Skeletal System Questions
Answer key
1. Does every person on earth have 206 bones? Explain your answer. Be sure to include age as part of your answer.
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Babies born with 270
o
Bones fuse as you develop
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(ex: hands, feet, clavicle was 2 bones, os coxae)
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Extra bones in hands, feet, or cranium
o
Sesamoid, sutural, or just plain extra bones
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Some bones in hands/ feet may have fused
2. How do bones grow? Use the terms endochondrial, ossification, hyaline cartilage, and epiphyseal plate as part of
your answer.
All bones start out as hyaline cartilage and undergo ossification (the process of becoming bone). Long bones undergo
endochondrial ossification, where they start as solid cartilage, then develop periosteum and a medullary cavity and blood
supply begins to go throughout. The bones takes shape, with development of spongy bone and compact (cancellous) bone. The
epiphyseal plates develop, and bones grow longer from the plates outward.
3. What is the role of nutrition in bone growth and development?
Proper nutrition is important to bone growth and development. Deficiencies in vitamins A, C, and D can result in bone
development issues.
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Lack of:
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slow development
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collagen problems that cause fragility
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rickets and osteomalacia b/c can’t use Calcium (need D to absorb it)
4. How is movement using a lever system? Use the terms bar, fulcrum, resistance and force as part of your answer.
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Rigid bar- bone
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Fulcrum- the joint
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Object moved against resistance is the bone you are moving (which is always below the joint)
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Force- the muscle’s force to move the bones
So the muscle on top of bone (the bar) above a joint uses force to move the bones below (the object). The point of movement,
the fulcrum, is the joint itself.
5. How does the skeleton change as we age? Use the terms ossification, hyaline, calcitonin, parathyroid hormone,
fontanel, osteoclast, osteoblast, and osteoporosis in your answer.
As we age, the skeleton goes from a rough outline of completely hyaline cartilage to bone through the process of ossification.
Long bones undergo endochondrial ossification, while flat bones undergo intramembranous ossification. An example of
intramembranous ossification is when the fontanels (“soft spots”) on a newborn’s cranium become bone. Osteoblasts always
build bone, and the hormone responsible for this is calcitonin. During our youth, osteoblast activity outpaces osteoclast
activity and bone is deposited, resulting in high bone density, as long as there is sufficient calcium and vitamins A, C, and D in
the diet. As we live our younger lives, there is a balance between osteoblast activity, controlled by calcitonin, and osteoclast
activity, controlled by PTH (parathyroid hormone). Bone is maintained while blood calcium levels remain basically constant
(one of our homeostatic mechanisms). However, as we age, osteoclast activity increases and we lose bone mass. This can
result in osteoporosis, where bones become less dense and therefore brittle and break very easily.
6. What information can be used to distinguish between male and female skeletons? Why do these differences exist?
Are the differences 100% apparent in all cases? Explain.
Male and female skeletons differ fairly distinctly in the cranium, including the mandible, as well as in the pelvis. However,
differences can also be seen in how rough the bones are and the size of the bones. These differences are a result of the action
of hormones during development. The differences are not 100%. There can be a range of typical bone features for either
gender, and more athletic females may have some general bone differences that are more “masculine”, while less athletic
males may have more “feminine” bone markings. But, in general, it is fairly easy to determine the sex of a skeleton.
7. How do the skeletons of active and inactive people differ? Why is this? Use the word prominence in your answer.
Active people have more noticeable prominances on their bones for muscle attachments. Their bones are more “pointy” for
attachment sites for larger muscles that are gained from higher levels of activity. Less active people have more rounded bones,
which are usually thinner in diameter, lighter, as well as less dense, than those of active people.
8. What are the different types of bone fractures (breaks) that can occur? You may illustrate these, use straws that
you tape to the paper and label, or use words to explain.
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Impacted fractures are those that occur from bones pushing into each other; one cause could be from impact (think
falling on a wrist or jumping from a high height)
Spiral fractures are from a twisting of the bone, which can happen in a small child from grabbing an arm tightly
while they twist away
Transverse fractures are those that are straight across a bone (transverse plane)
Oblique fractures are fractures on the oblique plane, on the diagonal of a bone
Complete fractures are the that the bone is completely separated and no longer in line
Comminuted fractures are those where they bone is fragmented or crushed
Fissured fractures are incomplete longitudinal breaks
Greenstick fractures (called this because of how a green stick can twist but not completely break) are incomplete
breaks on the curved surface of a bone