1. Introduction

The excretory system is the system in our body that removes waste products produced during metabolism.

When cells carry out life processes, harmful substances such as urea, excess water, and salts are formed. These must be removed from the body to keep it healthy.

The process of removing these wastes is called excretion.

2. Organs of the Human Excretory System

The human excretory system mainly consists of four parts:

Kidneys
Ureters
Urinary bladder
Urethra

Diagram idea (for exam)

Kidney → Ureter → Urinary bladder → Urethra

3. Kidneys

Humans have two kidneys located in the back of the abdominal cavity on either side of the backbone.

Functions of Kidneys

Filter blood
Remove wastes like urea
Maintain water balance
Maintain salt balance

The kidneys produce urine.

Structure of Kidney

Each kidney contains millions of tiny filtering units called nephrons.

4. Nephron

The nephron is the basic unit of the kidney.

Each kidney has about 1 million nephrons.

Parts of Nephron

Glomerulus
Bowman’s capsule
Tubule
Collecting duct

Function

Nephrons filter the blood and form urine.

5. Formation of Urine

Urine is formed in three steps.

1. Filtration

Blood is filtered in the glomerulus.

2. Reabsorption

Useful substances such as:

glucose
water
salts

are reabsorbed back into the blood.

3. Secretion

Extra wastes are secreted into the tubule.

Finally, urine is produced.

6. Ureters

The ureters are two thin tubes that carry urine from the kidneys to the urinary bladder.

Functions:

Transport urine
Prevent backflow of urine

7. Urinary Bladder

The urinary bladder is a muscular sac that stores urine temporarily.

Functions:

Stores urine
Expands as urine fills
Sends signal when it is full

8. Urethra

The urethra is the tube through which urine leaves the body.

This process is called urination.

9. Other Organs that Help in Excretion

Besides the main excretory system, other organs help remove wastes.

1. Lungs

Remove carbon dioxide and water vapour.

2. Skin

Sweat glands remove:

water
salts
small amounts of urea

3. Liver

Converts harmful substances into less toxic ones.

10. Composition of Urine

Urine mainly contains:

Water (about 95%)
Urea
Salts
Uric acid
Creatinine

11. Importance of the Excretory System

The excretory system:

Removes harmful wastes
Maintains water balance
Maintains salt balance
Keeps blood clean
Maintains internal environment

12. Diseases of the Excretory System

1. Kidney Stones

Hard deposits formed in kidneys due to mineral accumulation.

2. Kidney Failure

Kidneys stop functioning properly.

Treatment may include dialysis or kidney transplant.

13. Dialysis

Dialysis is a medical process that removes waste products from blood when kidneys fail.

A machine called a dialysis machine acts like an artificial kidney.

14. Tips to Keep Kidneys Healthy

Drink plenty of water
Eat healthy food
Avoid too much salt
Exercise regularly
Maintain hygiene

15. Key Terms

Term	Meaning
Excretion	Removal of waste from body
Kidney	Organ that filters blood
Nephron	Filtering unit of kidney
Ureter	Tube carrying urine
Urinary bladder	Organ storing urine
Urethra	Tube that removes urine

16. Short Summary

The human excretory system removes metabolic wastes from the body. It consists of kidneys, ureters, urinary bladder, and urethra. The kidneys filter blood and produce urine, which is stored in the bladder and expelled through the urethra. This system helps maintain a healthy internal environment in the body.

✅ If you want, I can also provide:

Labelled diagram of the human excretory system (for ICSE exams)
MCQs and short questions from this chapter
Difference between excretion and egestion
Long 3000–5000 word ICSE notes for this chapter.

Human Excretory System (Class 7 Level Notes)

The excretory system in humans is the system that removes waste substances produced in the body during metabolism. These wastes can be harmful if they remain in the body for a long time, so they must be removed regularly.

1. What is Excretion?

Excretion is the process of removing metabolic waste products from the body.

Examples of wastes removed:

Urea (formed from protein breakdown)
Excess water
Salts
Carbon dioxide

These wastes are produced in cells during life processes.

2. Main Organs of the Human Excretory System

The human excretory system mainly consists of four organs:

Kidneys
Ureters
Urinary Bladder
Urethra

3. Kidneys

Humans have two kidneys.
They are bean-shaped organs.
Located on either side of the backbone in the abdominal cavity.
Each kidney is about 10–12 cm long.

