Understanding Muscular Systems: Levers, Movement & Coordination

1. Chapter 11 The Muscular System Lecture Outline

2. INTRODUCTION • The voluntarily controlled muscles of the body make up the muscular system. • The muscular system and muscle tissue contribute to homeostasis by producing movement, stabilizing body position, regulating organ volume, moving substances within the body, and producing heat. • This chapter discusses how skeletal muscles produce movement and describes the principal skeletal muscles. Principles of Human Anatomy and Physiology, 11e

3. Chapter 11The Muscular System • Skeletal muscle major groupings • How movements occur at specific joints • Learn the origin, insertion, function and innervation of all major muscles • Important to allied health care and physical rehabilitation students Principles of Human Anatomy and Physiology, 11e

4. HOW SKELETAL MUSCLES PRODUCE MOVEMENT Principles of Human Anatomy and Physiology, 11e

5. Muscle Attachment Sites:Origin and Insertion • Skeletal muscles shorten & pull on the bones they are attached to • Origin is the bone that does not move when muscle shortens (normally proximal) • Insertion is the movable bone (some 2 joint muscles) • Fleshy portion of the muscle in between attachment sites = belly Principles of Human Anatomy and Physiology, 11e

6. Tenosynovitis • Inflammation of tendon and associated connective tissues at certain joints • wrist, elbows and shoulder commonly affected • Pain associated with movement • Causes • trauma, strain or excessive exercise Principles of Human Anatomy and Physiology, 11e

7. Lever Systems and Leverage • A lever is a rigid structure that moves around a fixed point, the fulcrum (F) • The lever is acted on by two different forces: (Figure 11.1b). • resistance (load) (L), which opposes movement • effort (E) which causes movement Bones serve as levers and joints serve as fulcrums. • Leverage, the mechanical advantage gained by a lever, is largely responsible for a muscle’s strength and range of motion (ROM), i.e., the maximum ability to move the bones of a joint through an arc. Principles of Human Anatomy and Physiology, 11e

8. Levers Principles of Human Anatomy and Physiology, 11e

9. Levers are categorized into three types – • First class levers (EFL) e.g. a seesaw – the head on the vertebral column (Figure 11.2a) • Second-class (FLE) eg. a wheelbarrow(Figure 11.2b) • Third-class (FEL) (Figure 11.1b) e.g. forceps - the elbow joint (Figure 11.2c). Principles of Human Anatomy and Physiology, 11e

10. Lever Systems and Leverage • Muscle acts on rigid rod (bone)that moves around a fixed point called a fulcrum • Resistance is weight of bodypart & perhaps an object • Effort or load is work doneby muscle contraction • Mechanical advantage • the muscle whose attachment is farther from the joint will produce the most force • the muscle attaching closer to the joint has the greater range of motion and the faster the speed it can produce Principles of Human Anatomy and Physiology, 11e

11. First - Class Lever • Can produce mechanical advantage or not depending on location of effort & resistance • if effort is further from fulcrum than resistance, then a strong resistance can be moved • Head resting on vertebral column • weight of face is the resistance • joint between skull & atlas is fulcrum • posterior neck muscles provide effort Principles of Human Anatomy and Physiology, 11e

12. Second - Class Lever • Similar to a wheelbarrow • Always produce mechanical advantage • resistance is always closer to fulcrum than the effort • Sacrifice of speed for force • Raising up on your toes • resistance is body weight • fulcrum is ball of foot • effort is contraction of calf muscles which pull heel up off of floor Principles of Human Anatomy and Physiology, 11e

13. Third - Class Lever • Most common levers in the body • Always produce a mechanical disadvantage • effort is always closer to fulcrum than resistance • Favors speed and range of motion over force • Flexor muscles at the elbow • resistance is weight in hand • fulcrum is elbow joint • effort is contraction of biceps brachii muscle Principles of Human Anatomy and Physiology, 11e

14. Fascicle Arrangements • A contracting muscle shortens to about 70% of its length • Fascicular arrangement represents a compromise between force of contraction (power) and range of motion • muscles with longer fibers have a greater range of motion • a short fiber can contract as forcefully as a long one. Principles of Human Anatomy and Physiology, 11e

