Musculo-Skeletal Anatomy
What have we been learning??
Making the
body move!
• Types of Muscle
• Muscle Structure
• Muscle Stimulation
Goals
• Important muscle groups to know
• Review muscle functions, types, and
general anatomy
• In-depth look at skeletal muscle:
– Connective tissue covering
– Skeletal muscle fibers
– Neuromuscular junction
Three types of muscle
1. Skeletal
2. Cardiac
3. Smooth
The
Anterior
(see
handout)
Anterior = “Front”
The Posterior (See handout)
Posterior = “back”
Functions of Muscle
•
•
•
•
Producing movement.
Maintaining posture.
Stabilizing joints.
Generating heat.
Characteristics of Muscles
(some review, some *new*!)
• Muscle cells are elongated
(*muscle cell = muscle fiber)
• *Contraction of muscles is due to the
movement of microfilaments
• *All muscles share some terminology
– Prefix myo refers to muscle
– Prefix mys refers to muscle
– Prefix sarco refers to flesh
Skeletal Muscle Characteristics
•
•
•
•
•
*Most are attached by tendons to bones
Cells have many nuclei
Striated – have visible banding
Voluntary – subject to conscious control
*Cells are surrounded by and bundled by
connective tissue
Skeletal Muscle
• Striated, long,
cylindrical, multinucleated.
• Attached to bones
• Voluntarily controlled
• * Range of contractile
speed
Cardiac Muscle
• Striated, one nucleus,
branching chains of cells,
intercalated discs (= dark
bands)
• Found only in the heart.
• Involuntary contraction.
• *Slow speed of
contraction.
• *Rhythmic contraction.
Smooth Muscle
• One nucleus, no
striations.
• *Found along the
walls of blood vessels
and digestive canals.
• Involuntary
contraction.
• *Very slow
contraction.
Skeletal Muscle Attachments
• What structures do muscles attach to?
– Bones
– Cartilages
– **extensions of connective tissue coverings
Connective tissue coverings
• Layers of connective tissue enclose and
separate all parts of a skeletal muscle
1. Fascia
2. Epimysium
3. Perimysium
4. Endomysium
Friends
Enjoy
Protecting
Each other
Fascia
• layers of connective tissue that separate
individual skeletal muscles from each
other
– hold muscles in position
– May extend beyond muscle to form:
• Tendon – cord-like structure
• Aponeuroses – sheet-like structure
Connective Tissue Wrappings of
Skeletal Muscle
• Fascia – on the
outside of the
epimysium
• Epimysium –
covers the entire
skeletal muscle
Figure 6.1
Connective Tissue Wrappings of
Skeletal Muscle
• Perimysium –
around a fascicle
(bundle) of fibers
• Endomysium –
around single
muscle fiber
Figure 6.1
How does the structure of the coverings
arrangement allow the muscles to function?
• Structure: layers of connective tissue
enclose and separate all parts of a skeletal
muscle
• Function:
– allows parts to move somewhat independently
– Blood vessels and nerves pass through the
layers Æ allows for blood/nutrient supply and
stimulation
Review
•
•
•
•
Produce movement
Maintain posture
Stabilize joints
Generate heat
• Connective tissue coverings ?
Overall structure of muscle
• Muscle
• Fascicles (bundles)
• Muscle fibers (cells)
• Myofibrils
• Thick and thin
filaments
Modeling Activity
• In pairs, using the available materials,
create a model of a muscle (include fiber,
fascicles, muscle fibers, fascia,
epimysium, perimysium, endomysium)
Muscle fibers
• Definition: single cell that contracts in
response to stimulation, relaxes when
stimulation ends
• Thin, elongated cylinder that could extend
full length of muscle
Muscle fibers
• Cells are multinucleate
• Nuclei are just beneath the sarcolemma
Microscopic Anatomy of Skeletal
Muscle
• Sarcolemma –
specialized plasma
membrane
• Sarcoplasmic
reticulum –
specialized smooth
endoplasmic
reticulum
Figure 6.3a
Microscopic Anatomy of
Skeletal Muscle
• Myofibril
– Bundles of myofilaments
– Myofibrils are aligned to give distinct bands
• I band =
light band
• A band =
dark band
• Bands make muscle look STRIATED
Figure 6.3b
Microscopic Anatomy of
Skeletal Muscle
• Sarcomere
– Contractile unit of a muscle fiber
– From Z disc to Z disc
Figure 6.3b
Microscopic Anatomy of Skeletal Muscle
• sarcomere organization (Section of
myofibrils)
– Thick filaments = myosin filaments = dark
band
• Composed of the protein myosin
• Has ATPase enzymes (for contraction)
Figure 6.3c
Microscopic Anatomy of
Skeletal Muscle
• Organization of the sarcomere
– Thin filaments = actin filaments = light band
• Composed of the protein actin
Figure 6.3c
Microscopic Anatomy of
Skeletal Muscle
• Myosin filaments have heads (extensions,
or cross bridges)
• Myosin and
actin overlap
somewhat
Figure 6.3d
Microscopic Anatomy of
Skeletal Muscle
• At rest, there is a bare zone that lacks
actin filaments
• Sarcoplasmic
reticulum
(SR) – for
storage of
calcium
Figure 6.3d
Modeling activity
• In pairs, using the available materials,
create a model of a myofibril segment
between 2 M lines.
• Include/indicate sarcomere, actin, myosin,
2 M lines, I band, and A band