Facial nerve

The facial nerve (n. Facialis) combines the facial nerve itself and the intervening nerve.

Actually the facial nerve (n. Facialis) is formed by motor nerve fibers. The intermediate nerve (n. Intermedius; nerve of Vriesberg) contains sensitive taste and vegetative parasympathetic fibers. Sensitive fibers terminate on the single-path nucleus neurons, motor fibers begin from motor nucleus cells. Vegetative fibers originate from the upper salivary nucleus. The facial nerve emerges at the posterior edge of the bridge, laterally from the abduction nerve, lateral to the olive. This nerve is directed forward and lateral and enters the internal auditory meatus. On the lower side of the internal auditory meatus, the nerve goes in the channel of the facial nerve of the temporal bone first transversely with respect to the long axis of the pyramid of the temporal bone. Then, at the level of the cleft of the canal of the large stony nerve, the facial nerve forms the first curve almost at right angles to the back. Further, a small distance passes in the upper part of the medial wall of the tympanum, then turns downward (the second bend). At the first bend (knee of the facial canal) there is a knot of the knee (ganglion geniculi) formed by the bodies of pseudo-unipolar neurons. The knee joint refers to the sensitive part of the facial (intermediate) nerve. The facial nerve leaves the eponymous canal through the stylophyllary aperture on the base of the skull and gives its branches to the mimic muscles of the head.

In the canal of the facial nerve, several branches leave from it:

1. the large stony nerve (n. Petrosus major) departs in the region of the knee and leaves the channel of the facial nerve through the cleft of the channel of the large stony nerve. Then a large stony nerve passes along the front surface of the pyramid of the temporal bone, along the groove of the large stony nerve, perforates the cartilage in the region of the lacerated hole and enters the pterygoid canal. In this channel, together with a deep stony nerve (n. Petrosus profundus, a sympathetic nerve from the inner carotid plexus) forms the nerve of the pterygoid canal (n. Canalis pterygoidei; vidic nerve) that approaches the pterygoid node (see "Ternary nerve"). The large stony nerve consists of the fibers of the intervening nerve. These are preganglionic parasympathetic fibers, which are axons of the neurons of the upper salivary nucleus;
2. connecting branch (with a plexus plexus) [r. Communicans (cum plexus tympanico)] departs from the node of the knee or from the large stony nerve, goes to the mucosa of the tympanic cavity;
3. the nerve (n. Stapedius), the motor nerve, departs from the descending part of the facial nerve, penetrates into the tympanic cavity to the stremna muscle;
4. The drum string (chorda tympani) is formed by parasympathetic (preganglionic) and sensitive (taste) fibers. Sensitive fibers are the peripheral processes of the pseudo-unipolar neurons of the knot assembly. Sensitive fibers of the drum string begin on taste buds located in the mucosa of the anterior 2/5 tongue and soft palate. The drum string is separated from the trunk of the facial nerve before exiting it from the eponymous canal (above the stylophyllary orifice) and passes into the tympanic cavity. In the tympanic cavity, the drum string passes under the mucosa along the upper part of its medial wall, between the long leg of the anvil and the hammer handle. Without giving up the branches in the tympanic cavity, the drum string exits to the outer surface of the skull base through the stony-drum slot. Then the drum string goes forward and downwards and at an acute angle (between the medial and lateral pterygoid muscles) joins the lingual nerve.

The facial nerve immediately after exiting from the stylophyllar aperture gives away the posterior ear nerve, which goes back and upwards along the anterior surface of the mastoid process of the temporal bone and innervates the occipital abdomen of the supracranial muscle, the hindbrain and upper ear muscles (the posterior auricularis posterior). Here, from the facial nerve, a two-abdominal branch (r .digastricus) departs to the posterior abdomen of the digastric muscle and the stylohyocerical branch (r. Stylohyoideus) - to the siloid-lingual muscle.

Further, the facial nerve enters the thickness of the parotid salivary gland, where its branches exchange fibers, resulting in the formation of the parotid plexus (plexus intraparotideus). From this plexus the branches of the facial nerve go up, forward and downward to the mimic muscles. Due to the peculiar arrangement of the parotid plexus and the branches of the facial nerve that depart from it, it is called the "great goose paw" (pes anserinus major).

The branches of the parotid plexus are the temporal, cheekbone, cheek branches, the marginal branch of the lower jaw, the cervical branch.

The temporal branches (rr. Temporales) in an amount of two or three go up and innervate the ear muscles, the frontal abdomen of the supracranial muscle, the circular muscle of the eye, and also the muscle wrinkling the eyebrow.

The cheek branches (rr. Zygomatici) in the number of three or four are directed anteriorly and upward, innervate the circular muscle of the eye, the large zygomatic muscle.

Three to four cheek branches (rr. Buccales) are directed forward along the external surface of the masticatory muscle to the large and small cheek muscles, the muscle lifting the upper lip, the muscle lifting the corner of the mouth, the circular muscle of the mouth, the buccal muscle, the nasal muscle and the muscle of laughter.

The cranial branch of the lower jaw (r. Marginalis mandibulae) goes forward and down the outer surface of the body of the lower jaw to the muscles lowering the lower lip and the corner of the mouth to the chin muscle.

The cervical branch (r. Coli) passes behind the corner of the lower jaw downward to the subcutaneous muscle of the neck. This branch connects with the transverse nerve of the neck (from the cervical plexus), forming a superficial cervical loop.

With the branches of the facial nerve, the fibers from the ear-temporal nerve (behind the articular process of the lower jaw) are connected, from the supraorbital, infraorbital, chin nerves. These connective branches contain sensitive fibers that pass from the branches of the trigeminal nerve to the branches of the facial nerve.

[1], [2], [3]