Crossword Puzzle Blood VesselsOnline version Circulatory System-Blood Vessels by Edith Lucía López Ramírez 1 2 They are so thin that only one blood cell can pass through at a time 3 Capillaries are so small that they are called ______. 4 5 ____ are exchanged in the capillaries 6 Nutrients are exchanged here 7 They (plural) carry oxygen rich blood 8 9 Veins have these to aid blood on its way back to the heart 10 Arteries have a thick layer of smooth_______, therefore it can withstand high pressures. 11 12 They(plural) carry blood going from the body to the heart 13 Veins have a _____ layer of smooth muscle 2 12 9 5 4 7 3 13 10 1 8 11 6