Muscles of Mastication UCLH PDF

Muscles of mastication Miss H Rogers GDC ILOS  1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their application to patient management  1.1.6 Describe relevant and appropriate physiology and explain its application to patie...

Muscles of mastication Miss H Rogers GDC ILOS  1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their application to patient management  1.1.6 Describe relevant and appropriate physiology and explain its application to patient management Related topics:  Anatomical terminology  Muscles  Muscles of facial expression  Skull and its landmarks  Regional anatomy 2 Aim To gain an overview of the muscles involved in the process of mastication, and their functions Learning Outcomes By the end of this lecture you should be able to: 1.List the muscles of mastication 2.Describe the origin, insertion, action, innervation and blood supply of each muscle 3 What are the muscles of mastication? The muscles of mastication join to the mandible allowing for its movement during processes such as chewing and grinding They allow the mandible to move in 5 main ways, do you know what these are? Hint: Try moving your own mandible!  Forwards (Protrusion)  Backwards (Retraction)  Up/close (Elevation)  Down/open (Depression)  Side-to-side (Rotation) 4 Why do we need to know these muscles?  Impact of ID Block through muscle (bruising/post treatment discomfort)  Pain during mastication  Trismus (e.g. difficulty opening following radiotherapy)  Clenching and grinding- potentially stress related (masseter pain) 5 Grab a mirror and get ready to pull some funny faces as we test out your muscles! 6 Principle Muscles of Mastication Masseter A thick quadrilateral muscle consisting of two parts: 1. Superficial 2. Deep  Origin:  Origin: Arises from the anterior two- Arises from the posterior third thirds of the lower border of of the lower border and the the zygomatic arch whole of the medial surface of the zygomatic arch  Insertion:  Insertion: The fibres pass downwards The fibres pass downwards and and backwards to be backwards to be inserted on inserted on the outer surface the ramus above the angle of of the ramus of the mandible the mandible (superior to the superficial part) 8 Action Fibres contract to close mouth/elevates Nerve Supply Masseteric nerve (anterior division of the mandibular nerve) Blood Supply Facial branch of the superficial temporal artery Masseteric branch of the maxillary artery 9 Temporalis A fan shaped muscle situated on either side of the head Origin Fibres arise from the whole of the temporal fossa that is bound at the top by the inferior temporal line These fibres converge as they descend into a tendon which passes through a gap between the zygomatic arch and the side of the head 10 Insertion The top and medial surface of the coronoid process, and the anterior border of the ramus of the mandible Action Anterior fibres run vertically and contract to elevate the mandible Posterior fibres run obliquely and horizontally contracting to elevate the mandible and retract the head of the condyle back into the glenoid fossa 11 Nerve Supply Anterior and posterior deep temporal nerves (anterior division of the mandibular nerve) Blood Supply Middle temporal branch of the superficial temporal artery Deep temporal branches of the maxillary artery 12 Lateral Pterygoid A short, thick muscle, triangular in shape arising from 2 heads: 1. Upper Head 2. Lower Head  Origin  Origin The infratemporal surface and The lateral surface of the crest of the greater wing of lateral pterygoid plate of the sphenoid bone sphenoid bone Insertion The fibres merge and insert into the pterygoid fovea on the anterior aspect of the neck of the mandible. Some fibres may insert with structures of the TMJ. 13 Action Bilateral contraction- opens and protrudes the mouth. When the two pterygoid muscles on one side of the head act alternately with those of the other side, grinding or side to side movement is produced Nerve Supply Lateral pterygoid nerve (anterior branch of the mandibular nerve) Blood Supply Pterygoid branches of the maxillary artery 14 Medial Pterygoid A thick quadrilateral muscle Origin Arises by two heads:  Large Deep Head- from the medial surface of the lateral pterygoid plate of the sphenoid bone  Small Superficial Head- from the tuberosity of the maxilla, and pyramidal process of the palatine bone 15 Insertion The fibres pass downwards, backwards and laterally to be inserted into the medial surface of the ramus and angle of the mandible (below and behind the inferior dental foramen) Action Elevates the mandible and, in conjunction with the lateral pterygoid muscle, protrudes the mandible Nerve Supply Medial pterygoid branch of the mandibular nerve Blood Supply Pterygoid branches of maxillary artery 16 17 Accessory Muscles of Mastication 18 Digastric Origin Insertion Meet above the hyoid bone at  Anterior Belly- arises from the the intermediate tendon. This digastric fossa on lower is held by a fibrous sling border of the mandible. anchoring it to the body of the hyoid bone.  Posterior Belly- arises from the digastric notch on the mastoid process of temporal bone 19 Action Depression of the mandible Elevate the hyoid bone during chewing and swallowing Nerve Supply Anterior Belly- mylohyoid nerve Posterior Belly- digastric branch of the facial nerve VII Blood Supply Anterior Belly- submental branch of facial artery Posterior Belly- posterior auricular/occipital artery 20 Buccinator This muscle forms the cheek Origin Pterygomandibular raphae and buccal alveolar bone (in maxillary and mandibular molars regions) Insertion Fibres run horizontally blending with the Orbicularis Oris at the corners of mouth 21 Action Pulls corner of the mouth back and compresses cheek against the buccal surfaces of molars Muscle regulates the vestibular region with the tongue keeping food between teeth during mastication Nerve Supply Facial Nerve, buccal branch Blood Supply Facial & maxillary arteries 22 Geniohyoid A narrow muscle situated above the medial part of the mylohyoid line Origin Arises from the inferior genial tubercle Insertion Fibres run downwards and backwards into the body of the hyoid bone 23 Action Aids in deglutition and opening the mouth by depressing the mandible Nerve Supply Hypoglossal Nerve Blood Supply Sublingual branch of the lingual artery 24 Genioglossus Origin Arises from the superior genial tubercle on the inner surface of the mandible Insertion Enters the dorsum of the tongue where it forms a large fan shaped muscle Superior fibres pass upwards to the tip of the tongue. Inferior fibres insert on to the body of the hyoid bone 25 Action Depresses of the tongue Inferior fibres retract the tongue Superior fibres protrude the tongue Nerve Supply Hypoglossal nerve Blood Supply Sublingual branch of the lingual artery Submental branch of the facial artery 26 Summary You can use the summary table to consolidate the muscles of mastication, or add them to a table you already have. 27 Additional Resources Websites https://www.kenhub.com/en/library/anatomy/the-muscles-of-mastication https://geekymedics.com/muscles-of-mastication/ YouTube Sam Webster-Muscles Temporomandibular joint & muscles of mastication [Warning: he shows a dead bird at the start- not sure why!] https://youtu.be/hlXh-lhV4ZY Muscles of facial expression and mastication https://youtu.be/EUVD8cwKfFQ Journal Soboleva, U., Laurina, L., and Slaidina, A. (2005). The masticatory system – an overview. Baltic Dental and Maxillofacial Journal. (7) 77-80. Available at: https://sbdmj.lsmuni.lt/053/053-03.pdf 28 References  Kenhub.com. 2020. Facial Muscles. [online] Available at: https://www.kenhub.com/en/library/anatomy/the- facial-muscles [Accessed 2 December 2020].  Teachmeanatomy.info. 2021. The Muscles of Mastication. [online] Available at: https://teachmeanatomy.info/head/muscles/mastic ation/ [Accessed 20 October 2021] 29