The membrane found wrapping the bones, except within the joint cavity, is the:
(a) Periosteum
(b) Endosteum
(c) Perforating fibers
(d) A, b, and c are correct

Verified step by step guidance

1. Step 1: Understand the structure and function of each membrane or component listed in the options. The periosteum is a dense layer of vascular connective tissue enveloping the bones except at the surfaces of the joints.
2. Step 2: Recognize that the endosteum is a thin vascular membrane lining the inner surface of the bony tissue that forms the medullary cavity of long bones, not wrapping the outer surface.
3. Step 3: Identify that perforating fibers (also called Sharpey's fibers) are collagen fibers that connect the periosteum to the bone, but they are not a membrane themselves.
4. Step 4: Compare the definitions and locations of these structures to determine which one fits the description of a membrane wrapping the bones except within the joint cavity.
5. Step 5: Conclude that the correct answer is the periosteum, as it is the membrane that covers the outer surface of bones except at joint surfaces.

Key Concepts

Periosteum

The periosteum is a dense, fibrous membrane that covers the outer surface of all bones except at the joints. It contains blood vessels, nerves, and cells important for bone growth and repair, serving as a protective layer and attachment point for tendons and ligaments.

Endosteum

The endosteum is a thin membrane lining the inner surface of the bone, including the medullary cavity. It contains osteogenic cells that contribute to bone growth, remodeling, and repair from the inside, but it does not cover the outer bone surface.

Perforating fibers (Sharpey's fibers)

Perforating fibers are collagen fibers that anchor the periosteum firmly to the underlying bone. They penetrate the bone matrix, helping to secure the periosteum and transmit mechanical forces from tendons and ligaments to the bone.