I only know some of them nicely so I am answering.
It is a machine to purify blood when the kidneys are not able to do so.It also act on waste and is also called artificial kidneys.
It is a process by which wastes is eleminated from human body. Through kidneys, lungs and skin it is performed in vertibrates.
Importance of Excreation
Without Excreation waste products will build diseses and will cause serious health issues.
Urine Examination's necessity for doctors
It is conducted so that doctors come to know about what is giong in our body. With help of urine tests doctors can examine infections and also deadly diseases like diabetes.

Dialysis The proces of cleaning blood of a person ( with kidney failure ) by seprating the toxic waste products, using a dialysis machine is called dialysis  

Urine examination Useful for doctors 
the urine examination is useful for doctors because With the help of urine tests doctors can examine many deadly diseases and infections.

The process of removal of waste products,produced in the cells of the living organisms is called excretion 

Importance of Excretion
without this the waste materials will form serious infections diseases etc..