(1) The osseous tissue that fills the interior or cavity of bones with a latticework of small spicules or flat pieces of mineralized bars (trabeculae) and interstices containing bone marrow or fat.
(2) The tissue inside of bones that resembles a sponge or a honeycomb with spaces containing bone marrow or fat.
This type of osseous tissue lies subjacent to the compact bone, and is made distinct by its spongy structure. It is found at the ends of long bones and in the vertebrae. It has low density and strength but has high surface area that allows room for blood vessels and marrow. The outer surface layer of this tissue contains the red bone marrow where hematopoiesis takes place.
Word origin: spongy < from Latin spongia, from Greek spongiā, from spongos; bone.
Synonym: cancellous bone, trabecular bone, spongy substance, substantia spongiosa (Latin name), spongiosa.
Compare: compact bone.
See also: bone marrow, hematopoiesis.