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The Muscular System. Chapters 9 & 10. Overview. Functions: movement maintain posture stabilize joints generate heat . 3 Types. 1) Skeletal 2) Cardiac 3) Smooth Striated - striated - not striated voluntary - involuntary - involuntary . Gross Anatomy.

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The Muscular System

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the muscular system

The Muscular System

Chapters 9 & 10



  • movement
  • maintain posture
  • stabilize joints
  • generate heat
3 types
3 Types

1) Skeletal 2) Cardiac 3)Smooth

  • Striated - striated - not striated
  • voluntary - involuntary - involuntary
gross anatomy
Gross Anatomy
  • made of muscle fibers, blood vessels, nerve fibers and connective tissue
CT wrappings surrounding muscle fibers
  • endomysium – fine layer CT that surrounds each fiber
  • perimysium – collagenic sheath that surrounds each fascicle (bundle of muscle fibers)
epimysium –CT that binds several fascicles together to surround the entire muscle
  • deep fascia – coarser sheet of CT that binds muscles into functional groups
Nerve and Blood Supply
  • each muscle contains an artery and one or more veins
  • origin – attachment to immovable, or less movable, bone
  • insertion – attached to movable bone
  • in muscles of the limbs, origin typically lies proximal to the insertion
microscopic anatomy of a skeletal muscle fiber
Microscopic Anatomy of a Skeletal Muscle Fiber
  • sarcolemma = plasma membrane
  • sarcoplasm = cytoplasm
  • sarcoplasmic reticulum = endoplasmic reticulum
  • width = 10-100um
  • length = up to 30 cm (12 in)
  • there are hundreds to thousands in each muscle fiber, depending on its size
  • account for 80% of volume and organelles are squeezed around them
  • functional unit of muscle
  • portion of myofibril between two Z discs
muscle metabolism
Muscle Metabolism
  • energy stored in ATP
    • comes from cellular respiration, hydrolysis of creatine phosphate and lactic acid fermentation
contraction of motor units
Contraction of Motor Units
  • a motor unit consists of a single motor neuron and all of the muscle cells it stimulates
  • recruitment = when more motor units need to be stimulated for increased strength
the advantage of having only a few muscle cells per motor unit is to allow precise movements
  • small motor units, containing fewer cells, provide precise movements
    • muscles of the eye
  • large motor units, containing many cells, provide gross movements
    • movement of thigh
muscle tone is achieved by random, asynchronous motor unit contractions that provide a constant state of low-level tension
    • without stimulation, muscle loses tone
the sliding filament theory
The Sliding Filament Theory
  • involves 5 molecules plus Ca+ ions
    • actin
    • myosin
    • tropomyosin
    • troponin
    • ATP
The Theory
  • The contraction of a muscle cell occurs as the thin filament slides past the thick filament.
  • During contraction the sarcomere shortens and the thin and thick filaments overlap to a great degree
Thick filaments
  • made of myosin filaments
    • myosin head = cross bridge

Thin filaments

  • made of actin, tropomyosin & troponin
    • tropomyosin covers actin binding sites in a unstimulated muscle
smooth muscle
Smooth Muscle
  • Diameter 3-6 um
  • Length 100-500 um
  • Lack neuromuscular junctions found in skeletal muscle, but have varicosities that release neurotransmitters into a wide synaptic cleft in the general area of smooth muscle cells
  • Have actin and myosin filaments, but no sarcomeres
intermediate filaments are interlaced through the cell much like the threads in a pair of "fish-net" stockings
  • because smooth muscle is not as organized as skeletal muscle, shortening occurs in all directions
cardiac muscle
Cardiac Muscle
  • Has myofibrils that are organized into sarcomeres, but the myofibrils have irregular thickness
major skeletal muscles of the body
Major Skeletal Muscles of the Body
  • There are over 600 skeletal muscles!
  • You will only be held responsible for the names and locations of the 32 shown in the following slides.
  • Temporalis – closes jaw, elevates mandible; maintains posture of mandible at rest
  • Masseter – elevates mandible
  • Frontalis – raises eyebrows and wrinkles forehead skin horizontally
  • Orbicularis oris – closes lips; purses and protrudes lips
  • Orbicularis oculi – produces blinking, squinting and draws eyebrows downward
  • Zygomaticus – raises lateral corners of the mouth upward
  • Sternocleidomastoid - prime mover of active head flexion; acting alone, each muscle rotates head towards side and tilts or laterally flexes head to its own side
  • Trapezius – stabilizes, raises, retracts and rotates scapula
  • Deltoid – prime mover of arm abduction
  • Triceps brachii – powerful forearm extensor
  • Biceps brachii – flexes elbow joint and supinates forearm (movements usually happen at same time)
  • Brachioradialis – helps with forearm flexion
  • Pectoralis major – prime mover of arm flexion
  • Intercostals – elevate and depress ribs to aid in breathing
  • Latissimus dorsi –prime mover of arm extension; medially rotates arm at shoulder
  • Rectus abdominis – flex and rotate lumbar region of vertebral column
  • External oblique – aid rectus abdominus in flexing vertebral column; help with trunk rotation and lateral flexion
  • Transverse abdominis – compress abdominal contents
gluteal region
Gluteal Region
  • Gluteus maximus – major extensor of thigh; laterally rotates thigh
  • Gluteus medius – abducts and medially rotates thigh; steadies pelvis
  • Tensor fascia lata – flexes and abducts thigh; rotates thigh medially
  • Sartorius – flexes and laterally rotates thigh; flexes knee
  • Gracilis – adducts thigh, flexes and medially rotates leg, especially during walking
  • Rectus femoris – extends knee and flexes thigh at hip
  • Vastus lateralis – extends knee
  • Vastus medialis – extends knee; inferior fibers stabilize patella
  • Biceps femoris – extends thigh and flexes knee
  • Semitendinosus – extends thigh at hip; flexes knee
  • Adductor muscles – adduct and laterally rotate the thighs
  • Tibialis anterior – prime mover of dorsiflexion; inverts foot
  • Gastrocnemius – plantar flexes foot when knee is extended
  • Fibularis longus – plantar flexes foot
other fun facts1
Other Fun Facts
  • Calcaneal tendon = tendon of gastrocnemius = achilles tendon = achilles heel