Face, Scalp & Parotid Region PDF

Scalp, Face, & Parotid Region DPM Program Learning Objectives: 1. Describe the layers of the scalp 3.0 2. Describe the lymphatic drainage from the face and scalp. 3.0 3. Describe the cutaneous innervation of the face. 3.0 4. Discuss the muscles of facial expression and their innervation. 3.0 5. Des...

Scalp, Face, & Parotid Region DPM Program Learning Objectives: 1. Describe the layers of the scalp 3.0 2. Describe the lymphatic drainage from the face and scalp. 3.0 3. Describe the cutaneous innervation of the face. 3.0 4. Discuss the muscles of facial expression and their innervation. 3.0 5. Describe the superficial temporal artery. 3.0 7. Describe the facial artery and its major branches. 3.0 8. Describe the tributaries of the internal jugular system of veins to the face. 3.0 9. Describe the parotid gland and its relationship to the facial nerve. 3.0 10. Describe the parasympathetic innervation of the parotid gland. 3.0 11. Discuss the role of the otic ganglion. 3.0 11. Describe the sympathetic innervations of the face. 3.0 12. Describe the “danger areas” of the face and scalp, nature of scalp injuries and the spread of infection through the pterygoid plexus and/or into the dural venous sinuses. 4.0 13. Define Bell's palsy. 4.0 1 The Scalp S: SKIN The skin of the scalp contains sweat and sebaceous glands and usually numerous hair follicles C: CONNECTIVE TISSUE The tissue between the skin and the aponeurotic layers is composed of dense collagenous connective tissue and contains the arteries, veins and nerves supplying the scalp. When the scalp is cut the dense connective tissue surrounding the vessels tends to hold cut vessels open, resulting in profuse bleeding. A: APONEUROSIS The superficial musculoaponeurotic system of the scalp consists of the occipitofrontalis muscle and its investing fascia. This fascia is specialized to form a tendinous epicranial aponeurosis known as the galea aponeurotica L: LOOSE CONNECTIVE TISSUE A sponge-like layer of loose connective tissue forms a subaponeurotic compartment that enables free movement of the top three scalp layers across the pericranium. It also contains the emissary veins. Infections tend to localize and spread through the loose connective tissue. P: PERICRANIUM The pericranium is the periosteum over the external surface of the skull where the fibrous tissue knits into the sutures. 2 Aponeurotic Layer of the Scalp The deepest layer of the first three layers is the aponeurotic layer. Firmly attached to the skin by the dense connective tissue of the second layer, this layer consists of the occipitofrontalis muscle, which has a frontal belly anteriorly, an occipital belly posteriorly, and an aponeurotic tendon— the epicranial aponeurosis (galea aponeurotica)— connecting the two. The occipitofrontalis muscle moves the scalp, wrinkle the forehead, and raise the eyebrows. The frontal belly is innervated by temporal branches of the facial nerve and posterior belly by the posterior auricular branch. 3 Innervation of the Scalp Sensory innervation of the scalp is from two major sources, cranial nerves or cervical nerves, depending on whether it is anterior or posterior to the ears and the vertex of the head. Branches of the trigeminal nerve [V] supply the scalp anterior to the ears and the vertex of the head. These branches include the: -supratrochlear nerve -supra-orbital nerve -zygomaticotemporal nerve -auriculotemporal nerve Posterior to the ears and vertex, sensory innervation of the scalp is by cervical nerves, specifically branches from spinal cord levels C2 and C3. These branches include the: -great auricular nerve -lesser occipital nerve -greater occipital nerve -third occipital nerve 4 5 Bones of the Viscerocranium NOTE: All bones of the skull will be studied in the laboratory session Anterior View 6 Lateral View 7 Posterior View 8 Parotid Region The parotid region is bound by the anterior border of the sternocleidomastoid posteriorly, the masseter muscle and the mandibular ramus anteriorly, and the zygomatic arch superiorly. It lies superficial to the masseter muscles. -largest of the three paired salivary glands -the parotid duct passes from the anterior edge of the gland. It pierces the buccinator muscle to open