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Quick Check and Active Learning
Answer Keys
CHAPTER 8
QUICK CHECK
Page 173
1. The primary organs of the skeletal system are the bones. (Students can list any of the 206 bones.)
2. Support, protection, movement, storage, and hematopoiesis
3. Long, short, flat, and irregular
4. The major features of the long bone include: diaphysis—shaft; medullary cavity—hollow area inside
the diaphysis; epiphyses—ends of the long bone; articular cartilage—thin layer of cartilage covering
each epiphysis; periosteum—strong fibrous membrane covering a long bone everywhere except at
joint surfaces; and endosteum—thin membrane that lines the medullary cavity.
Page 177
1. Osteons or haversian systems
2. Osteocytes are mature bone cells. Osteocytes lie between the hard layers of the lamellae in little
spaces called lacunae.
3. In cartilage, collagenous fibers are embedded in a firm gel instead of in a calcified cement substance
like they are in bone. Because of this, cartilage has the flexibility of a firm plastic rather than the
rigidity of bone.
4. Ossification is bone formation. Osteoblasts are bone-forming cells. They first lay down organic
material followed by calcium salts.
Page 185
1. The axial skeleton is made of the bones in the center or axis of the body (skull, spine, chest, and
hyoid bone). The appendicular skeleton consists of the bones of the upper extremities and the lower
extremities.
2. Sutures are immoveable joints located in the skull. Fontanels (soft spots) are areas where
ossification is incomplete at birth. Sinuses are spaces or cavities inside some of the cranial bones.
3. Cervical (7 bones), thoracic (12 bones), and lumbar (5 bones)
4. False ribs (eighth, ninth, and tenth pairs) are attached to the cartilage of the seventh rib pair, whereas
true ribs 1-7 are attached to the sternum by costal cartilage.
Page 190
1. Upper extremity: clavicle, scapula, humerus, radius, ulna, carpals, metacarpals, and phalanges.
Lower extremity: coxal, femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges.
2. Ilium, ischium, and pubis
3. The arches that form the foot are medial longitudinal, lateral longitudinal, and the transverse or
metatarsal. These arches provide great supporting strength and a highly stable base.
4. The female hipbone forms a wider structure than the male hipbone. The woman’s pelvis has a
broader, shallower shape, more like a basin. Also, the woman’s pelvic inlet and pelvic outlet are both
normally much wider than in the male.
Page 194
1. Synarthroses: sutures between cranial bones; amphiarthroses: symphysis pubis and joints between
the bodies of the vertebrae; diarthroses: knee, hip, and elbow.
2. Synovial membrane
3. A ligament is a strong fibrous connective tissue that connects bone to bone.
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Answer Keys
4. Examples of a hinge joint are elbow, knee, and the joints between the fingers. Hinge joints allow
movement in only two directions–flexion and extension.
Page 198
1. Osteosarcoma and chondrosarcoma
2. Osteoporosis
3. Rickets (young children) and osteomalacia (adults)
4. Osteomyelitis
Page 202
1. Open fracture
2. Osteoarthritis
3. Rheumatoid arthritis
ACTIVE LEARNING
Review Questions
1. a. Support—bones form the body’s supporting framework, giving it shape.
b. Protection—hard bony boxes protect delicate structures enclosed within them.
c. Movement—muscles are anchored to bones. As muscles contract and shorten, they pull on
bones and thereby move them.
d. Storage—bones play an important part in maintaining homeostasis of blood calcium.
e. Hematopoiesis—blood cell formation is a vital process carried on in red bone marrow, which is
soft connective tissue in some bones.
2. Bone matrix is organized into numerous structural units called osteons. Each circular, tube-like
osteon is composed of calcified matrix arranged in multiple layers. Each ring is called a concentric
lamella. The circular rings or lamellae surround the central canal that contains a blood vessel.
Osteocytes lie between the hard layers of the lamellae in little spaces called lacunae. Tiny passages
or canals called canaliculi connect the lacunae with one another and with the central canal in each
osteon. Nutrients pass from the blood vessel in the osteon through the canaliculi to the osteocytes.