15. Coordination Within Muscle Groups • Most movement is the result of several muscle working at the same time • Most muscles are arranged in opposing pairs at joints • prime mover or agonist contracts to cause the desired action • antagonist stretches and yields to prime mover • synergists contract to stabilize nearby joints • fixators stabilize the origin of the prime mover • scapula held steady so deltoid can raise arm Principles of Human Anatomy and Physiology, 11e

16. HOW SKELETAL MUSCLES ARE NAMED • The names of most of the nearly 700 skeletal muscles are based on several types of characteristics. • These characteristics may be reflected in the name of the muscle. • The most important characteristics include the direction in which the muscle fibers run, the size, shape, action, numbers of origins, and location of the muscle, and the sites of origin and insertion of the muscle • Examples from Table 11.2 • triceps brachii -- 3 sites of origin • quadratus femoris -- square shape • serratus anterior -- saw-toothed edge Principles of Human Anatomy and Physiology, 11e

17. PRINCIPLE SKELETAL MUSCLES • Exhibits 11.1 through 11.20 list the principle skeletal muscles in various regions of the body. • Figure 11.3 shows general anterior and posterior views of the muscular system. • The exhibits contain objectives, an overview which provides a general orientation to the muscles, muscle names, origins, insertions, and actions, “relating muscles to movements,” innervation, and Figures (11.4-11.23) that show the muscles under consideration. Principles of Human Anatomy and Physiology, 11e

18. Muscles of Facial Expression • Arise from skull & insert onto skin • Encircle eyes, nose & mouth • Express emotions • Facial Nerve (VII) • Bell’s palsy = facial paralysis due Principles of Human Anatomy and Physiology, 11e

19. Muscles of Facial Expression • Orbicularis oculi closes the eye • Levator palpebrae superioris opens the eye • Orbicularis oris puckers the mouth • Buccinator forms the muscular portion of the cheek & assists in whistling, blowing, sucking & chewing Principles of Human Anatomy and Physiology, 11e

20. Extrinsic Muscles of the Eyeballs • Extrinsic muscles insert onto white of eye • Fastest contracting & most precisely controlled • Cranial nerves 3, 4 & 6 innervate the six muscles • 4 Rectus muscles & 2 obliques • Intrinsic muscles are found within the eyeball • Levator palpebrae superioris raises eyelid Principles of Human Anatomy and Physiology, 11e

21. Muscles that Move the Mandible • Masseter, temporalis & pterygoids • Arise from skull & insert on mandible • Cranial nerve V (trigeminal nerve) • Protracts, elevates or retracts mandible • Temporalis & Masseter elevate the mandible (biting) • temporalis retracts Principles of Human Anatomy and Physiology, 11e

22. Jaw Muscles -- Deep Dissection • Lateral pterygoid protracts mandible • sphenoid bone to condyle of mandible • Medial pterygoid elevates & protracts mandible • sphenoid bone to angle of mandible • Together move jaw side to side to grind food. Principles of Human Anatomy and Physiology, 11e

23. Muscles that Move the Tongue • 4 extrinsic mm ariseelsewhere, but insertinto tongue • Genioglossus • from inside tip of mandible • Styloglossus • from styloid process • Palatoglossus • from hard palate • Hyoglossus • from hyoid bone • Together move tongue in various directions • Intubation is necessary during anesthesia since Genioglossus relaxes & tongue falls posteriorly blocking airway Principles of Human Anatomy and Physiology, 11e

24. Muscles of the Floor of the Oral Cavity • Suprahyoid muscles lie superior to hyoid bone. • Digastric m. extends from mandible to mastoid process • used to open the mouth • Mylohyoid m. extends from hyoid to mandible • supports floor of mouth & elevates hyoid bone during swallowing • Stylohyoid & Geniohyoid elevate the hyoid during swallowing Principles of Human Anatomy and Physiology, 11e

