Quick Facts
Spongy bone is bone substance made up of thin intersecting lamellae, usually found internal to compact bone (Dorland, 2011).
Related parts of the anatomy
Structure/Morphology
Spongy bone is arranged into trabeculae. These trabeculae form a mesh-like network of bony spicules of various sizes that are aligned along regions of biomechanical stress. The trabeculae are small semilunar plates of bone of varied dimensions (50-400 µm) (Standring, 2016). Trabeculae project into the medullary cavity from the internal circumferential lamellae of the cortical bone. The trabecular bone is laminated bone with occasional osteons present. Osteons are seen in thick portions of trabeculae, primarily in parts closest to the cortical bone.
Spongy bone is similar to cortical bone in the fact that it is laminated, but osteons are most likely to be present only near cortical bone or in the thicker trabeculae. As it is often devoid of osteons, it relies on diffusion of nutrients through the extracellular fluid within the canalicular system.
Anatomical Relations
Spongy bone sits inside the internal circumferential lamellae of the cortical bone. It is lined with endosteum which separates it from the marrow cavity internally. The endosteal layer is irregular in appearance as it tightly adheres to the irregular surfaces of the trabeculae.
Function
The large surface area of spongy bone facilities metabolic activities. Due to its trabecular arrangement, it is lighter than cortical bone and helps reduce the overall weight of the bone (Standring, 2016).
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series: Elsevier Limited.
