All the sensitive innervation of the face is under the dependence of the trigeminal nerve (5th cranial pair or V) and of the superficial cervical plexus.

The intracranial origin of the trigeminal nerve is the ganglion of Gasser which will emit three sensitive nervous trunks to which comes to be added a motor root which will accompany the inferior branch, mandibular. From top to bottom as follows one finds:

Ophthalmic nerve or V1, Maxillary nerve or V2, Mandibular nerve or V3 with its motor root; each nerve determining a sensitive territory corresponding.

Ophthalmic nerve or V1

It approaches the face by the superior orbital fissure and gives in the orbit three branches which are of inside outwards:

• Nasociliary nerve giving the ciliary nerve; the infratrochlear nerve; the anterior ethmoidal nerve (or nasal nerve) and internal nasal branches;
• Frontal nerve which is divided into, supratrochlear nerve moving towards the medial orbital angle, and supraorbital nerve which leaves the orbit by the supraorbital foramen;
• Lacrimal nerve.

Is the largest terminal branch of the frontal nerve [1,4]; it leaves the orbit trough the supraorbital foramen or incisure [1,4], to emerge onto the forehead; it goes up on the face accompanied by its supraorbital artery and is divided into two trunks [2], medial superficial and more provided [3] and lateral deeper. It supply the forehead zone until the coronal linea excluded the medial zone above the root of the nose, under the dependence of the supratrochlear nerve.

It supply also the superior eyelid.

Supratrochlear nerve

It is the medial branch of the frontal nerve. It gives a descending branch to the infratrochlear nerve. Ascends onto the forehead through the frontal notch, in the fronto-nasal angle and goes up with its artery about the middle of the face above the nose for supply the teguments until coronal linea and the medial part of the superior eyelid. It complemente thus medialy the supraorbital territory.

Lacrimal nerve

It is smallest and external of the branches of V1. It moves towards the side and superior area of the orbit. It supply the skin covering the lateral part of the upper eyelid [1]. The lacrimal nerve communicates with the zygomaticotemporal nerve (V2) in connection with the maxillary nerve [4, 5, 1].

Nasociliary nerve

It skirts the higher bottom of the orbit and gives [4, 6] several branches of which:
The posterior ethmoidal nerve; the infratrochlear nerve supply the root of the nose. And the anterior ethmoidal nerve or nasal nerve; it passes trough the anterior ethmoidal foramen and go to the nasal cavity; that is divided into two branches [4]:

• the internal nerve supplies the anterior septal mucosa, the anterior part of the lateral nasal wall;
• the external nerve [1], at the lower border of he nasal bone and descends under the transverse part of nasalis to supply the nasal teguments under the nasal bone [4] (above under the dependence of the infratrochlear nerve) and point of nose, except the nasal ala and the external nares (under the dependence of infraorbital nerve).

Maxillary nerve or V2

It leaves the skull via the foramen rotundum, which leads directly into the posterior wall of the pterygopalatine fossa, or it gives its terminal branches:

• meningeal and orbital branches
• zygomatic branches
• superior alveolar nerve; posterior and middle branches
• pterygopalatine and parasympathetic branches
• palatine and pharyngeal branches
• infraorbital nerve continuing the axis of the maxillary nerve

At its arrival with the foramen rotundum, this nerve is presented in the form of a plexus, at the upper part of the pterygopalatine fossa [1, 4], in which it is almost alone.

This level, it will give its terminal branches and it will be accessible here for a complete maxillary block.

Zygomaticotemporal nerve

The zygomaticotemporal nerve is a terminal branch of the zygomatic nerve. It crosses the zygomatic bone and emerges on the anterior part of the temporal zone, above the zygomatic arch where it supply the skin of the temple [1]. It communicates with the facial nerve and the auriculotemporal nerve [1, 4]; and also an anastomosis with the lacrimal nerve.

Zygomaticofacial nerve

Terminal branch of the zygomatic nerve; it crosses the lower and lateral angle of the orbit and emerges on the face by a bone foramen. It supplies the skin on the prominence of the cheek [1,4].