25. Principles of Human Anatomy and Physiology, 11e

26. Muscles that Move the Head • Sternocleidomastoid muscle • arises from sternum & clavicle & inserts onto mastoid process of skull • innervated by cranial nerve XI (spinal accessory) • contraction of both flexes the cervical vertebrae & extends head • contraction of one, laterally flexes the neck and rotates face in opposite direction Principles of Human Anatomy and Physiology, 11e

27. Muscles of Abdominal Wall • Notice 4 layers of muscle in the abdominal wall Principles of Human Anatomy and Physiology, 11e

28. Muscles of Abdominal Wall • 4 pairs of sheetlike muscles • rectus abdominis = vertically oriented • external & internal obliques and transverses abdominis • wrap around body to form anterior body wall • form rectus sheath and linea alba • Inguinal ligament from anterior superior iliac spine to upper surface of body of pubis • Inguinal canal = passageway from pelvis through body wall musculature opening seen as superficial inguinal ring • Inguinal hernia = rupture or separation of abdominal wall allowing protrusion of part of the small intestine (more common in males) Principles of Human Anatomy and Physiology, 11e

29. Transverse Section of Body Wall • Rectus sheath formed from connective tissue aponeuroses of other abdominal muscles as they insert in the midline connective tissue called the linea alba Principles of Human Anatomy and Physiology, 11e

30. Muscles Used in Breathing • Breathing requires a change in size of the thorax • During inspiration, thoracic cavity increases in size • external intercostal lift the ribs • diaphragm contracts & dome is flattened • During expiration, thoracic cavity decreases in size • internal intercostal mm used in forced expiration • Diaphragm is innervated by phrenic nerve (C3-C5) but intercostals innervated by thoracic spinal nerves (T2-T12) Quadratus lumborum fills in space between 12th rib & iliac crest to create posterior body wall Principles of Human Anatomy and Physiology, 11e

31. Principles of Human Anatomy and Physiology, 11e

32. Female Pelvic Floor & Perineum • Both the pelvic diaphragm ( coccygeus & levator ani) and the muscles of the perineum fill in the gap between the hip bones • supports pelvic viscera & resists increased abdominal pressure during defecation, urination, coughing, vomiting, etc • pierced by anal canal, vagina & urethra in females • levator ani may be damaged during episiotomy during childbirth (urinary incontinence during coughing) Principles of Human Anatomy and Physiology, 11e

33. Muscles of Male Perineum • Perineum contains more superficial layer of muscle • urogenital triangle contains external genitals • muscle arrangement forms urogenital diaphragm assists in urination (external urethral sphincter) and ejaculation (ischiocavernosus, bulbospongiosus) • anal triangle contains anus • external anal sphincter Principles of Human Anatomy and Physiology, 11e

34. Stabilizing the Pectoral Girdle • Anterior thoracic muscles • Subclavius extends from 1st rib to clavicle • Pectoralis minor extends from ribs to coracoid process • Serratus anterior extends from ribs to inner surface of scapula • Posterior thoracic muscle • Trapezius extends from skull & vertebrae to clavicle & scapula • Levator scapulae extends from cervical vertebrae to scapula • Rhomboideus extends from thoracic vertebrae to vertebral border of scapula Principles of Human Anatomy and Physiology, 11e

35. Axial Muscles that Move the Arm • Pectoralis major & Latissimus dorsi extend from body wall to humerus. Principles of Human Anatomy and Physiology, 11e

36. Muscles that Move the Arm • Deltoid arises from acromion & spine of scapula & inserts on arm • abducts, flexes & extends arm • Rotator cuff muscles extend from scapula posterior to shoulder joint to attach to the humerus • supraspinatus & infraspinatus: above & below spine of scapula • subscapularis on inner surface of scapula Principles of Human Anatomy and Physiology, 11e

37. Flexors of the Forearm (elbow) • Cross anterior surface of elbow joint & form flexor muscle compartment • Biceps brachii • scapula to radial tuberosity • flexes shoulder and elbow & supinates hand • Brachialis • humerus to ulna • flexion of elbow • Brachioradialis • humerus to radius • flexes elbow Principles of Human Anatomy and Physiology, 11e

