Download Unit 20: Superficial Face and Parotid Region Dissection Instructions

Unit 20: Superficial Face and Parotid Region
Dissection Instructions:
The skin of the face is thin and muscles of facial expression often have attachment to it,
therefore, it must be removed carefully. The skin of the eyelids is the thinnest. Make the following
incisions as outlined in Figure 18-1. Make a mid-line incision extending from the bottom of the chin
to the top of the head (A to B). Make a second incision from the bridge of the nose, around the
eyelids C to D). Encircle the mouth with another incision, leaving the mucosa of skin of the lips
intact and extend the incision to the ear (E and E to F). Also, encircle the nostrils (G ). The skin
from both the face and scalp should be reflected as indicated in Figure 20-1.
Fig. 19– 1
Once the skin of the face and scalp is reflected, clean the surface of the parotid gland out to
its margin (Plate 23, 25; 7.13). The branches of the facial nerve (Plates 25, 61; 7.7, 7.13, 7.39A,
B) which innervate the muscles of facial expression will exit the parotid gland at its margins. Locate
the duct of the parotid gland as it leaves the gland at its anterior margin, paralleling the zygomatic
arch and lying a fingers breadth below it. It crosses superficial to the masseter muscle and pierces
the buccinator muscle to open into the mouth cavity opposite the second upper molar tooth (Plates
25, 61, 72; 7.12,). As the branches of the facial nerve and the parotid duct are cleaned, identify the
muscles of facial expression.
Identify the orbicularis oculi muscle as it encircles the palpebral fissure. It is used to close
the eye (Plates 26, 123; 7.12, Table 7.1 and figures p. 629). Note its orbital and palpebral parts.
Identify the orbicularis oris muscle as it encircles the mouth. Observe that a number of
other muscles mingle with the orbicularis oris muscle (Plates 26, 123; 7.15, Table 7.1 and figures p.
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629). Locate as many of the following muscles as possible: the levator labii superioris muscle
which has three parts, a medial part called the levator labii superioris alaeque nasi, a middle part
and a lateral part called the zygomaticus minor; the zygomaticus major muscle which is lateral to
the zygomaticus minor muscle; the levator anguli oris muscle which is deep to the above muscles
and is useful in smiling; the risorius muscle which has horizontal fibers running from the angle of
the mouth and it broadens the smile; the depressor anguli oris which is triangular in shape with its
base inferior and its upper angle at the angle of the mouth; the depressor labii inferioris which is
deep and medial to the depressor angulae oris muscle; and the mentalis muscle which is deep to the
skin of the chin.
Locate the buccinator muscle an important muscle of facial expression (Plates 26, 54, 60,
61, 68;7.12, 7.13, Table 7.1 and figures p. 629). Again note the parotid duct piercing the muscle.
Observe the platysma muscle, the largest of the muscles of facial expression..
Look again at the branches of the facial nerve. Usually the nerve divides into upper and
lower divisions within the substance of the parotid gland (Plates 25, 123; 7.13, 7.39, Table 9.9 and
figures p. 830). The upper division has branches which go to the temporal, zygomatic and
buccal regions to innervate muscles in those areas. The lower division has branches which go to
the cervical, mandibular and buccal regions. The facial nerve also has a posterior auricular
branch serving muscles posterior to the ear. The posterior belly of the digastric muscle and the
stylohyoid muscle are also innervated by the facial nerve.
At the angle of the mandible (Plates 23, 25, 54; 7.41; 7.46), clean the masseter muscle and
note its origin from the zygomatic arch and its insertion on the angle and ramus of the mandible.
This is a muscle of mastication. Follow its anterior border to the lower border of the mandible and
locate the facial artery. Follow the facial artery which is a branch of the external carotid artery onto
the face (Plates 23, 36, 69, 85; 7.12, 7.13 8.10, Table 7.3 and figures p. 632). It has named
branches to the lower and upper lips, but supplies the entire anterior facial area. At the orbit, it
anastomoses with the superficial branches of the ophthalmic artery, thus connecting internal and
external carotids. The superior labial artery branches contributes to the circulation of the nasal
mucosa. It also anastomoses with the transverse facial branch of the superficial temporal artery,
one of the terminal branches of the external carotid. The left and right facial arteries anastomose
across the mid-line. Note its relationship to the facial vein.
Follow the superficial temporal artery and vein, a terminal branch of the external
carotid artery to the side of the head and scalp which it supplies (Plates 23; 7.13, 7.21, Table 7.4
and figure p. 633). These are superficial and anterior to the tragus of the ear, where the pulse of
the artery can be felt. The external carotid artery ends deep and posterior to the neck of the
mandible. Note the retromandibular vein as it accompanies the external carotid artery.
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Carefully pick away the parotid gland on one side of the face to observe the facial nerve,
retromandibular vein and carotid arteries (Plates 25, 61, 70, 123; 7.13, 7.39B). Leave some gland
tissue on the parotid duct so it can be recognized later, but otherwise remove the entire gland. When it
is completely removed, the styloid process, stylohyoid muscle and posterior belly of the digastric
muscle should be seen anterior to the mastoid process.
Clean and study the sensory innervation of the face. Locate the terminal branches found in the face
and scalp of the ophthalmic, maxillary and mandibular divisions of the trigeminal nerve (Plates 24, 36,
45, 71, 122; 7.15, 7.16C Table 7.2 and figures-p. 605 figures p. 631).
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Be sure to identify all of the following in this unit:
parotid gland
duct of parotid gland
facial nerve
masseter muscle
buccinator muscle
frontalis muscle
occipitalis muscle
galea aponeurotica
orbicularis oculi muscle
corrugator supercilii muscle
orbicularis oris muscle
posterior belly of digastric muscle
infratrochlear nerve
supratrochlear nerve
levator anguli muscle
risorius muscle
depressor anguli oris muscle
levator labii superioris muscle
zygomaticus major muscle
zygomaticus minor muscle
mentalis muscle
platysma muscle
facial artery
angular artery
superior labial artery
superficial temporal artery
facial vein
retromandibular vein,
anterior branch of auriculotemporal nerve
styloid process of temporal bone
stylohyoid muscle
lacrimal nerve
dorsal nasal nerve
infraorbital nerve
zygomaticofacial nerve
zygomatico-orbital nerve
depressor labii inferioris muscle
mentalis muscle
levator labii superioris alaeque nasi muscle
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