SOLUTIONS TO EXERCISES, LESSON 4
1.
The skeleton supports (holds up) the body.
Joints and attached skeletal muscles enable the parts of the body to move with
respect to each other; this is called motion. Such linkages in the lower members make
locomotion possible.
The skeleton helps to protect vital organs.
The skeleton is involved in the formation of blood (hematopoiesis) cells.
The skeleton also stores various minerals. (para 4-2)
2.
Each bone is built upon a framework of FCT. Upon this framework, apatite
crystals are deposited in regular order. When compressed, these crystals produce a
local electric current. This phenomenon is called the piezoelectric effect. Bones tend to
lose mass when they are not subjected to at least ordinary forces. (para 4-4)
3.
The living cells of the bones are osteocytes. When these cells are building up
bone tissue, they are called osteoblasts. When they are tearing down bone tissue, they
are called osteoclasts. The building and rebuilding respond direly to the directions of
4.
The envelope surrounding the "typical" long bone is the periosteum. Adjacent to
the surface of the bone, there is a special layer of bone-forming cells called the
osteogenic layer. When a long bone is fractured without loss of the periosteum, the
fracture is healed by the combined action of the osteogenic layer of the periosteum and
5.
In the early years of life, near each end of the long bones, there is a plate of
cartilage called the epiphyseal plate. Between puberty and adulthood, this cartilage is
replaced by bone development. The dense bony line remaining is called the epiphyseal
line.
Meanwhile, the bone also grows in width. As bony tissue is added to the outside
of the bone by the osteogenic layer, osteoclastic activity removes bone material from
6.
When the growth of the cranial flat bones is complete, the osteogenic layer of the
periosteum disappears. Osteoblastic activity repairs only the margins of a spatial
defect. Thus, the missing portions of the tables will not be replaced. (para 4-12b)
MD0007
4-22