Skeletal Design

Functions of a skeletal system

support

movement

protection

hematopoiesis [blood cell formation]

Structure of bone

general structure

compact bone

periosteum

Sharpey’s fibers

endosteum

yellow marrow

cancellous [spongy] bone

red marrow

long bones

epiphysis

diaphysis

flat bones

inner and outer tables

diploë

sesamoid bones

Osteogenesis

dramatis personae

osteoblasts

osteocytes

chondroblasts

chondrocytes

osteoclasts

intramembranous ossification

endochondral ossification

bone collar

epiphyseal plate





Questions for thought

1.   What is the difference between ossification and calcification.?
2.   An elderly patient has a broken femur that is healing very slowly. A young resident suggests using a device that will create an electrical field in the area of the fracture to help speed the healing process. Why might this possibly help?
3.   Todd is 13 and lives in an urban apartment. He spends most of his time watching TV and eating “junk” food. One afternoon, during recess, he falls on the playground and breaks his leg. Although he appears to be healthy, his leg takes longer to heal than expected. What might be the cause of the longer healing time?
4.   What is osteopenia? Name and define two forms of osteopenia.
5.   During the growth of a long bone, how is the epiphysis forced farther from the shaft?
These answers are sufficient to receive credit, but it is hoped the student would add more content.
1.   Ossification means specifically the conversion of connective tissue into bone tissue. Calcification means the depositing of calcium salts in any tissue, including bone.
2.   Osteoblasts are attracted to electrical fields produced by bone crystals when they are stressed. This is one of the reasons that trabeculae of bones are organized along stress lines. If the same type of electrical field could be duplicated at the site of the fracture, osteoblasts may be stimulated to migrate to the area and increase the rate of bone production and thus healing of the fracture.
3.   Assuming that there is no other disease process involved, Todd's problem is probably related to his poor diet. Good nutrition is important for promoting the healing process. Insufficient quantities of protein, vitamin C, vitamin A, and vitamin D would cause the normal healing process to occur at a much slower rate. Todd's inactivity may also contribute to his slower rate of healing.
4.   Osteopenia is a general term for reduced bone mass. Osteoporosis and osteomalacia are forms. Osteoporosis is a condition of reduced bone density, bone weakness, and pain resulting from the loss of mineral from bone with advancing age. Osteomalacia is bone weakness caused by i nsufficient calcium deposits. It is known as rickets in the young.
5.   The chondrocytes of the epiphyseal cartilage enlarge and divide, increasing the thickness of the cartilage. On the shaft, the chondrocytes become ossified, "chasing" the expanding epiphyseal cartilage away from the shaft.

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