CH 9
Skeletal Muscle Histology
J.F. Thompson, Ph.D.
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
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
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
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
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
Skeletal
Muscle Cells
• Long, cylindrical cells
• Striated (banded)
• Multinucleate
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
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; 100’s
to 1000’s per cell
• Sarcomeres: the
repeating unit of
contraction in each
myofibril
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
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
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
Summary of Muscle Structure
End CH 9
Skeletal Muscle Histology