What term describes the tough connective tissue covering the outer surface of bones?

The term that describes the tough connective tissue covering the outer surface of bones is periosteum. This structure is a dense layer of vascular connective tissue that envelopes the bones except at the surfaces of the joints. The periosteum plays a critical role in bone health and function, serving several important purposes. It provides a protective layer that helps to shield bones from damage and infection, serves as an attachment point for tendons and ligaments, and contains blood vessels that supply nutrients to the bone tissue. Additionally, the periosteum contains osteoblasts, which are essential for the growth and repair of bones, highlighting its role in maintaining bone density and integrity.

In contrast, the endosteum lines the inner surface of bones, cartilage provides flexible support in various structures within the body, and membranes can refer to various types of tissues that cover or line spaces in the body but are not specifically related to bone surfaces.