Scalp, Face & Parotid Anatomy Overview

Scalp, Face & Parotid - Learning Outcomes

• List the layers of the scalp, its blood supply, and bleeding from the scalp
• Describe the superficial temporal artery and the facial artery
• Describe the veins of the face and temporal region
• Identify the major muscles of the face and jaw
• Describe the seventh cranial nerve: its relations, lesions, and testing
• Describe the parotid gland and its duct, their relations and clinical conditions and its secretomotor innervation
• Describe the anatomy of the ophthalmic division of the trigeminal nerve, including how their integrity is tested clinically

The Scalp

• Skin: Thin, except in the occipital region. Contains sweat, sebaceous glands, and hair follicles. Abundant arterial supply, good venous and lymphatic drainage.
• Connective tissue layer/sub-Cutaneous tissue: Contains numerous blood vessels and nerves. Wounds bleed profusely as blood vessels are prevented from retraction by fibrous tissue.
• Aponeurosis: Tendinous sheet of occipitofrontalis. Loose connective tissue. Dangerous layer of scalp.
• Periosteum: Cephalhaematoma.
• Blood in the Connective tissue: Drained by emissary veins, some entering skull bones and cranial cavity. Blood flow is from superficial to deep, and these veins can carry infection into the intracranial cavity.

The Face

• Anterior aspect: From the forehead to the chin and from one ear to the other.
• Skin: Elastic, vascular (bleeds profusely but heals rapidly). Contains numerous sweat and sebaceous glands. Connected to underlying bones by loose connective tissue containing muscles of facial expression. Superficial fascia contains facial muscles, blood vessels, nerves, and fat tissue (absent in the eyelids). No deep fascia in the face except over...
• Facial Muscles: Muscles of facial expression lie in superficial fascia, originate from facial bones, and insert into skin. Embryologically develop from 2nd pharyngeal arch, supplied by facial nerve. Serve as sphincters or dilators of the orbit, nose, and mouth.

Muscles of the Face

• Facial expression: Responsible for various facial expressions. Originate on facial bones and insert into skin.
• Embryological development: Develop from the mesoderm of the second pharyngeal arch, thus supplied by the facial nerve.
• Function: Serve as sphincters or dilators of orifices of the face (e.g., orbit, nose, mouth)
• Examples of muscles: Orbicularis oculi, levator palpebrae superioris, corrugator supercilii, compressor naris, dilator naris, procerus, levator labii superioris alaeque nasi, orbicularis oris, the buccinator, the zygomaticus minor and major, levator anguli oris (deep to zygomatic muscles), risorius, depressor anguli oris, depressor labii inferioris, and mentalis.

Muscles Around the Orbit, Nose, and Mouth

• Orbit: Orbicularis oculi, levator palpebrae superioris, corrugator supercilii.
• Nose: Compressor naris, Dilator naris, Procerus, Levator labii superioris alaeque nasi.
• Mouth: Orbicularis oris, Levator labii superioris, Zygomaticus minor and major, Levator anguli oris (deep to zygomatic muscles), Risorius, Depressor anguli oris, Depressor labii inferioris, Mentalis. (buccinator)

The Masseter, Temporalis, Medial Pterygoid, Lateral Pterygoid

• These are the mastication (chewing) muscles.
• They act to move the lower jaw (mandible). Innervated by the trigeminal nerve.

The Parotid Gland

• Largest salivary gland. Composed mostly of serous acini, and enclosed by thick parotid fascia derived from the investing layer of deep cervical fascia.
• Secretes 25% of saliva, which is serous (watery).
• Location: Close to the ear.
• Structures within the gland: External carotid artery, maxillary and superficial temporal arteries, retro mandibular vein, facial nerve, parotid lymph nodes.
• Duct (Stensen's): A thick-walled duct, about 5 cm long, emerging from the middle of the gland's anterior border. It runs forward on the masseter muscle, with the transverse facial artery and upper buccal branch above and the lower buccal branch below. It opens into the vestibule of the mouth opposite the crown of the upper second molar tooth.

Parotid Gland Innervation

• Parasympathetic: Fibers from the inferior salivatory nucleus travel with the glossopharyngeal nerve (IX), then branch into lesser petrosal nerve to the otic ganglion. Pos synaptic fibers hitch a ride with the auriculotemporal nerve.
• Clinical Applications: Tumors, inflammation (parotitis), Frey's Syndrome.

Facial Nerve

• A mixed nerve consisting of both sensory and motor roots.
• It has a parasympathetic function that travels through the sensory root.
• Located at the lower boundary of the Pons, between the olive and inferior cerebellar peduncle.
• Branches: Temporal, zygomatic, buccal, mandibular and cervical branches.
• Testing Motor Function: Different Facial expressions.

Branches of Facial Nerve

• Greater petrosal nerve : In the facial canal.
• Nerve to Stapedius: Supplies the Stapedius muscle.
• Chorda tympani nerve: A taste and preganglionic secretomotor nerve that runs from the nerve about 6 mm above stylomastoid foramen. It supplies the anterior 2/3 of the tongue and preganglionic secretomotor fibers for the submandibular and sublingual salivary glands.
• Posterior auricular nerve: Supplies muscles around the auricle and occipital belly of occipito-frontalis.
• Nerve to posterior belly of digastric and Nerve to stylohoid muscle: In the face: temporal, zygomatic, buccal, marginal mandibular and cervical.
• Clinical Application: Facial nerve paralysis/Bell's palsy.