3. Cartilage consists more of intracellular substance than cells. Innumerable collagenous fibers
reinforce the matrix of both bone and cartilage; however, in cartilage, the fibers are embedded in a
firm gel instead of a calcified cement substance as they are in bone. Cartilage has the flexibility of
firm plastic rather than the rigidity of bone. Cartilage cells, called chondrocytes, are located in
lacunae. In cartilage, lacunae are suspended in the cartilage matrix much like bubbles in a block of
gelatin. There are no blood vessels in cartilage.
4. When the skeleton begins to form in a baby before birth, it consists of cartilage and fibrous structures
shaped like bones. Gradually, these cartilage models become transformed into bone when the
cartilage is replaced with calcified bone matrix. This process of remodeling a growing bone as it
changes from a cartilage model to the characteristic shape and proportion of the adult bone is called
endochondral ossification and requires the continuous activity of bone-forming cells called
osteoblasts and bone-resorbing cells called osteoclasts. The laying down of calcium salts in the gellike matrix of bone is an ongoing process. This calcification process is what makes bone hard. The
combined action of osteoblasts and osteoclasts sculpt bone into their adult shape.
5. Long bone grows and ultimately becomes ossified from small centers located in both ends of the
bone called epiphyses and from a larger center located in the shaft of the bone. These growth areas
are made of cartilage. As long as any cartilage, called epiphyseal plates, remains between the
epiphyses and shaft of the bone, growth can continue. Growth ceases when all epiphyseal cartilage
is transformed into bone.
6. The axial skeleton includes bones of the center, or axis, of the body. The skull, spine, chest, and the
hyoid bone in the neck are all in the axial skeleton. The bones of the appendicular skeleton include
the bones of the upper and lower extremities or appendages. The bones of the shoulder, pectoral
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Answer Keys
7.
8.
9.
10.
11.
12.
13.
14.
girdle, arms, wrists, hands, hip, pelvic girdle, legs, ankles, and feet make up the appendicular
skeleton.
a. Cervical vertebrae—located in the upper neck region and contain 7 vertebrae.
b. Thoracic vertebrae—located in the center of the back and contain 12 vertebrae.
c. Lumbar vertebrae—located in the small of the back and contain 5 vertebrae.
d. Sacrum—in a child there are 5 separate vertebrae that form the sacrum and in an adult the
vertebrae are fused into one.
e. Coccyx—in a child there are 3-5 separate vertebrae and in an adult the vertebrae are fused into
one.
The first seven pairs of ribs are attached to the sternum by costal cartilage and are called true ribs.
The eighth, ninth, and tenth pairs of ribs are attached to the costal cartilage of the seventh rib pair
and these are called false ribs. The last two pairs of ribs are attached only to the vertebrae and seem
to “float free” in the front; these are called floating ribs.
A synarthrotic joint has fibrous connective tissue growing between the articulating bones, holding
them close together. Synarthroses do not allow any significant movement between the joint bones.
An example of this type of joint is the cranial bones, in which there is no movement.
An amphiarthrotic joint has cartilage connecting articulating bones. Amphiarthroses allow slight
movement between the joined bones. The symphysis pubis, the joint between the two pubic bones,
is an amphiarthrotic joint.
Diarthrotic joints allow considerable movement, sometimes in many directions and sometimes in only
one or two directions. They all have a joint capsule, a joint cavity, and a layer of cartilage over the
ends of two joining bones. There are several types of diarthrotic joints: ball-and-socket, hinge, pivot,
saddle, gliding, and condyloid. Shoulders and hips are examples of ball-and-socket joints. Elbows,
knees, and the joints in the fingers are hinge joints.
A joint capsule is made of fibrous connective tissue and is lined with a smooth, slippery synovial
membrane. The capsule fits over the ends of the two bones like a sleeve. Because it attaches firmly
to the shaft of each bone to form a covering, the joint capsule holds the bone securely together, but at
the same time, permits movement of the joint.
