In rats subjected to traumatic brain injury (TBI), at the stage of acute development of traumatic disease, the platelet number, ultrastructural changes in liver sinusoid hemocapillaries (SCs), and microcirculation disorders in their lumen were studied. The results of the study showed that, in local brain injury, on the third day of post-traumatic period, thrombocytopenia, expressed lesions of liver SCs, and intrasinusoid microcirculation disorders, which are aggravated on the seventh day post injury, are detected. On the 12th day after TBI, the sinusoid endothelium is detected to be of usual appearance, but yet areas of its swelling and edema occur. In 79% of sinusoid hemocapillaries, the blood flow is recovered, while in 21% macro- and micro aggregates of erythrocytes, bubbles, cellular detritus, and platelets are detected. Analyzing the obtained data, we can conclude that the detected lesions of liver SC endotheliocytes in the acute period of TBI make it possible to consider them one of the key, and earliest, links of pathogenesis of the vascular–platelet link of hemostasis.