Page 306 - Clinical Anatomy

ECA5 7/18/06 6:50 PM Page 291

The salivary glands 291

can easily be felt by a finger rolled over the masseter if this muscle is tensed
by clenching the teeth.

The relations of the facial nerve to the parotid
The facial nerve is unique in traversing the substance of a gland, a fact of
considerable importance to the surgeon. This coexistence is explained
embryologically; the parotid gland develops in the crotch formed by the
two major branches of the facial nerve. As the gland enlarges it overlaps
these nerve trunks, the superficial and deep parts fuse and the nerve comes
to lie buried within the gland. The fanciful comparison between the nerve
and the two parotid lobes and sandwich–filling between two slices of bread
is not valid because the two lobes of the parotid come to fuse intimately
with each other both around and between the branches of the nerve.
The facial nerve emerges from the stylomastoid foramen, winds later-
ally to the styloid process and can then be exposed surgically in the
inverted V between the bony part of the external auditory meatus and the
mastoid process. This has a useful surface marking, the intertragic notch of
the ear, which is situated directly over the facial nerve.
Just beyond this point the nerve dives into the posterior aspect
of the parotid gland and bifurcates almost immediately into its two main
divisions (occasionally it divides before entering the gland). The upper
division divides into temporal and zygomatic branches; the lower division
gives the buccal, mandibular and cervical branches (Figs 209 and 264).
These two divisions may remain completely separate within the
parotid, may form a plexus of intermingling connections, or, most usually,
display a number of cross-communications which can be safely divided
during dissection without jeopardy.

Fig. 209◊The named
branches of the facial
nerve which traverse the
parotid gland.