In an open fracture or compound fracture, the bone pierces the skin and invites the possibility of
infection. In a closed fracture or simple fracture, the bone does not pierce the skin and lessens the
possibility of infection. A comminuted fracture produces many bone fragments.
Rheumatoid arthritis is believed to be an autoimmune disease. It involves chronic inflammation of the
connective tissues. It begins in the synovial membrane and spreads to cartilage and other tissues,
often causing severe crippling. Gouty arthritis (gout) is a metabolic condition in which uric acid
increases in the blood. Excess uric acid is deposited as sodium urate crystals in distal joints and
other tissues. These crystals trigger the chronic inflammation and tissue damage characteristic of
gouty arthritis. Infectious arthritis can be caused by a variety of pathogens that can infect the synovial
membrane and other joint tissues.
Critical Thinking
15. A transplant of bone marrow is a procedure that can possibly restore or enhance the body’s ability to
form blood cells.
16. The tiny passageways, or canals, called canaliculi, connect the lacunae with the central canal in each
haversian system. Nutrients pass from the blood vessels through the canal to the osteocytes. This
allows bone to heal itself when injured. Because there are no blood vessels in cartilage, nutrients
must diffuse through the matrix to reach the cells. Because of the lack of blood vessels, cartilage
rebuilds itself very slowly after an injury.
17. If osteocytes were missing, bone maintenance would be lacking and calcium storage and removal
would be changed. If osteoblasts were missing, the bone would be weak and might not even form. If
osteoclasts were missing, the bone would get very heavy as a result of the bone formation without
bone destruction. A balance would be missing.
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Answer Keys
18. Differences between the male and female hip bones have functional importance. The female pelvis is
made so that the body of a baby can be cradled in it before birth and can pass through it during the
birth process. The individual male hip bones are generally larger than the individual female hip bones
and together they form a narrower structure than do the female hip bones. A man’s pelvis is shaped
like a funnel, but a woman’s pelvis has a broader, shallower shape, more like a basin. The pelvic
inlet and outlet are both normally wider in the female than in the male; the angle at the front of the
female pelvis where the two pubic bones join is wider than it is in the male.
19. Until bone growth is complete, the epiphyseal plate remains between the diaphysis and the epiphysis.
The epiphyseal plate allows the diaphysis of a long bone to increase in length. Any serious trauma to
this area may impact a child’s or young adult’s normal bone growth.
20. Osteoporosis is characterized by excessive loss of calcified matrix and collagenous fibers from bone.
The name osteoporosis means “condition of bone pores,” referring to pores formed as the bone
tissue is lost. Bone porosity results from decreased volume of organic bone matrix and causes the
bones to become brittle and easily broken. Because sex hormones play important roles in stimulating
osteoblast activity after puberty, decreasing levels of these hormones in the blood of elderly persons
reduces new bone growth and existing bone mass. Treatment or preventive measures include
hormone therapy and dietary supplements of calcium and vitamin D.
In osteomalacia, the volume of bone matrix remains the same, but the mass of hard mineral crystal
decreases. The demineralization of bone is usually caused by deficiency of vitamin D.
Paget disease is a metabolic disorder characterized by abnormal bone remodeling. Normal spongy
bone is replaced by disorganized new bone. The new bone often grows in marrow spaces and
causes thickening of the entire bone.
21. Mastoiditis is an inflammation of the air spaces within the mastoid portion of the temporal bone.
These air spaces do not drain into the nose like other paranasal sinuses; thus, infectious material that
accumulates may damage the bony partition between the air cells and the brain. If this occurs, the
infection may spread to the brain or membrane coverings of the brain, causing a life-threatening
situation.
