Umbhobho wegazi yityhubhu engumthambo ethwala igazi xa lihamba lijikeleza umzimba. Imithambo yegazi ethatha igazi entliziyweni ingoonothumela. Ize imithambo yegazi ebuyisela igazi entliziyweni ibengoonobuyisa. Imithambo ezii-Capillaries yona iphakathi koonobuyisa noonothumela kwaye ezi-capillaries zondla igazi nge-tissue.