Bones and Skeletal Tissues
An osteon has
a central canal carrying blood vessels,
osteocytes in lacunae,
that connect lacunae to the central canal,
all of these.
Te organic portion of matrix is important in providing all but
ability to resist stretch,
Te ﬂat bones of the skull develop from
ﬁbrous connective tissue,
Te remodeling of bone is a function of which cells?
chondrocytes and osteocytes,
osteoblasts and osteoclasts,
chondroblasts and osteoclasts,
osteoblasts and osteocytes.
Bone remodeling in adults is regulated and directed mainly by
Where within the epiphyseal plate are the dividing cartilage cells
nearest the shaF,
in the marrow cavity,
from the shaF,
in the primary ossiﬁcation center.
Wolﬀ’s law is concerned with
calcium homeostasis of the
the shape of a bone being determined by mechanical
stresses placed on it,
the electrical charge on bone surfaces.
²ormation of the bony callus in fracture repair is followed by
ﬁbrocartilaginous callus formation,
formation of granulation tissue.
Te fracture type in which the bone ends are incompletely
Te disorder in which bones are porous and thin but bone
composition is normal is
Short Answer Essay Questions
Compare bone to cartilage tissue relative to its resilience, speed of
regeneration, and access to nutrients.
Describe in proper sequence the events of endochondral
Osteocytes residing in lacunae of osteons of healthy compact bone
are located quite a distance from the blood vessels in the central
canals, yet they are well nourished. How can this be explained?
As we grow, our long bones increase in diameter, but the
thickness of the compact bone of the shaF remains relatively
constant. Explain this phenomenon.
Describe the process of new bone formation in an adult bone. Use
the terms osteoid seam and calciﬁcation front in your discussion.
Compare and contrast controls of bone remodeling exerted by
hormones and by mechanical and gravitational forces, including
the actual purpose of each control system and changes in bone
architecture that might occur.
(a) During what period of life does skeletal mass increase
dramatically? Begin to decline? (b) Why are fractures most
common in elderly individuals? (c) Why are greenstick fractures
most common in children?
Yolanda is asked to review a bone slide that her professor has set
up under the microscope. She sees concentric layers surrounding
a central cavity. Is this bone section taken from the diaphysis or
the epiphyseal plate of the specimen?
and Clinical Application
²ollowing a motorcycle accident, a 22-year-old man was rushed
to the emergency room. X rays revealed a spiral fracture of his
right tibia (main bone of the leg). ±wo months later, X rays
revealed good bony callus formation. What is bony callus?
Mrs. Abbruzzo brought her 4-year-old daughter to the doctor,
complaining that she didn’t “look right.” Te child’s forehead was
enlarged, her rib cage was knobby, and her lower limbs were bent
and deformed. X rays revealed very thick epiphyseal plates. Mrs.
Abbruzzo was advised to increase dietary amounts of vitamin
D and milk and to “shoo” the girl outside to play in the sun.
Considering the child’s signs and symptoms, what disease do you
think she has? Explain the doctor’s instructions.
You overhear some anatomy students imagining out loud what
their bones would look like if they had compact bone on the
inside and spongy bone on the outside, instead of the other way
around. You tell them that such imaginary bones would be poorly
designed mechanically and would break easily. Explain your
reason for saying this.
What would a long bone look like at the end of adolescence if
bone remodeling did not occur?
Why do you think wheelchair-bound people with paralyzed
lower limbs have thin, weak bones of the leg and thigh?
Jay Beckenstein went to weight-liFing camp in the summer
between seventh and eighth grade. He noticed that the camp
trainer put tremendous pressure on him and his friends to
improve their strength. AFer an especially vigorous workout,
Jay’s arm felt extremely sore and weak around the elbow. He
went to the camp doctor, who took X rays and then told him that
the injury was serious, for the “end of his upper arm bone was
starting to twist oﬀ.” What had happened? Could the same thing
happen to Jay’s 23-year-old sister, ±rixie, who was also starting a
program of weight liFing? Why or why not?
Old Norse stories tell of a famous Viking named Egil, who lived
around 900 ³´. His skull was greatly enlarged and misshapen,
and the cranial bones were thickened (6 cm, more than 2 inches,
thick). AFer he died, his skull was dug up and it withstood the
blow of an ax without damage. In life, he had headaches from
the pressure exerted by enlarged vertebrae on his spinal cord. So
much blood was diverted to his bones to support their extensive
remodeling that his ﬁngers and toes always felt cold and his heart
was damaged through overexertion. What bone disorder did Egil
Related Clinical Terms
mold, shape) A congenital condition involving
defective cartilage and endochondral bone growth so that the
limbs are too short but the membrane bones are of normal size; a
type of dwarﬁsm.
Abnormal projection from a bone due to bony
overgrowth; common in aging bones.
pain) Pain in a bone.
inﬂammation) Inﬂammation of bony
AT T H E C L I N I C