Dialysis blocks the passage of larger substances (for example, red blood cells, large proteins). This replicates the filtering process that takes place in the kidneys when the blood enters the kidneys and the larger substances are separated from the smaller ones in the glomerulus. The two main types of dialysis, hemodialysis and peritoneal dialysis, remove wastes and excess water from the blood in different ways. Hemodialysis removes wastes and water by circulating blood outside the body through an external filter, called a dialyzer, that contains a semipermeable membrane. The blood flows in one direction and the dialysate flows in the opposite.
Organ printing are some organ-specific structural elements that must be addressed for successful creation of a transplantable printed organ. The transfer of nutrients and oxygen to cells throughout a printed organ is essential for its function. In very small or thin tissues of less than a millimeter in thickness, cells can receive nutrients through diffusion. However, larger organs require the transportation of nutrients to cells deeper inside the tissue, which requires that the tissue be vascularized, and thus able to receive blood for the exchange of cargo like oxygen and cell wastes. Early organ printing techniques created solid tissues that were unable