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Chapter 11 Muscles

Chapter 11 Muscles. I. Fascicle arrangement. A. Fascicles: bundles of muscle fibers in skeletal muscle 1. fibers in each fascicle are parallel, but fascicle arrangement can vary

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Chapter 11 Muscles

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  1. Chapter 11 Muscles

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

  3. c. 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 d. Circular muscles- (sphincter) arranged around openings • when contracted, diameter decreases

  4. B. Classes of Levers 1. Nature and site of muscle connection determine force, speed, and range of motion a. lever (bone) moves when the applied force (AF) is great enough to overcome the load (L) or resistance (R) that would prevent the movement b. joint acts as a fulcrum, and muscles provide the applied force c. load can vary (weight of limb, object held, or entire body)

  5. d. levers can change the following: • direction of applied force • distance & speed of movement • effective strength of applied force 2. Classes of levers a. first class: fulcrum in the middle (teeter totter) b. second class: load in the middle (wheel barrow), small force can move a large weight, at the expense of speed and distance

  6. c. 3rd 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)

  7. C. Muscle Origins & Insertions 1. Ends of muscle are attached to structures that limit their motion (bone, cartilage, connective tissue) a. origin-the place where fixed end of muscle attaches b. insertion-the site where the moveable end attaches to another structure c. action- movement produced when muscle contracts

  8. 2. Actions are described a. by bone or region affected (flexion of forearm) b. by joint involved (flexion of elbow) c. 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

  9. 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

  10. D. Naming muscles- descriptive 1. Locational terms a. regional terms are common; abdominis- abdomen, capitis- head, femoris- femur, etc (PG 342) 2. Origin and Insertion a. first part of name indicates the origin, second part, the insertion ex: sternocleidomastoid originates at sternum, inserts at the clavicle (cleido)

  11. 3. Fascicle organization a. Rectus: straight, parallel muscles that run along long axis of body (rectus abdominis) b. transverse/oblique: muscles have fibers that run at an angle to long axis of body (external obliques) 4. Position a. externus/superficialis: visible at the body surface b. internus/profundus:deeper muscles c. Intrinsic: located within an organ

  12. E. Naming muscles-Structural Characteristics 1. number of tendons (biceps brachii, triceps brachii) 2. shape- muscles named after their shape: trapezius, deltoid(triangle), rhomboid 2. length and size: a. longus (long), longissimus (longest) b. teres (long & round), brevis (short) c. magnus (large), major (bigger), or maximus (biggest) d. minor (small), or minimus (smallest)

  13. II. Individual MusclesA. Muscles of facial expression 1. Orbicularis oculi • Sphincter muscle of eyelid • O: frontal & maxillary bones • I: tissue of eyelid • Action: closes eye • Nerve: facial (11.6)

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

  15. B. Muscles of mastication 1.Masseter • O: zygomatic arch • I: angle & ramus of mandible • Action: elevate mandible • Nerve: trigeminal nerve / CN V Masseter (11.7a)

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

  17. C. Extrinsic tongue muscles 1. Styloglossus • O: styloid process of temporal bone • I: tongue • Action: retract & elevate tongue • Nerve: hypoglossal n. / CN XII Styloglossus (11.7c)

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

  19. D. Muscles of neck & throat 1. 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. (anterior belly), facial n. (posterior belly) Posterior belly Anterior belly (11.8a)

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

  21. 3. Sternohyoid • O: manubrium & medial end of clavicle • I: hyoid bone • Action: depress hyoid Sternohyoid (11.8a)

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

  23. 5. 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)

  24. Muscles of neck & throat • Sternocleidomastoid

  25. E. Muscles of the Back 1. Errectorspinae (extensor) muscles- include superficial & deep layers a. superficial layer: spinalis, longissimus, and iliocostalis groups -when contracting together, extend the spine, when contracting on one side, laterally flex the spine

  26. i. Spinalis group • O: spines of upper lumbar and lower thoracic vertebrae • I: spines of upper thoracic and cervical vertebrae • Action: extends vertebral column

  27. ii. Longissumus group O: tranverse processes of vertebrae I: tranverse processes of vertebrae above origin A: extends neck and vertebral column, lateral flexion of spine or neck

  28. iii. Iliocostalis group O: superior borders of ribs, iliac crest, sacral crest I: transverse processes of cervical vertebrae, inferior surfaces of ribs A: extends neck, elevates ribs, stabilizes thoracic vertebrae, extends vertebral column

  29. b. Deep layer of back muscles i. semispinalis group (multifudus, interspinales, intertransversarii, and rotatores) - smaller muscles, interconnect and stabilize the vertebrae -produce slight rotations, and adjust positions of individual vertebrae

  30. c. Flexor muscles of the back –most muscles on the back are extensors due to the large trunk muscles that flex the vertebral column but there are a few flexors i. longuscapitis & longuscolli-rotate or flex the neck ii. Quadratuslumborum- large trunk flexors on l &r side of vertebral column O: iliac crest I: last rib, trans. Process of lumbar vertebrae A. together, depress the ribs, alone, laterally flexes vertebral column

  31. F. Deep thorax muscles 1. External & internal intercostals • O & I: inferior & superior border of ribs • Action: inspiration and expiration Internal (11.10a)

  32. 2.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)

  33. G. Abdominal wall muscles 1. Rectus abdominis • O: near pubic symphysis • I: xiphoid process • Action: flex & rotate lumbar vertebrae, fix & depress ribs, stabilize pelvis during walking, increase intra-abdominal pressure * 3 tendinous insertions, aponeurosis & linea alba (11.11ab)

  34. 2. Other muscles to know: a. Internal and external Obliques b. Transversusabdominis Look at diagram a on Pg 355 (11.11ab)

  35. Part 2: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 O: Occipital bone, ligamentumnuche & spinous processes of vertebrae I: spine of scapula, clavicle A: stabilize, elevate, retract, adduct, depress scapula, extend neck (lift head) -regions can contract independently so the action varies -superficial muscle (close to surface of body)

  38. (11.13b)

  39. 2. Rhomboid O: attaches to cervical and thoracic vertebrae I: inserts at the vertebral border of the scapula A: adducts (retracts) scapula, downward rotation - is a deep muscle, under trapezius, and is split into major and minor 3. Levatorscapulae O: transverse process of c1-4 I: vertebral border of each scapula A: elevates scapula -is also a deep muscle

  40. 4. Serratus anterior- on the chest, fan shaped O: on anterior side of ribs I: anterior margin of vertebral border of the scapula A: protracts scapula, swings shoulder forward -superficial

  41. 5. Subclavius O: 1st rib I: inferior border of clavicle A: depresses & protracts clavicle & shoulder 6. Pectoralis Minor O: anterior surface of ribs 3-5 I: coracoid process of scapulae A: complements action of subclavius, also produces downward rotation of shoulder

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

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

  44. 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

  45. 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

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