Chapter Test
1. articular cartilage
2. medullary cavity
3. trabeculae
4. Haversian systems
5. lacunae
6. osteoclasts
7. osteoblasts
8. endochondral ossification
9. epiphyseal plate
10. axial, appendicular
11. synarthroses, amphiarthroses, diarthroses
12. ligaments
13. scoliosis
14. osteoporosis
15. osteomyelitis
16. compound or open
17. osteoarthritis
18. c. Heat production
19. b. periosteum
20. a. endosteum
21. d. epiphysis
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Quick Check and Active Learning
Answer Keys
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
c. diaphysis
b. chondrosarcoma
c. gouty arthritis
b. upper extremity (arm, forearm, wrist, and hand)
a. skull
b. upper extremity (arm, forearm, wrist, and hand)
d. lower extremity (thigh, leg, ankle, and foot)
d. lower extremity (thigh, leg, ankle, and foot)
c. trunk
d. lower extremity (thigh, leg, ankle, and foot)
c. trunk
b. upper extremity (arm, forearm, wrist, and hand)
d. lower extremity (thigh, leg, ankle, and foot)
b. upper extremity (arm, forearm, wrist, and hand)
a. skull
d. lower extremity (thigh, leg, ankle, and foot)
a. skull
b. upper extremity (arm, forearm, wrist, and hand)
a. skull
b. upper extremity (arm, forearm, wrist, and hand)
a. skull
Case Studies
1. The term greenstick fracture refers to a type of incomplete fracture in which a bone bends and then
breaks only along the outside curve of the bend. This type of fracture is so named because it imitates
the incomplete break commonly seen when one tries to snap a green (fresh) wooden stick into two
pieces. Greenstick fractures and other types of incomplete fractures heal more rapidly than other
fractures because the broken edges of bone tissue remain close to one another after the injury—
facilitating the repair process.
2. As Figure 8-16 (page 184), C and D, shows, such an abnormality may result from scoliosis—
abnormal lateral curvature of the vertebral column. Common among adolescent women, scoliosis
can be treated in a variety of ways. The text mentions braces (e.g., the Milwaukee brace),
transcutaneous muscle stimulation, and spinal fusion surgery as possible treatments. Other
treatments you may know include prescribed exercises, traction (pulling on the vertebral column to
straighten it), body casts, or other therapies.
3. Osteoporosis, literally “bone porosity,” is characterized by the loss of bone volume as open spaces or
pores develop in bone tissue. Such bone loss causes the skeleton to become brittle and thus easily
broken. Sometimes the bone weakness is so profound that seemingly normal stresses cause
fractures, often called spontaneous fractures, because they seem to have no direct cause. Fractured
bone, as with any broken or damaged tissue, may become infected, especially if proper medical
treatment is delayed. Osteomyelitis is infection of bone tissue and may result from infection
secondary to a fracture.
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Answer Keys
CHAPTER 9
QUICK CHECK
Page 215
1. Skeletal muscles are voluntary muscles with crosswise stripes and multiple nuclei. Smooth muscles
are involuntary muscles with tapered cells and a single nucleus. Cardiac muscles are involuntary
muscles with cross striations, cylindrical branched cells, and intercalated disks.
2. A fascicle is a group of muscle fibers. Fascia is the loose connective tissue outside the muscle
organs that forms a flexible, sticky “packing material” between muscles, bones, and the skin.
3. A muscle’s origin is its attachment to a stationary bone. The insertion is the muscle’s attachment to
the more moveable bone.
4. The myofilaments are formed from myosin and actin proteins. Each myosin molecule has a “head”
that sticks out toward the actin molecules. At rest, the actin is blocked from connecting with the
myosin. During contraction, however, actin is released and myosin heads connect to form
crossbridges between the thick and thin filaments. Calcium ions bind the thin filaments together and
release actin to react with myosin. The myosin heads pull, release, and then pull again. This
ratcheting of myosin heads pulls the thin filaments toward the center of the sarcomere, producing
contraction.
Page 218
1. Movement, posture or muscle tone, and heat production.
2. As the prime mover contracts, the antagonist relaxes.
3. Posture is a result of tonic contraction. Good posture is a positioning of the body that balances the
distribution of weight and therefore puts less strain on muscles, tendons, ligaments, and bones.
4. The contraction of muscle fibers produces most of the heat required to maintain body temperature.
5. The term oxygen debt describes the continued increased metabolism that must occur in a cell to
remove excess lactic acid that accumulates during prolonged exercise.