Functions of kidneys:

Filter waste from the blood.
Remove excess water and salts.
Produce urine.

Structure inside the kidney: The kidney contains millions of tiny filtering units called nephrons.

Nephrons:

Basic structural and functional unit of the kidney.
Each kidney has about 1 million nephrons.
They filter blood and form urine.

4. Ureters

Two thin tubes.
Carry urine from the kidneys to the urinary bladder.
Each ureter is about 25–30 cm long.

5. Urinary Bladder

A muscular sac.
Stores urine temporarily.
When the bladder becomes full, we feel the urge to urinate.

6. Urethra

A tube that carries urine from the bladder to outside the body.
Urine leaves the body through this tube.

7. Formation of Urine

Urine is formed in three main steps:

Filtration
Blood enters the kidney and waste materials are filtered.
Reabsorption
Useful substances like glucose, water, and salts are reabsorbed back into the blood.
Secretion
Extra wastes are added to the filtrate to form urine.

8. Composition of Urine

Urine mainly contains:

95% water
Urea
Salts
Uric acid
Creatinine

Normal urine is pale yellow in colour.

9. Other Organs That Help in Excretion

Besides the kidneys, some other organs also help remove wastes:

1. Lungs

Remove carbon dioxide and water vapour.

2. Skin

Sweat glands remove water, salts, and small amounts of urea.

3. Liver

Converts ammonia into urea.

10. Importance of the Excretory System

The excretory system:

Removes harmful wastes.
Maintains water balance.
Maintains salt balance.
Keeps the body’s internal environment stable.

11. Difference Between Excretion and Egestion

Excretion	Egestion
Removal of metabolic wastes	Removal of undigested food
Done by excretory organs	Done by digestive system
Example: Urea in urine	Example: Faeces

12. Common Diseases of the Excretory System

Kidney stones
Hard deposits of salts in kidneys.
Kidney failure
Kidneys stop working properly.
Urinary infection
Infection in urinary organs.

Treatment may include dialysis or kidney transplant.

13. Dialysis

Dialysis is a process used when kidneys fail.

A machine filters the blood.
Removes wastes and extra fluids.

14. Interesting Facts

Humans produce about 1–1.5 litres of urine daily.
Kidneys filter about 180 litres of blood filtrate per day.
The excretory system helps maintain homeostasis (balance in the body).

If you want, I can also provide:

Labelled diagram of the human excretory system
MCQs and short questions for ICSE exams
Very long 3000–5000 word detailed notes
Sample question paper from this chapter.

Human Excretory System – Detailed Notes (Class 7 ICSE)

The human excretory system is responsible for removing harmful waste products from the body. During different life processes such as digestion, respiration, and metabolism, various waste substances are produced. If these wastes accumulate in the body, they can become poisonous and disturb normal body functioning. Therefore, the body must eliminate them regularly.

1. Meaning of Excretion

Excretion is the biological process through which the body removes metabolic waste substances produced during cellular activities.

Examples of metabolic wastes:

Urea
Uric acid
Carbon dioxide
Excess water
Mineral salts

These wastes are removed through different organs of the body.

2. Excretory Organs in Humans

The human excretory system consists of the following organs:

Kidneys
Ureters
Urinary bladder
Urethra

Together these organs form the urinary system.

3. Kidneys

The kidneys are the most important organs of the excretory system.

Location

Humans have two kidneys.
They are located on the back side of the abdominal cavity on either side of the backbone.
The right kidney is slightly lower than the left kidney.

Shape and Size

Bean-shaped organs.
Each kidney is about 10–12 cm long.
Weight of each kidney is about 150 grams.

Functions of Kidneys

The kidneys perform several important functions:

Filtration of blood
Removal of nitrogenous wastes
Regulation of water balance
Maintaining salt concentration
Maintaining acid–base balance

4. Internal Structure of the Kidney

The kidney has three main parts:

1. Renal Cortex

The outer layer of the kidney.

2. Renal Medulla

The middle region containing pyramid-shaped structures.

3. Renal Pelvis

The inner hollow space where urine collects before entering the ureter.

5. Nephron – Functional Unit of Kidney

The nephron is the basic structural and functional unit of the kidney.

Each kidney contains approximately 1 million nephrons.

