10.5
Kemik iliği:
Çoğu kemik yoğun ve süngerimsi osteöz doku içerir, ancak dağılımı ve konsantrasyonu kemiklerin genel işlevine bağlı olarak değişir.
Kemik iliği, korti…
Kompakt veya kortikal kemik, tüm kemiklerin korteksinde bulunan sert, katı bir kemik dokusudur. Aynı zamanda uzun kemiklerde diyafizin büyük kısmını oluşturur.
Kompakt kemiğin yapısal birimi, haversian sistemi olarak da adlandırılan osteondur. Uzun eksen boyunca sıkıştırma kuvvetlerine dayanacak şekilde paralel olarak düzenlenmiş uzun, silindirik birimlerdir.
Her osteon, merkezi bir osteonik veya haversian kanalını çevreleyen konsantrik lameller içerir. Her bir lamel halkasının kollajen lifleri dönüşümlü olarak yönlendirilir, böylece bükülme kuvvetlerine direnir.
Lameller arasında, olgun kemik hücreleri olan osteositleri barındıran lakuna adı verilen boşluklar vardır.
Haversiyen kanalı, kanalikül adı verilen küçük kanallar aracılığıyla osteositlere bağlanan kan damarlarını, lenfatik damarları ve sinirleri çevreler.
Enine Volkmann kanalı, osteonları ana kana ve kemiğe giden sinir kaynağına bağlar.
Osteonlar arasında interstisyel lameller bulunur. Bunlar, kemik yeniden şekillenmesi yoluyla geri dönüştürülen eski osteonların kalıntıları olan eksik kemik matrisi halkalarıdır.
Çevresel lameller osteonları çevreler ve kemiğin tüm çevresinde bulunur.
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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.