Lubrication is everywhere in the body and essential for the correct operation of biological systems when subjected to contact stress and wear. The body is like a continuously operating life machine. Friction and energy consumption throughout the body would increase dramatically without lubrication, causing physical damage, accelerating senescence and even endangering life. Therefore, it is vital to propose the notion of body lubrication and investigate in depth the irreplaceable role of lubricated matter in life. However, no article has yet summarized “lubricated matter” throughout the body. The need to understand the origin of the lubricated matter in body is driving this review, which could shed insight into degenerative processes and suggest therapeutic options for body disorders, including osteoarthritis, tendon injury, dry eye, etc. Initially, we present an overview of lubricated model and lubricated medium, and gather together the most important data on coefficient of friction about lubricated fluid and lubricated biomacromolecules in body. Subsequently, lubricated matter in body, such as motor system including joint, tendon, bone, muscle, intervertebral disc, shouldercuff, and ligament; digestive system including mouth, teeth, pharynx, esophagus, stomach, intestine, and peritoneum; respiratory system including nose, lung, trachea, and pleura; circulatory system including heart, blood vessel, urethra, and ureter; nervous system including eye and brain; skin system including skin and hair; and reproductive system including vagina, are emphasized. Following recent advances based on lubrication, the developments of lubricated therapy in body at a molecular level are reviewed. In conclusion, the most significant challenges and opportunities of lubricated matter in body are thoroughly discussed.

中文翻译：

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体内润滑物质


润滑遍布身体各处，对于生物系统在承受接触压力和磨损时的正确运行至关重要。身体就像一台不断运转的生命机器。如果没有润滑，全身的摩擦力和能量消耗就会急剧增加，造成身体损伤，加速衰老，甚至危及生命。因此，提出机体润滑的概念并深入研究润滑物质在生命中不可替代的作用至关重要。然而，目前还没有文章概括出全身的“润滑物质”。了解体内润滑物质起源的需要推动了这篇综述，这可以深入了解退行性过程，并为身体疾病（包括骨关节炎、肌腱损伤、干眼等）提出治疗选择。首先，我们概述润滑模型和润滑介质，并收集体内润滑流体和润滑生物大分子的摩擦系数的最重要数据。随后，润滑体内物质，如运动系统，包括关节、肌腱、骨骼、肌肉、椎间盘、肩袖、韧带；消化系统，包括口腔、牙齿、咽、食道、胃、肠和腹膜；呼吸系统，包括鼻、肺、气管和胸膜；循环系统，包括心脏、血管、尿道、输尿管；神经系统，包括眼睛和大脑；皮肤系统包括皮肤和毛发；强调了包括阴道在内的生殖系统。随着基于润滑的最新进展，我们回顾了分子水平上体内润滑疗法的发展。 总之，深入讨论了体内润滑物质最重大的挑战和机遇。