Chapter 11 Muscles

1. Chapter 11 Muscles Exam 1 will cover sections 11.1-11.4

2. Section 1 Fascicle Arrangement • Fascicles: bundles of muscle fibers in skeletal muscle • fibers in each fascicle are parallel, but fascicle arrangement can vary • parallel muscles- fascicles are parallel to long axis of muscle (biceps brachii), when muscle fibers contract, muscle shortens by 30 % • convergent muscles- fascicles extend over a broad area & meet (converge) at the attachment site, (pectoralis muscles)

3. Pennate muscles- (feather) fascicles form a shared angle w/ tendon • contracted muscle doesn’t move tendon as far as parallel muscles-fibers pull @ angle • contain more muscle fibers than parallel muscle, so they produce more tension • Circular muscles- (sphincter) arranged around openings • when contracted, diameter decreases

5. 11.2 Classes of Levers • Nature and site of muscle connection determine force, speed, and range of motion • lever (bone) moves when the applied force (AF) is great enough to overcome the load (L) or resistance (R) that would prevent the movement • in the body, each joint acts as a fulcrum, and muscles provide the applied force • the load can vary (weight of limb, object held, or entire body)

6. levers can change • direction of applied force • distance & speed of movement • effective strength of applied force • Classes of levers • first class: fulcrum in the middle (teeter totter) • second class: load in the middle (wheel barrow), small force can move a larger weight, at the expense of speed and distance

7. third class: most common in body, force is between the load and the fulcrum, speed and distance traveled are increased at the expense of effective force (muscles must generate 6X the tension to support the load)

8. 11.3 Muscle Origins & Insertions • Ends of skeletal muscle are attached to structures that limit their motion (bone, cartilage, connective tissue) • origin-the place where fixed end of muscle attaches • insertion-the site where the moveable end attaches to another structure • action- movement produced when muscle contracts

9. Actions • Actions are described • by bone or region affected (flexion of forearm) • by joint involved (flexion of elbow) • based on functions • agonist (prime mover)- contraction responsible for producing specific movement, ex: biceps brachii muscle produces flexion of elbow • antagonist- muscle whose action opposes the action of an agonist, ex: triceps brachii extends the elbow, going against the biceps brachii

10. synergist- helps a larger agonist work efficiently, may provide pull near insertion or may stabilize near origin; useful in start of motion • fixator- a synergist that stabilizes origin of agonist by preventing movement at another joint

11. 11.4 Descriptive terms • Locational terms • regional terms are common; abdominis- abdomen, capitis- head, femoris- femur, etc (PG 342) • Origin and Insertion • first part of name indicates the origin, second part, the insertion ex: sternocleidomastoid originates at sternum, inserts at the clavicle (cleido)

12. Fascicle organization • Rectus: straight, parallel muscles that run along long axis of body (rectus abdominis) • transverse/oblique: muscles have fibers that run at an angle to long axis of body (external obliques) • Position • externus/superficialis: visible at the body surface • internus/profundus:deeper muscles • Intrinsic: located within an organ

13. Structural Characteristics • number of tendons (biceps brachii, triceps brachii) • shape- muscles named after their shape: trapezius, deltoid(triangle), rhomboid • length and size: • longus (long), longissimus (longest) • teres (long & round), brevis (short) • magnus (large), major (bigger), or maximus (biggest) • minor (small), or minimus (smallest)

14. Stop! Test 1 will cover 11.1-11.4

15. 11.5 Muscles of facial expression • Orbicularis oculi • Sphincter muscle of eyelid • O: frontal & maxillary bones • I: tissue of eyelid • Action: closes eye • Nerve: facial / CN VII (11.6)

16. Muscles of facial expression • Zygomaticus • O: zygomatic bone • I: corners of mouth • Action: smiling • Nerve: facial / CN VII Major and Minor (11.6)

17. Muscles of mastication • Masseter • O: zygomatic arch • I: angle & ramus of mandible • Action: elevate mandible • Nerve: trigeminal nerve / CN V (foramen ovale) Masseter (11.7a)

18. Muscles of mastication • Temporalis • O: temporal fossa • I: coronoid process of mandible • Action: elevate and retract mandible • Nerve: trigeminal n. / CN V (11.7a)

19. Extrinsic tongue muscles • Styloglossus • O: styloid process of temporal bone • I: tongue • Action: retract & elevate tongue • Nerve: hypoglossal n. / CN XII Styloglossus (11.7c)

20. Extrinsic tongue muscles • Hyoglossus • O: hyoid bone • I: tongue • Action: depresses tongue • Nerve: hypoglossal n. / CN XII Hyoid bone (11.7c)

21. Muscles of neck & throat • Digastric • two muscle bellies with an intermediate tendon attached to the hyoid bone • O: inferior margin of mandible (anterior belly); mastoid process of temporal bone (posterior belly) • I: hyoid bone • Action: elevate hyoid, stabilize hyoid, depress mandible • Nerve: trigeminal n. / CN V (anterior belly), facial n. / CN VII (posterior belly) Posterior belly Anterior belly (11.8a)

