CIE IGCSE Biology Unit 13: Excretion

urea

formed in the liver from excess amino acids( deamination )

carbon dioxide

excreted through the lungs

role of the liver in the assimilation of amino acids

converting them to proteins, including plasma proteins, e.g. fibrinogen

deamination

the removal of the nitrogen-containing part of amino acids to form urea

kidneys

excrete urea and excess water and salts

volume and concentration of urine

affected by water intake, temperature and exercise

structure of kidney

cortex: brown outer layer

medulla: reddish inner area

pelvis: white area

Function of glomerulus

Filtration from the blood of excess water, glucose, urea and salts.

Ultrafiltration

The process where small molecules are forced from the blood out of the capillaries of the glomerulus, under high pressure, into the Bowman's capsule.

Function of kidney tubule

The reabsorption of all of the glucose, most of the water and some salts back into the blood, leading to the concentration of urea in the urine as well as loss of excess water and salts

ureters

transport urine from the kidney to the bladder where it is stored

bladder

stores urine before passing out through the urethra

urethra

allows urine to leave body, excretion

Kidney failure

when kidneys can no longer cleanse the blood and maintain homeostasis

the need for excretion

toxicity of urea and carbon dioxide

dialysis

a procedure to remove waste products from the blood of patients whose kidneys no longer function

The use of dialysis in kidney machines

to remove toxins, excess amino acids and mineral salts

The advantages and disadvantages of kidney transplants, compared with dialysis

Advantage: do not need dialysis treatment after kidney transplant

Disadvantage: chance of rejection from body