Page 220
1. Acetylcholine is a neurotransmitter found at the neuromuscular junction (NMJ). When released,
acetylcholine moves across the NMJ and triggers events within the muscle fiber that stimulate the
contraction process.
2. A motor unit is a single motor neuron with the muscle cells it innervates.
3. Muscles produce different levels of strength when different numbers of motor units are activated for
different loads.
4. Isotonic contraction produces movement at a joint. Isometric contraction is when the muscle
contracts and there is no movement.
5. Strength training involves contracting muscles against heavy resistance. This type of training results
in increased numbers of myofilaments in each muscle fiber, thus increasing the mass of the muscle.
Endurance training increases a muscle’s ability to sustain moderate exercise over a long period. The
number of blood vessels are increased (without significantly increasing muscle size), allowing a more
efficient delivery of oxygen and glucose to muscle fibers.
Page 223
1. During flexion, the angle between two bones at their joint is less than the angle during extension.
2. When a person abducts his/her arm, he/she moves the arm away from the midline of the body.
3. In dorsiflexion, the top of the foot is elevated with the toes pointing upward.
4. Extensors play their most important role in maintaining an upright posture.
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Page 227
1. The muscles of mastication are responsible for closing the mouth and producing chewing
movements.
2. The triceps brachii is often called the “boxer’s muscle” because it is responsible for delivering blows
during fights.
3. External oblique, internal oblique, and the transversus abdominis
4. The hamstrings serve as powerful flexors of the lower leg.
Page 230
1. Myositis is muscle inflammation. Fibromyositis is tendon inflammation that occurs with myositis.
2. Poliomyelitis is a viral infection of the nerves that control skeletal muscle movement. It often causes
paralysis that may progress to death.
3. Duchenne muscular dystrophy is caused by a missing gene in the X chromosome.
4. Myasthenia gravis is characterized by muscle weakness, especially in the face and throat.
ACTIVE LEARNING
Review Questions
1. Cardiac muscle is composed of cells that are cylindrical, branch frequently, and then recombine into a
continuous mass of interconnected tissue. They have cross-striations and unique dark bands, called
intercalated disks, where the plasma membranes of adjacent cardiac cells come into contact with
each other. These disks allow the muscle cells of the heart to contract as a unit, increasing the
efficiency of the heart muscle in pumping blood.
2. Smooth muscle fibers are tapered at each end, have a single nucleus, and lack the striations of
skeletal or cardiac muscle. When viewed under a microscope, they have a smooth, even
appearance. Smooth, or involuntary, muscle forms an important part of blood vessel walls and many
hollow visceral organs, such as the digestive tract, urethra, and ureters.
3. Tendons anchor muscles firmly to bone. Bursae are small fluid-filled sacs that lie between some
tendons and the bones beneath them. Like small flexible cushions, bursae make it easier for a
tendon to slide over a bone when the tendon’s muscle shortens. The synovial membrane secretes a
slippery, lubricating fluid, called synovial fluid, that fills the bursae.
4. The sliding filament model is a theory of muscle contraction in which sliding of thin myofilaments
toward the center of each sarcomere quickly shortens the muscle fiber and thereby the entire muscle.
The myofilaments are formed from myosin and actin proteins. Each myosin molecule has a “head”
that sticks out toward the actin molecules. At rest, the actin is blocked from connecting with the
myosin. During contraction, however, actin is released and myosin heads connect to form
crossbridges between the thick and thin filaments. Calcium ions bind the thin filaments together and
release actin to react with myosin. The myosin heads pull, release, and then pull again. This
ratcheting of myosin heads pulls the thin filaments toward the center of the sarcomere, producing
contraction.
5. Good posture is the definition of body positioning that favors best functioning of all body parts. Such
positioning balances the distribution of weight and therefore puts the least strain on muscles,
tendons, ligaments, and bones.
6. The respiratory, circulatory, nervous, and skeletal systems play essential roles in producing normal
movement. The respiratory system must supply the muscle with oxygen and the circulatory system
must carry the oxygen to the muscle. The nervous system must carry the impulse to the muscle so
that it can contract and the joints of the skeletal system must be free to move.
