Weber E, Sozio F, Borghini A, Sestini P, Renzoni E
Dept. of Molecular and Developmental Medicine, University of Siena, via A.Moro 2, 53100 Siena, Italy.
Dept. of Medicine, Surgery and Neuroscience, University of Siena, viale Bracci 16, 53100 Siena, Italy.
Ann Anat. 2018 Jul;218:110-117. doi: 10.1016/j.aanat.2018.02.011. Epub 2018 Apr 19.
Our understanding of lymphatic vessels has been advanced by the recent identification of relatively specific lymphatic endothelium markers, including Prox-1, VEGFR3, podoplanin and LYVE-1. The use of lymphatic markers has led to the observation that, contrary to previous assumptions, human lymphatic vessels extend deep inside the pulmonary lobule, either in association with bronchioles, intralobular arterioles or small pulmonary veins. Pulmonary lymphatic vessels may thus be classified into pleural, interlobular (in interlobular septa) and intralobular. Intralobular lymphatic vessels may be further subdivided in: bronchovascular (associated with a bronchovascular bundle), perivascular (associated with a blood vessel), peribronchiolar (associated with a bronchiole), and interalveolar (in interalveolar septa). Most of the intralobular lymphatic vessels are in close contact with a blood vessel, either alone or within a bronchovascular bundle. A minority is associated with a bronchiole, and small lymphatics are occasionally present even in interalveolar septa, seemingly independent of blood vessels or bronchioles. The lymphatics of the interlobular septa often contain valves, are usually associated with the pulmonary veins, and connect with the pleural lymphatics. The large lymphatics associated with bronchovascular bundles have similar characteristics to pleural and interlobular lymphatics and may be considered conducting vessels. The numerous small perivascular lymphatics and the few peribronchiolar ones that are found inside the lobule are probably the absorbing compartment of the lung responsible for maintaining the alveolar interstitium relatively dry in order to provide a minimal thickness of the air-blood barrier and thus optimize gas diffusion. These lymphatic populations could be differentially involved in the pathogenesis of diseases preferentially involving distinct lung compartments.
近期相对特异性淋巴管内皮标志物的发现，包括Prox-1、血管内皮生长因子受体3（VEGFR3）、血小板源性生长因子受体β（podoplanin）和淋巴管内皮透明质酸受体1（LYVE-1），推动了我们对淋巴管的认识。淋巴管标志物的应用使人们观察到，与之前的假设相反，人类淋巴管深入肺小叶内部，与细支气管、小叶内小动脉或肺小静脉相连。因此，肺淋巴管可分为胸膜淋巴管、小叶间隔淋巴管（位于小叶间隔内）和小叶内淋巴管。小叶内淋巴管可进一步细分为：支气管血管周围淋巴管（与支气管血管束相关）、血管周围淋巴管（与血管相关）、细支气管周围淋巴管（与细支气管相关）和肺泡间隔淋巴管（位于肺泡间隔内）。大多数小叶内淋巴管单独或在支气管血管束内与血管紧密接触。少数与细支气管相关，甚至在肺泡间隔中偶尔也有小淋巴管，似乎独立于血管或细支气管。小叶间隔淋巴管通常含有瓣膜，通常与肺静脉相关，并与胸膜淋巴管相连。与支气管血管束相关的大淋巴管具有与胸膜和小叶间隔淋巴管相似的特征，可被视为传导血管。小叶内众多的小血管周围淋巴管和少数细支气管周围淋巴管可能是肺的吸收部分，负责保持肺泡间质相对干燥，以提供最小厚度的气血屏障，从而优化气体扩散。这些淋巴管群体可能在优先累及不同肺区的疾病发病机制中发挥不同作用。
