Human Excretory System for Class 4 Science

• Excretion is the process of eliminating the waste produced in our bodies.
• The major waste produced in our bodies is carbon dioxide and uric acid. Uric acid is eliminated from the body in the form of urine.
• The Human excretory system helps in the process of excretion.
• The main organs of the excretory system are the kidneys, ureters, urinary bladder, and urethra.
• Kidneys are bean-shaped organs, also called the filters of our bodies.

Excretory System’s Function

Question 1:

What Kind of Wastes Are Eliminated by the Kidneys?

Answers:

• Mainly toxins from the blood are eliminated, such as ammonia, urea and uric acid.
• Excess salt and sugar are eliminated to maintain proper water and salt balance inside the body.
• The kidneys also eliminate drugs taken in the form of medicines.

Question 2:

Why Are Nephrons Called the Structural and Functional Units of the Kidney?

Answers:

• The nephrons are called the structural units of the kidney because many nephrons combine to form a kidney.
• Each nephron is specialised for the key steps of blood purification, i.e. filtration, reabsorption and secretion, hence called the functional unit.

Question 3:

What Is the Path of Excretion of Urine Through the Excretory System?

Answers:

The path of urine through the excretory system is-

Question 4:

Briefly Describe the Steps of Urine Formation.

Answers:

The process of urine formation can be divided into the following steps:

• Filtration by the nephrons
• Reabsorption by the nephrons
• Secretion by the nephrons

Question 5:

Why Do We Feel the Urge To Pee?

Answers:

• The urinary bladder is a balloon-like organ that stores urine inside it temporarily.
• When it fills with urine, it expands and increases the pressure on the bladder muscles.
• When the bladder exceeds its limit of storing urine, the urge to urinate is triggered.

Healthy Habits Related to Excretion

Question 1:

How Does the Weakening of Bones Be Related to Kidney Diseases?

Answers:

• Kidneys play a vital role in keeping the level of phosphorus balanced in our bodies.
• A balanced phosphorus level is necessary for balancing Vitamin D in our body. Vitamin D is essential for the absorption of calcium in the body.
• An increase in phosphorus levels does not allow calcium to get absorbed into the body, leading to weakening bones.

Question 2:

Explain How Kidney Stones Are Formed.

Answers:

• An increase in the concentration of uric acid and calcium salts in the blood may lead to the formation of kidney stones.
• This is because the kidney cannot filter these substances efficiently when their level increases, and they start depositing inside the kidneys in the form of kidney stones.

Question 3:

What is Dialysis?

Answers:

• Dialysis is an artificial method to purify blood in case of kidney failure.
• It is done using an artificial machine which functions like a kidney.
• The frequency of the dialysis depends on an individual's age, diet and medical condition.

Question 4:

Name the Blood Vessels Which Carry Blood to the Kidneys.

Answers:

• Renal veins and arteries carry blood to the kidneys.
• The renal artery carries the unfiltered blood from body parts to the kidneys for filtration.
• The blood, once filtered, is sent back to the body parts with the help of the renal vein.

Question 5:

How Is the Flow of Urine From the Urinary Bladder Regulated?

Answers:

• The sphincter muscles regulate the flow of urine from the urinary bladder.
• They contract to allow the urine to pass to the urethra and relax to allow the urinary bladder to hold the urine.