7. A twitch is a quick, jerky response to a stimulus. Twitch contractions can be seen in isolated muscles
during research, but they play a minimal role in normal muscle activity. A tetanic contraction is a
more sustained and steady response than a twitch. It is produced by a series of stimuli bombarding
the muscle in rapid succession. Contractions “melt” together to produce a sustained contraction or
tetanus.
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Answer Keys
8. Isotonic contraction of muscle produces movement at a joint. With this type of contraction, the
muscle shortens and the insertion end moves toward the point of origin. An example of this is the
action of walking or running; the movement is caused by isotonic contractions.
9. Isometric contraction of muscle increases the tension in the muscle, but the muscle does not shorten
and no movement results.
10. Flexion is the movement that makes the angle between two bones at their joint smaller than it was at
the beginning of the movement (bending). Extension is the movement that makes the angle between
two bones at their joint larger than it was at the beginning of the movement (straightening). Abduction
refers to a movement of a part away from the midline of the body. Adduction refers to a movement of
a part toward the midline of the body. Rotation is the movement of a body part around a longitudinal
axis.
11. Any two of the muscles listed in the Muscles of the Head and Neck section of Table 9-2 on page 224
of the text may be used.
12. Any two of the muscles listed in the Muscles That Move the Upper Extremities section of Table 9-2 on
page 225 of the text may be used.
13. Any two of the muscles listed in the Muscles of the Trunk section of Table 9-2 on page 225 of the text
may be used.
14. Any three of the muscles listed in the Muscles That Move the Lower Extremities section of Table 9-2
on page 225 of the text may be used.
15. A muscle strain involves stretching or tearing of muscle fibers. It is often accompanied by myalgia
and may include inflammation of the muscle or of the muscle and tendon. If the injury is near a joint
and involves ligament damage, it may be called a sprain.
16. Myasthenia gravis is an autoimmune disease with characteristic muscle fatigue and progressive
muscle weakness, caused by the immune system attacking muscle cells at the neuromuscular
junction. Nerve impulses from the motor neurons are then unable to fully stimulate the affected
muscle.
Critical Thinking
17. When the biceps brachii flexes the elbow, it is acting as the agonist, whereas the triceps brachii is the
antagonist. When the triceps brachii extends the elbow, it is the agonist, whereas the biceps brachii
is the antagonist. Note: the term “agonist” refers to the muscle that is opposing an action by another muscle, “antagonist.”
18. Several muscles contract while others relax to produce almost any movement. Of all the muscles
contracting simultaneously, the one that is mainly responsible for the production of the movement is
called the prime mover for that movement. The other muscles that help in producing the movement
are called synergists. As the prime mover and the synergist muscles contract, other muscles called
antagonists relax. When the antagonist muscles contract, they produce a movement opposite to that
of the prime movers and the synergist muscles.
19. During exercise, the stored ATP required for muscle contraction becomes depleted. Formation of
more ATP results in the rapid consumption of oxygen and nutrients that outstrips the ability of the
blood to replenish them. When oxygen supplies run low, the muscle cells switch to a type of energy
release that does not require oxygen. This process produces lactic acid. The term oxygen debt
describes the continued increased metabolism that must occur to remove the excess lactic acid that
accumulates during this period. This replaces the depleted energy reserves in the muscle. Labored
breathing after exercise is required to pay the oxygen debt brought on by the increased metabolism.
20. Muscles can only contract when a nerve impulse that stimulates the contraction is received. If a
nervous system disorder exists, such as in a spinal cord injury, impulses to the muscle are prevented
and that muscle is unable to receive stimuli, resulting in paralysis.
21. A muscle cannot contract very long if its blood supply is shut off. In order for muscle contractions to
occur, ATP must supply energy for the sarcomeres to shorten. The ATP supply in a muscle is very
limited and will rapidly become depleted. The formation of more ATP requires nutrients and oxygen.
