RBSE Solutions For Class 12 Biology Chapter 25: Excretory System of Human | Textbook Important Questions & Answers

RBSE Class 12 Biology Chapter 25 – Human Excretory system provides complete information related to the chapter. These important questions help students to ace their exams. By practising these important questions, students can analyze their preparation, get a thorough knowledge about all the important terminologies and perform best in their examinations.

The Rajasthan Board Class 12 Solutions are the best study material for both class assignments and other board examinations. By practising these important questions, students can gain deep knowledge about the topics explained in this chapter and also help them to be well prepared for their upcoming examinations.

RBSE Class 12 Biology Chapter 25 Important Questions

RBSE Biology Chapter 25: MCQ Type Questions

Q.1. The main excretory substance in human is

(a) Uric acid.

(b) Ammonia.

(c) Urea.

(d) Amino Acids.

Sol: (c) Urea.

Q.2. The main excretory organ of human is

(a) Lungs.

(b) Kidney.

(c) Liver.

(d) Skin.

Sol: (b) Kidney.

Q.3.Henle’s loop contains:

(a) Urea.

(b) Urine.

(c) Glomerular filtrate.

(d) Blood.

Sol: (c) Glomerular filtrate.

Q.4. A renal column of Bertini is related to

(a) Kidney.

(b) Urinary bladder.

(c) Liver.

(d) Testis.

Sol: (a) Kidney.

Q.5.Human kidneys are

(a) Pronephric.

(b) Metanephric.

(c) Mesonephric.

(d) All of the above.

Sol: (b) Metanephric.

Q.6.Ultrafilteration occurs in

(a) Glomerulus.

(b) Bowman’s capsule.

(c) Urinary bladder.

(d) Blood vessels.

Sol: (a) Glomerulus.

Q.7. The glomerular filtrate is

(a) Urine

(b) Blood without blood corpuscles

(c) Water, ammonia and blood corpuscles.

(d) Blood without blood corpuscles and plasma protein.

Sol: (d) Blood without blood corpuscles and plasma protein.

Q.8.Which of the following blood vessels brings blood back into the glomerulus?

(a) Efferent arteriole.

(b) Renal artery.

(c) Afferent arteriole.

(d) Renal vein.

Sol: (c) Afferent arteriole.

Q.9.How many layers are found in the wall of the urinary bladder?

(a) Five.

(b) Six.

(c) Three.

(d) Two.

Sol: (c) Three.

Q.10. A pain felt during the time of passing urine is called

(a) Dysuria.

(b) Polyuria.

(c) Gout.

(d) Uremia.

Sol: (a) Dysuria.

Q.11. ________is produced due to the decomposition of amino acids and proteins.

(a) Ammonia.

(b) Urea.

(c) Uric acid.

(d) All of the above.

Sol: (a) Ammonia.

RBSE Biology Chapter 25:Short Answer Type Questions.

Q.1. What is excretion? What are the important human excretory organs?

Sol: The process of removing metabolic waste products from the body is called excretion.The important human excretory organs are- kidneys, ureter, urethra, urinary bladder, skin, liver, intestine and lungs.

Q.2. What is Ammonotelic and Uricotelic?

Sol: Ammonotelic refers to those animals, which excrete ammonia.

Uricotelic refers to those animals, which excrete uric acid.

Q.3. What is ultrafiltration?

Sol: The process of filtration of blood from the glomerulus into the Bowman’s capsule because of the increased glomerular blood pressure is called ultrafiltration.

Q.4. What is the excretory unit of the kidney?

Sol: The tubular structures called nephrons, also called the uriniferous tubule are the unit of the kidney. They are located inside the kidneys and are called the structural and functional units of the kidney.

Q.5. Name the blood vessels coming out of the glomerulus.

Sol: Efferent arteriole. It is the only arteriole, which functions by carrying blood away from the glomerulus.

Q.6. What is Dysuria?

Sol: Dysuria is the medical term used to refer to pain or discomfort at the time of micturition. It is the one among the disorders related to the excretion.

Q.7. Where is the glomerulus found in the human excretory system?

Sol: The glomerulus is a cluster of nerve endings, formed from the fifty branches of afferent arterioles. They are found in the cavity of Bowman’s capsule. The glomerulus is mainly involved in the ultrafication process.

Q.8. What is the malpighian body?

Sol: The anterior part of the nephron is called the malpighian body. It includes glomerulus and Bowman’s capsule.

Q.9. What is Henle’s loop?

Sol: The Henle’s loop is the U shaped, thin, tubular and a middle part of the uriniferous tubule situated next to the proximal tubule.

