Compact vs Spongy Bone — Study Pack Flashcards

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Osteon

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The functional unit of compact bone composed of concentric lamellae around a central Haversian canal. It organizes bone matrix and houses blood vessels and nerves in the canal.

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Lamellae

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Concentric rings of bone matrix within an osteon. They provide strength and structure to compact bone by layering mineralized matrix.

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Lacunae

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Small cavities in bone matrix where osteocytes reside. Lacunae are arranged between lamellae and maintain bone tissue.

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Canaliculi

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Microscopic channels connecting lacunae, allowing nutrients and waste to move between osteocytes. Canaliculi enable cell-to-cell communication in dense bone.

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Haversian canal

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A central longitudinal channel in an osteon that contains blood vessels and nerves. It supplies compact bone with nutrients and removes waste.

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Volkmann's canals

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Transverse canals that link Haversian canals to the periosteum and the marrow cavity. They provide pathways for blood vessels to penetrate compact bone.

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Trabeculae

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Needle-like or plate-like struts forming the lattice of spongy bone. They support weight, absorb shock, and house red marrow in the spaces between them.

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Periosteum

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A fibrous membrane covering the outer surface of bones except at joints. It contains blood vessels and nerves important for growth, repair, and attachment of tendons.

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Endosteum

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A thin membrane lining internal bone surfaces and trabeculae within the marrow cavity. It contains osteogenic cells important for bone remodeling.

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Compact bone

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Dense, solid bone tissue that forms the outer layer of bones and provides strength. It contains osteons and resists bending and torsion.

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Spongy bone

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Porous bone tissue composed of trabeculae found mainly in epiphyses and inside flat bones. It is lightweight, reduces bone weight, and contains red marrow for blood cell production.

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Diaphysis

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The shaft or central part of a long bone primarily composed of compact bone. It often contains the marrow cavity and supports weight during locomotion.

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Epiphysis

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The rounded end of a long bone, typically containing spongy bone and articular cartilage. It helps form joints and distributes loads across joint surfaces.

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Red marrow

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Hematopoietic tissue found mainly in spongy bone that produces red and white blood cells and platelets. It fills spaces between trabeculae in bones like the vertebrae and pelvis.

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Yellow marrow

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Marrow rich in fat located in the medullary cavity of long bones. It serves as a fat storage site and can convert to red marrow in severe blood loss.

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Osteocyte

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A mature bone cell residing in a lacuna that maintains bone matrix. Osteocytes communicate via canaliculi to regulate mineral content and respond to mechanical stress.

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Marrow cavity

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The central hollow space within the diaphysis of long bones that contains yellow marrow. It reduces bone weight and stores fat while allowing nutrient passage.

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Haversian system

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Another term for an osteon: a cylindrical unit of compact bone with concentric lamellae and a central canal. It is essential for the delivery of nutrients and removal of wastes in compact bone.