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Portrait of Pons

Anatomy · Brain & nerves

Pons

Latin for 'bridge'

Brain · brainstem (middle part)

The bulging middle segment of the brainstem, lying between the midbrain above and the medulla oblongata below, in front of the cerebellum. Its name is Latin for 'bridge': broad bands of transverse fibres carry information from the cerebrum across to the cerebellum. It also houses the nuclei of cranial nerves V to VIII and helps regulate breathing and sleep.

How to spot them

  • ▸A rounded swelling on the front of the brainstem, ringed with transverse fibres
  • ▸A shallow groove down the midline of its front surface holds the basilar artery
  • ▸Attached to the little brain at the back by a thick middle peduncle on each side
  • ▸The trigeminal nerve leaves from its side, and three more cranial nerves emerge at its lower border

What to know

Latin for 'bridge', it lies between the midbrain and the medulla, in front of the little brain

Pons — sometimes called the pons Varolii.

Named after a sixteenth-century Bolognese anatomist who first described it

Pons — Costanzo Varolio (Constantius Varolius), whose name gives 'pons Varolii'.

Contains the nuclei of cranial nerves V, VI, VII and VIII, with the trigeminal nerve leaving on its side

Pons — trigeminal, abducens, facial and vestibulocochlear.

Broad transverse bands here pass fibres from the cerebrum across to the cerebellum via the middle peduncle

Pons — corticopontocerebellar pathway.

A blocked basilar artery supplying its front can leave a person conscious and able only to move the eyes and blink

Pons — locked-in syndrome, from a ventral pontine lesion.

Its pneumotaxic and apneustic centres help to smooth the rhythm of breathing

Pons — modulating the basic rhythm set in the medulla.

Over-rapid correction of low blood sodium can strip the myelin from its centre

Pons — central pontine myelinolysis.

Key ideas

  • Cranial nerves emerge in numerical order down the brainstem: V from the pons's side, VI, VII and VIII at its lower border, IX–XII from the medulla.
  • Fibres from the cerebral cortex synapse in the pons and then cross to the opposite cerebellar hemisphere, which is why each half of the cerebellum talks mostly to the opposite half of the cerebrum.

Quick-fire facts

  • •'Pons' is Latin for 'bridge'; it is also called the pons Varolii after the anatomist Costanzo Varolio, who described it in 1573
  • •Cranial nerves V (trigeminal), VI (abducens), VII (facial) and VIII (vestibulocochlear) attach to it
  • •The basilar groove on its front surface holds the basilar artery, formed by the two vertebral arteries
  • •The middle cerebellar peduncle, made of pontine fibres, is the largest of the three cerebellar peduncles
  • •The fourth ventricle lies behind it, between the pons and the cerebellum
  • •Locked-in syndrome, from a ventral pontine stroke, was described in Alexandre Dumas's The Count of Monte Cristo through the character Noirtier de Villefort, and named by Plum and Posner in 1966
  • •Central pontine myelinolysis is linked to overly rapid correction of hyponatraemia
  • •The pneumotaxic and apneustic respiratory centres lie in the pons

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