What is the term for the dense outer layer of bone?

The term for the dense outer layer of bone is cortical bone. This type of bone, also known as compact bone, forms the hard outer shell of bones and is responsible for much of their strength and structural integrity.

Cortical bone makes up the bulk of the diaphysis (the long shaft) of long bones and provides a protective layer that helps resist bending and compression forces. It is organized into tightly packed osteons, which are the basic structural units of this type of bone, allowing for efficient support and load-bearing capabilities.

In contrast, cancellous bone, also referred to as trabecular or spongy bone, is found internally and has a porous, lattice-like structure that supports the marrow and decreases the overall weight of the bone. Spongy bone is softer and less dense, which makes it different from the dense and solid nature of cortical bone. Medullary bone, on the other hand, refers to the inner cavity in long bones which contains marrow and fat and is not related to the dense outer structure.