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Muscular System

Explore the origin, insertion, and action of major muscles in the human body, from the scalp to the posterior thorax. Learn about the muscles of facial expression, mastication, and various neck and thoracic muscles, including their functions and anatomy.

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Muscular System

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  1. Muscular System Origin, Insertion, Action

  2. Muscles of the Scalp • Occipitofrontalis • Frontal Belly • Occipital Belly

  3. Frontalis • O: Galea aponeurotica • I: Skin of eyebrows • A: Raises eyebrows, wrinkles forehead skin

  4. Occipitalis • O: Occipital Bone • I: Galea aponeurotica • A: Pulls scalp posterior

  5. Muscles of Facial Expression

  6. Orbicularis Occuli • O: Frontal and Maxillary bones • I: Tissue of eyelid • A: Blinking, squinting

  7. Orbicularis Oris • O: Maxilla and Mandible • I: Encircles mouth, angles of mouth • A: Closes lips, purses and protrudes lips (kissing and whistling)

  8. Muscles of Mastication

  9. Masseter • O: Zygomatic arch and maxilla • I: Mandible • A: Closes jaw by elevating mandible

  10. Temporalis • O: Temporal fossa • I: Coronoid process of mandible • A: Closes jaw (elevates and retracts mandible)

  11. Buccinator • O: Maxilla and mandible • I: Orbicularis oris • A: Compresses cheek (whistling and sucking), holds food between teeth (during chewing)

  12. Muscles of the Anterior Neck and Throat (Swallowing) • Digastric • All of the muscles that attach to the hyoid

  13. Digastric • O: Mandible and mastoid process • I: Hyoid bone • A: Elevate hyoid during speech and swallowing, • Open mouth and depress mandible

  14. Anterolateral Neck Muscles

  15. Sternocleidomastoid • O: Sternum and Clavicle • I: Mastoid process of temporal bone • A: B/l – head flexion; unilateral – laterally flex towards and rotates away from itself

  16. Scalenes • O: Transverse processes of cervical vertebrae • I: 1st two ribs • A: elevate first two ribs (inspiration), flex and rotate neck

  17. Intrinsic Muscles of the Back

  18. Splenius Capitus • O: Ligamentum nuchae, spinous processes of C7 – T-6 • I: Occipital bone, mastoid process of temporal bone • A: b/l – extend head; unilateral – lateral flex and rotate towards

  19. Splenius Cervicis • O: Ligamentum nuchae, spinous processes of C7 – T-6 • I: Transverse Processes of C2 – C4 • A: b/l – extend neck; unilateral – lateral flex and rotate towards

  20. Erector Spinae (Sacrospinalis) • Iliocostalis (Most lateral) • Longissimus (Intermediate) • Spinalis (Most medial)

  21. Iliocostalis • O: iliac crest (lumborum); inferior 6 ribs (thoracis); ribs 3 to 6 (cervicis) • I: ribs (lumborum and thoracic); TPs of C6-C4 (cervicis) • A: B/L - Extend spine, posture; unilateral – lateral flex towards

  22. Longissimus • O: TPs of vertebrae • I: Superior TPs and superior ribs; capitis portion inserts on Mastoid process • A: B/L – extend spine; unilateral – laterally flex; capitis portion extends head and rotates towards

  23. Spinalis • O: Spines of upper lumbar and lower thoracic vertebrae • I: Spines of upper thoracic and cervical vertebrae • A: Extends spine, maintains erect posture

  24. Quadratus Lumborum • O: Iliac crest • I: TPs of upper lumbar vetebrae and 12th rib • A: Unilaterally – laterally flexes spine; b/l – extends L-spine

  25. Muscles of the Thorax (Breathing)

  26. External Intercostals • O: Inferior border of rib above • I: Superior border of rib below • A: Pull ribs toward one another, elevate rib cage; INSPIRATION • Fibers run down and anterior

  27. Internal Intercostals • O: Superior border of rib below • I: inferior border of rib above • A: Draw ribs together and depress rib cage; EXPIRATION • Fibers run down and posterior

