Pons

Relations of pons

Ventrally related to the clivus by separated from it by meninges, basilar artery and basilar plexus of veins

Laterally connected to the cerebellum by middle cerebellar peduncle

External features

Basilar sulcus

Middle cerebellar peduncle

Motor and sensory root of trigeminal

Ponto-cerebellar fibres

Ponto-medullary junction (attachment of 6th-8th nerves)

Dorsal surface

• Forms 4th floor of ventricle

• Facial colliculus

• Vestibular area

• Locus ceruleus (substantia ferruginea, rich in nor adrenaline)

Has superior border where crus cerebri is attached, inferior border at pontomedullary junction

Internal features

Divided into basilar/ventral part and dorsal/tegmental part

Basilar or ventral part

Occupied by longitudinal and transverse fibres

Longitudinal fibres made up of corticospinal, corticobulbar and corticopontine

Transverse fibres are axons from pontine nuclei (pontocerebellar)

Nuclei pontis

Tegmental part

Presence of salivatory nuclei, cranial nuclei (6th-8th) and reticular formation

Features at levels

• At lower level of facial colliculus

• At level of upper pons

The tegmental part differs in the upper and lower part but the basilar part continuous throughout

Transverse section at the level of the facial colliculus

Medial lemniscus

Spinal lemniscus (carry contralateral pain and temperature)

Trigeminal lemniscus (convey pain and thermal from face)

Lateral lemniscus (concerned with hearing, formed by contralateral ventral & dorsal cochlear nuclei and contralateral & ipsilateral fibres from trapezoid body and superior olivary complex )

Superior olivary nucleus composed of principal superior olivary nucleus, accessory and retro-olivar

Nucleus solitarius

Nucleus of spinal tract of trigeminal nerve

Motor nucleus of facial nerve

(Neurobiotaxis-migration of motor nucleus of VII towards spinal nucleus of V)

Medial longitudinal bundle

Tectospinal tract

Ventral and dorsal cochlear nuclei (line in inferior cerebellar peduncle)

Vestibular nuclei

Abducent nuclei

Cross section at upper level of pons

Superior cerebellar peduncles

Medial longitudinal bundle

Blood supply

Numerous pontine branches from basilar artery

Anterior inferior cerebellar artery

Millard Gubler syndrome (medial inferior pontine syndrome)

Pontocerebellar angle syndrome