalamic radiation Spinothalamic tract (Spinal lemniscus) VPL 3°neurons Spinal lemniscus anterior spinothalamic tract LaminaⅠ,Ⅳ~Ⅶ 2°neuron Lateral spinothalamic tract Spinal ganglia 1°neuron

  39. Ascending tracts Central thalamic radiation Trigeminothalamic tract (Trigeminal lemniscus) VPM 3°neurons Pontine nucleus of V 2°neuron Trigeminal lemniscus Trigeminal ganglion 1°neuron Spinal tract of trigeminal n. Spinal nucleus of V 2°neuron

  40. Ascending tracts Lateral lemniscus

  41. Descending tracts • Pyromidal tract • Corticospinal tract • Corticonuclear tract • Rubrospinal tract • Tectospinal tract • Vestibulospinal tract • Reticulospinal tract

  42. Reticular Formation of Brain Stem • Ascending reticular activating system (ARAS) • Motor central and vital centres • Reticulospinal tract • Cardiovascular center • Respiratory center • Serotonergic rapheal nuclei

  43. The characters of internal structure of brain stem

  44. Medulla oblongata Lower part (closed part) • Two decussations • Decussations of medial lemniscus • Decussations of pyramid

  45. 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

  46. Pons • Tegmentum of pons Directed upward continuation of medulla oblongata • Basilar part Contain both longitudinal and transverse fibers intermixed with pontine nuclei

  47. Midbrain Rectum of midbrain Includes superior and inferior colliculi Cerebral peduncle • Tegmentum contain ascending tracts, mesencephalic aqueduct, central gray matter, recticular formation and so on • Substentia nigra • Crus cerebri • Pyramidal tractmiddle three-fifths of the crus • Frontopontine tractmedial one-fifth • Pariatotempopontine tractlateral one-fifth

  48. Midbrain Rectum of midbrain Includes superior and inferior colliculi Cerebral peduncle • Tegmentum contain ascending tracts, mesencephalic aqueduct, central gray matter, red nucleus, recticular formation and so on • Substentia nigra • Crus cerebri • Pyramidal tractmiddle three-fifths of the crus • Frontopontine tractmedial one-fifth • Pariatotempopontine tract • lateral one-fifth