Final answer:
The major site to study bone marrow in adults is the iliac crest of the pelvic bones. Red bone marrow is critical for hematopoiesis, found in the femur's head, ilium, and scapula, while yellow marrow stores energy. Advances in medical technology have lessened the need for direct marrow samples.
Step-by-step explanation:
The major site to study bone marrow in an adult is the iliac crest of the pelvic bones. This area is usually selected due to its accessibility, being near the body's surface and its isolation from most vital organs. However, in modern practice, the necessity for direct sampling of the bone marrow has been reduced with advancements in medical technology.
Red bone marrow is found in the head of the femur, flat bones such as the ilium, and the scapula, where hematopoiesis, the process of creating new blood cells, occurs. In contrast, yellow bone marrow primarily serves as an energy reserve and consists of adipose cells. Although bone marrow plays a crucial role in hematopoiesis throughout life, other organs like the liver and spleen also possess the ability to produce formed elements of blood through a process known as extramedullary hemopoiesis, which can be particularly significant in cases where bone marrow activity is compromised.