Q.10.What are Renal columns of Bertin?

Sol: The pushing of the cortex part of the kidney into the medulla is termed the renal column or column of Bertin, also called the Bertin column. It consists of lines of blood vessels and urinary tubes and a fibrous material.

Q.11.What is the main role of kidneys in the body?

Sol: Kidneys are the main excretory organ of the human excretory system. It is mainl;y involved in the removal of nitrogenous waste products (urea) from the body.

Q.12.What is haemodialysis?

Sol: Haemodialysis is the process of removing urea and other waste products from the blood cells using the artificial process or artificial kidneys.

Q.13. What is Uremia?

Sol: When the presence of urea in the blood increases from 10 to 300mg per 100ml, then the condition caused is called uremia. The excessive storage of urea in the blood leads to the patient’s death.

Q.14.What is Glycosuria?

Sol: The presence of sugar in the urine is called glycosuria. This disorder is caused due to the lack of insulin hormone. The disease is called diabetes mellitus.

Q.15. What is Gout disease?

Sol: It is a hereditary disease, in which the amount of uric acid increases in the blood, which gets collected in the joints and kidney tissues. This disease also increases due to dehydration, keeping fast and increased production of urine or diuresis.

Q.16. What is Bright’s disease?

Sol: Bright’s disease, also called Nephritis. This disease is caused due to the infection caused by Streptococci bacteria in glomeruli. As a result of the infection, the glomerulus develops inflammation and its membranes become too permeable, due to which the red blood cells and proteins also sieve out in the filtrate.

Q.17. Describe the excretory organs in the human body other than the kidneys.

Sol: Other excretory organs in humans are:

Skin: Sweat glands are found in the human skin, which secretes out sweat containing water and other nitrogenous excretory substances.

Lungs: Lungs are the primary organs of the cellular respiration, which functions by releasing carbon dioxide as excretory substances, which are eliminated outside the body through the respiration process in the lungs.

Liver: Liver cells function by converting nitrogenous parts of amino acids into ammonia. The produced ammonia is converted into urea, which is released into the blood. The liver also forms bile pigments, which are excreted along with the bile juice into the intestine.

Q.18.What are the important functions of the human excretory system?

Sol: The important functions performed by the excretory system include- elimination of wastes, eliminate waste byproducts excreted by the cells, prevent the accumulation of harmful chemicals in the body, and maintain a balanced chemical concentration in the body.

Q.19.What are the different types of wastes eliminated by living organisms?

Sol: The different types of wastes eliminated by the living organisms include- ammonia, urea, and uric acid. The organisms are classified as ammonotelic, ureotelic and uricotelic based on the type of nitrogenous waste eliminated by the body.

Q.20.What is the Malpighian body?

Sol: The anterior part of each uriniferous tubule is called malpighian body. It is formed by two main parts: Bowman’s Capsule and Glomerulus.

RBSE Biology Class 12: Long Answer Type Questions

Q.1. What is the role of ultrafiltration in urine formation?

Sol: The process of urine formation is a passive process, which takes place from the glomerulus into the Bowman’s capsule.

The glomerular epithelium comprises various micropores, which increases the rate of filtration.

The process of ultrafiltration takes place due to the increased blood pressure in the glomerulus. The increase in the blood pressure is mainly due to the differences of afferent and efferent arterioles.

There is ultrafiltration of all the components of the blood except the blood corpuscles, plasma protein macromolecular foreign substances. The ultrafication forms a glomerular filtrate in the Bowman’s capsule.

The glomerular filtrate is plasma without the plasma protein.

Glomerular filtrate → Blood – Blood cell + Plasma proteins.

Glomerular filtrate → Plasma – Proteins.

The hydrostatic pressure in the glomerulus (GHP) is between 65 to 75mm of Hg. Out of it, the blood colloid osmotic pressure (BCOP) due to the plasma proteins is 30mm of Hg.

The capsular hydrostatic pressure (CHP) is 15 to 20mm of Hg. Therefore, the net effective glomerular filtration pressure (EFP) is 15 to 25 mm of Hg. which is responsible for ultrafication.

In humans, the glomerular filtration rate (GFR) is 125ml per minute.i.e.both the kidneys form 125ml of filtrate per minute.

Hence, 180 litres of filtrate is formed per day. Out of it only 1.2 litres of urine is produced per day, which is 0.8 percent of the total filtrate.

Q.2. What do you mean by kidney transplantation? Explain in brief.

