Excretion in Humans

Nephrons

Reason — Nephrons are the microscopic tubular structures, inside the kidney. They are also known as renal tubules.
The glomerulus is only a part of the nephron. It is a network of capillaries where filtration begins, but it is not the whole functional unit. Capillaries are tiny blood vessels present in many parts of the body, including within nephrons, but they are not the kidney’s functional unit. Neurons are nerve cells that transmit nerve impulses and have nothing to do with kidney structure.

Liver

Reason — Breakdown of excessive amino acids in liver results in formation of urea.
The kidneys do not produce urea. They filter urea from the blood and remove it from the body through urine. The spleen is involved in filtering blood and immune functions, not urea production. The urinary bladder only stores urine temporarily before it is excreted; it does not produce urea.

Urea

Reason — Urea and water are the major constituents of urine.
Nitric acid is not a normal component of urine in humans. Glucose is normally reabsorbed by the kidneys and should not be present in urine. Its presence may indicate conditions like diabetes. Bile pigments are related to liver function and may appear in urine only in certain diseases, but they are not a main component.

Nephrons

Reason — The Nephrons remove the waste substances by filtering it from the blood.
The collecting tubule mainly helps in collecting and concentrating urine, not in initial filtration. The ureter only transports urine from the kidneys to the urinary bladder. No filtration occurs here. The urinary bladder stores urine temporarily before excretion.

Liver

Reason — The process of the breakdown of excessive amino acids occurs in the liver.
The kidneys filter waste products like urea from the blood but do not break down amino acids. The small intestine is mainly responsible for digestion and absorption of nutrients, not amino acid breakdown for excretion. The lungs are involved in gas exchange (oxygen and carbon dioxide), not amino acid breakdown.

Excretion

Reason — The process of removal of nitrogenous waste products from the body of a living organism is called excretion.
Transpiration is the loss of water vapour from plants, mainly through stomata. It is not related to nitrogenous waste removal. Exudation refers to the oozing out of fluids like sap or gum from plants, not waste removal from animals. Evaporation is a physical process where liquid water changes into vapour, not a biological waste removal process.

Kidney

Reason — The kidneys play a crucial role in filtering waste products from the blood, including urea, which is then excreted in the urine.
The liver produces urea from excess amino acids but does not filter it out of the body. The skin removes small amounts of water, salts, and sweat, but urea is not primarily filtered here. The lungs remove carbon dioxide and water vapour, not urea.

Capsule

Reason — The outermost protective covering of the kidneys is termed as Capsule.
Epithelium is a type of tissue that lines organs and surfaces in the body, not a protective covering of kidneys. Pleura is the membrane surrounding the lungs, not the kidneys. The pericardium is the protective covering of the heart, not the kidneys.

Osmoregulation

Reason — The process of regulation of water and salt content in the body is called Osmoregulation.
Filtration is the process of separating waste substances from blood in the kidneys, not the overall regulation of water and salts. Ultrafiltration is a step in urine formation in the nephrons where blood is filtered under pressure, but it is not the overall regulatory process. Osmosis is the movement of water across a semi-permeable membrane, not the regulation of water and salts in the body.

Urination

Reason — The process of expulsion of urine from the body is termed as Urination.
Excretion is the overall process of removing metabolic wastes (like urea, CO₂, excess salts) from the body. It includes urine formation but is not just the expulsion of urine. Secretion is the process of release of useful substances by cells or glands (like enzymes, hormones), not waste removal.

Both A and R are true and R is the correct explanation of A.

Reason — A is true as during metabolism, the human body produces both useful substances (like hormones, enzymes) and waste or unwanted substances (like urea, carbon dioxide). These wastes need to be removed.
R is true as excretory wastes are harmful if they accumulate in the body. They can disturb normal physiological functions and may even be toxic, so they must be eliminated.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

Both A and R are true and R is the correct explanation of A.

Reason — A is true as humans have a pair of kidneys that filter blood and form urine. Anatomically, the right kidney is positioned slightly lower than the left kidney.
R is true as the liver, a large organ located in the upper right side of the abdomen, takes up significant space. Because of its size, it pushes the right kidney slightly downward, making it lie lower than the left kidney.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

A is false but R is true.

Reason — A is false as the blood entering the kidney through the renal artery is not “impure” in the sense of only containing wastes in large quantity. It is normal oxygenated blood that contains both useful substances and some wastes.
R is true as the blood does contain useful substances like oxygen and nutrients, but it is sometimes referred to as "impure" because it also carries nitrogenous wastes like urea, which need to be removed by the kidneys.

Therefore, A is false but R is true is the correct option.

Both A and R are true but R is not the correct explanation of A.

Reason — A is true as the skin is considered an accessory excretory organ because sweat glands help remove excess water, salts, and small amounts of urea and uric acid from the body.
R is true as sweat glands are located in the skin (dermis layer). Their main function is to produce sweat, which helps in cooling the body through evaporation, and the amount of sweat depends on environmental conditions.

Therefore, Both A and R are true but R is not the correct explanation of A is the correct option.

A is true but R is false.

Reason — A is true as diabetes mellitus is a hormonal disorder (related to insulin) in which blood glucose levels become higher than normal due to insufficient insulin production or improper use of insulin.
R is false as eating too many sweets does not directly cause diabetes mellitus. Diabetes is not caused simply by sugar intake; it is mainly due to either lack of insulin production or insulin resistance.

