Chapter 11: The Muscular System

1. Chapter 11:The Muscular System

2. Organization of Skeletal Muscle Fibers 4 patterns of fascicle organization: parallel convergent pennate circular

3. Parallel Muscles Fibers parallel to the long axis of muscle e.g., biceps brachii The center or body of the muscle thickens when parallel muscle contracts Parallel muscles contract about 30%

4. Convergent Muscles A broad area converges on attachment site (tendon, aponeurosis, or raphe) Muscle fibers pull in different directions, depending on stimulation e.g., pectoralis muscles

5. Pennate Muscles Form an angle with the tendon Do not move as far as parallel muscles Contain more myofibrils than parallel muscles Develop more tension than parallel muscles

6. Circular Muscles Also called sphincters Open and close to guard entrances of body e.g., obicularis oris

7. 3 Classes of Levers Depend on the relationship between applied force, fulcrum, and resistance: first class second class third class

8. First-Class Levers Seesaw is an example Center fulcrum between applied force and resistance Force and resistance are balanced

9. Second�Class Levers Wheelbarrow is an example Center resistance between applied force and fulcrum A small force moves a large weight

10. Third-Class Levers Most common levers in the body Center applied force between resistance and fulcrum Greater force moves smaller resistance Maximizes speed and distance traveled

11. Origins and Insertions Muscles have 1 fixed point of attachment (origin) and 1 moving point of attachment (insertion) Most muscles originate or insert on the skeleton Origin is usually proximal to insertion

12. Actions Movements produced by muscle contraction Body movements e.g., flexion, extension, adduction, etc. Described in terms of bone, joint, or region

13. Muscle Interactions Muscles work in groups to maximize efficiency Smaller muscles reach maximum tension first, followed by larger, primary muscles Agonists and antagonists work in pairs: when 1 contracts, the other stretches i.e., flexors�extensors, abductors�adductors, etc.

14. Muscle Terminology Based on Function Agonist (prime mover): produces a particular movement Antagonist: opposes movement of a particular agonist Synergist: a smaller muscle that assists a larger agonist helps start motion or stabilize origin of agonist (fixator)

15. Naming Skeletal Muscles

16. Naming Skeletal Muscles

17. Descriptive Names for Skeletal Muscles Location in the body - e.g., temporalis muscle Origin and insertion - e.g., genioglossus muscle Fascicle organization i.e., rectus (straight), transversus, oblique Relative position i.e., Externus (superficialis), Internus (profundus) Structural characteristics Number of tendons:bi = 2, tri = 3 Shape: trapezius, deltoid, rhomboid Size: maximus, minimus, major, minor, brevis, longus Action Movements: e.g., flexor, extensor, retractor Occupations or habits: e.g., risor = laughter

18. Axial and Appendicular Muscles

19. Divisions of the Muscular System Axial muscles: position head and spinal column move rib cage 60% of skeletal muscles Appendicular muscles: support pectoral and pelvic girdles support limbs 40% of skeletal muscles

20. 6 Muscle Groups of the Head and Neck Muscles of facial expression: originate on skull Extrinsic eye muscles: originate on surface of orbit control position of eye Muscles of mastication: move the mandible Muscles of the tongue: names end in glossus Muscles of the pharynx: begin swallowing process Anterior muscles of the neck: control position of larynx depress the mandible support tongue and pharynx

21. Muscles of Facial Expression

22. Summary: Muscles of Facial Expression

23. Summary: Muscles of Facial Expression

24. Extrinsic Eye Muscles Also called extra-ocular muscles

25. 6 Extrinsic Eye Muscles Inferior rectus Medial rectus Superior rectus Lateral rectus Inferior oblique Superior oblique

26. Summary: Extrinsic Eye Muscles

27. 3 Muscles of Mastication Masseter: the strongest jaw muscle Temporalis: helps lift the mandible Pterygoid muscles: position mandible for chewing

28. Summary: Muscles of Mastication

29. Muscles of the Vertebral Column

30. Muscles of the Vertebral Column Spinal extensors or erector spinae muscles Superficial Spinalis group Longissimus group Iliocostalis group Deep (transversospinalis) Spinal flexors Neck: longus capitis and longus colli rotate and flex the neck Lumbar: quadratus lumborum muscles flex spine and depress ribs

31. Summary: Muscles of the Vertebral Column

32. Summary: Muscles of the Vertebral Column

33. Oblique and Rectus Muscles - Lie within the body wall

34. Oblique and Rectus Muscles Oblique muscles: compress underlying structures rotate vertebral column Rectus muscles: flex vertebral column oppose erector spinae

35. Oblique Muscles Cervical region: scalene muscles flex the neck Thoracic region: intercostal muscles (external and internal intercostals): respiratory movements of ribs transversus thoracis: cross inner surface of ribs Abdominopelvic region (same pattern as thoracic): external oblique muscles internal oblique muscles Transversus abdominis

36. Rectus Group Rectus abdominis: between xiphoid process and pubic symphysis divided longitudinally by linea alba divided transversely by tendinous inscriptions Diaphragmatic muscle or diaphragm: divides thoracic and abdominal cavities performs respiration

37. Summary: Oblique and Rectus Muscles

38. The Appendicular Muscles

39. Divisions of Appendicular Muscles Muscles of the shoulders and upper limbs Position the pectoral girdle Move the arm Move the forearm and hand Move the hand and fingers Muscles of the pelvis and lower limbs Pelvic girdle is tightly bound to axial skeleton: permits little movement & has few muscles

