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. T
QUESTION
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 lumbar vertebral body.
Short Answer Questions
Define the following terms, used in the case and also in associated questions (1 point each):
- hemorrhage
- fracture
- proximal
- diaphysis
- One way bones are classified is by their shape. How would you classify the bones fractured by Mrs. Morgan (3 points)?
- The body of Mrs. Morgan’s vertebra is fractured. What type of bone tissue makes up the majority of the vertebral body (1 point)? Describe the structure and function of this type of bone (2 points).
- The diaphysis of Mrs. Morgan’s humerus is fractured. What type of bone tissue makes up the majority of the diaphysis of long bones like the humerus (1 point)? List and describe/define the layers (lamellae) of bone tissue found here (3 points).
- Most connective tissue, including bone, is highly vascular. Which anatomical structures in Mrs. Morgan’s compact bone house blood vessels (2 points)? What sign or symptom in Mrs. Morgan’s case is directly related to disruption of these structures by her bone fractures (1 point)? How is the sign or symptom related to these anatomical structures (1 point)?
- Within days after a fracture, a “soft callus” of fibrocartilage forms. What fibers are found in this type of cartilage (1 point)? Identify the cells required for fibrocartilaginous callus formation and list their functions (2 points).
- 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 (1 point)? Identify which bone cell is responsible for this process (1 point)and explain how it occurs (2 points).
- 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 (1 point)? Which bone cell would be best suited for this task (1 point)?
- 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 (2 points)? Describe the cellular mechanism involved in breaking down this matrix; include the bone cell required for the process (2 points).
ANSWER
A Case Study on Bone Tissue Structure and Repair: Understanding Injuries and Healing
Introduction
In this case study, we examine the injuries sustained by Mrs. Debbie Morgan, a 45-year-old female who experienced a workplace accident. The assessment reveals fractures in her left humerus, occipital bone, and the third lumbar vertebral body. This essay will address specific terms related to the case and explore the classification of the fractured bones, bone tissue types, bone structure, vascularization, cartilage formation, bone repair, and the extracellular matrix of bone.
Definition of terms
Hemorrhage: Hemorrhage refers to the escape or loss of blood from the circulatory system, often caused by injury or trauma.
Fracture: A fracture is a break or disruption in the continuity of a bone, usually resulting from external force or trauma.
Proximal: Proximal refers to a location closer to the point of attachment or origin of a structure in relation to the body.
Diaphysis: The diaphysis is the long, tubular, and cylindrical shaft of a long bone, located between the proximal and distal ends.
Classification of fractured bones
Based on shape, the bones fractured by Mrs. Morgan can be classified as long bones. Long bones are characterized by their elongated shape and consist of a shaft (diaphysis) and two ends (epiphyses). Examples of long bones include the humerus and the femur.
Bone tissue in the vertebral body
The majority of the vertebral body is composed of cancellous or spongy bone tissue. This type of bone tissue has a lattice-like structure with trabeculae, providing strength while reducing weight. The cancellous bone also contains red bone marrow, which produces blood cells.
Bone tissue in the diaphysis of the humerus
The majority of the diaphysis of long bones, like the humerus, is composed of compact bone tissue. Compact bone is dense and provides strength and support. It consists of concentric layers called lamellae, which enclose small channels called Haversian canals that house blood vessels and nerves. The lamellae form the osteons or Haversian systems, which are the basic functional units of compact bone.
Vascularization and related symptom
Blood vessels within the compact bone are housed in the Haversian canals. Disruption of these structures by bone fractures can lead to compromised blood flow, resulting in a symptom of severe pain experienced by Mrs. Morgan.
Fibrocartilaginous callus formation
Fibrocartilaginous callus formation occurs within days after a fracture. The fibers found in this type of cartilage are predominantly collagen fibers. Fibroblasts, which are connective tissue cells, are responsible for fibrocartilaginous callus formation. Their functions include producing collagen fibers and creating a temporary structure to bridge the fracture site.
Addition of new bone tissue
The process of adding new bone tissue to the injury site is known as bone deposition or ossification. Osteoblasts, the bone-forming cells, are responsible for this process. They synthesize and secrete collagen fibers and other organic components, which mineralize and form new bone tissue.
Breaking down of osseous tissue
The breaking down of osseous tissue is called bone resorption. Osteoclasts, specialized bone cells, are responsible for this process. They secrete enzymes and acids that break down the organic and inorganic components of the extracellular matrix, allowing for remodeling and removal of damaged or old bone tissue.
Components of the extracellular matrix (ECM)
The organic portion of the ECM is primarily composed of collagen fibers, which provide flexibility and tensile strength. The inorganic portion consists mainly of hydroxyapatite crystals, which are calcium phosphate salts. These crystals contribute to the hardness and rigidity of bone tissue.
Cellular mechanism involved in breaking down the ECM
Bone resorption involves the action of osteoclasts. These cells attach to the bone surface and secrete enzymes and acids, such as acid phosphatase and carbonic anhydrase, respectively. The enzymes break down the organic components, while the acids dissolve the inorganic mineralized matrix, allowing for the breakdown and removal of the ECM.
Conclusion
This case study highlights the importance of understanding bone tissue structure and repair. By examining the fractures sustained by Mrs. Morgan, we have explored various terms, such as hemorrhage and fracture, classified the fractured bones as long bones, discussed the composition and function of bone tissue, vascularization in bone, cartilage formation during healing, bone deposition, bone resorption, and the components of the extracellular matrix. Through this analysis, we gain insights into the complexities of bone injuries and the remarkable healing mechanisms involved.
