Human Anatomy
Parotid regionParotid region
The parotid region is the region that located in the posterolateral part of the facial region , bounded by the :• Zygomatic arch superiorly .
• External ear and anterior border of the sternocleidomastoid posteriorly .
• Ramus of the mandible medially .
• Anterior border of the masseter muscle anteriorly .
• Angle and inferior border of the mandible inferiorly.
the parotid region includes the parotid gland and duct , the facial nerve, the retromandibular vein, the external carotid artery , and the masseter muscle.
Parotid gland
The parotid gland is the largest of three paired salivary glands. It composed mostly of serous acini. Although the facial nerve ( cn VII) is embedded within the parotid gland , the branches extending from the gland to innervate the muscles of facial expression are divides the gland into superficial and deep lobes.
The parotid gland is enclosed within a tough, unyielding, fascial capsule the parotid sheath (capsule), derived from the investing layer of deep cervical fascia. The parotid gland has an irregular shape because the area occupied by the gland, the parotid bed is anteroinferior to the external acoustic meatus, where it is wedged between the ramus of the mandible and the mastoid process. The apex of the parotid gland is posterior to the angle of the mandible, and its base is related to the zygomatic arch.
The parotid duct passes horizontally from the anterior edge of the gland . at the anterior border of the masseter , the duct turns medially , pierces buccal pad of fat , buccinators muscle, buccopharyngeal fascia and buccal mucosa and enters the oral cavity through a small orifice opposite the 2and maxillary molar tooth.
The oblique passage of the duct in the buccinators muscle acts as a valve-like mechanism & prevents inflation of the duct during blowing . about a fingerbreadth below the zygomatic arch the duct accompanied by the: transverse facial vessels above and buccal branch of facial nerve below
The duct is represented by the middle 1/3 of a line extending from the tragus of the aurcle to a point midway between the ala of nose & upper lip .
Embedded within the substance of the parotid gland , from superficial to deep, are the facial nerve (cn VII) and its branches, the retromandibular vein , and the external carotid artery . on the parotid sheath and within the gland are parotid lymph nodes .
Innervation of parotid gland and related structures :
Although the CN VII is embedded within the gland the CN VII does not provide innervation to the gland . the auriculotemporal nerve , a branch of CN V3 (mandibular branch of trigeminal N.) , is closely related to the parotid gland and passes superior to it with the superficial temporal vessels. The auriculotemporal nerve and the great auricular nerve ( a branch of the cervical plexus) composed of fibers from C2 and C3 spinal nerve , innervates the parotid sheath as well as the overlying skin.
The parasympathetic component of the glossopharyngeal nerve (CN IX) supplies presynaptic secretory fibers to the otic ganglion . the postsynaptic parasympathetic fibers are conveyed from the ganglion to the gland by the auriculotemporal nerve (parasympathetic secretomotor supply arises from the glossopharyngeal nerve , the nerve reach the gland via the tympanic branch, the lesser petrosal nerve , the otic ganglion , and the auriculotemporal nerve) .
Stimulation of the parasympathetic fibers produces a thin , watery saliva , sympathetic fibers are derived from cervical ganglia through the external carotid nerve plexus on the external carotid artery . the vasomotor activity of these fibers May reduce secretion from the gland sensory nerve fibers pass to the gland through the great auricular and auriculotrmporal nerve.
The gland is an irregular lobulated mass, sends 'processes' in various directions these include:
1. Glenoid process that extends upward behind the temporomandibular joint in front of external auditory meatus .
2. Facial process that extends anteriorly onto the masseter muscle .
3. Accessory process (part) , small part of facial process lying along the parotid duct .
4. Pterygoid process that extends forward from the deeper part lies between the medial pterygoid muscle & the ramus of mandible .5. Carotid process that lies posterior to the external carotid artery .
A portion of fascia extending from the styloid process to the angle of mandible is called stylomandibular ligament. It separates the parotid gland from the submandibular gland.
Arterial supply : external carotid artery & its terminal branches
Venous drainage : into the retro-mandibular vein .
Lymph drainage: into the parotid & then into the deep cervical lymph nodes .
The buccal pad of fat
The buccal fat is one of several encapsulated fat masses in the cheek. It is a deep fat pad located on either side of the face between the buccinators muscle and several more superficial muscles ( including the masseter, the zygomaticus major, and the zygomaticus minor). The inferior portion of the buccal fat pad is contained within the buccal space.
The blood supply to the buccal fat pad originates from:
1. The buccal and deep temporal branches of the maxillary artery .2. the transverse facial branch of the superficial temporal artery .
3. branches of the facial artery.
This rich vascularity allows a reliable long axial flap and explains the rapid surface re-epithelialization.
The buccal and zygomatic branches
of the facial nerve and the parotid duct
lie lateral to the fat pad and should not
be injured during flap mobilization.
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