Osteocyte, artwork. An osteocyte is an osteoblast (bone-producing cell) that has become trapped within a bone cavity (lacuna). Osteocytes produce and secrete the organic matrix of the bone (osteoid). Long thin processes (red) extend from the cell into small channels within the bone and connect to other osteocytes. Within the cell are the organelles. The nucleus (dark pink) contains the cell's genetic information. Endoplasmic reticulum (ER, pink lines) produces, modifies and transports proteins. The Golgi apparatus (orange) also modifies proteins, as well as packing them into vesicles for transport out of the cell. The mitochondria (oval, pink) provide the cell with energy.