8.22
Bone as Supporting Connective Tissue
Q1: What are the two main types of bone tissue and how do they differ?
Bone tissue is classified into compact (cortical) bone and spongy (trabecular) bone. Compact bone is hard and dense, forming the outer layer with concentric rings called lamellae. Spongy bone is porous and located in the interior, containing thin branching structures called trabeculae that provide strength while reducing weight.
Q2: What role do osteocytes play in bone tissue?
Osteocytes are mature bone cells that reside in spaces called lacunae within the bone matrix. They communicate with each other through microchannels called canaliculi and regulate bone mineral deposition by controlling the activity of other bone cells, maintaining bone homeostasis and supporting bone remodeling.
Q3: How does the bone matrix contribute to bone strength and flexibility?
The bone matrix contains two types of material: an organic matrix rich in collagen fibrils that provides flexibility, and an inorganic matrix of mineral salts, primarily calcium, that adds stiffness. Together, these components give bone its characteristic strength and resilience.
Q4: What is bone remodeling and which cells are involved?
Bone remodeling is the cycle of bone loss and formation that maintains skeletal health. Osteoclasts, large multinucleate cells, remove mineral deposits from old bone tissue through resorption. Osteoblasts then deposit circulating minerals to create new bone, regulated by osteocytes.
Q5: What structures are found within compact bone tissue?
Compact bone is organized into subunits called osteons. Each osteon contains a blood vessel and nerve in the central Haversian canal, surrounded by radiating circles of lacunae arranged in lamellae. Microchannels called canaliculi connect lacunae to facilitate nutrient diffusion between osteocytes.
Q6: How does bone tissue change with aging?
With age, the thin plates called trabeculae in spongy bone become thinner and less resilient, making bones more prone to fractures. This structural weakening reduces the bone's ability to withstand stress and increases fracture risk in older individuals.
Q7: What are the three main types of bone cells and their functions?
Osteoblasts are active in bone growth and remodeling, depositing bone matrix and differentiating into osteocytes. Osteocytes regulate mineral deposition and communicate through cellular processes. Osteoclasts break down bone tissue during remodeling, aiding in mineral homeostasis maintenance.