286
UNIT TWO
Layers of connective tissue, therefore, enclose and separate
all parts of a skeletal muscle. This organization allows the
parts to move somewhat independently. Also, many blood
vessels and nerves pass through these layers.
A tendon or the connective tissue sheath of a tendon (tenosynovium)
may become painfully inF
amed and swollen following an injury or
the repeated stress of athletic activity. These conditions are called
tendinitis
and
tenosynovitis,
respectively. The tendons most com-
monly affected are those associated with the joint capsules of the
shoulder, elbow, hip, and knee and those involved with moving the
wrist, hand, thigh, and foot.
The layer of connective tissue that closely surrounds a
skeletal muscle is called the
epimysium.
Another layer of con-
nective tissue, called the
perimysium,
extends inward from
the epimysium and separates the muscle tissue into small sec-
tions. These sections contain bundles of skeletal muscle F bers
called
fascicles
(fasciculi). Each muscle F ber within a fascicle
(fasciculus) lies within a layer of connective tissue in the
form of a thin covering called
endomysium
(
f gs.
9.2 and
9.3
).
Bone
Muscle
Tendon
Fascia
(covering muscle)
Epimysium
Perimysium
Endomysium
Axon of motor
neuron
Fascicle
Fascicles
Muscle fibers (cells)
Myofibrils
Thick and thin filaments
Blood vessel
Muscle fiber
Myofibril
Sarcolemma
Nucleus
Sarcoplasmic
reticulum
Filaments
FIGURE 9.2
A skeletal muscle
is composed of a variety of tissues,
including layers of connective tissue.
±ascia covers the surface of the muscle,
epimysium lies beneath the fascia, and
perimysium extends into the structure
of the muscle where it separates muscle
cells into fascicles. Endomysium separates
individual muscle ²
bers.
A
compartment
is the space that contains a particular group of mus-
cles, blood vessels, and nerves, all tightly enclosed by fascia. The
limbs have many such compartments. If an injury causes F
uid, such
as blood from an internal hemorrhage, to accumulate in a compart-
ment, the pressure inside will rise. The increased pressure, in turn,
may interfere with blood F
ow into the region, reducing the supply
of oxygen and nutrients to the a³
ected tissues. This condition, called
compartment syndrome, often produces severe, unrelenting pain.
Persistently elevated compartmental pressure may irreversibly dam-
age the enclosed muscles and nerves. Treatment for compartment
syndrome may require an immediate surgical incision through the
fascia (fasciotomy) to relieve the pressure and restore circulation.
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