Question 1 Define the term excretion?

Question 2 Where are two kidneys located in human being?

Question 3 What is transpiration?

Question 4 Name the excretory unit of kidney?

Question 5 Where is urine carried through ureters?

Question 6 what are the vital functions of kidneys?

Question 7 What is the function of blood capillaries surrounding the nephron?

Question 8 What is urethra?

Question 9 With the help of diagram describe the excretion in human being?



Excretion is a biological process by which an organism get rid of excess or toxic waste products of metabolism.

Excretion removes unwanted by-products of metabolism,toxic chemical substances,regulate the ionic concentration of body fluids,regulates water content of body,regulate pH of body fluids.

Excretion in human being

Excretory system consist of Pair of kidney,pair of ureters,urinary bladder,urethra.

Kidney:2 kidneys are located in the abdomen,one on either side of backbone.Left kidney is larger and higher than right kidney.

Urine produced in the kidney passes through the ureters into urinary bladder where it is stored until it is released through urethra.

 Internally a kidney is made of numerous microscopic excretory units called nephrons.

The function of kidney is filtration of blood to excrete the waste products of metabolism.The kidney filters about 190 litres of blood to produce 0.9-2 l of urine daily.

 Structure of nephron

Each nephron has cup shaped upper end called Bowman’s Capsule.It contain bundles of blood capillaries called glomerulus.The Bowman’s capsule and glomerulus together form globular body called renal corpuscle.

 The blood in the capillaries of glomerulus come from aorta by renal arteries and after passing through glomerulus it returns to the posterior vena cava via renal vein.The blood entering into glomerulus carries waste material which are filtered out in the Bowman’s capsule.

Filteration is possible because walls of glomerular capillaries and Bowman’s capsule are very thin and selectively permeable.

Thus membrane allow only small molecules and water in the blood to pass through them.

Once the waste is filtered out,the blood free from waste goes into renal vein from where it goes into heart through posterior vena cava.

The fluid containing waste material is forced out of glomerular capillaries in the Bowman’s Capsule.The filtered out fluid is called Glomerular Filtrate.

Bowman’s Capsule leads to a long tubular structure before meeting collecting duct.During the flow of glomerular filtrate in this long tube,reabsorption of useful material take place.

The fluid reaching the end of collecting duct is called urine.

Finally the urine moves through ureter and collects in the urinary bladder till thrown out of body.

Excretion in Plants

The major waste substances produced by plants are oxygen,carbon dioxide and water.

They can get rid of excess water by transpiration.Many of the toxic waste products are stored within dead permanent tissue which are removed periodically.

Waste products are stored in leaves which may fall off.

Some waste products such as latex,gum,resins are stored in old Xylem.

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