The cells will often excrete the waste through their cell membrane into the blood where it is often transported to the kidney. The waste products can be removed by any different method e.g active transport or diffusion depending on levels of the substance and how harmful it might be.
Through the umbilical cord. The waste products in the blood stream of the fetus is passed into the blood stream of the mother. Then, she, ahem, gets rid of the waste herself for the both of them. Through the umbilical cord and placenta.
excretory system is important to a human begin because through the excretory system we are able to get rid of all the waste products in our body the lungs get rid of waste air, the body get rid of waste and the kidneys get rid of urine.