Skeletal muscle is composed of bundles of muscle fibers surrounded by connective tissue. Each muscle fiber contains contractile filaments that slide past each other, allowing the muscle to contract. Blood vessels and nerves supply the muscle fibers with oxygen and nutrients and signals for contraction. The fibers are bundled and attached to bones via tendons, allowing muscles to pull on bones and enable movement.

1. Unit 6
The
Muscular System
DeFord
Section 3
Skeletal Muscle Structure

2. Skeletal Muscle Structure
Although muscle fiber makes up most of the muscle
tissue, a large amount of connective tissue, blood vessels,
and nerves are also present.
• Connective tissue covers and supports each muscle fiber and
reinforces the muscle as a whole.
• The heath of muscle depends on a sufficient nerve and blood supply.
Each skeletal muscle has a nerve ending that controls its activity.
• Active muscles use a lot of energy and require a continuous supply
of oxygen and nutrients, which are supplied by arteries. Muscles
produce large amounts of metabolic waste that must be removed by
veins.

3. Gross Anatomy of Skeletal Muscles
Cells are surrounded and bundled by connective tissue!
Connective Tissue Organization:
• Endomysium – encloses a single muscle fiber
• Perimysium – wraps around a fascicle (bundle) of
muscle fibers
• Epimysium – covers the entire skeletal muscle
• Fascia – outer layer of the epimysium

4. Blood Vessel
Perimysium
(surrounds fascicle)
Epimysium
(wraps around
entire muscle,
surrounded by fascia)
Muscle
Fiber (cell)
Fascicle
(bundle of muscle
fibers, surrounded by
perimysium)
Endomysium
(encloses each muscle
fiber)
Tendon
Bone

5. Arrangement of Fascicles
The fascicles of muscles can be arranged in a variety of
ways – the most common are:
• Parallel – fascicles are parallel to the long axis of the muscle. Some
of these are also classified as fusiform muscles.
• Pennate – the fascicles are short and attach to a central tendon.
Can be unipennate, bipennate or multipennate.
• Convergent – the muscle has a broad origin but the fascicles
converge to one tendon.
• Circular – muscle has the fascicles arranged in concentric circles.

7. Skeletal Muscle Attachments
Skeletal muscles attach to bones, cartilage, and
connective tissue coverings.
•Epimysium blends into a connective tissue attachment
•Tendons – cord-like structures
•Mostly collagen fibers
•Often cross a joint due to toughness and small size
•Aponeuroses – sheet-like structures
•Attach muscles indirectly to bones, cartilages, or
connective tissue coverings

8. Microanatomy of Skeletal Muscles
• Sarcolemma – specialized cell membrane
• Sarcoplasm – muscle cell cytoplasm
• Sarcoplasmic Reticulum – specialized smooth
endoplasmic reticulum
• used to store and maintain calcium ion levels
• surrounds the myofibril

9. Microanatomy of Skeletal Muscles
• T Tubules – tubules running through the muscle fibers
through which calcium ions flow
• Sarcomeres – repeating contractile unit of the myofibril
• Myofibril – long contraction organelle aligned to
give distinct bands
• I band = light band that contains
only thin filaments called actin.
• A band = dark band that contains
thick filaments called myosin.
• Z-lines at each end provide anchors for thin
filaments