Which of the following tissues is NOT commonly associated with organ donation?

Organ donation typically refers to the process of transferring organs or tissues from one person to another for the purpose of transplantation. While all the options listed can be involved in medical procedures, the brain is generally not associated with organ donation in the same way as the others.

Blood is a critical component of many medical procedures and emergencies, often donated in large volumes to support transfusions. Skin is often donated for regenerative medicine, particularly in burn victims or for reconstructive surgeries. Cartilage can also be harvested and used for various medical applications, particularly in joint repair.

The brain, however, is unique because it is the control center for the body and does not function in the same transplantation context as organs like the heart, kidneys, or liver. It is typically assessed in the context of brain death rather than as a transplantable organ, making it the correct answer in this context. Brain donation usually involves donation of specific tissues for research or study rather than transplantation for life-saving procedures.