In short, irregular, and flat bones, what is the inner layer of spongy bone called?

In short, irregular, and flat bones, what is the inner layer of spongy bone called?

• A. Diploe
• B. Endosteum
• C. Periosteum
• D. Trabeculae

Answer: (A)

The inner spongy bone layer in flat bones (and the cancellous region in irregular bones) is called the diploë. In flat bones like those of the skull, there are two outer compact bone layers with a central cancellous layer between them—the diploe. This sponge-like network of trabeculae lightens the bone while creating spaces that can house marrow. Endosteum lines the inside surface of the bone, periosteum covers the outside, and trabeculae are the individual lattice pieces within the spongy bone. So the recognizable inner, spongey layer is the diploe.

The inner spongy bone layer in flat bones (and the cancellous region in irregular bones) is called the diploë. In flat bones like those of the skull, there are two outer compact bone layers with a central cancellous layer between them—the diploe. This sponge-like network of trabeculae lightens the bone while creating spaces that can house marrow. Endosteum lines the inside surface of the bone, periosteum covers the outside, and trabeculae are the individual lattice pieces within the spongy bone. So the recognizable inner, spongey layer is the diploe.