connective The outer layer of a blood vessel (artery or vein) is called the tunica externa or tunica adventitia.See http://training.seer.cancer.gov/module_anatomy/unit7_3_ca â¦ rdvasc_blood1_classification.html pericardium is the layer of the blood vessel that is made of tough  connective tissue.onnective The outer layer of a blood vessel (artery or vein) is called the tunica externa or tunica adventitia.
As of June 2000, the fastest running human is Michael Johnson, the American track and field star who on August 1, 1996 set the world record of running 200 meters in 19.32 seconds.
Eliud Kipchoge Runs Worldâs Fastest Marathon, in Nikeâs Special Shoes. Eliud Kipchoge crossing the finish line at the Monza Formula One racetrack in Italy, on Saturday. Even in a highly controlled environment, the sub-two-hour marathon remains elusive â just barely.