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Unformatted text preview: he passage of the infant's head
during childbirth. 1. Age-related loss of bone mass is the result of a
slowing in the rate of bone remodeling; rates of bone
loss exceed rates of bone deposition as cell renewal
rates slow. 2. An osteoarthritic joint loses cartilage, the bone wears,
and bone spurs develop around the joint margins.
These changes lead to tissue inflammation, which
causes pain, and stiffness and joint immobility as the
lubricating fluid and cartilage are lost, 3. The density of minerals in bone is what gives bone its
strength. With a loss of the mineral matrix, the bone
becomes more porous and weaker, and so more
inclined to fracture. Muscle Structure and Function (page 57)
1. Smooth muscle, also called involuntary muscle, has
spindle shaped cells with one central nucleus per
cell and a smooth appearance with no striations. Its
contractions are diffuse and it is not under conscious
control so it is involved in movement of visceral
organs such as the gut. Striated (skeletal) muscle is
voluntary and is responsible for the skeletal muscle
movement over which we have conscious control. It
has a striated or striped appearance and the cells are
multinucleate with peripheral nuclei. Cardiac muscle
is involuntary muscle responsible for the contraction
of the heart. Although it is striated, it does not fatigue
in the same way as skeletal muscle. There is one
nucleus per cell and structures called intercalated
discs (electrical junctions) join individual cells. 2. (a) The banding pattern results from the overlap
pattern of the thick and thin filaments (dark =
thick and thin filaments overlapping, light = no
(b) I band: Becomes narrower as more filaments
overlap and the area of non-overlap decreases.
H zone: Disappears as the overlap becomes
maximal (no region of only thick filaments).
Sarcomere: Shortens progressively as the
overlap becomes maximal. 3. They protect the muscle from friction and give
structural integrity to the tissue. The perimysium
(surrounding the fascicle...
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- Winter '13