Kwelinye icala lalo mthanjana oyi-cappilary, liyajika libe ngumthanjana omncinane kanobuyisa obizwa ngokuba yi-venule ngesi. Le mithanjana ke izii-venules yeyona mithambo yakhe yamincinane kunayo yonke imithambo engonobuyisa. Imithambo engoobuyisa ithatha igazi iliphindisele entliziyweni. Bathi ke ngokuya besondela ngasentliziyweni baye bekhula besiba bakhulu kunangaphambili. Oyena nobuyisa mkhulu kwi-systematic circulation eyenzeka emzimbeni zii-vena cava. Zimbini ii-vena cava. Kukho i-vena cava engezantsi (ekuthiwa yiinferior vena cava ngesiNgesi) nethatha igazi kumazantsi omzimba ilise kwicala elingasekunene kwentliziyo. (kwi-anatomy, igama elithi inferior lithetha ukuthi ngaphantsi) I-vena cava engasentla (nebizwa ngokuba yi-superior vena-cava) yona ithatha igazi elikumantla omzimba ilise entliziyweni. (igama elithi superior lithetha ukuthi ngasentla).