Final answer:
Spongy bone lacks osteons and instead has a less dense, lattice-like structure called trabeculae, which strengthens bone while lightening it to ease muscle movement. Trabeculae contain osteocytes in lacunae and foster hematopoiesis in contained red marrow.
Step-by-step explanation:
The spongy bone equivalent of osteons, which are the functional unit of compact bone, is called trabeculae. Unlike the densely packed osteons found in compact bone, spongy bone features a lattice-like network of matrix spikes known as trabeculae that contain osteocytes within lacunae. These trabeculae are not organized into concentric circles but form along the lines of stress within the bone, providing strength while also making the bone lighter and easier for muscles to move.
Spongy bone also contains red marrow within some of the spaces of the trabecular network, which is where hematopoiesis (the formation of blood cells) occurs. While both compact and spongy bone contains osteocytes housed in lacunae connected by canaliculi for nutrient and waste exchange, their structural organization differs significantly, reflecting their distinct functional roles in the skeletal system.