2015血液净化原理.ppt

Continuous Education Training Program Medical Dept FME Asia Pacific * A semipermeable membrane is a type of thin, flexible filter—a barrier that allows only particles smaller than a certain size to pass through it. Think of the membrane as a strainer you might use to drain noodles. The water drains out, but the noodles are too big to pass through the holes. In dialysis, the semipermeable membrane’s holes allow small molecules, such as water and urea, to pass through easily. Middle molecules can also pass through, but more slowly. The small size of the pores keeps larger molecules and blood cells from passing through the membrane. * * * 1 浓度梯度：半透膜两侧液体的浓度各为多少？溶质顺浓度梯度穿过半透膜，从高浓度的一侧移动到低浓度侧。溶质可以自由通过半透膜，但是总是由高浓度的一侧流向低浓度的一侧。浓度即差异，浓度梯度即溶质浓度的差异增加，则溶质运动增加。当半透膜两侧浓度相同时，弥散停止。浓度梯度使病人血液中的废物被透析液带走，并使透析液和血液中的电解质浓度达到平衡 Concentration gradients: How concentrated is the fluid on each side of the membrane? Solutes move through a semipermeable membrane from an area of greater concentration to an area of lesser concentration. Solutes can move through a membrane in either direction, but always toward the area of lesser concentration. A gradient is a difference. As the concentration gradient—the difference in solute concentration—increases, solute movement increases, too. Diffusion stops when the concentrations on both sides of the membrane are equal. Concentration gradients allow dialysate to remove wastes from a patient’s blood and to balance electrolytes in the blood with electrolytes in the dialysate. * * 2 溶质的分子量：溶质颗粒的大小如何？小分子能更加迅速和容易的进行弥散。大颗粒的血液成分，例如红细胞、白细胞、白蛋白、血小板，以及细菌和病毒，因其颗粒较大，所以弥散的非常缓慢。小分子，例如尿素和各种盐，弥散的较快。中等大小的分子也能通过，但是速度较慢。 2. Molecular weight of the solutes: How large are the dissolved particles? Smaller molecules diffuse more easily and quickly than larger ones. Large blood components, such as red blood cells, white blood cells, albumin, and platelets—as well as viruses and bacteria—diffuse more slowly because they are bigger. Small molecules, such as urea and salts, diffuse