BIOS 251 Week 6 Case Study: Bone

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Chamberlain University

BIOS-251 Anatomy & Physiology I

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Week 6 Case Study: Bone

Bone tissue development involves four key cell types, each with specific functions essential for bone formation, maintenance, and repair. Understanding these cells and the processes of fracture repair is critical for comprehending bone physiology.

Key Bone Cell Types

1. Osteogenic Cells
Osteogenic cells, derived from embryonic mesenchyme, are stem cells that play a foundational role in bone development. Their primary function is to proliferate and differentiate into osteoblasts, the bone-forming cells. These cells are crucial for the generation of new bone tissue and act as precursors in the bone formation process (Saladin et al., 2021).

2. Osteoblasts
Osteoblasts are responsible for synthesizing the organic matter of the bone and promoting its mineralization. They also participate in endocrine functions, secreting osteocalcin, which stimulates insulin secretion by the pancreas, increases insulin sensitivity in adipocytes, and limits adipose tissue growth. These cells line up in rows along the periosteum and endosteum during the bone-building process called osteogenesis. Fractures and stress stimulate the proliferation of osteoblasts, enabling bone repair and strengthening (Saladin et al., 2021).

3. Osteocytes
Mature osteoblasts trapped in the bone matrix transform into osteocytes. These cells maintain communication with other osteocytes through gap junctions, exchanging nutrients and metabolic waste. They play a role in resorbing and depositing bone matrix, maintaining bone density, and regulating blood calcium and phosphate levels. Osteocytes also act as strain sensors, adapting the bone to mechanical stress (Saladin et al., 2021).

4. Osteoclasts
Osteoclasts are large, multinucleated cells that resorb bone tissue. Located on bone surfaces, they possess a ruffled border that increases surface area and enhances their bone-resorption efficiency. These cells are vital for bone remodeling and calcium homeostasis (Saladin et al., 2021).

Fracture Repair Process

The repair of fractures occurs in four stages: hematoma formation, bone generation, bony callus formation, and bone remodeling.

Hematoma Formation: When a fracture occurs, torn blood vessels lead to clot formation (hematoma), cutting off blood supply to bone cells and causing their death. Within days, capillaries invade the hematoma, and phagocytic cells clear dead tissue (Boundless, n.d.).
Bone Generation: Fibroblasts and osteoblasts form collagen fibers and spongy bone, respectively, bridging the broken bone ends with repair tissue (Boundless, n.d.).
Bony Callus Formation: The fibrocartilaginous callus is replaced by a bony callus made of spongy bone within two months, firmly joining the bone ends (Boundless, n.d.).
Bone Remodeling: Osteoclasts and osteoblasts remodel the bony callus, removing excess material and forming compact bone to restore the bone’s original structure (Boundless, n.d.).

Epiphyseal Plate and Fracture Type

The epiphyseal plate facilitates the longitudinal growth of long bones. A fracture in this region could lead to deviations in length or alignment during healing. In this case, the fracture type appears to be a stable fracture, where bone ends align with minimal displacement. Stable fractures, such as a tibial fracture without significant shattering or skin breakage, generally heal with fewer complications (OrthoInfo, n.d.).

References

Boundless. (n.d.). Boundless Biology. Lumen. Retrieved October 11, 2021, from https://courses.lumenlearning.com/boundless-biology/chapter/bone/.

Fractures (broken bones) – OrthoInfo – AAOS. (n.d.). Retrieved October 11, 2021, from https://orthoinfo.aaos.org/en/diseases–conditions/fractures-broken-bones/.