Final answer:
The outer layer of periosteum is a fibrous layer that surrounds the bone, providing nutrients through blood vessels and serving as an attachment point for tendons and ligaments.
Step-by-step explanation:
The outer layer of periosteum is a fibrous layer. The periosteum is a crucial part of bone structure, as it forms the outer surface of all bones. This fibrous membrane houses blood vessels, nerves, and lymphatic vessels that are essential for nourishing compact bone, as well as serving as an attachment point for tendons and ligaments. It covers the entire outer surface of bones except at the joints where articular cartilage is present.
Within the periosteum, there are two layers: the outer fibrous layer made of dense irregular connective tissue, and the inner osteogenic layer, which contains cells that assist in bone growth and healing. Deep to the periosteum, the medullary cavity is lined by a membranous endosteum, which also plays a role in bone growth, repair, and remodeling. Hence, the periosteum is not only a protective layer for bone but also supports its physiological functions such as growth and repair.