Anatomy Practice Exam

What is yellow bone marrow primarily composed of?

1. Blood cells

2. Fatty tissue

3. Nervous tissue

4. Cartilage

The correct answer is: Fatty tissue

Yellow bone marrow is primarily composed of fatty tissue, which serves several important functions in the body. The primary role of yellow bone marrow is to act as an energy reserve, since fat is a significant source of energy. In adults, yellow bone marrow can replace red bone marrow (which is involved in blood cell production) and is found in the central cavities of long bones. As individuals age, the proportion of yellow marrow increases while the amount of red marrow decreases, leading to a greater storage of fat within the marrow. This transformation is important for maintaining energy balance in the body, particularly when there are changes in dietary intake or energy expenditure. Additionally, yellow marrow does not participate in the formation of blood cells like red bone marrow does, which is why it is not associated with the production of blood components such as red blood cells or white blood cells. Understanding the composition and function of yellow bone marrow is essential for recognizing its role in overall bone health and energy metabolism.