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U N I T 1 2
Musculoskeletal Function
Such conditions occur when tendons are deflected over
bone or where skin must move freely over bony tissue.
Bursae may become injured or inflamed, causing dis-
comfort, swelling, and limitation in movement of the
involved area.
In addition to bursae, structures called
tendon
sheaths
also reduce friction at joints. Tendon sheaths
are tubelike bursae that wrap around tendons where
there is considerable friction. This occurs where ten-
dons pass through synovial cavities, such as the ten-
don of the biceps brachi muscle at the shoulder joint.
Similar areas of friction are found at the wrist and
ankle, where many tendons come together in a con-
fined space and may be torn as the result of an injury
(see Chapter 44).
SUMMARY CONCEPTS
■■
Joints (or articulations) are areas where two
or more bones are joined together by fibrous
tissue, cartilage, or bone. In fibrous joints, or
synarthroses, such as those of the skull, the bones
are joined by fibrous tissue. In cartilaginous
joints, or amphiarthoses, bones are jointed by
hyaline cartilage (as in the epiphyseal plate
during childhood and early adolescence). In
fibrocartilaginous joints (as in those that join
the vertebrae and intervertebral disks) the
articular surface is covered with hyaline cartilage,
which in turn is fused to an intervening pad of
fibrocartilage.
■■
Synovial joints or diarthroses are freely moveable
joints in which the surfaces of the articulating
ends of bones are enclosed in a fibrous joint
capsule.The joint capsule consists of two layers:
an outer fibrous layer and an inner synovial
membrane (or synovium).The synovial fluid,
which is secreted by the synovium into the
joint capsule, acts as a lubricant and facilitates
movement of the joint’s articulating surfaces.The
articulating surfaces of synovial joints are covered
with a layer of avascular cartilage that relies on
oxygen and nutrients contained in the synovial
fluid.
■■
Tendons and ligaments are dense connective
tissue structures that connect the muscles and
bones of diarthroidal joints. Bursae, which are
closed sacs containing synovial fluid, prevent
friction in areas where tendons are deflected over
bone or where skin must move freely over bony
tissue.
R E V I EW E X E R C I S E S
1.
Hyaline cartilage degenerates when the
chondrocytes become metabolically inactive and
die, causing the matrix to calcify and be replaced
by bone.
A.
Explain how this process can contribute to
normal skeletal growth during childhood and
adolescence, but cause joint pain and immobility
when it occurs during adulthood.
2.
Persons with end-stage kidney disease have a
deficiency of activated vitamin D.
A.
Explain why this occurs, and what effect it
would have on the persons’ bones.
B.
How might this deficiency be treated?
3.
Recent studies have revealed that estrogen
deficiency as well as normal aging may produce a
decrease in osteoblast activity.
A.
Explain how this would contribute to a
disruption in bone remodeling and the
development of osteoporosis.
4.
Often pain from injury to the knee is experienced
as pain in the hip.
A.
Explain why this might occur.
B I B L I O G R A P H Y
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remodeling and therapeutic potential of novel inhibitory
molecules in musculoskeletal disease.
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2006;55(1):15–18.
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. 6th ed. Philadelphia, PA: Wolters
Kluwer Health/Lippincott Williams & Wilkins; 2012:1199–1218,
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Hall JE.
Guyton and Hall Textbook of Medical Physiology
. 12th ed.
Philadelphia, PA: Saunders Elsevier; 2011:955–966.
Hofbauer LC, Schoppet M. Clinical implications of osteoprotegrin/
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Holick MF. Vitamin D deficiency.
N Engl J Med.
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Injury.
2011;42(6):551–555.
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6th ed. Philadelphia, PA: Wolters Kluwer Health/Lippincott
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