Principal terminal branch of the maxillary nerve, it crosses the maxillary bone to emerges onto the face at the infraorbital foramen. It is presented there in the a largest nervous plexus of which is detached from the groups of nerves with local destiny:

• palpebral branches, going up towards the inferior eyelid than they supply, being anastomosed with the facial nerve and the zygomaticofacial nerve

• nasal branches, for the lateral wall of the nose(alar portion), the movable part of the nasal septum, and join the branches of the external nasal nerve;

• labial superior branches, large and numerous, for the anterior part of the cheek and the superior lip.

The other branches of the maxillary to endo-oral destiny and are simply evoked.

Alveolar superior nerve, posterior and middle for the superior teeth, being detached from the maxillary at the bottom of the foramen rotundum towards the oral cavity;

Pharyngeal nerve, supply the mucosa of the nasopharynx;

Palatine nerves (greater and lesser) for the posterior roof of the mouth;

Pterygopalatine ganglion and nasopalatine nerve with the sympathetic and parasympathetic branches [6] giving of the nasal and nasopalatine branches [7].

The mandibular nerve is the largest trigeminal branch. at emerges of the oval foramen very quickly will give two branches [6], anterior and medial motor branch , the only one of the trigeminal nerve [1] and another continuing the principal axis of the mandibular giving the sensitive terminal branch. It is thus appeared as two trunks [1, 4, 5, 6].

The anterior trunk of mandibular nerve gives

• the buccal nerve
• the motor root for the mastication muscles.

The posterior trunk gives:

• the auriculotemporal nerve
• the lingual nerve
• the inferior alveolar nerve terminal branch of mandibular nerve and which on the level of the mental foramen gives the mental nerve
• the mylohyoid nerve.

We will see the cutaneous branches and the deep branches

Branches with cutaneous destiny

Buccal nerve

Small medial branch, being detached from the anterior motor trunk. It carries the motor fibres to lateral pterygoid giving the sensitive supply of a small zone of the skin above the superior lip and the buccal mucous membrane.

Mental nerve

The mental nerve is the terminal branch of the inferior alveolar nerve. It enters the face through the mental foramen and which supply the inferior lip, the chin and the incisivo-canin dental group [6, 7].

Auriculotemporal nerve

It is detached from the mandibular very high on the level of the temporomandibular joint, and then becomes surface and goes up towards the tragus, posterior with the superficial temporal vessels. It gives superficial branches starting from the tragus for

• the tragus and the entry of the auditory canal, part of the cheek in the pretragus area [8]
• the anterior part of auricle of the ear
• the posterior part of the temple.

It gives anastomosis easily with the facial nerve and zygomatic nerve.

Other branches

• Motor mandibular branches for the muscles of the mastication:
  To masseter, to lateral pterygoid, to temporal [1, 9].
• Lingual nerve
  Connect medial going down along the vertical branch from the mandible and which moves towards the base of the tongue to give the sensitivity for the anterior two-thirds of the tongue, the floor of the mouth and the mandibular lingual gingivae [4, 6, 9].
• Inferior alveolar nerve
  Significant lateral branch which goes down towards the mandible and enter the mandibular canal via the mandibular foramen in its horizontal portion, traversing this one, to end in the mental nerve.
  He gives the inferior dental innervation [1, 6, 9].
• Meningeal branch
• Medial pterygoid nerve

The superficial cervical plexus

By its superficial branches coming from C2 and C3, it takes part in the sensitive innervation of the face; primarily;

• great auricular nerve; its arises from the second and third cervical rami, is detached from the plexus at the Erb point at the posterior border of the sternocleidomastoid muscle (SCM) and which moves in top towards the ear lobe [1, 6, 9]. Its supply the back of the auricle (except its upper part), the lobule and the concha; but he innerve also the skin of the angle of the mandible (in complement of the mandibular).
• lesser occipital nerve exit of second cervical nerve which gives, amongst other things, the innervation of the upper part of the ear lobe [1, 4], and lateral occipital zone.

Remember, these nerves are very intricate at the face, the anaesthesia for only one nerve is not recommended; a zonal anaesthesia is the best technic.