Parts of a nephron:

Glomerulus
A network of tiny blood capillaries where filtration occurs.
Bowman’s capsule
A cup-shaped structure surrounding the glomerulus.
Renal tubule
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
Collecting duct

These structures work together to form urine.

6. Formation of Urine

Urine formation occurs in three main stages.

1. Filtration

Blood enters the kidney through the renal artery.
Waste materials are filtered in the glomerulus.
The filtered liquid enters Bowman’s capsule.

2. Reabsorption

Useful substances such as:
- Glucose
- Amino acids
- Water
- Mineral salts
  are reabsorbed back into the blood.

3. Tubular Secretion

Additional wastes are secreted into the tubule.
The final liquid formed is urine.

7. Ureters

The ureters are narrow tubes that connect the kidneys to the urinary bladder.

Characteristics

Each ureter is about 25–30 cm long.
They carry urine through peristaltic movements (wave-like contractions).

Function

Transport urine from the kidneys to the bladder.

8. Urinary Bladder

The urinary bladder is a muscular sac.

Functions

Stores urine temporarily.
Can hold about 400–600 ml of urine.

When the bladder fills, the brain sends signals that create the urge to urinate.

9. Urethra

The urethra is a tube that carries urine from the bladder to the outside of the body.

Differences in males and females

Males: Longer urethra.
Females: Shorter urethra.

10. Composition of Urine

Urine contains:

Substance	Percentage
Water	95%
Urea	2–3%
Mineral salts	Small amount
Uric acid	Small amount
Creatinine	Small amount

Urine is usually light yellow in colour due to a pigment called urochrome.

11. Role of Other Organs in Excretion

Besides kidneys, several organs help in excretion.

1. Lungs

Remove:

Carbon dioxide
Water vapour

2. Skin

Sweat glands remove:

Water
Salts
Small amounts of urea

3. Liver

The liver plays an important role by:

Converting ammonia into urea.
Detoxifying harmful substances.

12. Homeostasis

The excretory system helps maintain homeostasis, which means maintaining a stable internal environment inside the body.

This includes regulation of:

Water level
Salt balance
Blood pH
Body temperature

13. Disorders of the Excretory System

1. Kidney Stones

Hard deposits of minerals that form inside the kidneys.

Symptoms:

Severe pain
Difficulty in urination
Blood in urine

2. Urinary Tract Infection (UTI)

Infection in the urinary organs caused by bacteria.

Symptoms:

Burning sensation during urination
Frequent urge to urinate

3. Kidney Failure

Kidneys lose their ability to filter blood.

Treatment:

Dialysis
Kidney transplant

14. Dialysis

Dialysis is a medical process used when kidneys stop working properly.

Process

Blood is taken out of the body.
A dialysis machine filters waste and excess water.
Clean blood is returned to the body.

15. Kidney Transplant

In severe kidney failure, doctors may perform a kidney transplant.

A healthy kidney from a donor is transplanted into the patient.
The donor may be a living person or a deceased donor.

16. Difference Between Excretion and Egestion

Excretion	Egestion
Removal of metabolic wastes	Removal of undigested food
Occurs in kidneys, lungs, skin	Occurs in digestive system
Example: Urea	Example: Faeces

17. Importance of the Excretory System

The excretory system is essential because it:

Removes toxic wastes.
Maintains water balance.
Regulates salt levels.
Maintains blood pressure.
Keeps the body healthy.

If you want, I can also give:

Labelled diagram of the human excretory system (very important for ICSE exams)
50 MCQs from this chapter
Short and long exam questions
5000-word full ICSE revision notes.

Human Excretory System – Extended Notes (Class 7 ICSE)

The excretory system is one of the most important systems of the human body. It removes harmful metabolic wastes produced during life processes and maintains the internal balance of the body.

1. Need for Excretion

During different life processes like digestion, respiration, and cellular metabolism, several waste products are produced. Some of these wastes are nitrogenous wastes, which are toxic and must be removed from the body.

Main nitrogenous wastes:

Ammonia
Urea
Uric acid

If these wastes remain in the body, they can damage cells and organs.

2. Types of Excretory Products

The human body produces different types of wastes.

1. Carbon dioxide

Produced during respiration and removed by the lungs.

