Chapter 8 Muscles of the Head and Neck Superficial Muscles facial expression muscles of the Head All innervated by facial nerve Muscles of the Scalp Occiptofrontalis two bellies frontal and occipital connected by galea aponeurotica five groups Frontal belly raises the eyebrow active in formation of transversal wrinkling of the forehead expression of astonishment active during movements of auricle Occipital belly drawing back of galea aponeurotica active during smiling and yawning can be Temporoparietalis muscles around the ear also called auricle muscle Muscles around the Eye Orbicularis Oculi Muscle three parts orbital outer part thick encircles region palpebral part thin and covers tarsal plate eyelid lacrimal part deep medial contraction forms wrinkles and folds creating an expression of concern and worry leads to Crow s feet Orbital part closes eye tightly Palpebral part closes the eye lightly protects superficial structures of eye Lacrimal part pulls eye medially and may help in expelling tears from lacrimal sac Corrugator Supercilii creates vertical folds thinker s brow expression contraction brings the skin and the eyebrow down medially protecting eye against light Muscles around the Nose Procerus contraction forms wrinkles on the skin of the bridge of the nose Nasalis transverse part from maxilla to dorsum of nose alar part maxilla to alar cartilage and skin of naris Involved in respiration Transverse part compresses nostril Alar part dilates nostril giving expressions of desire demand and sensuousness Levaotr Labii Superioris Alaeque Nasi elevates upper lip and nasal wing that opens nostrils can present an expression of displeasure Muscles around the Mouth Levator Labii Superioris medial fibers may intermingle with the alar part of the nasalis Zygomaticus Minor aids the function of the zygomaticus major contraction deepens the nasolabial groove Zygomaticus Major some fibers intermingle with the depressor anguli oris elevates the angle of the mouth while smilng and laughing Levator Anguli Oris helps elevate angle of mouth Orbicularis Oris Muscle no bony attachment helps during eating and drinking contraction closes the lips aids in sucking Risorius aids in laughing with zygomaticus major Buccinator forms lateral wall of oral cavity pulls angle of mouth upward compresses cheek helps in holding food between teeth while chewing aids in blowing air out of the mouth keeps the mucous membrane of the cheek free of folds contraction gives expression of satisfaction Depressor Anguli Oris pulling angle of mouth down and giving an expression of sadness Depressor Labi Inferioris contraction brings down lower lip Mentalis contractions form wrinkles in chin can aid in pushing up lower lip Platysma contraction depresses the angle of the mouth Muscles of Mastication All innervated by their own respective branches of mandibular nerve Temporalis Elevation of lower jaw Masseter elecation of the mandible and closing the jaw Lateral Ptyerygoid two heads mandibular movements guiding muscle Medial Ptyerygoid elevates the mandible and pushes it forward Muscles of the Neck Sternocleidomastoid unilateral contraction turns head to opposite side and bends ipsilaterally bilateral contraction lifts head aids in respirtation by elevating upper part of thorax Innervation accessory nerve CN XI and C2 C3 for proprioception and pain Trapezius belongs to cranial muscle group that inserts on shoulder girdle supports shoulder and scapula shrugging the shoulders help in slight elevation of arm via superior fibers pull scapula and clavicle toward vertebrae making retratction of scapula possible all parts superior and inferior parts also rotate scapula and adduct arm Innervation Spinal root of accessory nerve motor innervation C3 C4 nerves involved in seneory information proprioception and pain Cervical Plexus innervates skin and several muscles of infrahyoid originates from C1 C4 roots includes upper and lower roots of the cervical ansa lesser occipital nerve greater auricular nerve transverse cervical nerve the supraclavicular nerves and the phrenic nerve Suprahyoid Muscles Digastric Muscle raises hyoid bone and stabilizes it during speaking and swallowing brings down mandible Innervation anterior belly nerve to mylohyoid by branch of mandibular nerve CN V posterior belly branch of facial nerve CN VII Stylohyoid Muscle elevates and retracts hyoid bone elongates floor of mouth Innervation cervical branch of facial nerve Mylohyoid Muscle elevates the hyoid and the floor of the mouth and tongue during swallowing and speaking Innervation mylohyoid nerve originating from inferior alveolar branch of mandibular n Geniohyoid Muscle pulls hyoid bone anterosuperiorly shortens the floor of the mouth widens pharynx Innervation C1 via hypoglossal nerve Infrahyoid Muscles contraction lowers hyoid bones bringing it closer to the thyroid cartilate All innervated by cervical ansa C1 C3 of cervical plexus Omohyoid Muscle depresses hyoid opens mouth helps in lateral flexion of head it s a fascia tensor and dilates the internal jugular vein helps return to the heart Sternohyoid Muscle Sternothyroid Muscle Thyrohyoid Muscle Deep Muscles of the Neck Paravertebral Muscles Rectus capitis anterior head flexion innervated by C1 Longus capitis head flexion and turning of head innervated by C1 C4 nerves Longus colli flexion of cervical spine innervated by C1 C8 nerves Scalene Muscles assist in respiration movement of thoracic cage by elevating upper ribs can bend the neck Subclavian artery brachial plexus run through scalene gap formed by latter two muscles