Regional Muscle Review Will Kleinelp Associate Professor Department of Biology

HEAD & NECK MUSCLES

Digastric ORIGIN Anterior belly: digatric fossa on posterior surface of symphysis menti. posterior belly: base of medial aspect of mastoid process INSERTION Fibrous loop to lesser cornu of hyoid bone ACTION Elevates hyoid bone. Aids swallowing and depresses mandible

Mylohyoid ORIGIN Mylohyoid line on internal aspect of mandible INSERTION Anterior three quarters : midline raphe. posterior quarter: superior border of body of hyoid bone ACTION Elevates hyoid bone, supports and raises floor of mouth. Aids in mastication and swallowing

Masseter ORIGIN Anterior two thirds of zygomatic arch and zygomatic process of maxilla INSERTION Lateral surface of angle and lower ramus of mandible ACTION Elevates mandible (enables forced closure of mouth)

Sternocleidomastoid ORIGIN Anterior and superior manubrium and superior medial third of clavicle INSERTION Lateral aspect of mastoid process and anterior half of superior nuchal line ACTION Flexes and laterally rotates cervical spine. Protracts head when acting together . Extends neck when neck already partially extended

Temporalis ORIGIN Temporal fossa between inferior temporal line and infratemporal crest INSERTION Medial and anterior aspect of coronoid process of mandible ACTION Elevates mandible and posterior fibers retract

Occipitalis

Orbicularis oris ORIGIN Near midline on anterior surface of maxilla and mandible and modiolus at angle of mouth INSERTION Mucous membrane of margin of lips and raphe with buccinator at modiolus ACTION Narrows orifice of mouth, purses lips and puckers lip edges

Orbicularis oculi ORIGIN Medial orbital margin and lacrimal sac (orbital, palpebral and lacrimal parts) INSERTION Lateral palpebral raphe ACTION Closes eyelids, aids passage and drainage of tea

Buccinator ORIGIN External alveolar margins of maxilla and mandible by molar teeth, to maxillary tubercle and pterygoid hamulus and posterior mylohyoid line respectively, then via pterygomandibular raphe between bones INSERTION Decussates at modiolus of mouth and interdigitates with opposite side ACTION Aids mastication, tenses cheeks in blowing and whistling, aids closure of mouth

Scalenes (ant scalene) ORIGIN Anterior tubercles of transverse processes of C3-6 INSERTION Scalene tubercle on superior aspect of 1st rib ACTION Accessory to inspiration. lateral flexion of neck when 1st rib fixed

Splenius ORIGIN Lower ligament nuchae, spinous processes and supraspinous ligaments T1-3 INSERTION Lateral occiput between superior and inferior nuchal lines ACTION Extends and rotates cervical spine

Zygomaticus major ORIGIN Anterior surface of zygomatic bone INSERTION Modiolus at angle of mouth ACTION Elevates and draws angle of mouth laterally

Zygomaticus minor ORIGIN Lateral infra-orbital margin INSERTION Skin and muscle of upper lip ACTION Elevates and everts upper lip

Chest Abdomen & Spine

Pectoralis Major ORIGIN Clavicular head-medial half clavicle. Sternocostal head-lateral manubrium and sternum, six upper costal cartilages and external oblique aponeurosis INSERTION Lateral lip of bicipital groove of humerus and anterior lip of deltoid tuberosity ACTION Clavicular head:flexes and adducts arm. Sternal head: adducts and medially rotates arm . Accessory for inspiration

Pectoralis minor ORIGIN 3, 4, 5 ribs INSERTION Medial and upper surface of coracoid process of scapula ACTION Elevates ribs if scapula fixed, protracts scapula (assists serratus anterior)

External Oblique ORIGIN Anterior angles of lower eight ribs INSERTION Outer anterior half of iliac crest, inguinal lig, public tubercle and crest, and aponeurosis of anterior rectus sheath ACTION Supports abdominal wall, assists forced expiration, aids raising intraabdominal pressure and, with muscles of opposite side, abducts and rotates trunk

Internal oblique ORIGIN Orbital surface of maxilla behind orbital margin INSERTION Post/inferior quadrant of sclera behind equator of eyeball ACTION Elevates eye in adduction. Laterally rotates eye in abduction

Transversus abdominis ORIGIN Costal margin, lumbar fascia, anterior two thirds of iliac crest and lateral half of inguinal ligament INSERTION Aponeurosis of posterior and anterior rectus sheath and conjoint tendon to pubic crest and pectineal line ACTION Supports abdominal wall, aids forced expiration and raising intra-abdominal pressure. Conjoint tendon supports posterior wall of inguinal canal

Rectus abdominis ORIGIN Pubic crest and pubic symphysis INSERTION 5, 6, 7 costal cartilages, medial inferiorcostal margin and posterior aspect of xiphoid ACTION Flexes trunk, aids forced expiration and raise intra-abdominal pressure

Diaphragm ORIGIN Vertebral:crura from bodies of L1, 2 (left), L1-3 (right). Costal: medial and lateral arcuate ligs, inner aspect of lower six ribs . Sternal: two slips from posterior aspect of xiphoid INSERTION Central tendon ACTION Inspiration and assists in raising intra-abdominal pressure

External Intercostals ORIGIN Inferior border of ribs as far back as posterior angles INSERTION Superior border of ribs below, passing obliquely downwards and backwards ACTION Fix intercostal spaces during respiration. Aids forced inspiration by elevating ribs

Internal intercostals ORIGIN Inferior border of ribs as far back as posterior angles INSERTION Superior border of ribs below , passing obliquely downwards and backwards ACTION Fix intercostal spaces during espiration. Aids forced inspiration by elevating ribs

Erector Spinae (Sacrospinalis) ORIGIN Transverse processes INSERTION Transverse processes several levels above ACTION Extends spine