The accumulation of platelets at the site of penetrating vascular injury forms a seal to prevent the loss of plasma proteins. (A) The initial recruitment of platelets stems the loss of blood cells and begins to reduce plasma leakage. (B) The prevention of vascular leakage is enhanced by intrathrombus remodeling through ADP and integrin α_IIbβ₃ signaling resulting in formation of a contracted thrombus core. The figure has been adapted from Figure 7 in the article by Welsh et al that begins on page 1598.