Excretion

• Excretion is the process of removing nitrogenous metabolic waste products from the body.
• These wastes include ammonia, urea, and uric acid produced during body activities.
• Along with nitrogenous wastes, excess water, salts, and pigments are also removed.
• Excretion helps keep the internal environment of the body stable.
• This stable internal condition is called homeostasis.
• The main excretory products of the body are urea, uric acid, ammonia, carbon dioxide, and water.
• Some wastes are also removed as extra salts such as sodium, potassium, chloride, sulphate, and phosphate.

Need for Excretion

• During metabolism, carbohydrates, fats, and proteins are broken down in the body.
• This breakdown produces waste substances that can disturb body cells if they collect.
• When the concentration of wastes increases, it interferes with normal cell functioning.
• For example, excess carbon dioxide and ammonia can deteriorate the working of cells.
• Too much mineral salts and water in the body also affects cell functioning.
• Therefore, excretion is necessary to expel these toxic waste products and keep the body healthy.

Multiple Choice Questions (MCQs)

1. What is the primary definition of excretion?
(a) Removal of undigested food
(b) Removal of nitrogenous metabolic wastes
(c) Removal of oxygen
(d) Removal of enzymes

2. The stable internal environment maintained by excretion is known as:
(a) Respiration
(b) Digestion
(c) Homeostasis
(d) Circulation

3. Which of the following are the main excretory products?
(a) Urea, uric acid, ammonia, CO₂, water, salts
(b) Glucose, proteins, fats
(c) Saliva, bile, enzymes
(d) Oxygen, nitrogen

4. Identify the correct components of the human urinary system.
(a) Lungs, skin, liver, kidneys
(b) Kidneys, ureters, urinary bladder, urethra
(c) Heart, blood vessels, kidneys
(d) Stomach, intestine, kidneys

5. What is the main organ of excretion in the human body?
(a) Liver
(b) Lungs
(c) Kidney
(d) Skin

6. The structural and functional unit of the kidney is called the:
(a) Neuron
(b) Nephron
(c) Alveolus
(d) Villus

7. Approximately how many nephrons are present in each kidney?
(a) 100-200
(b) 1,000-2,000
(c) 10,000-20,000
(d) 1-2 million

8. Which blood vessel carries impure, oxygenated blood to the kidney?
(a) Pulmonary Vein
(b) Renal Vein
(c) Renal Artery
(d) Aorta

9. Which blood vessel carries purified, deoxygenated blood away from the kidney?
(a) Renal Vein
(b) Renal Artery
(c) Pulmonary Artery
(d) Capillary

10. The tube that carries urine from the kidney to the bladder is the:
(a) Urethra
(b) Uterus
(c) Ureter
(d) Oesophagus

11. The urinary bladder is best described as a:
(a) Flat-like structure
(b) Sac-like structure
(c) Tube-like structure
(d) Bone-like structure

12. The process of expelling urine from the body is called:
(a) Filtration
(b) Micturition
(c) Circulation
(d) Fertilisation

13. The term “Diuresis” refers to the:
(a) Breaking down of food
(b) Production and excretion of urine
(c) Exhalation of carbon dioxide
(d) Production of sweat

14. Kidney stones are primarily formed due to the:
(a) Presence of excess glucose in the blood
(b) Accumulation of mineral substances
(c) Lack of oxygen in the kidneys
(d) Presence of excess bile from the liver

15. The process of dialysis involves:
(a) Storing urine in the bladder
(b) Cycling blood through a machine to remove waste
(c) Removing urea through sweat glands
(d) Removing oxygen via the lungs

Answer Key

Question No.	Answer
1	(b)
2	(c)
3	(a)
4	(b)
5	(c)
6	(b)
7	(d)
8	(c)
9	(a)
10	(c)
11	(b)
12	(b)
13	(b)
14	(b)
15	(b)

Subjective Questions & Answers

1. Discuss any three types of excretory products produced in our body.

Answer:
Three main types of excretory products produced in our body are:

1. Urea, Uric Acid, and Ammonia: These are nitrogenous wastes produced from the breakdown of proteins and are primarily removed from the blood by the kidneys and excreted in urine.
2. Carbon Dioxide: This waste gas is produced during respiration in cells and is carried by the blood to the lungs, from where it is excreted during exhalation.
3. Excess Water, Salts, and Pigments: These are also filtered out by the kidneys and excreted in urine to maintain a stable internal environment, a process known as homeostasis.

2. Differentiate between the cortex and medulla region of kidney.

Answer:
The kidney is divided into two main regions:

• The Cortex is the outer, dark-colored region of the kidney.
• The Medulla is the inner, lighter-colored region of the kidney.
  Both of these regions contain numerous microscopic filtering units called nephrons, which are responsible for removing nitrogenous wastes from the blood.

3. Why do kidneys of some people fail to function properly? What treatment is given to such patients?

Answer:
Sometimes a person’s kidneys fail to function properly due to injury, disease, or infection. When this happens, the kidneys cannot effectively filter nitrogenous wastes like urea from the blood.
The treatment given to such patients includes:

• Dialysis: In this process, the patient’s blood is cycled through a machine (an artificial kidney) that filters out the metabolic wastes, effectively cleaning the blood.
• Kidney Transplant: In severe cases of kidney failure, a healthy kidney from a donor is surgically transplanted into the patient’s body to replace the non-functioning kidneys.