Compact Bone
Bennion explained that the outer layer of bone, known as the “compact bone,” is a dense exterior found in all bones. Despite its density, it can be relatively thin at the ends of bones and is not entirely solid.
On a microscopic level, compact bone reveals a surprisingly porous structure. It features a complex network of interconnected canals that house blood vessels and repeating circular units called osteons. These osteons are aligned parallel to the length of the bone, providing significant strength and durability.
Extracellular Matrix
Bennion referred to the dense bone tissue forming the circular plates of bone as the extracellular matrix. This matrix gives bone unique properties, combining strength with a touch of flexibility.
Collagen and Hydroxyapatite
A closer look at the extracellular matrix reveals that bone comprises collagen and hydroxyapatite, a remarkable, crystal-like substance. This mineral gives bone unique properties and exceptional strength, enabling it to withstand compression and crushing.
Hydroxyapatite is formed from calcium phosphate and hydroxide, making calcium essential for bone health. Its critical role lies in producing hydroxyapatite, which ensures the resilience and durability of our bones.
Spongy Bone
Beneath the compact bone lies spongy bone, an intricate and highly organized structure of tiny, beam-like formations called trabeculae. These trabeculae create small interconnected spaces where blood vessels weave in and out, bringing nutrients close to the bone cells that form the beams.
Nestled within these spaces is red bone marrow, a vital tissue responsible for producing red blood cells (erythrocytes), white blood cells (lymphocytes), and platelets (thrombocytes). Blood vessels passing through the red bone marrow collect these newly formed blood cells and distribute them throughout the body.
Exercise and Bone Health
Bennion explained the roles of two key cells in bone health: osteoclasts and osteoblasts. Osteoclasts break down and reabsorb old bone tissue, while osteoblasts create new bone tissue by depositing extracellular matrix. Over time, this matrix calcifies, trapping the osteoblasts and transforming them into osteocytes.
When osteoblast activity matches that of osteoclasts, bone density remains stable. However, as we age, bone density naturally declines. Engaging in exercises, particularly resistance training, can stimulate osteoblasts to work more actively than osteoclasts, leading to increased bone density and stronger bones.
Wrap Up
Resistance training and proper nutrition become essential for maintaining healthy bones as we age. A well-rounded diet should include calcium, vitamin D, vitamin K, magnesium, omega-3 fatty acids, and key macronutrients to support bone strength. Regular exercise helps slow the loss of bone density and reduces the risk of developing common bone-related conditions later in life.
More In Research
References
- Wu M, Cronin K, Crane JS. Biochemistry, Collagen Synthesis. [Updated 2023 Sep 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507709/
- Dawson-Hughes, B., Harris, S. S., Krall, E. A., & Dallal, G. E. (1997). Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older. The New England journal of medicine, 337(10), 670–676. https://doi.org/10.1056/NEJM199709043371003
- Nguyen, T. V., Sambrook, P. N., & Eisman, J. A. (1998). Bone loss, physical activity, and weight change in elderly women: the Dubbo Osteoporosis Epidemiology Study. Journal of bone and mineral research: the official journal of the American Society for Bone and Mineral Research, 13(9), 1458–1467. https://doi.org/10.1359/jbmr.1998.13.9.1458