into the vestibule of the mouth opposite the 2nd upper maxillary molar. Temporal branches - passing through the parotid gland are the: - facial nerve and its branches - retromandibular vein (and tributaries) external carotid artery (and terminal branches) - preganglionic parasympathetics destined for the parotid gland exit the brain in the glossopharyngeal nerve, and synapse in the otic ganglion. Postsynaptic parasympathetic axons ‘hitchhike’ on the auriculotemporal branch of the mandibular division of trigeminal to reach the parotid gland. Zygomatic branches Facial nerve (VII) Posterior auricular artery Parotid duct Retromandibular vein Buccal branches Parotid gland Buccinator External carotid artery Masseter External jugular vein Mandibular branches Cervical branches 9 Nerve Supply to the Parotid Gland Preganglionic Parasympathetic Fibers -Originate from nerve cell bodies in the inferior salivatory nucleus and leave the brain in the glossopharyngeal nerve (cn ix). They pass through its tympanic branch to the lesser petrosal nerve and terminate in the otic ganglion by synapsing on the postganglionic parasympathetic nerve cell bodies. Postganglionic Parasympathetic Fibers -Once they exit from the otic ganglion they join the AURICULOTEMPORAL NERVE (V3) and travel to the parotid gland. 10 Cutaneous Innervation to the Face Cutaneous innervation to the face is supplied by all three divisions of the TRIGEMINAL NERVE (CRANIAL NERVE V): OPHTHALMIC DIVISION (V1) a. Supplies the skin of the forehead, upper eyelid, and nose b. Exits the cranial vault through the superior orbital fissure, as it breaks up into its branches it passes through the orbit, and then its branches exits the orbit via the orbital aperture and supraorbital notch (foramen) c. Major branches of V1 include (these will be discussed in greater detail during the orbit lecture): Lacrimal nerve, supraorbital nerve, supratrochlear nerve, infratrochlear nerve, nasociliary nerve MAXILLARY DIVISION (V2) a. Supplies the skin over an oblique area between the mouth and the eyes (includes: the lower eyelid, upper lip, alae of the nose, upper part of the cheek, and part of the temporal region) b. Exits the cranium via the foramen rotundum, enters the orbit through the inferior orbital fissure and then passes through the floor of the orbit to exit the facial skeleton by passing through a number of foramina, including the infraorbital foramen c. Major branches of V2 include: Infraorbital nerve, Zygomaticotemporal nerve, Zygomaticofacial nerve MANDIBULAR DIVISION (V3) a. Supplies the skin over the remainder of the face (i.e., skin of the chin, lower lip, lower part of the cheek, part of the auricle, and a portion of the temporal region b. Exits the cranial vault via the foramen ovale, gives off a number of branches in the infratemporal fossa, enters the mandible via the mandibular foramen as the inferior alveolar nerve which leaves the mandible through the mental foramen as the mental nerve c. Major branches of V3 include (will discuss in greater detail during the infratemporal fossa lecture): Auriculotemporal nerve, buccal nerve, Inferior alveolar nerve, Mental nerve 11 Supraorbital foramen/notch (supraorbital v.a.n) Infraorbital foramen (infraorbital v.a.n.) Mental foramen (mental v.a.n.) 12 13 Muscles of Facial Expression The muscles of facial expression are a group of thin muscles that are located within the subcutaneous tissues of the face, neck, and the anterior and posterior scalp. These muscles are unique as they are attached to the skin and thus they produce movements for facial expression. Superficial Deep 14 Orbital Group Muscle Innervation Function 1) Palpebral part Facial nerve [VII] Closes the eyelid gently and some wrinkling of the forehead 2) Orbital part Facial nerve [VII] Closes the eyelid forcefully Orbicularis oculi 15 Nasal Group Muscle Innervation Function Nasalis Facial nerve [VII} Compresses and dilates nasal apertures 16 Muscles- Mouth Found on next page Muscle Function Orbicularis oris Closes lips; protrudes lips Buccinator Presses the cheek against teeth; compresses distended cheeks Zygomaticus major Draws the corner of the mouth upward and laterally Zygomaticus minor Draws the upper lip upward Levator labii superioris Elevates