Artificial Kidney or Hemodialysis 

The blood of a person having both kidney failure can be cleaned regularly by using a kidney machine (or dialysis machine). The procedure used for cleaning the blood of a person, by separating the nitrogenous waste substance (urea) from it is called dialysis.

• Artificial kidney called hemodialyzer, is a machine that is used to filter the blood of a person whose kidneys are damaged. The process is called haemodialysis.

• The blood from an artery in the patient’s arm is made to flow into the dialyzer or dialysis machine made of long tubes of semipermeable membrane (like cellophane which are coiled in a tank containing dialyzing solution). The dialyzing solution contains water, glucose and salts in similar concentrations to those in normal blood. It does not have urea. As the patient’s blood passes through the dialyzing solution, most of the wastes like urea present in it pass through the semipermeable cellophane tubes into the dialyzing solution by diffusion. The clean blood is pumped back into a vein of the patient’s arm.

1.0Drawbacks of artificial kidney

(i) It involves a great deal of discomfort and a risk of formation of blood clots. 

(ii) It may cause fever, cardiovascular problems and hemorrhage.  

2.0Excretion in plants

In plants, no definite excretory system or organ is present for removal of waste. The excretory products which are easily diffusible are removed by the process of diffusion or osmosis. In higher plants, waste materials are deposited in various body parts, which are later eliminated.

The gaseous waste of respiration and photosynthesis in plants are removed through the stomata in leaves and lenticels in woody stem into the atmosphere.

The main waste products produced by plants are carbon dioxide, water vapour and oxygen. Carbon dioxide is produced as waste during respiration by plants.

Carbon dioxide produced during respiration in daytime is all used by the plant itself in photosynthesis. Plants excrete oxygen as a waste only during daytime. Oxygen is produced as a waste during photosynthesis. 

Plants get rid of excess water by transpiration. Many plant waste products are stored in cellular vacuoles. Plants also store some of the waste products in their body parts (leaves, bark and fruits).  e.g., Tannins, essential oils, latex, gums, resins. 

The plant gets rid of stored solid and liquid wastes by the shedding of leaves, peeling of bark and falling of fruits.

Aquatic plants lose most of their metabolic wastes by direct diffusion into water surrounding them.

3.0Special points

• Kidney stones (Nephrolithiasis) are formed due to crystallization or deposition of uric acid or oxalate of minerals and waste materials found in urine. They grow & become a painful irritant that may require surgery or ultrasound treatments.

• A condition in which the body's internal environment remains relatively constant within limits is called homeostasis.

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