Solutions To Exercises Lesson

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 force applied to the body. (para 4-5)

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 the osteoblasts of the bone itself. (para 4-8e)

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 the wall of the marrow cavity. (para 4-9d-f)

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)

7. a. In a young individual, if the brain is injured by a force applied to the cranium, where will the injury usually be located? Immediately below the location of the applied force.

b. In an older adult, the injury will usually be located on the opposite side from the applied force or it may be diverted to the base of the cranium. (para 4-12c)

8. Enclosing the joint area of a "typical" synovial joint is the joint capsule. Lubricating the joint is the synovial fluid. Holding the bones together at the joint are the ligaments and skeletal muscles. Producing motion when properly stimulated are the skeletal muscles. (paras 4-22 thru 4-25)

9. The upper part of the vertebral column, the neck region, and associated muscles provide the head with its various motions. The upper two vertebrae are specifically constructed for motions of the head. (para 4-31)

10. The vertebral bodies, the intervertebral discs, and the articular processes of the vertebrae serve to support the body weight. The sacrum receives the body weight from above and transfers it to the pelvic bones. (para 4-32)

11. A semiflexible rod is formed by the vertebrae, the intervertebral discs, and the associated ligaments. The spinous and transverse processes of the neural arches serve as attachments for skeletal muscles and act as levers.

The intervertebral discs allow motion to occur between adjacent vertebrae. Second, they act as shock absorbers.

The curvatures of the vertebral column also function as shock absorbers for the body. (para 4-34)

12. The construction of the upper member serves to place the grasping hand into as many positions as possible. This is particularly helpful in grasping food and placing it into the mouth. (para 4-40)

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