2. Nitrogenous wastes

Produced from the breakdown of proteins and removed by the kidneys.

3. Excess water

Removed through urine, sweat, and breathing.

4. Mineral salts

Removed through urine and sweat.

3. Blood Supply of the Kidney

The kidneys receive a large amount of blood.

Blood vessels connected to the kidney:

Renal artery

Carries impure blood containing waste substances to the kidneys.

Renal vein

Carries purified blood away from the kidneys back to the heart.

The kidneys filter the blood continuously.

4. Detailed Structure of Nephron

Each nephron performs filtration of blood.

Main parts:

1. Glomerulus

A network of capillaries.
Filters blood under pressure.

2. Bowman’s capsule

A cup-shaped structure that collects the filtrate.

3. Proximal convoluted tubule

Reabsorbs water, glucose, and nutrients.

4. Loop of Henle

Helps concentrate urine.

5. Distal convoluted tubule

Further regulates salt and water balance.

6. Collecting duct

Carries urine to the renal pelvis.

5. Process of Ultrafiltration

The filtration of blood in the kidney is called ultrafiltration.

During ultrafiltration:

Blood enters the glomerulus under pressure.
Small molecules like water, glucose, salts, and urea pass through the membrane.
Large molecules like proteins and blood cells remain in the blood.

The filtered fluid is called glomerular filtrate.

6. Selective Reabsorption

In the nephron, useful substances are reabsorbed back into the blood.

Substances reabsorbed:

Glucose
Amino acids
Mineral salts
Most of the water

This process is called selective reabsorption.

7. Regulation of Water Balance

The kidneys regulate the amount of water in the body.

When the body has excess water:

Kidneys produce large amounts of dilute urine.

When the body lacks water:

Kidneys produce small amounts of concentrated urine.

This helps maintain water balance in the body.

8. Micturition (Urination)

The process of passing urine out of the body is called micturition.

Steps involved:

Urine collects in the bladder.
The bladder expands.
Nerve signals are sent to the brain.
The brain signals the bladder muscles to contract.
Urine passes out through the urethra.

9. Artificial Kidney

An artificial kidney is a machine used in dialysis.

Functions:

Filters blood.
Removes urea and excess salts.
Maintains water balance.

This machine is used when natural kidneys fail.

10. Care of the Excretory System

To keep the excretory system healthy:

Drink plenty of water
Maintain personal hygiene
Avoid excessive salt intake
Eat a balanced diet
Exercise regularly
Avoid holding urine for long periods

11. Interesting Facts About Kidneys

Kidneys filter about 180 litres of fluid every day.
Only about 1–1.5 litres becomes urine.
The kidneys receive about 20–25% of the heart’s blood supply.
A person can live with one healthy kidney.

12. Summary

The human excretory system is essential for survival. It removes harmful metabolic wastes and maintains the internal balance of the body.

The main organs of this system are:

Kidneys
Ureters
Urinary bladder
Urethra

The kidneys contain millions of nephrons, which filter blood and produce urine. Proper functioning of this system is necessary for maintaining good health.

If you want, I can also give:

Labelled ICSE diagram of the human excretory system
100 MCQs for exam practice
Short questions and long questions
Full 5000–7000 word ICSE exam notes.

Human Excretory System – Additional Detailed Notes (Class 7 ICSE)

1. Introduction

All living organisms perform many life processes such as digestion, respiration, and metabolism. During these processes, waste substances are produced. These waste materials can be harmful if they accumulate in the body. Therefore, they must be removed regularly.

The human excretory system is responsible for removing these waste substances and maintaining the balance of water and salts in the body.

2. Main Functions of the Excretory System

The excretory system performs several important functions:

Removal of metabolic wastes
Regulation of water balance
Maintenance of salt concentration
Maintenance of blood pH
Regulation of blood pressure
Maintaining homeostasis

3. Organs of the Excretory System

The excretory system includes the following organs:

1. Kidneys

The kidneys are the most important organs of the excretory system.

Functions of kidneys:

Filter blood
Remove nitrogenous wastes
Regulate water balance
Maintain mineral balance

2. Ureters

Ureters are long muscular tubes that connect the kidneys to the urinary bladder.

Functions:

Transport urine from kidneys to bladder.
Use peristaltic movements to move urine.

3. Urinary Bladder

The urinary bladder is a muscular storage sac.

