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The muscular system

Explore how skeletal muscles work together or in opposition, with prime movers, antagonists, synergists, and fixators. Learn about skeletal muscle names, organization, and head and neck muscle functions. Discover the classification and arrangement of muscle fibers.

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The muscular system

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  1. The muscular system PART A

  2. Interactions of Skeletal Muscles • Skeletal muscles work together or in opposition • Muscles only pull (never push) • As muscles shorten, the insertion generally moves toward the origin • Whatever a muscle (or group of muscles) does, another muscle (or group) “undoes

  3. Muscle Classification: Functional Groups • Prime movers – provide the major force for producing a specific movement • Antagonists – oppose or reverse a particular movement • Synergists • Add force to a movement • Reduce undesirable or unnecessary movement

  4. Muscle Classification: Functional Groups • Fixators – synergists that immobilize a bone or muscle’s origin

  5. Names of skeletal muscles • Names give clues to muscle characteristics • Location: femoris, temporalis, etc • Fascicle organization: rectus, oblique, etc • Relative position: profundus, superficialis, etc • Structure: biceps, triceps, etc

  6. Names of skeletal muscles • Size: maximus, longus, etc • Shape: trapezius, deltoid, etc • Origin and insertion: sternocleidomastoid, etc • Action: flexor, pronator, etc

  7. Organization of skeletal muscle fibers • Parallelmuscle • Convergent muscle • Pennate muscle • Unipennate • Bipennate • Multipennate • Circular muscle (sphincter) • Fusiform

  8. Arrangement of Fascicles

  9. Muscles of the Head

  10. Muscles of the Head

  11. Muscles of the Head • Facial expression muscles • Orbicularis oris • O: maxilla and mandible • I: lips • A: compresses lips • Buccinator • O: maxilla and mandible • I: orbicularis oris • A: compresses the cheek (whistling)

  12. Muscles of the Head • Occipitofrontalis muscles • Occipital • O: occipital bone • I: galea aponeurotic • A: pulls the scalp posteriorly • Frontalis • O: galea aponeurotic • I: skin of the eyebrow • A: raise the eyebrow

  13. Muscles of the Head • Orbicularis oculi • O: frontal and maxillary bones • I: eyelid • A: closes eyes • Corrugator supercilli • O: frontal bone • I: skin of eyebrow • A: draws eyebrow inferiorly and medially

  14. Muscles of the Head • Levator labii superioris • O: zigomatic and maxilla bone • I: upper lip • A: raises upper lips • Depressor labii inferioris • O: mandible • I: lower lip • A: pulls lower lip inferiorly

  15. Muscles of the Head • Depressor anguli oris • O: mandible • I: angle of mouth • A: pulls corner of mouth down and laterally • Mentalis • O: mandible • I: skin of chin • A: protudes lower lip

  16. Muscles of the Head • Zigomatics • O: zigomatic bone • I: corner the mouth • A: smiling muscle • Risorius • O: masseter • I: angle of the mouth • A: pulls corner of lips laterally

  17. Muscles of Mastication

  18. Muscles of Mastication

  19. Muscles of Mastication • Masseter muscles • O: zigomatic and maxilla bones • I: mandible • A: closes the jaw • Temporalis muscles • O: temporal fossa • I: mandible • A: closes the jaw

  20. Muscles of Mastication • Pterygoids • O: sphenoid, palatine and maxillary bones • I: mandible • A: elevates mandible • Buccinator

  21. Extrinsic muscles of the eye

  22. Extrinsic muscles of the eye • Inferior and superior rectus muscles • Lateraland medial rectus muscles • Inferior oblique muscles • Elevates the eye and turns it laterally • Superior oblique muscles • Depresses the eye and turns it laterally

  23. Summary of Cranial Nerves and Muscle Actions Figure 15.3c

  24. Muscles of the Neck

  25. Muscles of the Neck

  26. Muscles of the Neck • Platysma • O: fascia of chest and deltoid • I: mandible, skin, corner of the mouth • A: depresses mandible, pulls lip back and down • Sternocleidomastoid • O: manubrium and clavicle • I: temporal and occipital bones • A: flexion forward of the neck

  27. Muscles of the Neck • Scalenes – anterior, middle, posterior • O: cervical vertebrae • I: first 2 ribs • A: elevates first 2 ribs • Digastric • O: mandible and mastoid process • I: hyoid • A: elevates hyoid bone

  28. Muscles of the Neck • Mylohyoid • O: mandible • I: hyoid bone • A: elevates hyoid bone • Sternohyoid • O: manubrium and clavicle • I: hyoid bone • A: depresses hyoid bone

  29. Muscles of the Thorax • Muscles inserting on the scapula: • Rhomboid muscles • O: vertebrae • A: adducts and stabilizes scapula • Levator scapulae muscles • O: vertebrae • A: elevates scapula

  30. Muscles of the Thorax

  31. Muscles of the Thorax • Abductors of the shoulder joint: • Deltoid muscles(major abductor) • O: clavicle and scapula • I: humerus • Supraspinatus muscles • O: scapula • I: humerus

  32. Muscles of the Thorax

  33. Muscles of the Thorax • Lateral rotation of the shoulder joint: • Infraspinatus muscles • O: scapula • I: humerus • Teres minor muscles • O: scapula • I: humerus

  34. Muscles of the Thorax • Medial rotators of the shoulder joint • Teres major muscles • O: scapula • I: humerus (anterior surface)

  35. Muscles of the Thorax

  36. Muscles of the Thorax • Origin on the ribs and insertion on the scapula: • Serratus anterior muscles • A: fixates, protracts the scapula • Pectoralis minor muscles • A: ribs fixed: moves scapula forward and inferiorly and with scapula fixed it moves up the rib cage

  37. Muscles of the Thorax

  38. Muscles of the Thorax • Flexion of the shoulder joint (agonist): • Pectoralis major muscles • O: clavicle, sternum, ribs, external oblique muscle • I: humerus • Extension of the shoulder joint (agonist): • Latissimus dorsi muscles • O: vertebrae, ribs, ilium • I: humerus

  39. Muscles of the Thorax

  40. Muscles of the Thorax

  41. Muscles of respiration • External intercostal • O: rib above • I: rib below • A: elevates rib cage • Internal intercostal • O: rib below • I: rib above • A: depresses rib cage

  42. Muscles of Respiration

  43. Muscles of Respiration

  44. Muscles of Respiration • Diaphragm • O: ribs and its cartilage, sternum, vertebrae • I: central tendon of the cartilage • A: prime action in inspiration

  45. Muscles of Respiration

  46. Muscles of the Abdomen • Rectus abdominis • O: pubis • I: xiphoid process, ribs • A: flexes vertebral column,increase abdominal pressure • External oblique • O: ribs • I: linea alba, ilium • A: see above, helps trunk rotation and lateral flexion

  47. Muscles of the Abdomen • Internal oblique • O: lumbar fascia, ilium, inguinal ligament • I: linea alba, pubis, ribs • A: same as external oblique • Transversus abdominis • O: ribs, inguinal ligament, ilium, lumbar fascia • I: linea alba, pubis • A: compresses abdominal content

  48. Muscles of the Abdomen

  49. Muscles of the Arm

  50. Muscles of the Arm • Biceps brachii muscle • O: scapula, shoulder joint • I: radius • A: agonist flexor of the elbow • Brachioradialis • O: humerus • I: radius • A: synergists for flexion of the elbow

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