Chapter 10 Anatomy of the Muscular System

  1. Introduction (Figs. 10-1, 10-2)
  1. More than 600 skeletal muscles
  2. Comprise of 40-50% of body weight
  1. Skeletal Muscle Structure (p. 281)
  1. Each skeletal muscle is an organ
  2. Muscle fibers, connective tissue, blood vessels, and nerve fibers make up a muscle
  3. Connective tissue components
  1. Endomysium- connective tissue membrane that covers individual skeletal muscle cells or muscle fibers
  2. Perimysium- connective tissue that binds together groups of muscle fibers (fascicles)
  3. Epimysium- connective tissue that covers the muscle as a whole (deep fascia-covers the epimysium)
  4. Tendon- continuation of connective tissue components of muscle to form astrong, tough cord that is continuous with the fibrous periosteum covering of the bone.
  5. Aponeurosis- continuation of connective tissue components to form a broad flat sheet of connective tissue
  6. Fascia- fibrous connective tissue under the skin, also surrounds skeletalmuscle, organs and bone
  7. Tendon sheaths- tube-shaped structures of fibrous connective tissue thatencloses certain tendon (wrist and ankle)
  1. Fiber arrangement (p. 282)
  1. Parallel (Fig. 10-4 A)- fibers are parallel to the long axis of the muscle
  1. Ex. Straplike- sartorius muscle of the thigh
  1. Convergent (Fig. 10-4 B)- converge to a narrow attachment (triangular)
  1. Broad origin to a single tendon
  2. Pectoralis Major muscle
  1. Pennate (Fig. 10-4 C)- fibers are oblique
  1. muscle fibers are short
  2. Extensor digitorum of the leg (unipennate)
  1. Bipennate (Fig. 10-4 D)- double feathered, fibers oblique in opposite directions, Ex. Rectus femoris of the thigh
  2. Sphincter (Fig. 10-4 E)- curved or circular fibers, Ex. Orbicularis oris
  1. Attachment of muscles (Fig. 10-5)
  1. Origin- point of attachment that does not move with muscle contraction
  2. Insertion- point of attachment that moves with muscle contraction
  1. Muscle actions (p. 283)
  1. Prime mover (agonist)- muscle or group of muscle that directly perform a specific movement; Ex. Biceps brachii- flexion offorearm
  2. Antagonist- muscles that oppose the prime mover
  3. Synergist- facilitate/ complement prime mover to produce more effective movement
  4. Fixator- function as joint stabilizers, also aids in maintaining upright posture
  1. Lever systems
  1. lever- any rigid bar free to turn about a fixed point called its fulcrum
  2. In most joints, the muscle which moves that joint lies proximal to it
  3. Bones = Levers, joints = fulcrum, muscles = pulling force
  1. Naming of Skeletal muscles (Figs. 10-1, 10-2)
  1. Criteria
  1. Location of the muscle, Ex. Brachialis (arm), gluteus (buttock)
  2. Function or action of the muscle, Ex. Adductor muscles of the thigh
  3. Shape of the muscle, Ex. Deltoid (triangular- delta)
  4. Direction of the fibers, Ex. Rectus abdominis (rectus = straight)
  5. Number of heads or divisions of origin, Ex. Biceps = 2, triceps = 3
  6. Points of attachment- origin and insertion points in its name, origin is named first, Ex. Sternocleidomastoid- origin (sternum and clavicle), insertion (mastoid process of temporal bone)
  7. Relative size of the muscle, Ex. Maximus (largest), Minimus (smallest), Longus or brevis
  1. Hints on how to deduce muscle actions (p. 286)
  1. Be familiar with name, shape, and location (Table 10-1)
  2. From shape and location, deduce name of origin and insertion
  3. Determine which bone moves when the muscle contracts
  4. Deduce action/ function- insertion moves toward origin

IV.Important Skeletal Muscles (p. 286)

A Muscles of facial expression (Fig. 10-7, Table 10-3)

B. Muscles of mastication ( Fig. 10-7, Table 10-3)

  1. Muscles that move the head Fig. 10-8, Table 10-4)
  1. Trunk muscles
  1. Muscles of the thorax (Fig. 10-9, Table 10-5)
  2. Muscles of the abdominal wall (Fig. 10-10, Table10-6)
  3. Muscles of the back (Fig. 10-11, Table 10-7)
  4. Muscles of the pelvic floor (Fig. 10-12, Table 10-8)
  1. Upper Limb Muscles (p. 293)
  1. Muscles acting on the shoulder girdle (Fig. 10-13, Table 10-9)
  2. Muscles that move the upper arm (Fig. 10-14, 10-15, Table 10-10)
  3. Muscles that move the forearm (Fig. 10-16, 10-17, Table 10-11)
  4. Muscles that move the wrist, hand, and fingers (Fig. 10-18, 10-19, 10-20, Table 10-12)
  1. Lower Limb Muscles (p. 300)
  1. Muscles that move the thigh and lower leg (Fig. 10-1, 10-2, 10-22 to 10-27, Table 10-13, 10-14)
  2. Muscles that move the ankle and foot (Fig. 10-28, 10-29, Table 10-15)
  1. Posture (p. 306)- How Posture is maintained- muscles exert a continual pull on bones in the opposite direction from gravity