Functions:

Stores urine temporarily.
Expands as urine collects.
Signals the brain when it becomes full.

4. Urethra

The urethra is the final passage for urine.

Functions:

Carries urine from the bladder to the outside of the body.

4. Structure of the Kidney

The kidney is divided into three main regions:

Renal Cortex

Outer region of the kidney.
Contains many nephrons.

Renal Medulla

Inner region.
Contains pyramid-shaped structures.

Renal Pelvis

Funnel-shaped cavity.
Collects urine before it enters the ureter.

5. Nephron Structure (Detailed)

Each nephron consists of:

Glomerulus
Bowman’s capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct

These structures work together to filter blood and produce urine.

6. Mechanism of Urine Formation

Urine formation involves three important processes:

1. Glomerular Filtration

Blood enters the glomerulus under pressure. Small molecules pass into Bowman’s capsule forming filtrate.

2. Selective Reabsorption

Useful substances are absorbed back into the blood:

Glucose
Amino acids
Water
Salts

3. Tubular Secretion

Additional wastes such as hydrogen ions and potassium ions are secreted into the tubule.

7. Volume of Urine

The amount of urine produced depends on:

Water intake
Temperature
Physical activity
Health condition

Average urine production: 1–1.5 litres per day.

8. Role of Hormones in Excretion

Certain hormones regulate kidney function.

Antidiuretic Hormone (ADH)

Controls water reabsorption in kidneys.
When ADH increases, urine becomes more concentrated.

Aldosterone

Regulates salt balance in the body.

9. Disorders of the Excretory System

1. Kidney Stones

Solid deposits formed from minerals and salts.

Symptoms:

Severe pain
Blood in urine
Difficulty urinating

2. Nephritis

Inflammation of the kidney.

Causes:

Infection
Immune disorders

3. Uremia

A condition where urea accumulates in the blood due to kidney failure.

10. Dialysis (Artificial Blood Purification)

When kidneys fail, dialysis is used.

Steps of dialysis:

Blood is removed from the body.
It passes through a dialysis machine.
Waste substances diffuse into a special fluid.
Clean blood returns to the body.

11. Kidney Transplantation

A kidney transplant involves replacing a damaged kidney with a healthy donor kidney.

Conditions:

Donor kidney must match the patient.
Surgery must be performed in a hospital.

12. Importance of Water for Excretion

Water plays a major role in the excretory system.

Benefits:

Helps dissolve waste products.
Helps kidneys filter blood efficiently.
Prevents kidney stones.

13. Hygiene and Care of Excretory System

To keep kidneys healthy:

Drink 6–8 glasses of water daily.
Avoid excessive salty foods.
Maintain proper hygiene.
Do not hold urine for long periods.
Exercise regularly.

14. Interesting Facts

Kidneys filter blood about 300 times a day.
The human bladder can hold about 500 ml of urine.
People can survive with only one kidney.

15. Conclusion

The human excretory system plays a vital role in maintaining health by removing harmful wastes and maintaining the internal balance of the body.

The organs involved—kidneys, ureters, urinary bladder, and urethra—work together to filter blood and eliminate waste in the form of urine.

Without this system, toxic substances would accumulate in the body, which could be life-threatening.

If you want, I can also give:

• Labelled diagram of the human excretory system (ICSE exam drawing)
• 100 MCQs from this chapter
• Short answer and long answer exam questions
• 10-page revision notes for quick study.

Human Excretory System – Very Detailed Notes (Class 7 ICSE)

1. Introduction to the Excretory System

The human excretory system is a system of organs that removes waste products produced during metabolism. Every cell in the body performs chemical reactions to obtain energy and maintain life. These reactions produce waste substances which can be harmful if they accumulate in the body.

Therefore, the body needs a system to remove these wastes. This system is called the excretory system.

The main waste removed by this system is urea, which is formed in the liver when proteins are broken down.

2. Definition of Excretion

Excretion is the process of removing metabolic wastes and toxic substances from the body.

Examples of metabolic wastes include:

Urea
Uric acid
Creatinine
Carbon dioxide
Excess water
Mineral salts

3. Organs of the Human Excretory System

The human excretory system includes the following organs:

Kidneys
Ureters
Urinary bladder
Urethra

These organs together form the urinary system.

