The structure indicated is the facial nerve
(cranial nerve VII).
The facial nerve is responsible for supplying the muscles of facial expression
. In addition, the facial nerve provides taste sensation
to the anterior 2/3 of the tongue
and secretomotor function
to the salivary, lacrimal, nasal and palatine glands.
The facial nerve originates from the cerebellopontine angle
, laterally at the junction between the pons
and the medulla
. It has two roots
: a motor root
and the nervus intermedius
, which carries the parasympathetic and sensory fibres. Intracranial branches
- Greater petrosal nerve
- Nerve to stapedius
- Chorda tympani
- Posterior auricular nerve
- Branches to stylohyoid and posterior belly of digastric
- 5 branches emerge from parotid gland: temporal, zygomatic, buccal, mandibular, cervical
The upper facial muscles receive bilateral innervation from upper motor neurones, whereas the lower facial muscles receive only contralateral innervation from the upper motor neurones. In a unilateral upper motor neurone lesion, the muscles to the forehead will therefore be spared due to the bilateral innervation. There is no sparing of the forehead muscles in a lower motor neuron lesion, resulting in complete ipsilateral weakness of the facial muscles.
Learn more about the cranial nerves
in this anatomy tutorial.