Muscles of Facial Expression Sumamry We all like to pull silly faces from time to time - but how do we do that? It is important that you know the muscles of facial expression... Definitions Medial: Towards the midline/middle Distal: Towards the back/away from the midline Lateral: Side of bone/muscle/etc that is furthest away from the midline (when something lays close to the outside of the head and neck) Inferior: Below/lower than Superior: Above/higher than Anterior: In front of/most in front Posterior: Behind/furthest back IntroductionReviseDental.com There are many muscles of facial expression, and many sources differ when discussing the key ones. This covers the main aspects of the muscles of facial expression, and will divide them into manageable groups. All muscles of facial expression are derived from the 2nd pharyngeal arch and are supplied by motor control by the Facial Nerve (CN VII). These muscles all insert into areas of the skin to control its movement. Diagram showing the Muscles of Facial Expression Note: The modiolus is a 'knot' of several facial muscles, near the angle of the mouth. ReviseDental.com Tables of Key Points General Muscle Origin Insertion Action Other Buccinator ridge on Controls food Angle of mouth Creates Alveolar process of synergistically with and lateral portion sucking Buccinator Mandible and Maxilla tongue + provides of upper and action and Maxilla: Pterygomandibular muscular structure of lower lips controls bolus raphe cheek. ReviseDental.com ReviseDental.com Image illustrating the Buccinator muscle Muscle Origin Insertion Action Other Incisive fossa of Skin of chin/lower Elevation and protrusion of Used in Mentalis Mandible lip lower lip and skin of chin 'pouting'. ReviseDental.com ReviseDental.com Image illustrating the Mentalis muscle Auricular Muscle Origin Insertion Action Anterior auricular Anterior part of temporal fascia Helix of ear Draws ear forwards Epicranial aponeurosis on side Superior auricular Upper part of auricle Elevates ear of head Mastoid process of temporal Convexity of concha of Draws ear upward and Posterior auricular bone ear backward ReviseDental.com Image illustrating the Auricular muscles These muscles tend to be involuntary and can be very small movements. Orbital Muscle Origin Insertion Action Other Fibres form Medial palpebra ligament + muscle around Orbicularis oculi Forceful closure frontal process of maxilla + the orbit and – orbital of eyelid nasal portion of frontal bone attach to overlying skin Orbicularis oculi Medial palperbral ligament Lateral palpebral Gentle closure of – palpebral and lacrimal bone raphe eyelid Orbicularis oculi - Lacrimal bone Lacrimal fascia Aids tears Lacrimal Draws eyebrows Superciliary together - Posterior to Corrugator arch/Supraorbital ridge of Skin of eyebrow frowning orbicularis Supercilii frontal bone (medially and oculi inferiorly) ReviseDental.com Image illustrating the Orbital muscles Nasal Muscle Origin Insertion Action Other Nasal bone + Wrinkles skin over Skin overlying bridge of the Procerus lateral nasal the bridge of the nose cartilage nose Brings septum Nasal bone Antagonistic to Depressor Septi Maxilla forward to aponeurosis/Nasal septum Dilator Naris constrict nostril Nasalis – Dilator Maxilla Nostril cartilage Flares nostrils Naris Nasalis - Its counterpart on the other Maxilla Constricts nostrils Compressor Naris side of the face Image illustratingReviseDental.com the Nasal muscles Oral Muscle Origin Insertion Action Other Anteromedial surface of Skin and fascia Compression and Used to purse Orbicularis oris maxilla and mandible + of lips protrusion of lips lips shut modiolus Levator Anguli Angle of the Elevation of angle Canine fossa of maxilla oris mouth of the mouth Angle of mouth Anterolateral part of Pulls angle of Antagonises Depressor and blends with inferior border of mandible mouth laterally elevator anguli anguli oris fibers of (near external oblique line) and downward oris orbicularis oris Zygomaticus Zygomatic bone (in front of Raise upper lip, Inserts more into Angle of mouth major zygomaticotemporal suture) smiling angle of mouth Above major, Zygomaticus Zygomatic bone (in front of Raise upper lip, Inserts into Upper lip minor zygomaticotemporal suture) smiling middle part of upper lip Aids in grimacing Facsia of lateral cheek and Skin of angle of Risorius by pulling corners parotid mouth of mouth laterally Important when Levator Labii Infra-orbital margin of Skin of upper Elevation of upper administering Superioris maxilla lip lip infraorbital injections Middle portion Anterolateral part of body of lower lip; Pulls lip Depressor Labii of Mandible (below mental blends with downwards and Inferioris foramen) fibres of other laterally side Levator labii Skin of lateral Upper frontal process of Lifts upper lip + Also dilates the superioris part of nostril maxilla nose nose alequae nasi and upper lip ReviseDental.com images illustrating the Oral Muscles Scalp Muscle Origin Insertion Action Other Pulls back scalp, Galea aponeurotica of Subcutaneous tissue in Wrinkles scalp – attached to region of forehead and forehead, Has no bony Occipitofrontalis overlying dense CT eyebrows (galea Elevates attachment and skin aponeurosis) eyebrows and skin of forehead ReviseDental.com ReviseDental.com Image illustrating the Occipitofrontalis Muscle Notes: This muscle can sometimes be split into the occipitalis and frontal. In this case, the origin of the occipitalis is classed as the mastoid process + superior nuchal line (1). The Layers of the Scalp (1) An easy way to remember the layers of the scalp, is that it is its own mnemonic: S = Skin Contains hair follicles Thickest layer C = Connective tissue Vascularised portion of scalp Emissary veins connect here via venous sinuses (1) - this allows spread of infection A = Aponeurosis (Galea aponeurosis) Continuous with Occipitofrontalis muscle. Therefore, if this layer is disrupted (eg. wound/surgery), it will gape open. Blends with temporal fascia L = Loose areolar connective tissue Thin + moves easily Extends from eyebrows to superior nuchal line. Allows bacteria and blood to pass freely. P = Pericranium Covers cranium Neck See 'The Neck'ReviseDental.com lesson for more detail on the muscles involved. In terms of innervation by the facial nerve and a muscle of facial expression, the platysma muscle is considered part of this group. Muscle Origin Insertion Action Other External jugular vein lies Fascia of pectorals Inferior border of the Wrinkles skin of Platysma beneath the platysma and deltoid muscles mandible the neck. (1) ReviseDental.com ReviseDental.com Image illustrating the muscles of Facial Expression Conclusion We work around the head and neck muscles everyday, so it is important to know where they are and how they work. As you can see, the muscles of facial expression are an important group, not only for patient movement, but to identify parafunction in the Facial Nerve (CN VII) or if an ID block has been administered too distally. You should now be aware of which muscle is affected if a movement cannot be elicited. Move onto the next lesson to cover the next group of muscles: The Muscles of Mastication. Third Party Links https://teachmeanatomy.info References Books: 1. Norton NS. Netter's head and neck anatomy for dentistry e-book. Elsevier Health Sciences; 2016 Sep 13 2. Atkinson ME. Anatomy for dental students. Oxford University Press; 2013 Mar 14. 3. Berkovitz BK, Holland GR, Moxham BJ. Oral Anatomy, Histology and Embryology E-Book. Elsevier Health Sciences; 2017 Jul 11. Please note: The images in this lesson are original drawings and have been used by collating and averaging images from the sources above. This content has been written by and uploaded to ReviseDental.com. It is the work of the author and should not be reproduced without express prior permission from the author through ReviseDental.com. © Revise Dental. All rights reserved. ReviseDental.com.