Final answer:
The outer layer of periosteum is a fibrous layer, consisting of dense irregular connective tissue, which functions to protect the bone, and provides attachment sites for tendons and ligaments.
Step-by-step explanation:
The outer layer of periosteum is a fibrous layer. The periosteum is a key component of bone structure, serving multiple crucial functions. It is a fibrous membrane that covers the outer surface of all bones, except at the joints of long bones where articular cartilage is present. This membrane is composed of dense irregular connective tissue. It plays an important role in the attachment of tendons and ligaments, providing sites at which these structures can securely attach to the bone, aiding in the transmission of the forces generated by muscle contractions.
The periosteum contains blood vessels, nerves, and lymphatic vessels that nourish the underlying compact bone. Additionally, because the periosteum includes osteoblasts - cells responsible for the production of new bone tissue, it also plays an important role in the growth, repair, and remodeling of bone. Given these characteristics, the correct answer to the question, "The outer layer of periosteum is a(n) ______," would be B) fibrous layer