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

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

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

Answer: (A)

In flat bones, the middle layer is a sheet of spongy bone called the diploe. Think of flat bones as a sandwich: two outer thin layers of dense, compact bone with a softer, lattice-like layer in between. This middle spongy layer, made up of trabeculae, lightens the bone while still providing strength and housing marrow spaces. The diploe is lined by the endosteum on its inner surfaces and is distinct from the outer periosteum that covers the bone’s exterior. So the inner layer of spongy bone in flat bones is the diploe.

In flat bones, the middle layer is a sheet of spongy bone called the diploe. Think of flat bones as a sandwich: two outer thin layers of dense, compact bone with a softer, lattice-like layer in between. This middle spongy layer, made up of trabeculae, lightens the bone while still providing strength and housing marrow spaces. The diploe is lined by the endosteum on its inner surfaces and is distinct from the outer periosteum that covers the bone’s exterior. So the inner layer of spongy bone in flat bones is the diploe.