22. Muscles of neck & throat • Stylohyoid • O: styloid process of temporal bone • I: hyoid bone • Action: elevate & retract hyoid, swallow • Nerve: facial n. / CN VII Stylohyoid (11.7c)

23. Muscles of neck & throat • Sternohyoid • O: manubrium & medial end of clavicle • I: hyoid bone • Action: depress hyoid Sternohyoid (11.8a)

24. Muscles of neck & throat • Pharyngeal constrictors • O: mandible, pterygoid process, hyoid, laryngeal cartilages • I: posterior medial raphe of pharynx • Action: peristaltic contraction / swallow Superior Middle Inferior (11.8b)

25. Muscles of neck & throat • Sternocleidomastoid • O: manubrium & medial clavicle • I: mastoid process of temporal bone • Action: head & neck flexion, rotate head contralaterally • Nerve: accessory n. / CN XI (11.8a)

26. Muscles of neck & throat • Sternocleidomastoid

27. Back muscles • Spinalis • O: spines of upper lumbar and lower thoracic vertebrae • I: spines of upper thoracic and cervical vertebrae • Action: extends vertebral column (11.9d)

29. Deep thorax muscles • External & internal intercostals • O&I: inferior & superior border of ribs • Action: inspiration and expiration Internal (11.10a)

30. Deep thorax muscles • Diaphragm • O: inferior internal surface of rib cage & sternum, inferior costal cartilages, lumbar vertebrae • I: central tendon • Action: flattens on contraction (inspiration) • Nerve: phrenic nerves Xiphoid process (11.10b)

32. Abdominal wall muscles • Rectus abdominis • O: pubic crest & symphysis • I: xiphoid process and costal cartilages of ribs 5-7 • Action: flex & rotate lumbar vertebrae, fix & depress ribs, stabilize pelvis during walking, increase intraabdominal pressure • Note: 3 tendinous insertions, aponeurosis & linea alba (11.11ab)

35. Section 11.6 Appendicular Muscles • Position & stabilize pectoral & pelvic girdles • Move upper & lower limbs • Split into 2 major groups: • Muscles of shoulder & upper limb • Muscles of pelvis & lower limb

36. Differences in function: • Pectoral girdle has muscular connections with axial skeleton, acts as a shock absorber • Example: can use hands when you run • Pelvic girdle transfers weight from axial muscles to appendicular skeleton, needs more bony support

37. I. Shoulder & Upper Limb • Muscles that position the pectoral girdle 1.Trapezius- covers back & parts of the neck *reaches the base of the skull *inserts on the clavicles and spines of the scapulae *regions can contract independently so the action varies *superficial

38. Superificial thorax muscles • Trapezius • I: spine of scapula, clavicle • Action: stabilize, elevate, adduct, depress scapula, extend head (11.13b)

39. B. Rhomobid *adducts (retracts) scapula * attaches to cervical and thoracic vertebrae *inserts at the scapula *deep C. Levator scapulae *elevates scapula * deep

41. Superficial thorax muscles

42. D. Serratus anterior- on the chest *fan shaped *originates on chest side of ribs *inserts on the scapula *protracts scapula, swings shoulder forward (pushing) *superficial

43. E. Subclavius *deep chest muscle * originates on rib 1 *inserts on inferior border of clavicle * depresses & protracts clavicle & shoulder F. Pectoralis Minor * originates on ribs 3-5 *inserts on coracoid process of scapulae *complements contraction of subclavius, downward rotation of shoulder

44. Superficial thorax muscles • Pectoralis minor • O: anterior surface of ribs 3-5 • I: coracoid process of scapula • Action: pulls scapula anterior & inferior (11.13a)

45. B. Muscles that move the arm 1. deltoid *originates on clavicle & scapulae *inserts on humerus *major abductor of arm (away from body) 2. supraspinatus * superior to posterior portion of deltoid (under trapezius) *helps w/start of abduction movement

46. 3. Subscapularis *located on anterior side of scapula * rotates arm medially 4. Teres major *helps rotate arm medially

47. 5. Infraspinatus *located on the posterior side of the scapula, deep to deltoid *located below the scapular spine * rotates arm laterally (away from body) 6. Teres minor *aides in lateral rotation

48. 7. Rotator cuff muscles • Act to stabilize head of humerus in glenoid cavity and prevent dislocation, can be a frequent site of sports injuiries • Supraspinatus • Infraspinatus • Teres minor • Subscapularis Remember SITS

49. 8.Coracobrachialis * small muscle * only muscle attached to scapula that flexes & adducts humerus 9. Pectoralis major * originates on ribs 2-6 cartilage,body of sternum, and inferior portion of clavicle * inserts on greater tubercle of humerus * flexes, adducts, and medially rotates humerus 10. Latisumusdorsi *extends between the thoracic vertebrae & lesser tubercle of humerus * extends arm