38. Extensors of the Forearm (elbow) • Cross posterior surface of elbow joint & forms extensor muscle compartment • Triceps brachii • long head arises scapula • medial & lateral heads from humerus • inserts on ulna • extends elbow & shoulder joints • Anconeus • assists triceps brachii in extending the elbow Principles of Human Anatomy and Physiology, 11e

39. Cross-Section Through Forearm • If I am looking down onto this section is it from right or left arm? Principles of Human Anatomy and Physiology, 11e

40. Muscle that Pronate & Flex • Pronator teres • medial epicondyle to radius so contraction turns palm of hand down towards floor • Flexor carpi muscles • radialis • ulnaris • Flexor digitorum muscles • superficialis • profundus • Flexor pollicis Principles of Human Anatomy and Physiology, 11e

41. Muscles that Supinate & Extend • Supinator • lateral epicondyle of humerus to radius • supinates hand • Extensors of wrist and fingers • extensor carpi • extensor digitorum • extensor pollicis • extensor indicis Principles of Human Anatomy and Physiology, 11e

42. Retinaculum • Tough connective tissue band that helps hold tendons in place • Extensor & Flexor retinaculum cross wrist region attaching from bone to bone (carpal tunnel syndrome = painful compression of median nerve due to narrowing passageway under flexor retinaculum Principles of Human Anatomy and Physiology, 11e

43. Intrinsic Muscles of the Hand • Origins & insertions are within the hand • Help move the digits • Thenar muscles move the thumb • Hypothenar muscles move the little finger • Opposition, flexion, extension, abduction & adduction Principles of Human Anatomy and Physiology, 11e

44. Muscles that Move the Vertebrae • Quite complex due to overlap • Erector spinae fibers run longitudinally • 3 groupings • spinalis • iliocostalis • longissimus • extend vertebral column • Smaller, deeper muscles • transversospinalis group • semispinalis, multifidis & rotatores • run from transverse process to dorsal spine of vertebrae above & help rotate vertebrae Principles of Human Anatomy and Physiology, 11e

45. Scalene Muscle Group • Attach cervical vertebrae to uppermost ribs • Flex, laterally flex & rotate the head Principles of Human Anatomy and Physiology, 11e

46. Muscles Crossing the Hip Joint • Iliopsoas flexes hip joint • arises lumbar vertebrae & ilium • inserts on lesser trochanter • Quadriceps femoris has 4 heads • Rectus femoris crosses hip • 3 heads arise from femur • all act to extend the knee • Adductor muscles • bring legs together • cross hip joint medially • see next picture • Pulled groin muscle • result of quick sprint activity • stretching or tearing of iliopsoas or adductor muscle Principles of Human Anatomy and Physiology, 11e

47. Adductor Muscles of the Thigh • Adductor group of muscle extends from pelvis to linea aspera on posterior surface of femur • pectineus • adductor longus • adductor brevis • gracilis • adductor magnus (hip extensor) Principles of Human Anatomy and Physiology, 11e

48. Muscles of the Butt & Thigh • Gluteus muscles • maximus, medius & minimus • maximus extends hip • medius & minimus abduct • Deeper muscles laterally rotate femur • Hamstring muscles • semimembranosus (medial) • semitendinosus (medial) • biceps femoris (lateral) • extend hip & flex knee • Pulled hamstring • tear of origin of muscles from ischial tuberosity Principles of Human Anatomy and Physiology, 11e

49. Cross-Section through Thigh • 3 compartments of muscle with unique innervation • anterior compartment is quadriceps femoris innervated by femoral nerve • medial compartment is adductors innervated by obturator nerve • posterior compartment is hamstrings innervated by sciatic nerve Principles of Human Anatomy and Physiology, 11e

50. Muscles of the Calf (posterior leg) • 3 muscles insert onto calcaneus • gastrocnemius arises femur • flexes knee and ankle • plantaris & soleus arise from leg • flexes ankle • Deeper mm arise from tibia or fibula • cross ankle joint to insert into foot • tibialis posterior • flexor digitorum longus • flexor hallucis longus • flexing ankle joint & toes Principles of Human Anatomy and Physiology, 11e