Other organs like the lungs, skin, and liver also help in removing wastes from the body.

4. Kidneys

The kidneys are the main organs of the excretory system.

Location

Located in the abdominal cavity
One kidney lies on each side of the vertebral column
Protected by the lower ribs

Shape and Size

Bean-shaped organs
About 10–12 cm long
Dark red in colour
Each kidney weighs about 150 grams

5. Functions of Kidneys

The kidneys perform many important functions:

1. Filtration of Blood

They filter waste products from the blood.

2. Removal of Nitrogenous Wastes

They remove urea, uric acid, and creatinine.

3. Regulation of Water Balance

They control the amount of water in the body.

4. Maintenance of Salt Balance

They maintain proper levels of sodium and potassium.

5. Regulation of Blood Pressure

Kidneys help control blood pressure.

6. Internal Structure of the Kidney

A kidney has three main regions.

1. Renal Cortex

The outer region containing most of the nephrons.

2. Renal Medulla

The middle region containing pyramid-shaped structures called renal pyramids.

3. Renal Pelvis

A funnel-shaped cavity that collects urine.

7. Nephron – Functional Unit of Kidney

The nephron is the smallest working unit of the kidney.

Each kidney contains about 1 million nephrons.

Nephrons perform the filtration of blood and formation of urine.

8. Parts of a Nephron

A nephron has several parts.

1. Glomerulus

A network of capillaries where filtration occurs.

2. Bowman’s Capsule

A cup-shaped structure that surrounds the glomerulus.

3. Proximal Convoluted Tubule

Reabsorbs nutrients and water.

4. Loop of Henle

Helps concentrate urine.

5. Distal Convoluted Tubule

Regulates salt and water balance.

6. Collecting Duct

Carries urine to the renal pelvis.

9. Steps of Urine Formation

Urine is formed through three main processes.

1. Filtration

Blood is filtered in the glomerulus.

2. Reabsorption

Useful substances like glucose and water are reabsorbed.

3. Secretion

Extra wastes are secreted into the tubule.

10. Path of Urine in the Body

Urine follows this path:

Kidneys → Ureters → Urinary Bladder → Urethra → Outside the body

11. Ureters

The ureters are muscular tubes.

Functions

Carry urine from kidneys to the bladder.
Use rhythmic contractions called peristalsis.

12. Urinary Bladder

The urinary bladder is a muscular sac that stores urine.

Capacity

The bladder can hold about 400–600 ml of urine.

When it fills up, the brain sends signals to empty it.

13. Urethra

The urethra is the tube that carries urine outside the body.

Differences between males and females

Feature	Male	Female
Length	Longer	Shorter
Function	Urine and reproductive fluid	Only urine

14. Composition of Urine

Urine contains:

95% water
Urea
Uric acid
Creatinine
Mineral salts
Pigment called urochrome

The pigment gives urine its yellow colour.

15. Other Excretory Organs

1. Lungs

Remove carbon dioxide and water vapour.

2. Skin

Sweat glands remove water, salts, and small amounts of urea.

3. Liver

Converts ammonia into urea.

16. Importance of the Excretory System

The excretory system:

Removes toxic wastes
Maintains water balance
Maintains salt balance
Maintains pH balance
Prevents poisoning of the body

17. Diseases of the Excretory System

Kidney Stones

Hard mineral deposits in the kidney.

Nephritis

Inflammation of the kidneys.

Urinary Tract Infection

Infection in the urinary system.

Kidney Failure

Kidneys stop functioning properly.

18. Dialysis

Dialysis is a medical process used when kidneys fail.

In this process:

Blood is taken out of the body
A machine filters it
Clean blood returns to the body

The machine is called an artificial kidney.

19. Kidney Transplant

A kidney transplant is performed when kidneys stop working completely.

A healthy kidney from a donor is transplanted into the patient.

20. Care of the Kidneys

To keep kidneys healthy:

Drink enough water
Eat balanced food
Avoid too much salt
Maintain hygiene
Exercise regularly
Do not hold urine for long time

21. Interesting Facts

Kidneys filter about 180 litres of fluid daily.
Only 1–1.5 litres becomes urine.
Humans can live with one kidney.
Kidneys receive about 20% of the heart’s blood supply.