  28. Diaphragm • O: Inferior surface of rib cage and sternum, costal cartilages, lumbar vertebrae • I: Central tendon • A: Flattens on contraction; Prime mover of Inspiration

  29. Muscles of the Anterior and Lateral Abdominal Wall

  30. Rectus Abdominus • O: Pubic crest and symphysis • I: Xiphoid process and costal cartilages ribs 5-7 • A: Flex and rotate lumbar region, stabilize pelvis during walking

  31. External Oblique • O: Outer surfaces of lower eight ribs • I: Linea alba • A: B/L – aid in trunk flexion; unilateral – trunk rotation and lateral flexion

  32. Internal Oblique • O: Lumbar fascia, iliac crest • I: linea alba, pubic crest, costal margin last 3 – 4 ribs • A: B/L – aid in trunk flexion; unilateral – trunk rotation and lateral flexion

  33. Transverse Abdominus • O: Inguinal ligament, lumbar fascia, cartilage of last 6 ribs, iliac crest • I: Linea alba, pubic crest • A: Compresses abdominal contents

  34. Muscles of the Anterior Thorax

  35. Pectoralis Minor • O: Anterior surface of ribs 3-5 • I: Coracoid process of scapula • A: Ribs fixed – draws scapula forward and down; scapula fixed – draws rib cage superior

  36. Muscles of the Posterior Thorax

  37. Trapezius • O: Occipital bone, ligamentum nuchae, spines from C7 to T12 • I: Acromion and spine of scapula, lateral 1/3 of clavicle • A: Superior – elevates scapula; middle – retract (adduct) scapula; inferior – depress scapula

  38. Levator Scapulae • O: Transverse processes of C1 – C4 • I: Medial border of scapula (superior to spine) • A: Elevates / adducts scapula, flexes neck to same side

  39. Rhomboids • O: Spinous processes of C7 – T5 • I: Medial border of scapula • A: Retract (adduct) scapula, stabilize scapula

  40. Muscles Crossing the Shoulder Joint

  41. Pectoralis Major • O: Sternal end of clavicle, sternum, cartilage ribs 1-6 • I: Greater tubercle of humerus • A: Flexes arm, medially rotates arm, adducts arm (climbing, throwing, pushing)

  42. Latissimus Dorsi • O: Fascial connection to spines of T7 – L5, lower 3-4 ribs, iliac crest • I: Intertubercular sulcus of humerus • A: Arm extension, arm adductor, medially rotates arm (hammering, swimming)

  43. Deltoid • O: Embraces insertion of trapezius; lateral third of clavicle, acromion, spine of scapula • I: Deltoid tuberosity of humerus • A: Abducts arm; anterior fibers – flexion, medial rot.; posterior fibers – extension, lateral rot.

  44. Rotator Cuff Muscles • SITS • Suprapinatus • Infraspinatus • Teres Minor • Subscapularis

  45. Supraspinatus • O: Supraspinous fossa of scapula • I: Greater tubercle of humerus • A: Stabilizes shoulder joint. Prevents downward dislocation. Initiates shoulder abduction.

  46. Infraspinatus • O: Infraspinous fossa of scapula • I: Greater tubercle of humerus posterior to supraspinatus insertion • A: Holds head of humerus in glenoid cavity, shoulder stabilization

  47. Teres Minor • O: Lateral border of scapula (dorsal surface) • I: Greater tubercle of humerus inferior to infraspinatus insertion • A: Stabilize shoulder, adducts arm

  48. Subscapularis • O: Subscapular fossa of scapula • I: Lesser tubercle of humerus • A: Medial rotation of humerus, stabilizes shoulder joint

  49. Teres Major • O: Inferior angle of scapula • I: Intertubercular sulcus of humerus • A: Extends, medially rotates, and adducts humerus

  50. Coracobrachialis • O: Coracoid process of scapula • I: Medial humerus • A: Flexion and adduction of humerus

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