Unit 4

Pre-text assignments

1 Learn the key words and phrases:

broken, bone, blood clot, dilate, osteoblasts, multiply, fibroblasts, fibrocartilage, affected, osteoclasts, callus, hyaline, cartilage, endochondral bone, casts, metal pins

2 Match the terms to following definitions:

1) a tumour or swelling containing blood a) debris

2) one of the minute red granules of new b) granulation

capillaries formed on the surface of a c) cast

wound in healing d) hematoma

3) a large amount of fibrocartilage fills e) cartilaginous callus

the gap between the ends of the broken

bone

4) the remains of something broken

down or destroyed

5) a rigid dressing of gauze impregnated

with plaster of Paris for immobilizing a

diseased or broken part

Fractures

Although a fracture may involve injury to cartilaginous structures, it is usually defined as a break in a bone. A fracture can be classified according to its cause and the nature of the break sustained. For example, a break due to injury is a traumatic fracture, while one resulting from disease is a spontaneous or pathologic fracture.

If a broken bone is exposed to the outside by an opening in the skin, the injury is termed a compound fracture. Such a fracture is accompanied by the added danger of infection, since microorganisms almost surely enter through the broken skin. On the other hand, if the break is protected by uninjured skin, it is called a simple fracture.

Repair of a Fracture

Whenever a bone is broken, blood vessels within the bone and its periosteum are ruptured, and the periosteum is likely to be torn. Blood escaping from the broken vessels spreads through the damaged area and soon forms a blood clot, or hematoma. As vessels in surrounding tissues dilate, those tissues become swollen and inflamed.

Within days or weeks, the hematoma is invaded by developing blood vessels and large numbers of osteoblasts, originating from the periosteum. The osteoblasts multiply rapidly in the regions close to the new blood vessels, building spongy bone nearby. Granulation tissue develops, and in regions further from a blood supply, fibroblasts produce masses of fibrocartilage.

Meanwhile, phagocytic cells begin to remove the blood clot as well as any dead or damaged cells in the affected area. Osteoclasts also appear and resorb bone fragments, thus aiding in "cleaning up" debris.

In time, a large amount of fibrocartilage fills the gap between the ends of the broken bone, and this mass is termed a cartilaginous callus. The callus is later replaced by bone tissue in much the same way that the hyaline cartilage of a developing endochondral bone is replaced. That is, the cartilaginous callus is broken down, the area is invaded by blood vessels and osteoblasts, and the space is filled with a bony callus.

Usually more bone is produced at the site of a healing fracture than is needed to replace the damaged tissues.

However, osteoclasts are able to remove the excess, and

the final result of the repair process is a bone shaped very much like the original one.

The rate at which a fracture is repaired depends on several factors. For instance, if the ends of the broken bone are close together, healing is more rapid than if they are far apart. This is the reason for setting fractured bones and for using casts or metal pins to keep the broken ends together. Also, some bones naturally heal more rapidly than others. The long bones of the arms, for example, may heal in half the time required by the long bones of the legs. Furthermore, as age increases, so does the time required for healing.

Post-text assignments

1 Answer the following:

1 Define between traumatic and spontaneous fracture. 2 Define between simple and compound fracture. 3 What is hematoma? 4 What is cartilaginous callus?

2 Pick out the nouns that can combine with the given verbs:

to control, to move, to send:

findings, head, disease, pain, hands, movements, patient, respiration, letter, heartbeat, order, vision, legs

3 Pick out the verbs to be used together with the given nouns:

the pain can (be discharged, be estimated, be controlled); the area can (be extended, be published, be pumped); the smell can (be covered, be entered, be felt); the vision can (be breathed in, be investigated, be complicated)

4 Respond to the questions:

1 What steps do you think should be taken to reduce the chances of persons accumulating abnormal metallic elements such as lead, radium, and strontium in their bones?

2 Why do you think incomplete, longitudinal fractures of bone shafts (greenstick fractures) are more common in children than in adults?

3 When a child's bone is fractured, growth may be stimulated at the epiphyseal disk of that bone. What problems might this extra growth create in an arm or leg before the growth of the other limb compensates for the difference in length?

4 How would you explain the observation that elderly persons often develop bowed backs and appear shorter than they were in earlier years?

5 How might the condition of an infant's fontanels be used to evaluate its development? How might the fontanels be used to estimate intracranial pressure?

6 Why are women more likely to develop osteoporosis than men? What steps might be taken to reduce the risks of developing this condition?

Unit 5

Pre-text assignments