The nutrients needed in the Haversian system are supplied by blood vessels found in ________?

The correct answer is that the nutrients needed in the Haversian system are supplied by blood vessels found in the periosteum. The periosteum is a dense layer of vascular connective tissue that envelops the bones except at the surfaces of the joints. It contains blood vessels, lymphatic vessels, and nerves, all of which play a crucial role in nourishing the bone cells within the Haversian system, also known as the osteon.

The Haversian system itself is a structural unit of compact bone, formed by concentric layers of mineralized matrix surrounding a central canal that contains blood vessels and nerves. The presence of blood vessels in the periosteum is essential for providing oxygen and nutrients to the bone cells, which are vital for bone health, maintenance, and growth.

In contrast, other options such as joints, big bone, and cartilage do not serve as direct sources for the blood supply to the Haversian system. Joints are where two or more bones meet and are not responsible for nutrient supply to bone tissue. While "big bone" is a vague term that does not refer to a specific anatomical structure, cartilage serves as a flexible tissue that covers and protects the ends of bones but isn't involved in supplying nutrients to the H