Look Out Below: A Case Study on Bone Tissue Structure and Repair

Mrs. Debbie Morgan is a 45-year-old female who works as a stocking clerk for a local home improvement store. While she was at work today a large box of metal rivets fell from a 20-ft.-high overhead shelf, striking her outstretched arm and knocking her to the ground. The ambulance personnel reported that she had lost quite a bit of blood at the accident scene and was “knocked out” when they arrived. To minimize further hemorrhage, the paramedics applied a pressure bandage to her arm.

You meet the paramedics as they bring Mrs. Morgan into the emergency room and begin to assess her for injuries. She is awake and alert, but complaining of severe left arm and back pain, plus she has a “killer headache.” To fully examine her injuries you remove four blood-soaked bandages from her arm. You notice a large open wound on her arm with what appears to be bone tissue sticking out of the skin. She also has bruises covering her left shoulder, left wrist, and lower back. To determine the extent of her injuries Mrs. Morgan undergoes several x-rays, which reveal the following:

1) fracture of the left humerus at the proximal diaphysis,

2) depressed fracture of the occipital bone, 

3) fracture of the 3rd  lumbarvertebral body.

Short Answer Questions

2.   One way bones are classified is by their shape. How would you classify the bones fractured by Mrs. Morgan?

3.   The body of Mrs. Morgan’s vertebra is fractured. What type of bone tissue makes up the majority of the vertebral body? Describe the structure and function of this type of bone.

4.   The diaphysis of Mrs. Morgan’s humerus is fractured. What type of bone makes up the majority of the diaphysis of long bones like the humerus? Describe the layers of bone tissue found here.

5.   Most connective tissue, including bone, is highly vascular. Which anatomical structures in Mrs. Morgan’s compact bone house blood vessels? What sign or symptom in Mrs. Morgan’s case is directly related to disruption of these structures by her bone fractures? How is the sign or symptom related to these anatomical structures?

6.   Within days after a fracture, a “soft callus” of fibrocartilage forms. What fibers are found in this type of cartilage? Identify the cells required for fibrocartilaginous callus formation and list their functions.

7.   As a fracture is repaired, new bone is added to the injury site. What term is used to describe the addition of new bone tissue? Identify which bone cell is responsible for this process and explain how it occurs.

8.   In the final stage of bone repair, some of the osseous tissue must be broken down and removed. What term is used to define the breaking down of osseous tissue? Which bone cell would be best suited for this task?

9.   The extracellular matrix (ECM) of bone is considered to be a composite material made up of organic and inorganic matter. What makes up the organic and inorganic portions of the matrix? Describe the cellular mechanism involved in breaking down this matrix; include the bone cell required for the process.