If you want, I can also give you:

• Labelled diagram of the human excretory system (ICSE drawing)
• 50–100 MCQs for exam practice
• Short questions and answers
• One-page quick revision notes for exams.

Human Excretory System – Extra Detailed Study Notes (Class 7 ICSE)

What Happens if Excretion Does Not Occur?
Excretion is extremely important for survival. If waste substances are not removed from the body:
Toxic substances accumulate in the blood.
Cells stop functioning properly.
Organs may get damaged.
The body may suffer from serious diseases.
For example, if urea accumulates in the blood, it can lead to a dangerous condition called uremia.
Nitrogenous Wastes in Humans
When proteins are broken down in the body, nitrogen-containing wastes are produced.
Types of nitrogenous wastes
Ammonia
Very toxic.
Produced during protein metabolism.
Converted into urea in the liver.
Urea
Less toxic than ammonia.
Main nitrogenous waste in humans.
Removed through urine.
Uric Acid
Formed during the breakdown of nucleic acids.
Role of the Liver in Excretion
The liver plays an important role in excretion.
Functions of the liver in excretion
Converts ammonia into urea.
Detoxifies harmful chemicals.
Breaks down old red blood cells.
Produces bile pigments that are excreted through the digestive system.
The urea formed in the liver is transported by blood to the kidneys.
Detailed Working of the Kidney
Blood enters the kidneys through the renal artery.
Inside the kidney:
Blood reaches the glomerulus.
Filtration of waste substances occurs.
The filtrate enters Bowman’s capsule.
Useful substances are reabsorbed.
Waste products remain and form urine.
Purified blood leaves the kidney through the renal vein.
Glomerular Filtration Rate
The glomerular filtration rate (GFR) is the rate at which blood is filtered in the kidneys.
In humans:
About 125 ml of filtrate is produced per minute.
About 180 litres of filtrate is formed per day.
Most of this filtrate is reabsorbed.
Concentration of Urine
The kidneys can change the concentration of urine depending on the body’s needs.
When water intake is high
Urine becomes dilute
More water is removed
When water intake is low
Urine becomes concentrated
Kidneys conserve water
This process helps maintain water balance.
Role of the Nervous System in Urination
The nervous system helps control urination.
Steps involved:
Urine collects in the bladder.
Stretch receptors send signals to the brain.
The brain controls the opening of the urethra.
Urine is released when the bladder muscles contract.
This process is called urination reflex.
Sweat Glands and Excretion
The skin also helps remove waste.
Sweat glands produce sweat, which contains:
Water
Salts
Small amounts of urea
Sweating helps:
Remove wastes
Regulate body temperature
Role of Lungs in Excretion
The lungs remove gaseous waste products.
During respiration:
Oxygen enters the body.
Carbon dioxide is produced as a waste.
The lungs remove carbon dioxide and water vapour during breathing.
Osmoregulation
Osmoregulation is the control of water and salt balance in the body.
The kidneys perform this function by:
Controlling water excretion
Regulating mineral salts
Maintaining proper blood concentration
Urine Test
Doctors sometimes analyze urine to detect diseases.
A urine test can detect:
Sugar (diabetes)
Protein (kidney disease)
Bacteria (infection)
Blood (injury or disease)
Urine tests are useful for medical diagnosis.
Kidney Stone Formation
Kidney stones form when minerals crystallize in the kidney.
Causes
Low water intake
Excess salts in food
Certain infections
Symptoms
Severe abdominal pain
Blood in urine
Difficulty urinating
Prevention of Kidney Problems
Kidney diseases can often be prevented by:
Drinking enough water
Maintaining a balanced diet
Avoiding excessive junk food
Controlling blood pressure
Maintaining hygiene
Interesting Biological Facts
Kidneys filter blood about 300 times per day.
The human bladder can stretch to store urine.
The average person urinates 6–8 times per day.
Kidneys receive about 1.2 litres of blood per minute.
Quick Revision Points
Excretion removes metabolic wastes.
The kidneys are the main excretory organs.
The nephron is the functional unit of the kidney.
Urine formation occurs through filtration, reabsorption, and secretion.
The ureters carry urine to the bladder.
The bladder stores urine.
The urethra releases urine from the body.
If you want, I can also give you these important exam materials for Class 7 ICSE:
Labelled diagram of the human excretory system
50 important short questions
100 MCQs from this chapter
Very short one-page revision sheet for quick study
ICSE sample question paper from this chapter.

