What are acupoints? From local microenvironments to systemic networks: A clinical review

Acupoints have traditionally been regarded as specific loci along meridians for regulating Qi, Blood, and organ function. This review is a clinically oriented narrative review summarizing current evidence on the anatomical, neurophysiological, and clinical characteristics of acupoints. We first reviewed the structural basis of acupoints, including peripheral nerve endings, connective tissue planes, fascia, microvascular components, and immune-related elements. We then discussed how mechanical stimulation by acupuncture may be transformed into electrical, biochemical, and neural signals through mechanisms involving sensory afferents, endogenous opioids, neurotransmitters, adenosine, mast cells, and neuroimmune interactions. The concept of the Neural Acupuncture Unit was introduced as a framework for understanding acupoints as three-dimensional functional interfaces rather than simple surface points. We also examined the relationship between acupoints, Ashi points, myofascial trigger points, Five-Shu Points, Back-Shu Points, De-Qi sensation, needling depth, and acupoint sensitization. Finally, this review proposed that acupoints should be understood as dynamic cutaneous functional windows that reflect local tissue microenvironments and systemic physiological or pathological states. Further studies are needed to refine acupoint localization, safety assessment, and precision acupuncture practice.