CHAPTER 3

CHAPTER 3 EXCRETION

INTRODUCTIONMany chemical reactions in the body produce waste products.The body needs to remove these waste products to stay healthy.

Like rubbish, waste products are toxic. We need to remove them from our bodyDEFINITION The process of removing waste products, produced during chemical processes in cells is called EXCRETION.Excretion helps to remove wastes produced by cells.If wastes are not removed, toxic substances build up and these can damage organs in the body.This can lead to death.Excretory organs and excretory products.

Organ : SkinProducts : By Sweating (water, urea, mineral salts)Organ : Lungs Products : By Respiration (water, carbon dioxide)Organ : KidneysProducts : By Urination (water, urea, mineral salts)What is urea and urine???Urea are waste from your body, and it comes in particular from our kidney. (major organic component found in human urine)Urine, is urea and water, and that is what comes out of our body.

The importance of excretionHelps to maintain a healthy body.Example: (respiration) COCarbon dioxide from respiration must be removed quickly because a high level of this gas will increase the acidity of the blood.

The importance of excretionExample: (sweating) urea Urea , if left to accumulate in the body, will become toxic.

Example: (urination) water and mineral saltsHelps to maintain the balance of water content, chemical composition and pH in the body system.

Question And Answer

Why do we need to excrete urea?Urea is formed from excess amino acids. The accumulation of excess urea can harm our body.What if there is too much carbon dioxide in our blood?

A high level of carbon dioxide can reduce the pH of blood and make it acidic.Excessive mineral salts can increase the concentration of blood and make it thicker.

Why does our body need to maintain the salt content in blood?

After the sweat evaporates from the skin, I feel cooler. Excretion controls my body temperature.Excretion helps to regulate and balance the level of water content in our body.THE URINARY SYSTEM IN HUMANSWhat does the human urinary system consist of?

These part helps to remove waste products like urea, water and mineral salts.Human urinary system is made up of:Kidneys BladderUreterUrethra The Human Urinary System

Function.

KidneyExcretory organ that removes wastes like urea, water and mineral salts from the blood into the urine.UrethraTube that carries urine from the bladder for removalUreter Tube that carries urine from the kidney to the bladderBladderTemporary storage for the urine before removalStructure of the kidney

Kidney When the kidney is cut longitudinally, it is seen to consist of 2 parts;

Kidney From the pelvis, a long narrow tube called the ureter, leads to the bladder.

Function of the KidneyMost important function:

Others:

To filter blood and remove urea, excess mineral salts and water to form urine.Regulate the water and chemical balance in the body.ContinueThe amount of water that is reabsorbed depends on the amount of water required in the body.If the body has too much water, reabsorption will be less.The urine produced will be diluted.When body system lacks water, more water will be reabsorbed into the blood.The urine will be concentrated.Q: Why does our urine sometimes appear dark yellowish?A: Well, it means that your body lacks water. The urine becomes more concentrated because more water is reabsorbed into the blood.Importance of maintaining healthy kidneysWe must avoid taking excessive salt, sugar, drugs and alcohol that can harm the kidneys.To maintain healthy kidneys, we need to drink plenty of water every day.Kidneys excrete harmful substances from our body. Therefore we must look after the kidneys.How can people with kidney failure be saved?Kidney failure is a common disease nowadays.Although we can live with only one kidney, failure of both can result in death.However, kidney failure can be treated through dialysis or kidney transplant.Dialysis Common treatment for kidney failure and is carried out with the use of a machine.

In dialysis, blood is filtered through an artificial membrane in the dialysis machine.

What is dialysis?

Dialysis is a technique of separating particles of different sizes in a liquid mixture.How does a dialysis machine work?Works like an artificial kidney.

A patients blood need to pass through the dialysis machine many times to make sure all wastes are removed.The patient must be connected to the machine for about 5 hours, 2 or 3 times a week.Dialysis not cheap.Dialysis does not cure the damaged kidneyExcretion in Plants

Shedding flowersSimple diffusion Retained in the plant bodyDiffusion into the soilStorage in specialized cellsShedding barkShedding leaves Deposited in the leaves