Anatomy of the Muscular System

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Anatomy of the Muscular System
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A Few Facts

• There are more than 600 skeletal muscles in the
  body
• They constitute 40-50 of our body weight
• Along with the skeleton they determine the form
  and contours of our body

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Skeletal Muscle Structure
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Connective Tissue Components

• Muscles cells (fibers) are covered by a delicate
  connective tissue membrane called the endomysium.
• Groups of skeletal muscle fibers are called
  fascicles, and bound together by a tougher
  connective tissue envelope called the perimysium.
• The muscle as a whole is covered by a course
  sheath called the epimysium.

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Skeletal Muscle Structure
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• Tendon bands or cords of fibrous connective
  tissue that attach a muscle to a bone or other
  structure
• Aponeurosis broad, flat sheet of connective
  tissue
• Fascia surrounds the muscle organ and outside
  the epimysium
• Superficial
• Deep

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Size, Shape, and Fiber Arrangement

• Skeletal muscles are organs
• Vary widely in size and shape
• Muscle fiber arrangement differs
• Parallel to the long axis of the muscle
• Converge to a narrow attachment
• Oblique and pennate (like a feather pen)
• Bipennate (double-feathered)
• Curved -- sphincter

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Fiber Arrangement

1. Parallel
2. Convergent
3. Pennate

• Bipennate
• Sphincter

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Attachment of Skeletal Muscle

• Most muscles span at least one joint and attach
  to both articulating bones
• Origin attachment of a muscle to the bone,
  which does not move when contraction occurs
• Insertion attachment of a muscle to the bone
  that it moves when conctraction occurs

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Muscle Attachment
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Muscle Actions

• Most muscles act in groups and not alonesome
  contract while others relax
• Agonist (prime mover) used to describe a muscle
  or group of muscles that directly performs a
  specific movement. Example biceps brachii is
  the prime mover in the flexion of the forearm.
• Antagonists muscles that, when contracting,
  directly oppose prime movers they relax while
  the prime mover is contracting

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• Synergists muscles that contract at the same
  time as the prime mover
• Fixator muscles generally function as joint
  stabilizers
• Most muscles function not only as prime movers
  but also as antagonists, synergists, and
  fixators. A prime mover in a particular movement
  , such as flexion, may be an antagonist during
  extension

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Lever Systems

• A lever is any rigid bar free to turn about a
  fixed point called its fulcrum.
• Bones serve as levers and joints serve as
  fulcrums

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First Class Lever
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Second Class Lever
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Third Class Lever
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How Muscles are Named

• Most are Latin in origin (some Greek)
• Location (gluteus buttock)
• Function (adductor)
• Shape (deltoid triangular)

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Muscle Naming Continued

• Direction of fibers (rectus straight)
• Number of heads of divisions (biceps two points
  of origin)
• Points of attachment (sternocleidomastoid
  origin on the sternum and clavicle and inserts on
  the mastoid process)
• Size of muscle (maximus largest)

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