The brain stem

SHANDONG UNIVERSITY

Liu Zhiyu

The brain stem

Consists of Midbrain Pons Medulla oblongata

The brain stem

Position The brain stem occupies th

e posterior cranial fossa of the skull

Gross Appearance of the Brain Stem

Ventral Surface of the Brain Stem

Medulla oblongata Pyramid:

Composed of bundles of nerve fiber, pyra

midal tract Decussation of pyramid: Formed by crossing fibers of pyramidal tr

act 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

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 a

nd middle cerebellar peduncles Pontocerebellar trigone: The junction of medulla, pons and cerebellu

m

Ventral Surface of the Brain Stem

Midbrain Crus cerebri Interpeduncular fossa

Oculomotor nerve emerges on the medial side crus cerebri

Posterior perforated substance

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

Dorsal Surface of the Brain Stem

Pons Superior cerebellar peduncle Superior medullary velum Trochlear nerve

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

Fourth ventricle

Position Situated ventral to cerebellum,

and dorsal to pons and cranial half of medulla

Central canal →fourth ventricle →mesencephalic aqueduct→third ventricle

Floor of the Fourth ventricle — Rhomboid Fossa

Boundaries Inferolateral: gracile and cune

ate tubercles, inferior cerebellar peduncle

Superolateral: superior cerebellar peduncle

Lateral recess

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

Floor of the Fourth ventricle — Rhomboid Fossa

Facial colliculus Overlies nucleus of abducent n. and g

enu of facial nerve Hypoglossal triangle Overlies hypoglossal nucleus Vagal triangle Overlies dorsal nucleus of vagus ner

ve Funiculus separans Area postrema Locus ceruleus

Bluish-gray in color, it owes its color to a group of deeply pigmented nerve cells

Roof of the Fourth ventricle

Anterior part: Formed by superior cerebellar

peduncle and superior medullary velum

Posterior part: Formed by inferior medullary ve

lum and choroid plexus of fourth ventricle

Three apertures Median aperture of fourth ventri

cle Two lateral apertures of fourth v

entricle

Tela choroidea and choroid plexus

Internal structure of the brain Stem

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 nucleiSpecial visceral motor nuclei

General visceral motor nuclei

Visceral sensory nuclei ( general and special )

General somatic sensory nucleiSpecial visceral motor nuclei

Cranial nerve nuclei

General somatic motor nuclei

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

General somatic motor nuclei

Nucleus of oculomotor n. Nucleus of trochlear n. Nucleus of abducent n. N

ucleus of hypoglossal n.

Nucleus Site Cranial n. Function

Nucleus of oculomotor n.

Midbrain Ⅲ Supreior, inferior,and medial recti, inf. obliquus, levator palpebrae superioris

Nucleus oftrochlear n.

Midbrain Ⅳ Superior obliquus

Nucleus of abducent n.

Pons Ⅵ Lateral rectus

Nucleus of hypoglossal n.

Medulla Ⅻ Muscles of tongue

General somatic motor nuclei

Special visceral motor nuclei

Motor nucleus of trigeminal n.

Nucleus of facial n. Nucleus ambiguus Accessory nucleus

Special visceral motor nuclei

Motor nucleus of trigeminal n.

Nucleus of facial n. Nucleus ambiguus Accessory nucleus

Special visceral motor nuclei

Nucleus Site Cranial n.

Function

Motor nucleus of trigeminal n.

Pons Ⅴ Masticatory muscles, anterior belly of digastric, mylohyoid

Nucleus of facial n.

Pons 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

General visceral motor nuclei

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

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

Visceral sensory nuclei ( general and special )

Nucleus of solitary tract

Visceral sensory nuclei ( general and special )

Nucleus Site Cranial n. Function

Nucleus of solitary tract

Medulla Ⅶ, ,Ⅸ Ⅹ Taste and visceral sensation

General somatic sensory nuclei

Mesencephalic nucleus of trigeminal n.

Pontine nucleus of trigeminal n. Spinal nucleus of trigeminal n.

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 Ⅴ Tactile sensation of head

Spinal nucleus of trigeminal n.

Medulla Ⅴ Pain and temperature sense of head

Special somatic sensory nuclei

Cochlear nuclei Vestibular nuclei

Special somatic sensory nuclei

Nucleus Site Cranial n. Function

Cochlear nuclei Pons and medulla

Ⅷ Sense of hearing

Vestibular nuclei Pons and medulla

Ⅷ Sense of equilibrium

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

Relay nuclei

Non-cranial nerve nuclei

Nucleus SiteSuperior colliculus Midbrain

Nucleus of inferior colliculus Midbrain

Red nucleus Midbrain

Substantia nigra Midbrain

Pretectal area Midbrain

Superior olivery nucleus Pons

Pontine nucleus pons

Nucleus ceruleus pons

Gracile nucleus Medulla (underneath gracile tubercle)

Cuneate nucleus Medulla (underneath cuneate tubercle)

Inferior olivary nucleus Medulla

White matter

Ascending tracts Medial lemniscus Spinothalamic tract （ Spi

nal lemniscus ） Trigeminothalamic tract （ Trige

minal lemniscus ） Lateral lemniscus

Ascending tracts

Spinal ganglion 1°neuron

Fasciculus gracilis

Fasciculus cuneatus

Gracile and cuneate nuclei2°neuron

Decussation of medial lemniscus

Medial lemniscus

VPL 3°neurons

Central thalamic radiation

T4

Medial lemniscus

Spinal ganglia1°neuron

Lamina , ~Ⅰ Ⅳ Ⅶ 2°neuron

Lateral spinothalamic tract

anterior spinothalamic tract

Spinal lemniscus

VPL 3°neurons

Central thalamic radiation

Ascending tracts

Spinothalamic tract

（ Spinal lemniscus ）

Trigeminal ganglion1°neuron

Pontine nucleus of V 2°neuron

Spinal nucleus of V 2°neuron

Trigeminal lemniscus

Spinal tract of trigeminal n.

VPM 3°neurons

Central thalamic radiation

Ascending tracts

Trigeminothalamic tract

（ Trigeminal lemniscus ）

Ascending tracts

Lateral lemniscus

Descending tracts

Pyromidal tract Corticospinal tract Corticonuclear tract

Rubrospinal tract Tectospinal tract Vestibulospinal tract Reticulospinal tract

Reticular Formation of Brain Stem

Ascending reticular activating system (ARAS)

Motor central and vital centres Reticulospinal tract Cardiovascular center Respiratory center

Serotonergic rapheal nuclei

The characters of internal structure of brain stem

Medulla oblongataLower part (closed part) Two decussations

Decussations of medial lemniscus Decussations of pyramid

Medulla oblongata

Upper part (open part) Appearance of inferior olivary nucu

leus and inferior cerebellar peduncle

Enlargement of central canal to form the fourth ventricle floor

Pons

Tegmentum of pons Directed upward continuation of me

dulla oblongata Basilar part Contain both longitudinal and transv

erse fibers intermixed with pontine n

uclei

Midbrain

Rectum of midbrain Includes superior and inferior colliculi

Cerebral peduncle Tegmentum contain ascending tracts, mesencephal

ic 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

MidbrainRectum of midbrain Includes superior and inferior colliculi

Cerebral peduncle Tegmentum contain ascending tracts, mesencephalic a

queduct, 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