**Name the excretory organs and the excretory products Excretion Objectives: *Define excretion **Name the excretory organs and the excretory products ***Describe the structure of the urinary system and list the functions of liver

Excretion is the process of removing toxic materials, waste products of metabolism and excess substances from the body. Excretory organs: lung excrete CO2 Liver processes toxic materials like alcohol drugs etc to make them harmless Kidneys excrete urea, salt and excess water Excretory substances: CO2 is made in cells during respiration transported to the lungs in blood plasma. Here it diffuses out of the blood into the air in the alveoli and is exhaled. Urea is made in liver from excess amino acids by deamination. It is carried to the kidneys in the plasma where it is filtered out and leaves the body dissolved in the form of urine

Role of liver in excretion cells Built into proteins for growth Proteins digestion urea absorption ? ? Excess of it is taken to liver blood gut

Liver functions: Has about 200 functions Storing excess glucose as insoluble glycogen Making bile which helps to emulsify fats Breaking down hormones after they have circulated in the blood for a while Breaking down harmful substances like alcohol and drugs

Kidney is at the top of your abdominal cavity just under the diaphragm protected by backbone, lower rib cage and the fat surrounding them. Renal artery brings waste to the kidneys in the blood eg urea diffuses in the blood Renal veins takes cleaned blood away from the kidneys Kidneys removes urea and other chemicals from the blood Ureters carry urine down to the bladder Bladder stores urine Ring of muscles keeps the bladder closed until urination Urethra carries urine out of the body Urine is yellow because one of the waste substance is yellow pigment. Urea is colourless soluble in water , plasma and urine.

Inside kidney there is a network of filtering units called tubules ( the tubules decrease in number with age) as the blood flows through them small molecules such as glucose, salt , water and urea are forced out of the blood plasma to form a fluid called filtrate. As the filtrate passes through the tubules some of the useful substances as glucose and salt are reabsorbed in the blood. Water is also reabsorbed according to the need of the body.

What is the difference between excretion and egestion? Excretory substances are produced by cells in metabolism whereas undigested food pass through the gut after eating without being absorbed by the blood stream