upper lip; some talented individuals are able to use this muscle to evert their upper lip like chimpanzees Risorius Retracts angle of mouth (i.e., widens mouth) such as in grinning, expressions of mirth, pleasure, or joy Levator anguli oris Elevates angle of mouth Depressor anguli oris Depresses angle of mouth (frowning) Depressor labii inferioris Depresses (e.g, displeasure, disgust) and everts (pouts) lower lip Mentalis Assists in protrusion of lower lip Platysma Tenses skin of the neck; draws the corners of the mouth inferiorly (sadness, frowning) assists in depressing mandible ** All muscles innervated by Facial nerve (CN VII) 17 Muscles- Mouth 18 Facial Nerve Paralysis (Bell’s Palsy; Facial Palsy) Definition: A unilateral paralysis of the facial muscles supplied by the facial nerve Clinical Signs: -Asymmetry of the face with smoothing out of skin folds (i.e., masklike appearance) on the affected side. Marked asymmetry upon attempting to smile -Muffled speech -Food and saliva tend to collect between the affected cheek and the teeth -Sagging of the corner of the mouth with a tendency to drool. Food tends to dribble out of the affected side of the mouth. -Eye on affected side cannot be closed; lower lid tends to droop away from the eyeball -Inability to raise eyebrow or to wrinkle skin of forehead on affected side Tests for Facial Nerve Function: a) Request the patient to perform the following: 1) Raise their eyebrows (results from the paralysis of the Frontalis portion of Occipitofrontalis) 2) Close their eyelids tightly 3) Smile 4) Whistle 5) Pull the corners of their mouth inferiorly (i.e., an exaggerated frown) so as to raise skin of the neck (i.e., contraction of Platysma) 19 Arteries and Veins of the Face The face receives a rich supply of blood from the branches of the External Carotid Artery. The veins of the face follow the arteries: Facial Artery -arises directly from external carotid a. -appears at the inferior border of the mandible (where a pulse can be palpated) just anterior to the Masseter muscle and parotid gland. It runs obliquely to the angle of the eye Facial Vein -primary venous drainage of face -formed by union of supraorbital and supratrochlear veins and drains into internal jugular vein Superficial Temporal Artery -one of the terminal branches of external carotid artery (the other is maxillary artery; will be discussed in infratemporal fossa lecture) -supplies the temporal region of the face and scalp -gives off the transverse facial artery before it crosses the zygomatic arch (anastomoses with facial artery) Superficial Temporal Vein -the maxillary vein drains superficial temporal vein to form the retromandibular vein. Retromandibular vein drains into two branches; one passes anteriorly to join the internal jugular vein. The other joins the posterior auricular vein to form the external jugular vein which drains into subclavian vein. 20 21 22 Danger Area of the Face Triangular area of the face including the external nose and the upper lip The facial vein is unvalved and makes important connections with the cavernous sinus through the superior and inferior ophthalmic veins (in the orbit) and also through the pterygoid plexus (in the infratemporal fossa). Consequently, this represents a very important route for the possible spread of infection from the external face to the cranial vault. 23 Lymphatic Drainage of the Face & Scalp SUBMENTAL NODES Two to three nodes which like in the Mylohyoid muscle between the anterior bellies of the Digastric muscles (i.e., under the chin) -Drain lower lip, chin, and tip of tongue -Drain to the submandibular nodes SUBMANDIBULAR NODES Three to six nodes along the inferior border of the submandibular gland -Receives lymph from submental nodes (see above) -Drain upper lip, lateral part of lower lip, side of tongue, chin, nose and nasal fossae, cheeks, gums, lower surface of palate, and sublingual and submandibular glands -Drain to the deep cervical nodes PAROTID NODES A number of nodes associated with the parotid gland -Drain lateral part of the face and eyelids -Drain to the deep cervical nodes -The anterior & lateral scalp drains into parotid nodes OCCIPITAL NODES Posterior scalp drains into these nodes (overly the superior nuchal line) 24