Both of these are supplied to the muscle by the blood. If the blood supply is cut off, the muscle will
rapidly run out of ATP and be unable to contract.
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Answer Keys
22. The stimulus for the building of bone is stress on the bone. If there is too little stress, the bonebuilding process is not reinforced and the bone becomes weaker. During prolonged periods of
inactivity, the unused muscles shrink in size and become weaker, a condition called disuse atrophy.
The weakening of the bones and muscles places additional stress on the joints.
23. A marathon runner would want slow fibers muscles. These muscles can maintain contractions over a
long period of time without fatigue. A sprinter would want a muscle with a high proportion of fast
fibers. Fast fibers can respond much more rapidly; however, they use so much energy that they
fatigue quickly.
24. Duchenne muscular dystrophy is characterized by mild leg muscle weakness that progresses rapidly
to include the shoulder muscles. The first signs of Duchenne muscular dystrophy are apparent at age
3 and the child is usually severely affected within 5 to 10 years. Death from respiratory or cardiac
muscle weakness often occurs by the time the person is 21 years of age.
Chapter Test
1. Muscle fiber
2. heart
3. insertion
4. origin
5. Actin
6. Myosin
7. sarcomere
8. movement, posture, heat production
9. ATP
10. Lactic acid
11. motor unit
12. Threshold stimulus
13. Isotonic
14. Isometric
15. Abduction
16. Eversion
17. Supination
18. strain
19. fibromyositis
20. Poliomyelitis
21. Muscular dystrophy
22. Myasthenia gravis
23. b. voluntary muscle
24. a. visceral muscle
25. a. muscles of the head or neck
26. b. muscles that move the upper extremity
27. d. muscles that move the lower extremity
28. a. muscles of the head or neck
29. d. muscles that move the lower extremity
30. b. muscles that move the upper extremity
31. c. muscles of the trunk
32. d. muscles that move the lower extremity
33. a. muscles of the head or neck
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Answer Keys
34. c. muscles of the trunk
35. d. muscles that move the lower extremity
36. b. muscles that move the upper extremity
Case Studies
1. Pseudohypertrophic muscular dystrophy or Duchenne muscular dystrophy (DMD) is an X-linked
inherited disorder, so the cause of Tom’s condition is inheritance of a defective gene on the X
chromosome. More information on X-linked traits is found in Chapter 25. It is unlikely that Geri will
develop DMD because females rarely exhibit X-linked disorders. Your risk of developing DMD
depends on several different factors. First, if you are female you are not likely to develop DMD.
Second, Tom’s defective X chromosome had to have been inherited from his mother (see Chapter
25), so if you are related to Tom’s mother you are more likely to have the defective gene than if you
are not related to her. Third, because DMD typically strikes by age 3, you are unlikely to develop the
disease now. The false (pseudo) enlargement (hypertrophy) of Tom’s legs is the result of abnormal
levels of a cytoskeletal protein in patients with DMD. The body replaces atrophied (reduced) muscle
fibers with an overabundance of fat and fibrous tissue, which is a common occurrence in DMD.
2. Your friend has sustained a tear or overstretching of muscle fibers in a major lower leg muscle
located in the “calf” region. Elena is likely suffering from myalgia (muscle pain) and myositis (muscle
inflammation). The irritation of the injury and the resulting inflammatory response may also cause
muscle cramps. The gastrocnemius muscle plantar flexes the foot, causing the toes to point
downward. Almost any movement of the lower leg is likely to disturb the injured tissue, so Elena
should avoid leg movements as recommended by her physician. Walking or even standing are most
likely to worsen Elena’s injury.
3. Robert may have some increase or hypertrophy of his upper body muscles. However, because
racquetball primarily involves endurance or “aerobic” exercise, the increase will not be great.
Massive muscle hypertrophy or “body building” results from strength training or “anaerobic” exercise,
such as weight-lifting. Robert seems out of breath because the aerobic exercise undertaken in a
game of racquetball causes an oxygen debt that must be “repaid” after exercise by continued heavy
breathing, perhaps making it difficult for Robert to speak to you.
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