▁mechanism , ▁that ▁is , ▁the ▁imm une ▁system ▁and ▁facil it ating ▁an ▁effective ▁heat ▁and ▁mass ▁transfer ▁across ▁the ▁body ▁are ▁some ▁of ▁the ▁major ▁functions ▁which ▁blood ▁performs ▁in ▁the ▁human ▁body . ▁Blood ▁consists ▁of ▁the ▁red ▁blood ▁cells ▁or ▁er yth ro cy tes , ▁white ▁blood ▁cells ▁or ▁le uk ocy tes , ▁and ▁plate lets ▁or ▁th rom b ocy tes . ▁The ▁cells ▁which ▁are ▁involved ▁primarily ▁in ▁the ▁transport ▁of ▁o xygen ▁and ▁carbon ▁dio x ide ▁are ▁known ▁as ▁E ry th ro cy tes . ▁The ▁cells ▁which ▁are ▁involved ▁primarily ▁in ▁ph ag oc yt osis ▁( the ▁process ▁of ▁destruction ▁of ▁unknown ▁partic ulate ▁matter ) ▁and ▁imm une ▁responses ▁are ▁known ▁as ▁Le uk ocy tes ; ▁th rom b ocy tes ▁are ▁the ▁components ▁of ▁blood ▁which ▁are ▁involved ▁in ▁blood ▁cl ot ting . ▁In ▁addition ▁to ▁these ▁ 5 5 ▁to ▁ 6 0 ▁percent ▁of ▁blood ▁by ▁volume ▁consists ▁of ▁pl asma . ▁Pl asma ▁is ▁the ▁transparent , ▁am ber - color ed ▁liquid ▁in ▁which ▁the ▁cell ular ▁components ▁of ▁blood ▁are ▁susp ended . ▁Pl asma ▁contains ▁constitu ents ▁such ▁as ▁prote ins , ▁electro ly tes , ▁h orm ones , ▁and ▁nut ri ents . ▁The ▁ser um ▁is ▁blood ▁pl asma ▁from ▁which ▁cl ot ting ▁factors ▁have ▁been ▁removed . ▁Blood ▁accounts ▁for ▁ 6 ▁to ▁ 8 ▁percent ▁of ▁body ▁weight ▁in ▁normal , ▁health y ▁humans