AEB - Brainstem anatomy

Sulcus limitans

longitudinal groove on floor of the forth ventricle separating the medial motor nuclei from the lateral sensory nuclei.

Rhomboid fossa

diamond-shaped floor of the the forth ventricle formed by the dorsal pons and upper medulla.

Obex

point at the inferior end of the fourth ventricle where it narrows and becomes the central canal of the medulla.

Superior colliculi

paired elevations on the dorsal midbrain; process sensory information, coordinate visual reflexes and orienting movements of eyes/head.

Inferior colliculi

paired elevations; on the dorsal midbrain; process sound and coordinate auditory reflexes.

Cerebellar peduncles

three pairs of fibre bundles connecting brainstem to cerebellum.

Facial colliculi

paired elevations in the dorsal pons formed by CN VII (facial nerve).

Interpeduncular fossa

depression between cerebral peduncles on the ventral midbrain; associated with the exit of CN III (oculomotor nerve)

Cerebral peduncles

bundle of projection fibres carrying corticospinal, corticobulbar and corticopontine fibres from the cerebral cortex.

Basilar groove

groove in the midline of the ventral pons accomodating the basilar artery.

Base of pons (basis pontis)

ventral portion of the pons; contains pontine nuclei, pontocerebrellar fibres, and descending cortical fibres.

Olives

oval elevation on the ventrolateral medulla; underlying nuclei involved in motor coordination and motor learning via connections with the cerebellum.

Pyramids

longitudinal elevations on the ventral medulla containing corticospinal tracts for voluntary motor commands; most of which decussate.

Basal (ventral) brainstem

Tegmentum

Tectum

Cerebral peduncle

Base of pons (Basis pontis)

Pyramids

Superior colliculi

Inferior colliculi

Cerebral aqueduct

Fourth ventricle

Central canal

CN III (Oculomotor nerve)

CN IV (Trochlear nerve)

CN VI (Abducens nerve)

CN V (Trigeminal nerve)

CN VII (Facial nerve)

CN VIII (Vestibulocochlear nerve)

CN IX (Glossopharyngeal nerve)

CN X (Vagus nerve)

CN XI (Accessory nerve)

CN XII (Hypoglossal nerve)

Interpeducular fossa

Cerebral peduncles

Base of pons (Basis pontis)

Basilar groove

Middle cerebellar peduncle

Olives

Pyramids

Ventral median sulcus

Pyramidal dessucation

Superior colliculi

Inferior colliculi

CN IV (Trochlear nerve)

Superior cerebellar peduncles

Inferior cerebellar peduncles

Middle cerebellar peduncles

Sulcus limitans

Facial colliculi

Rhomboid fossa

Obex

Median sulcus

Motor nuclei

Sensory nuclei

Cuneate tubercules

Cuneate fasciculi

Gracile tubercules

Gracile fasciculi

Substantia nigra

darkly pigmented dopaminergic nucleus in midbrain with axons projecting to basal ganglia; involved in unconscious movement control.

Red nucleus

nuclei in the rubrospinal tract in midbrain; involved in unconscious movement control.

Dessucation of superior cerebellar fibres

axons from the cerebellum cross in the midbrain midline as they project to the thalamus; involved in unconscious movement control.

Corticopontine tract

fibres descending through outer thirds of cerebral peduncles to pontine nuclei in the basis pontis; for coordination of movement.

Pontocerebellar fibres

fibres passing from pontine nuclei via the middle cerebellar peduncle to the cerebellum; relay information from corticopotine tract.

Corticobulbar tract

fibres descend through middle third of cerebral peduncles to target cranial nerve motor nuclei in the pons and medulla; for voluntary movement of head muscles.

Corticospinal tract

fibres descend through middle third of cerebral peduncles, basis pontis, and pyramids to enter spinal cord; for voluntary movement of body muscles.

Lateral corticospinal tract

formed by 90% of corticospinal fibres dessucating at the spino-medullary junction; for voluntary movements of the limbs, especially distal muscles.

Ventral corticopsinal tract

formed by 10% of corticospinal fibres remaining uncrossed at the spino-medullary junction; for voluntary movements of the trunk.

Dorsal column/medial lemniscus pathway

ascending pathway carrying fine touch, vibration, pressure and conscious proprioception from the body to the cerebral cortex.

Gracile nuclei

nuclei in the caudal medulla that receive information from the lower body; second-order neurons then cross and form the medial lemniscus.

Cuneate nuclei

nuclei in the caudal medulla that receive information from the upper body; second-order neurons then cross and form the medial lemniscus.

Arcuate fibres

fibres arising from the gracile and cuneate nuclei crossing the medullar to form the medial lemniscus.

Medial lemniscus

ascending tract formed by decussating fibres from the gracile and cuneate nuclei; carries fine touch, vibration and proprioception to the thalamus.

Spinothalamic tract

ascending pathway carrying pain, temperature and crude touch from the body to cerebral cortex; fibres cross within the spinal cord shortly after entering.

Cerebral aqueduct

Midbrain section

Periaqueductal grey

Red nuclei

Tectum

Midbrain tegmentum

Cerebral peduncles

Substantia nigra

Superior cerebellar peduncles

Medial lemniscus

Spinothalamic tract

Corticopontine tracts

Corticospinal and corticobulbar tracts

Pons section

Fourth ventricle

Pons tegmentum

Spinothalamic tract

Medial lemniscus

Base of pons (Basis pontis)

Pontine nuclei

Corticospinal and corticobulbar tracts

Open medulla

Pyramids (corticobulbar and corticobulbar tracts)

Olives

Medial lemniscus with tracts from upper body