10.5
Osso Compacto
A maioria dos ossos contém tecido ósseo compacto e esponjoso, mas sua distribuição e concentração variam de acordo com a função geral do osso.
O osso…
O osso compacto ou cortical é um tecido ósseo duro e sólido encontrado no córtex de todos os ossos. Também forma a maior parte da diáfise em ossos longos.
A unidade estrutural do osso compacto é o ósteon, também chamado de sistema de Havers. São unidades longas e cilíndricas dispostas em paralelo para suportar forças de compressão ao longo do eixo longo.
Cada ósteon contém lamelas concêntricas ao redor de um canal osteônico central ou de Havers. As fibras colágenas de cada anel lamelar são orientadas alternadamente, resistindo assim às forças de torção.
Entre as lamelas existem espaços chamados lacunas, que abrigam osteócitos - as células ósseas maduras.
O canal de Havers envolve vasos sanguíneos, vasos linfáticos e nervos conectados aos osteócitos por meio de minúsculos canais chamados canalículos.
O canal transversal de Volkmann conecta os ósteons ao sangue principal e o suprimento nervoso para o osso.
Lamelas intersticiais são encontradas entre os ósteons. Eles são anéis incompletos de matriz óssea que são os restos de ósteons mais antigos sendo reciclados por meio da remodelação óssea.
As lamelas circunferenciais circundam os ósteons e estão presentes ao redor de toda a circunferência do osso.
View the full transcript and gain access to JoVE Core videos
Q1: What is an osteon and what role does it play in compact bone structure?
An osteon, also called a haversian system, is the structural unit of compact bone. It consists of concentric lamellae surrounding a central haversian canal containing blood vessels, nerves, and lymphatic vessels. Osteons are arranged in parallel to withstand compression forces along the long axis of bones, providing strength and support.
Q2: How do osteocytes receive nutrients within compact bone?
Osteocytes reside in spaces called lacunae within the lamellae of osteons. Tiny canals called canaliculi connect lacunae to the central haversian canal, allowing osteocytes to exchange nutrients and waste through blood vessels. This network ensures mature bone cells remain viable despite being embedded in solid matrix.
Q3: Why are collagen fibers arranged alternately in compact bone lamellae?
Collagen fibers in adjacent lamellae are oriented in alternating directions, creating a highly organized structure that resists twisting forces. This alternating fiber arrangement, combined with the parallel orientation of osteons, allows compact bone to withstand both compression and torsional stresses effectively.
Q4: What are interstitial lamellae and how do they form?
Interstitial lamellae are incomplete rings of bone matrix found between osteons. They represent remnants of older osteons that have been recycled during bone remodeling. These structures fill gaps left when the skeleton removes and replaces bone tissue, maintaining bone density and structural integrity.
Q5: How does the arrangement of osteons affect bone strength?
Osteons are arranged in parallel within compact bone, an orientation that resists compression forces along the bone's long axis. However, this parallel arrangement provides less resistance to perpendicular forces, which is why long bones like the femur can bear weight along their length but fracture when sufficient force is applied sideways.
Q6: What is the relationship between compact bone and the diaphysis of long bones?
Compact bone forms the bulk of the diaphysis, the shaft of long bones, and is found under the periosteum. This dense, solid osseous tissue provides the structural support and protection necessary for long bones to bear weight and resist mechanical stress during movement and activity.
Q7: What do Volkmann's canals do in compact bone?
Volkmann's canals are transverse canals that connect individual osteons to the main blood and nerve supply of the bone. These channels allow blood vessels and nerves to branch from the central supply and reach multiple osteons, ensuring all regions of compact bone receive adequate nutrition and nervous system communication.