Human Excretory System – Advanced Notes (Class 7 ICSE)

1. Importance of the Excretory System

The excretory system is essential for maintaining the health and balance of the human body. Without proper excretion, toxic waste materials would accumulate in the body and interfere with normal cell functions.

The system helps in:

Removing harmful metabolic wastes
Maintaining the chemical balance of blood
Regulating body fluids
Maintaining normal body temperature
Preventing the accumulation of toxic substances

2. Excretory Products of the Human Body

The human body produces different types of waste products.

Carbon Dioxide

Produced during respiration and removed through the lungs.

Urea

Formed in the liver from the breakdown of proteins and removed through urine.

Uric Acid

Formed during the breakdown of nucleic acids.

Creatinine

Produced during muscle metabolism.

Excess Water and Salts

Removed through urine and sweat.

3. Blood Flow Through the Kidney

The kidneys receive blood from the renal artery. This blood contains waste substances.

The path of blood flow in the kidney is:

Renal artery → smaller arteries → glomerulus → filtration → renal vein

After filtration, the purified blood leaves the kidney through the renal vein and returns to the heart.

4. Filtration in the Nephron

The nephron acts as a filtering unit.

During filtration:

Blood enters the glomerulus under pressure.
Small molecules pass through the filtering membrane.
Large molecules such as proteins and blood cells remain in the blood.

The liquid formed is called glomerular filtrate.

5. Reabsorption in the Nephron

After filtration, the filtrate passes through the renal tubules.

During this stage:

Useful substances are reabsorbed.
These substances include glucose, amino acids, salts, and water.

This prevents the loss of important nutrients from the body.

6. Tubular Secretion

Some substances are actively secreted into the tubules.

Examples include:

Hydrogen ions
Potassium ions
Certain drugs
Excess salts

This process helps regulate the chemical composition of the blood.

7. Regulation of Blood Pressure

The kidneys help control blood pressure by:

Regulating water levels in the blood
Controlling the amount of salt
Producing hormones that affect blood vessels

Proper kidney function is therefore essential for maintaining normal blood pressure.

8. Hormonal Control of Kidney Function

Several hormones regulate kidney activity.

Antidiuretic Hormone (ADH)

Controls water reabsorption.
When ADH levels increase, more water is reabsorbed and urine becomes concentrated.

Aldosterone

Regulates sodium and potassium balance.

These hormones help maintain the fluid balance of the body.

9. Urinary System and Body Balance

The urinary system maintains balance by controlling:

Water concentration
Salt concentration
Blood pH
Blood pressure

This balance is necessary for the proper functioning of cells.

10. Disorders of the Urinary System

Kidney Stones

Solid crystals formed in the kidneys.

Causes:

Excess salts
Low water intake

Urinary Tract Infection (UTI)

Bacterial infection affecting the urinary system.

Symptoms:

Pain during urination
Frequent urination
Fever

Kidney Failure

Kidneys lose their ability to filter blood.

Treatment may include:

Dialysis
Kidney transplant

11. Dialysis Procedure

Dialysis replaces the function of damaged kidneys.

Steps involved:

Blood is taken from the patient’s body.
It passes through a dialysis machine.
Waste substances diffuse into dialysis fluid.
Clean blood returns to the body.

Dialysis must be done regularly for patients with kidney failure.

12. Kidney Transplant

A kidney transplant involves replacing a diseased kidney with a healthy one.

The donor kidney may come from:

A living donor
A deceased donor

After transplant, patients must take medicines to prevent rejection of the new kidney.

13. Daily Habits for Healthy Kidneys

To keep the excretory system healthy:

Drink plenty of water
Avoid excessive salt
Maintain proper hygiene
Exercise regularly
Avoid holding urine for long periods
Eat balanced meals with fruits and vegetables

14. Scientific Terms Related to Excretion

Term	Meaning
Excretion	Removal of metabolic wastes
Nephron	Functional unit of kidney
Dialysis	Artificial purification of blood
Urea	Main nitrogenous waste
Osmoregulation	Control of water and salt balance

15. Final Summary

The human excretory system plays a vital role in maintaining health and stability of the body. The kidneys filter blood, remove waste products, and regulate the balance of water and salts.

The organs involved include: