Page 15 - LN- EXCRETION

faeces.
5. Salivary Glands
Heavy metals and drugs are excreted in the saliva.
Important Metabolic Wastes and Substances Excreted from the Body

Disorders of the Excretory System
Malfunctioning of kidneys can lead to several disorders of the excretory system.
Some of these are as follows
(i) Uremia It is the presence of an excessive amount of urea in the blood. Urea is highly
harmful as it poisons the cells at high concentration and may lead to kidney failure.
(ii) Kidney Failure (renal failure) Partial or total inability of kidneys to carry on excretory and
salt-water regulatory functions is called renal or kidney failure.
(iii) Renal Calculi It is the formation of stone or insoluble mass of crystallised salts (calcium,
magnesium, phosphates and oxalates etc.), formed within the kidney.
(iv) Glomerulonephritis It is the inflammation of glomeruli of kidney.
Artificial kidney (haemodialyser) is a machine that is used to filter the blood (to remove urea
and other nitrogenous wastes) of a person, whose kidneys are damaged.
The process is called haemodialysis.
The outline details of apparatus and the process are as follow
(i) It works on the principle of dialysis (i.e., diffusion of small solute molecules through a
semipermeable membrane (cellophane).
(ii) Blood of the patient is pumped from one of the arteries into the dialysing unit
(haemodialyser) after cooling it to 0°C and mixing with an anticoagulant (heparin).
(iii) Haemodialyser is a cellophane tube suspended in a dialysing fluid (salt-water solution) of