Final answer:
Compact bone is the hard, dense bone tissue found around the outer portion of a bone, providing support and protection through its osteon structure.
Step-by-step explanation:
The hard, dense bone tissue usually found around the outer portion of a bone is known as compact bone. This type of bone tissue forms the dense outer layer of bones and is found under the periosteum. Its functional unit is the osteon, which is an organized system of rings and canals that provide support and protection to the bone. Compact bone is very hard and strong, consisting of osteons which contain blood vessels, nerves, and lymphatic vessels in the central Haversian canal. On the other hand, spongy bone, also known as cancellous bone or trabecular bone, is found at the center of bones. It is much lighter and more porous than compact bone, as it consists of trabeculae allowing for the presence of bone marrow and blood vessels between them.