The new era of the lymphatic system: No longer secondary to the blood vascular system

The blood and lymphatic systems are the twomajorcirculatory systems in our body. Although the blood system has been studied extensively, the lymphatic system has received much less scientific and medical attention because of its elusive morphology and mysterious patho-physiology. However, a series of landmark discoveries made in the past decade has begun to change the previous misconception of the lymphatic system to be secondary to the more essential blood vascular system. In this article, we review the current understanding of the development and pathology of the lymphatic system. We hope to convince readers that the lymphatic system is no less essential than the blood circulatory system for human health and well-being. The human body has two major circulatorysystems: the blood and lymphatic systems. Although both systems were initially described by Hippocrates and share so many functional, structural, and anatomical similarities, the two vascular systems have had very different fates in science and medicine: Although the blood vascular system has been intensively and exten-sively studied for a long time, the lymphatic sys-tem, in contrast, has been considered less important, invisible, secondary to the blood vascular system, and thus largely neglected by scientists and clinicians until recent years. However, a series of landmark discoveries in past decades has unraveled much of the mystery of the lymphatic system and yielded a burst of new knowledge in the field of vascular biology and medicine. Modern molecular, cellular, and genetic approaches as well as the state-of-the-art imaging technologies have allowed true appreciation of the value of the lymphatic sys-tem as the other vascular system, no longer sec-ondary to the blood vascular system. In this review, we discuss the current understanding of the development and function of the lym-phatic system and human diseases related to the lymphatic system