40. Muscles that Position the Pectoral Girdle

41. 6 Muscles that Position the Pectoral Girdle Trapezius: superficial covers back and neck to base of skull inserts on clavicles and scapular spines Rhomboid and levator scapulae: deep to trapezius attach to cervical and thoracic vertebrae insert on scapular border Serratus anterior: found on the chest originates along ribs & inserts on anterior scapular margin Subclavius: originates on ribs & inserts on clavicle Pectoralis minor: attaches to scapula

42. Summary: Muscles that Position the Pectoral Girdle

43. Muscles that Move the Arm

44. 9 Muscles that Move the Arm Deltoid: the major abductor Supraspinatus: assists deltoid Subscapularis and teres major: produce medial rotation at shoulder Infraspinatus and teres minor: produce lateral rotation at shoulder Coracobrachialis: attaches to scapula produces flexion and adduction at shoulder Pectoralis major: produces flexion at shoulder joint between anterior chest and greater tubercle of humerus Latissimus dorsi: produces extension at shoulder joint between thoracic vertebrae and humerus

45. The Rotator Cuff Muscles involved in shoulder rotation supraspinatus, subscapularis, infraspinatus, teres minor, and their tendons

46. Summary: Muscles that Move the Arm

47. Muscles that Move the Forearm and Hand

48. Muscles that Move the Forearm and Hand Originate on humerus and insert on forearm Exceptions: the major flexor (biceps brachii) the major extensor (triceps brachii) Extensors: mainly on posterior and lateral surfaces of arm Flexors: mainly on anterior and medial surfaces

49. 13 Muscles that Move the Forearm and Hand Biceps brachii: flexes elbow & stabilizes shoulder joint originates on scapula & inserts on radial tuberosity Triceps brachii: extends elbow originates on scapula & inserts on olecranon Brachialis and brachioradialis: flex elbow Anconeus: opposes brachialis Palmaris longus: superficial & flexes wrist Flexor carpi ulnaris: superficial; flexes & adducts wrist Flexor carpi radialis: superficial; flexes & abducts wrist Extensor carpi radialis: superficial; Extends & abducts wrist Extensor carpi ulnaris: superficial; extends & adducts wrist Pronator teres and supinator: rotate radius; originate on humerus and ulna Pronator quadratus: originates on ulna; assists pronator teres

50. Summary: Muscles that Move the Forearm and Hand

51. Muscles that Move the Hand and Fingers

52. Muscles that Move the Hand and Fingers Also called extrinsic muscles of the hand Lie entirely within forearm Only tendons cross wrist (in synovial tendon sheaths) Extensor retinaculum: posterior surface of wrist wide band of connective tissue stabilizes tendons of extensor muscles Flexor retinaculum: anterior surface of wrist stabilizes tendons of flexor muscles C.T.S.

53. Summary: Muscles that Move the Hand and Fingers

54. Muscles that Position the Lower Limbs Muscles that move the thigh Muscles that move the leg Muscles that move the foot and toes

55. Muscles that Move the Thigh

56. Muscles that Move the Thigh

57. Gluteal Muscles Cover lateral surfaces of ilia Gluteus maximus: largest, most posterior gluteal muscle produces extension and lateral rotation at hip Tensor fasciae latae (TFL): works with gluteus maximus stabilizes iliotibial tract (ITT/ITB) Gluteus medius and gluteus minimus: originate anterior to gluteus maximus insert on trochanter

58. Adductors Adductor magnus: produces adduction, extension, and flexion Adductor brevis: hip flexion and adduction Adductor longus: hip flexion and adduction Pectineus: hip flexion and adduction Gracilis: hip flexion and adduction

59. Iliopsoas 2 hip flexors insert on the same tendon: Psoas major Iliacus Lateral Rotators Include: Piriformis & obturator

60. Summary: Muscles that Move the Thigh

61. Summary: Muscles that Move the Thigh

62. Muscles that Move the Leg

63. Flexors of the Knee Biceps femoris * Semimembranosus * Semitendinosus * Sartorius: originates superior to the acetabulum Popliteus: rotates the tibia to unlock the knee * Hamstrings

64. Extensors of the Knee 4 muscles of the quadriceps femoris: 3 vastus muscles (medialis, intermedius, lateralis) rectus femoris muscle The only one to cross the hip joint

65. Summary: Muscles that Move the Leg

66. Muscles that Move the Foot and Toes

67. Muscles that Move the Foot and Toes

68. 4 Muscles that Produce Extension at the Ankle Gastrocnemius * Soleus * Fibularis Tibialis posterior * Tricep surae � Share the calcaneal tendon (Achilles tendon):

69. Muscles that Produce Flexion at the Ankle Tibialis anterior: opposes the gastrocnemius Muscles that Produce Extension at the Toes Extensor digitorum longum Extensor hallucis longus Extensor retinacula: fibrous sheaths hold tendons of toes as they cross the ankle Muscles that Produce Flexion at the Toes Flexor digitorum longum Flexor hallucis longus: oppose the extensors

70. Summary: Muscles that Move the Foot and Toes

71. Effects of Aging on the Muscular System Skeletal muscle fibers become smaller in diameter Skeletal muscles become less elastic: develop increasing amounts of fibrous tissue (fibrosis) Decreased tolerance for exercise Decreased ability to recover from muscular injuries