Therefore, A is true but R is false is the correct option.

1. Nephron
2. Bowman's capsule
3. Collecting duct
4. Dialysis
5. Diabetes mellitus
6. Renal artery

1. False
   Corrected statement — Removal of all kind of unwanted and toxic metabolic wastes is called excretion.
2. False
   Corrected statement — The medulla drains the urine into a funnel-shaped structure called the renal pelvis which further passes it to the urinary bladder through ureters.
3. True
4. True

1. Urine formation — Kidneys
2. Transport of urine away from kidney — Ureter
3. Temporary storage of urine — Urinary bladder

1. Urea, uric acid, and ammonia
2. Kidneys, Ureters, Urinary bladder, and Urethra
3. Skin, Lungs, and Liver
4. Calcium oxalate, Calcium phosphate, and Uric acid
5. Vitamins B and C

1. Excretion — The process of removal of unwanted and toxic metabolic waste products from the body is called Excretion.
2. Excretory organs — The organs that remove the unwanted waste and toxic substance from the body are known as Excretory organs.
3. Dialysis — The process of filtration of blood with the help of machine, if both kidneys fail, is called Dialysis.
4. Nephron — Nephron is the structural and functional unit of kidney. It filters the blood, purifies it and produces urine.
5. Osmoregulation — The process of maintaining or regulating the water and salt concentration in the body is called osmoregulation. Kidneys help in osmoregulation in our body.

1. Kidney — The kidneys are situated towards the back of the abdomen, one on either side of the backbone at the level of the last two ribs. The right kidney is located slightly lower than the left one.

2. Urinary bladder — Urinary bladder is situated in the lower abdomen.

3. Renal cortex — Renal cortex is the outer darker region of the kidney.

4. Renal medulla — Renal medulla is the inner lighter region of the kidney, located within the renal cortex.

5. Pelvis — The renal pelvis is a funnel-shaped structure located in the center of the kidney.

1. Kidney — The primary function of the kidneys is to filter blood, removing waste products and excess substances to produce urine.

2. Ureter — The ureters are thin tubes that transport urine from the kidneys to the urinary bladder.

3. Urinary bladder — The urinary bladder stores urine until it is ready to be expelled from the body.

4. Urethra — When the bladder if full, the urine is expelled out through the urethra.

5. Skin — The skin excretes waste products like excess water, salts, traces of urea and uric acid in the form of sweat, through sweat glands located underneath the skin.

The body produces many substances of which some are useful while the others are useless. If retained in the body, unwanted and toxic metabolic waste substances may become poisonous and cause much harm and in severe cases, even death. That is why excretion is necessary in living beings.

The two ways by which a person can get relief in case of kidney failure are:

1. Dialysis
2. Kidney transplant

Kidney stones are formed when crystal forming substances such as calcium oxalate, calcium phosphate and uric acid are more than the fluid in the urine. When these chemicals start sticking together, they form crystals, called kidney stones. They may be formed in any area of the excretory system and cause severe pain.

Following are the symptoms of urinary tract infection:

1. Strong and frequent urge to urinate.
2. Painful urination.
3. Burning sensation while urinating.

Differences between Ureter and Uterus on the basis of Organ system:

Differences between Nephron and Neuron on the basis of Location in body / organ:

Differences between Lungs and Liver on the basis of Excretory products:

Differences between Blood of renal artery and renal vein on the basis of Nitrogenous wastes:

Differences between Urinary bladder and urethra on the basis of function:

Below diagram shows the vertical section of a human kidney:

1. In the given diagram, the organ system that is shown completely is Excretory system, and the organ system that is shown partially is Circulatory system.

2. The guidelines 1 to 4 shows :
   1 → Kidney
   2 → Ureter
   3 → Urinary bladder
   4 → Urethra

3. The muscular sheet that divides the thorax and abdomen is called the diaphragm.

4. The Renal artery supplies blood from the heart to the kidney.

5. The renal vein carries deoxygenated blood back to the heart, which has been filtered by the kidney and is now relatively devoid of nitrogenous wastes.

1. The process being shown in the given figure is Dialysis.

2. When both the kidneys of a person fail, the blood soon becomes loaded with urea and other waste substances, and the person may die. In such a condition, doctors suggest the regular Dialysis treatment to filter blood through machine.

3. If both kidneys of a person fail, then the doctors suggest Kidney transplant from a suitable donor, apart from Dialysis.

4. Yes, a person can live a normal, healthy life with one kidney.

5. An important function of the Hemodialysis machine is to filter and clean the blood. It removes waste products and excess fluid from the blood, acting as an artificial kidney when a person's kidneys are not functioning properly.

(a) Two substances that commonly form crystals in the excretory system are calcium oxalate and uric acid.

(b) When these crystals accumulate in the urinary tract, they form kidney stones which may block the flow of urine, causing severe pain, infection and difficulty in urination.

(c) These crystals can be removed by drinking plenty of water to flush them out, by medications, or in severe cases, by medical procedures such as surgery.

(d) Yes, the presence of excess uric acid in urine is harmful because it can crystallise to form stones, which may block urine flow and cause pain and kidney damage if untreated.

(e) Two other body parts where stone formation may occur apart from kidneys are urinary bladder and gall bladder.