Bo may tuan hoan bao gom : tim va cac mach mau. Tim co cau tao la mot khoi co r6ng, co vach ngan thanh
hai niia rieng biet goi la tim phai va tim trai. Tim trai chlia mau dong mach, tim phai chua mau tinh mach. Moi nua cua tim duoc chia lam hai buong la tam nhi va tam that. Giiia tam nhi va tam that co van nhi that, van hai la va van ba la (van hai la d tim trai va van ba la d tim phai). Giiia tam that va dong mach phoi co van to chim (con goi la van ban nguyet). Cac van nay co chiic nang dam bao cho dong mau di theo mot chieu (khong nguoc lai) tii tam nhi xuong tam that va tii tam that vao dong mach. To chiic tren hinh thanh hai bo phan tim va mach mau, no co chiic nang lien tuc dan mau luu thong trong he thong tuan hoan ciia co the. Neu co su co bi ngiing tuar hoan thi tinh trang con ngudi se bi nguy hiem de doa (su c h e t ) , neu phai ngung qua 4 phut thi te bao o nao so bi ton thuong kho hoi phuc duoc, co the luc nay bi de doa nghiem trong. Co truOng hop cong nhan lam viec nang nhoc, van dong vien dien kinh hay van dong vien thi dau cac mon the thao doi khang de co den dich hoac de co thuc hien mot nhiem vu ky thuat biic xuc trong thi dau de danh chien thang. Khi do lam cho tuan hoan qua nguong co the bi hut va se dinh tre tuan hoan, nen co truOng hop bi ngat xiu, tim ngiing dap trong giay lat (co the tii 30 giay den 1-2 phut), hien tuong nay goi la hien tuong lam sang (hoac chet lam sang).
He thong tuan hoan gom hai vong rieng biet: vong tuan hoan ldn con goi la vong dai tuan hoan co nhiem vu
mang mau co nhieu oxy va cac chat dinh duong tu tim trai theo dong mach chu dan den cac mao mach. O day mao mach cung cap dinh duOng cho mo, roi tap trung lai do vao tinh mach, tu do theo duong tinh mach ve tim phai; vong tuan hoan nho, hay con goi la tieu tuan hoan mang mau tinh mach tii tim phai theo dong mach phoi vao phoi nhan oxy va thai khi carbonic chuyen thanh mau dong mach theo cac tinh mach phoi ve tim trai.
To chiic cua tim la dong luc chinh cua he thong tuan hoan. Tim hut mau tu tinh mach ve tim va bom mau tu tim vao trong dong mach. Dong mach dan mau tii tim den mo, tinh mach dan mau tu mo ve tim. Mao mach la nhung mach mau nho nhat (trai nhu mot tran dia dan quan) noi giiia dong mach va tinh mach, chinh noi day phat sinh ra qua trinh trao doi chat giua mau va mo. Mo la mot to chiic soi rat nho, moi soi co la mot te bao co, lien ket thanh mot mang soi co bop khoe va tao ra thanh cau lan truyen hung phan. O day sau khi thuc hien mot vong tuan hoan thi luon luon dien ra mot vong tuan hoan khac, tuc la tim tiep tuc cii dap.
Co the con ngudi bao gom hang tram dong mach ldn va hang van dong mach vua - nho, co tren 4 ty mao mach de dam bao thuc hien mot su tuan hoan mau binh thudng. Trai tim phai (bop) day mau lien tuc chay qua tat ca hang trieu chiec ong nho di khdp co the, moi vong tuan hoan cua no tU 20 den 25 giay. Mau dong mach sau khi nap
day oxy, tii tim phai tro ve tim trai, roi duoc day vao dong mach chu, tii dong mach chii duoc phan cho cac nhanh dong mach nho day di khap moi to chiic (cua co the) noi tan cung nho nhat la mao mach. Nhu mao mach phoi, thanh ciia no rat mong, mong den mure oxy di qua de dang, de di den tung te bao. Dong thoi con co mot kha nang hemoglobin trong mau co the nha oxy d noi nao con thieu oxy. Luc do carbonic, diocid theo mau di nguoc lai dong. Luc nay mau doi oxy theo dudng tinh mach quay trd lai tim phai.
Su lam viec ciia trai tim rat nghiem ngat va nguyen t ic , khong bao gid duoc nghi ngoi tron ven tren toan bp trai am. Thoi gian lam viec va nghi ngoi ciia qua tim la cuc ky hop ly nhu : hai tam nhi co trong thoi gian 0.1 giay, gian ra trong thoi gian 0,7 giay. hai tam that co trong thoi gian 0,3 giay, roi gian ra trong thoi gian 0,5 giay (thoi ky tam thu). Sau do toan bo trai tim nghi 0,4 giay (thoi ky tam truong). Nhu vay trai tim cung chi lam viec duoc 8 gio trong mot ngay dem 24 giO (R.Hedeman). Tim van hanh nhu mot quy luat sinh ly da an dinh dien ra trong co the, neu bo phan nao co van dong nhieu thi mau duoc dua den noi do nhieu,... Khi bap thit nghi ngoi thi chi co 2-10% mang mao mach (gian nd) hoat dong, nhung khi bap thit van dong thi hau het mao mach deu gian ra va duoc nap day vao mau. Thanh mach mau co cac day than kinh dieu khien de phoi mau luu thong. Luc
nghi ngoi chi co 54% luong mau liru thong trong toan he tuan hoan, con phan kia, so mau duoc luu chua trong “cac kho” : d gan 20%, la lach 16%, da 10%. Khi nao bap thit tiep tuc van dong hoac phat sinh, sue lao dong thi luong mau du trii kia van hanh lap tuc duoc huy dong va qua trinh thay cu doi mOi cung xuat hien. Ddi mOi co y nghia quan trong la no se lam mau no oxy, tang chat song trong mau va thai carbonic. Trai tim ciia ta day nghi luc, giau tam ly, khong phai chi la mot khoi thit vo tu ma no con biet cung ta trong nhiing luc Uu tu, va trong nhiing noi buon vui thon thiic, mot trai tim than thuong cung ta lam viec suot nam thang, suot ca cuoc ddi...