1. SHANDONG UNIVERSITY Liu Zhiyu
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 superior colliculus
Brachium of inferior colliculus

11. Fourth ventricle Position
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
Central canal
Gray matter
Cranial nerve nuclei
Relay nuclei
White matter
Reticular formation of brain stem
General somatic motor nuclei
Special visceral motor nuclei
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. General somatic motor nuclei
Nucleus
Site
Cranial n.
Function
Nucleus of
oculomotor n.
Midbrain Ⅲ
Supreior, inferior,and medial recti, inf. obliquus, levator palpebrae superioris
trochlear n. Ⅳ
Superior obliquus
Nucleus of abducent n.
Pons Ⅵ
Lateral rectus
Nucleus of hypoglossal n.
Medulla Ⅻ
Muscles of tongue

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 Medulla-cervical cord
Nucleus
Site
Cranial n.
Function
Motor nucleus of trigeminal n.
Pons Ⅴ
Masticatory muscles, anterior belly of digastric, mylohyoid
Nucleus of facial n. Ⅶ
Facial m., platysma, posterior belly of digastric, stylohyoid, stapedius
Nucleus ambiguus
Medulla
Ⅸ,Ⅹ, Ⅺ
Skeletal m. of pharynx, larynx and upper part of esophagus
Accessory nucleus
Medulla-cervical cord Ⅺ
Sternocleidomastoid, trapezius

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

27. General visceral motor nuclei
Nucleus
Site
Cranial n.
Function
Accessory oculomotor nucleus
Midbrain Ⅲ
Sphincter pupillae and ciliary m.
Superior salivatory nucleus
Pons Ⅶ
Submandibular, sublingual and lacrimal glands
Inferior salivertory nucleus
Medulla Ⅸ
Parotid gland
Dorsal nucleus of vagus n.
medulla Ⅹ
Many cervical, thoracic and abdominal viscera

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

29. Visceral sensory nuclei ( general and special )
Nucleus
Site
Cranial n.
Function
Nucleus of solitary tract
Medulla
Ⅶ,Ⅸ,Ⅹ
Taste and visceral sensation

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
Nucleus
Site
Cranial n.
Function
Mesencephalic nucleus of trigeminal n.
Midbrain Ⅴ
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

32. Special somatic sensory nuclei
Cochlear nuclei
Vestibular nuclei

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

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
Nucleus
Site
Superior colliculus
Midbrain
Nucleus of inferior colliculus
Red nucleus
Substantia nigra
Pretectal area
Superior olivery nucleus
Pons
Pontine nucleus
pons
Nucleus ceruleus
Gracile nucleus
Medulla (underneath gracile tubercle)
Cuneate nucleus
Medulla (underneath cuneate tubercle)
Inferior olivary nucleus
Medulla

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

37. Ascending tracts Medial lemniscus Central thalamic radiation 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 Spinothalamic tract Central thalamic radiation
（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 Trigeminothalamic tract Central thalamic radiation
（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 Rubrospinal tract Tectospinal 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 Basilar part
Directed upward continuation of medulla oblongata
Basilar part
Contain both longitudinal and transverse fibers intermixed with pontine nuclei

47. Midbrain Rectum of midbrain Cerebral peduncle Tegmentum
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 tract middle three-fifths of the crus
Frontopontine tract medial one-fifth
Pariatotempopontine tract lateral one-fifth

48. Midbrain Rectum of midbrain Cerebral peduncle Tegmentum
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 tract middle three-fifths of the crus
Frontopontine tract medial one-fifth
Pariatotempopontine tract
lateral one-fifth