CH 9

1
CH 9

• Skeletal Muscle Histology

• J.F. Thompson, Ph.D.

2
Nerve and Blood Supply

• Each muscle fiber is supplied by a branch of a
  motor nerve
• Each muscle is supplied by its own arteries and
  veins
• Blood vessels branch profusely to provide each
  muscle fiber with a direct blood supply

3
Attachments (to bone)

• Insertion the part of a muscle attached to the
  bone that moves (relative to a particular motion)
• Origin the part of a muscle attached to the
  stationary bone (relative to a particular motion)
• Direct attachment epimysium fused to periosteum
• Indirect attachment connective tissue wrappings
  gathered into a tendon or aponeurosis which
  attaches to an origin or insertion on bone

4
Attachment Structure

• Attachments are extensions of connective tissue
  sheaths beyond a muscle, attaching it to other
  structures
• Tendon cord (of dense regular connective tissue)
• Aponeurosis sheet (of dense regular connective
  tissue)
• Tendon (synovial) sheaths allow tendons to slide
  over bones

5
Connective Tissue Wrappings of Skeletal Muscle
Tissue

• Superficial Fascia "hypodermis"
• Deep Fascia lines body walls extremities
  binds muscle together, separating them into
  functional groups
• Epimysium wraps an entire muscle
• Perimysium subdivides each muscle into
  fascicles, bundles of 10-100 muscle fibers
• Endomysium wraps individual muscle fibers

6
Characteristics of Skeletal Muscle

• Attached primarily to bones
• Voluntary (conscious) control (usually)
• Contracts quickly, tires easily (fatigable)
• Allows for wide range of forces to be generated

7
Skeletal Muscle Cells

• Long, cylindrical cells
• Striated (banded)
• Multinucleate

8
Microscopic Anatomy of A Skeletal Muscle Fiber

• Muscle fibers (cells) long, cylindrical, and
  multinucleate (individual muscle cells fuse
  during embryonic development)
• Sarcolemma the cell membrane of a muscle fiber
• Sarcoplasm the cytoplasm of a muscle fiber, rich
  in oxygen-storing myoglobin protein

9
Myofibrils of A Skeletal Muscle Fiber

• Myofibrils bundles of contractile protein
  filaments (myofilaments) arranged in parallel,
  fill most of the cytoplasm of each muscle fiber
  100s to 1000s per cell
• Sarcomeres the repeating unit of contraction in
  each myofibril

10
Organelles of A Skeletal Muscle Fiber

• Mitochondria provide the ATP required for
  contraction
• Sarcoplasmic reticulum (smooth ER) stores Ca2
  ions which serve as second messengers for
  contraction

11
Striations /Sarcomeres

• Z discs (lines) the boundary between sarcomeres
  proteins anchor the thin filaments bisects each
  I band
• A (anisotropic) band overlap of thick (myosin)
  filaments thin filaments
• I (isotropic) band thin (actin) filaments only
• H zone thick filaments only
• M line proteins anchor the adjacent thick
  filaments

12
Sarcomeres

• Components of the muscle fiber with myofilaments
  arranged into contractile units
• The functional unit of striated muscle
  contraction
• Produce the visible banding pattern (striations)
• The myofilaments between two successive z discs

13
Summary of Muscle Structure
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End CH 9

• Skeletal Muscle Histology