Bone Tissue Composition and Function

Bone is composed of 65% inorganic and 35% organic components.

Primarily calcium salts, especially hydroxyapatite crystals, giving bone strength and hardness.

Primarily collagen fibers (type I), giving bone flexibility and tensile strength. Also includes proteoglycans, glycoproteins, etc.

Form bone by synthesizing and secreting the organic bone matrix (osteoid).

Maintain bone and regulate mineral content, communicate with other cells

Resorb bone by dissolving inorganic and organic components.

The process of breaking down and rebuilding bone, aided by osteoclasts and osteoblasts.

Includes osteoblasts, osteocytes, and osteoclasts.

The basic structural unit of compact bone, consisting of concentric layers of lamellae surrounding a central canal containing blood vessels and nerves.

Concentric layers of bone matrix within an osteon, providing strength and alternating collagen fiber orientations for resistance against twisting forces.

The central channel of an osteon, containing blood vessels and nerves that supply the osteocytes within.

Small cavities within lamellae that house osteocytes, connected by canaliculi for nutrient and waste exchange.

Tiny channels connecting lacunae, allowing communication and transport between osteocytes and blood vessels.

Interconnected branches of bone that form a porous structure in spongy bone, providing support and housing bone marrow.

The process of bone formation directly from mesenchymal tissue, forming flat bones like the skull and clavicle.

The process of bone formation where cartilage is first formed and then replaced by bone, forming long bones.

As the osteoid calcifies, the osteoblasts become trapped within the hardened matrix, becoming mature osteocytes.

Trabeculae are interconnected beams of spongy bone. They provide strength and support while allowing for flexibility.

The periosteum is a tough membrane that covers the outer surface of bones. It contains osteoblasts and blood vessels, essential for bone growth and repair.

The bone collar is a layer of compact bone formed around the diaphysis of a cartilage model. This is the first step in endochondral ossification.

The medullary cavity is the hollow space within the diaphysis of a bone. It eventually contains bone marrow.

The process by which long bones increase in length primarily at the epiphyseal plate, a layer of hyaline cartilage near the ends of bones.

The inactive part of the epiphyseal plate containing cells that can be activated for growth, ensuring a supply of cartilage cells.

The zone where chondrocytes actively divide, contributing to the lengthening of the bone.

The zone where chondrocytes enlarge and mature, preparing for calcification.

The zone where chondrocytes die and the cartilage matrix becomes calcified, hardening the tissue.

The process by which bones increase in width, occurring at the outer surface of the bone beneath the periosteum.

As bone width increases, the medullary cavity (hollow inside of bone) also expands, keeping the bone proportionally strong and light.

Appositional growth can continue throughout life, influenced by physical activity, load, hormones, and nutrition.

Stimulates bone growth by increasing chondrocyte division in the epiphyseal plate (for length) and activating osteoblasts for both ossification and appositional (width) growth.

Testosterone promotes bone growth by increasing chondrocyte division (length) and osteoblast activity (width), contributing to more dense and wider bones in males.

The process of breaking down bone tissue, performed by osteoclasts which dissolve the mineralized matrix and organic components.

Bone resorption releases minerals (like calcium) back into the bloodstream for the body to use.

Bone resorption, along with deposition, is part of the bone remodeling process, which allows bones to adapt to stress and maintain their structure.

The process of forming new bone tissue by osteoblasts, which synthesize and secrete bone matrix.

Hormone secreted by the thyroid gland when blood calcium levels are high. It inhibits osteoclast activity, reducing bone resorption and lowering blood calcium.

Hormone secreted by the parathyroid glands when blood calcium levels are low. It stimulates osteoclast activity, increasing bone resorption and raising blood calcium.

Helps the body absorb calcium from food in the intestine, promoting bone deposition and maintaining calcium homeostasis.

The first stage of bone repair, where blood vessels rupture at the fracture site and a blood clot forms.

The second stage of bone repair, where fibroblasts and chondroblasts form a soft callus of collagen and cartilage.

The process of bone healing involves four main stages: hematoma formation, soft callus formation, hard callus formation, and bone remodeling.