Library · Histology
Spongy bone
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Bone is not solid. It comes in two types: cortical bone, which forms the shell on the outside, and trabecular bone, the bone on the inside, which almost everyone knows as spongy bone, because it looks like a sponge.
That sponge makes up barely twenty percent of the bone in the body, but it has ten times more surface area per unit of volume than compact bone. A lot of surface in very little space.
And it is not found just anywhere: it shows up where bone bears compression, that is, where loads press down on it. That is why it is in the bodies of the vertebrae, in the pelvis, and in the metaphyses, the wide areas near the ends of the long bones.
Picture a network of struts inside a hard shell. Bone marrow lives between those struts, and it is what makes blood cells in a process called hematopoiesis.
In brief
Bone comes in two subtypes: cortical bone, which forms the outer shell, and trabecular bone, also called spongy bone.
A network of struts inside a hard shell.
It makes up only twenty percent of the body's bone, but has ten times the surface-to-volume ratio of cortical bone.
It appears where there is compression: in the vertebral body, the pelvis, and the metaphyses of long bones.
Bone marrow lives within that trabecular bone and is responsible for hematopoiesis.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingHistology, Bone, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingEmbryology, Bone Ossification, StatPearlsPublished
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