the are found deep in the diaphyses of long bones and are filled with yellow marrow in the adult. located in the middle of osteons, the contain the arterial, venous, and nervous supply of the compact bones. filled with osteocytes, which are osteoblasts encased in matrix, are found between layers of concentric lamellae. osteocytes maintain contact with neighboring osteocytes in adjacent lamellae via dendrite-like extensions called .