start stage end stage continuous blood vessel endothelium endothelial blood brain barrier zebrafish_anatomy Blood vessel endothelium that restricts the passage of circulating substances from the blood to the brain parenchyma while actively facilitating the passage of nutrients and removal of waste products. The developing blood brain barrier undergoes a period of transcytosis and leaks that decrease as the mature form is established. The barrier matures in a posterior to anterior direction. 2020-07-30T10:25:52Z ZFA:0005927 larval:protruding-mouth adult