What is the double-layered connective tissue that covers and nourishes bone?

• A. Periosteum
• B. Endosteum
• C. Epiphysis
• D. Perichondrium

Answer: (A)

The tissue that covers bone is called the periosteum. It has two layers: an outer fibrous layer of dense connective tissue that provides protection and a strong anchor for tendons and ligaments, and an inner osteogenic (cambial) layer that contains osteoprogenitor cells capable of forming osteoblasts. This two-layer setup, along with a rich blood supply, allows the periosteum to nourish the bone and support growth and repair. It also attaches to bone via Sharpey's fibers. By comparison, the endosteum lines the inner surfaces of bone, the perichondrium surrounds cartilage, and the epiphysis is the end part of a long bone. So the double-layered tissue that covers and nourishes bone is the periosteum.