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

• Layers: Skin, Dense connective tissue, Aponeurotic layer, Pericranium, Loose connective tissue
• Skin: Thin except in the occipital region, abundant sweat, sebaceous glands, and hair follicles. Abundant arterial supply, good venous and lymphatic drainage.
• Connective tissue layer/sub-cutaneous tissue: Consists of 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

Internal Scalp Bleeding

• Clinical Application: Cephalohematoma, subgaleal hemorrhage

Facial Structures

• Anterior aspect of head: From forehead to chin and from one ear to the other
• Skin: Elastic, vascular (bleeds then heals rapidly), consists of numerous sweat and sebaceous glands, connected to underlying bones by loose connective tissue (contain muscle of facial expression)
• Superficial fascia: Contains facial muscles, blood vessels and nerves, fat tissues (absent in eye lids)
• No deep fascia in the face: Except over...?

Muscles of the Face

• Called muscles of facial expression: Lie in superficial fascia. They take origin from facial bones and are inserted in the skin.
• Embryologically: Develop from mesoderm of the 2nd pharyngeal arch, therefore supplied by facial nerve.
• Facial muscles: Serve as sphincters and dilators of orifices of the face (orbit, nose, and mouth)

Parotid Gland

• Largest salivary gland: Composed mostly of serous acini, enclosed by thick parotid fascia derived from investing layer of deep cervical fascia.
• Secretes 25% of saliva: Serous (watery secretions)
• Clinical application: Parotid gland tumour, Parotitis (inflammation- infective i.e. stone in duct, bacterial, viral (mumps))
• Frey's syndrome: A rare condition following trauma to the auriculotemporal nerve in the parotid area. Patients complain of redness and sweating on the cheek and temporal area whenever they eat or think about food

Parotid Duct (Stensen Duct)

• Thick-walled duct (~5cm long): Emerges from the middle of the anterior border of the gland.
• Runs forward on masseter: With the transverse facial artery and upper buccal above and lower buccal branch of facial nerve below
• Opens into the vestibule of the mouth opposite the crown of the upper 2nd molar tooth

Parasympathetic Innervation to the Gland

• Parasympathetics leave the brain with the glossopharyngeal nerve (IX)
• IX exits the skull through the jugular foramen, tympanic nerve ascends into the inferior tympanic canaliculus, and joins the tympanic plexus
• The lesser petrosal nerve comes out of the tympanic plexus and exits the petrous temporal bone via the foramen for the lesser petrosal
• The lesser petrosal nerve leaves the middle cranial fossa via the foramen ovale. It synapses in the otic ganglion, under the foramen ovale.

Structures within the Parotid Gland

• The external carotid artery lies deep within the gland, and divides into the maxillary and superficial temporal arteries
• The retromandibular vein forms from the maxillary and superficial temporal veins. It divides into anterior and posterior divisions within the gland.
• The facial nerve runs forward, dividing into five terminal branches: temporal, zygomatic, buccal, mandibular, and cervical.
• A few parotid lymph nodes (superficial and deep) also lie within the gland.

Jaw Muscles

• These are the muscles that move the lower jaw (mandible). The upper jaw (maxilla) is fixed to the base of the skull.
• Four principal muscles: masseter, temporalis, medial pterygoid, lateral pterygoid.
• Some authorities add a fifth, the digastric. Innervated by motor fibres from the trigeminal nerve.

Facial Nerve

• Introduction: Mixed nerve – contains sensory (nervus intermedius) and motor roots, has parasympathetic function, attached to the lower border of the pons
• Course of the facial nerve: Divided by the stylomastoid foramen into intracranial and extracranial part
• Branches: Temporal, zygomatic, buccal, mandibular, cervical
• Clinical application: Facial nerve paralysis: lesion at different levels : supranuclear, nuclear & infra-nuclear : Bell's palsy (lesion in the internal acoustic meatus, genu (geniculate ganglion), distal to the genu or below stylomastoid foramen).

Testing Motor Function of the Facial Nerve

• Tell the patient to: look upwards, raise eyebrows, wrinkle forehead, close eyes tightly, puff out cheeks, grin and show teeth, contract platysma