Sol: In a human being when kidneys stop functioning and are not curable by the medical treatment, then a kidney of the other healthy person is to be transplanted. This process is called the kidney transplantation. The kidney is obtained from a donor, should be the nearest relative whose blood and tissue structure are to be similar. The person who donates a kidney is known as a kidney donor.

If the kidney of an unknown person is transplanted, then the immune system of the diseased person may reject the new kidney, as such the transplanted kidney may not function and the patient will die due to the lack of excretion process in the body.

Q.3. What are the disorders of the Excretory System?

Sol: The excretory system is responsible for the elimination of wastes from the body of an organism. Organs such as liver, kidney, skin and sweat glands eliminate the nitrogenous waste from the body. Any disorder in the excretory system leads to the accumulation of nitrogenous wastes in the body that leads to certain disorders of the Excretory System.

Listed below are the major disorders of the Excretory System

  1. Uremia.
  2. Oedema.
  3. Renal Failure.
  4. Diabetes Insipidus.
  5. Renal Tubular Acidosis.
  6. Nephritis or Bright’s Disease.
  7. Renal Calculi or Kidney Stones.
  8. Hypertension due to Renin Secretion.

Q.4. What is Excretion? What is its significance to humans?

Sol: Excretion is the physiological process of eliminating metabolic wastes from the body.

Human excretory system includes organs that facilitate the removal of nitrogenous wastes from the body. The important human excretory organs are- kidneys, ureter, urethra, urinary bladder, skin, liver, intestine and lungs.

  1. Kidneys filter the blood and urine is the filtrate obtained.
  2. Urine passes to the urinary bladder via ureter and is expelled out of the body. This is known as micturition.
  3. Kidneys also regulate the osmotic pressure of a mammal’s blood through excessive purification and filtration. This is known as osmoregulation.

Significance of excretion to humans:

  1. Carbon dioxide released by humans during exhalation.
  2. It eliminates wastes, which are usually toxic when they accumulate in the body.
  3. Sweat, the fluids secreted by the sweat glands help in bringing down the temperature of the body because high temperatures can be fatal or cause life-threatening injuries.

Q.5. Describe the various diseases associated with the excretory system.

Sol: Kidney is the primary organ of the excretory system. It functions by filtering out the wastes from the body. Irregular functioning of excretory systems results in excretion, which leads to various disorders in humans. There are many potential causative factors for disorders of the excretory system. Underlying illness, environmental factors, pathogenic microbes and even ingestion of certain substances can cause major functions of the excretory system to fail.

Listed below are a few of the primary disorders related to the excretory system.

Uremia:

This condition is caused when the amount of urea in the blood is comparatively high, which is more than 10 to 30 mg / 100 ml. The excess amount of urea in blood is harmful, which can lead to the patient’s death. In such cases, excess urea is removed by hemodialysis.

Gout:

This condition is caused when the amount of uric acid increases in the blood, which gets collected in the joints and kidney tissues. This is a hereditary disease and can also be caused due to the dehydration, keeping fast and increased production of urine or diuresis.

Kidney Stones:

Kidney stones are also called Renal Calculi. It is caused by the result of the deposition of dissolved minerals or insoluble salts on the inner lining of the kidney. These increase in size and cause immense pain in the patients when passed.

Bright’s disease:

This disorder is also called Nephritis. This disease is caused due to the infection caused by Streptococci bacteria in glomeruli. As a result of the infection, the glomerulus develops inflammation and its membranes become too permeable, due to which the red blood cells and proteins also sieve out in the filtrate. If this disorder is left untreated, then the accumulation of the fluid increases, resulting in the swelling of the legs, which is called the Dropsy or Edema.

Diabetes Insipidus:

Diabetes Insipidus results due to the deficiency of Antidiuretic hormone. The hormone leads to the reabsorption of water by distal parts of the nephron and thus prevents diuresis (urine production). Deficiency in ADH secretion results in excessive production of dilute urine and intense thirst.

Oedema:

Oedema is the accumulation of excess fluid in the tissues. Excess sodium ions result in an increase in the volume of the interstitial fluid without a change in their osmolality.

Glycosuria:

The presence or excretion of glucose in the urine is called the glycosuria. This disease is caused due to the insulin hormone.

Polyurea:

The increased amount of urine due to the less absorption of water is called the polyurea.

Jaundice: The presence of bile pigments in huge amounts in urine is a symptom of jaundice. It is seen during hepatitis or due to the blockage of the bile duct.

Alkaptonuria:

Alkaptonuria is defined as the presence of alkaline or homogentisic acid in the body. When the alcapton comes in contact with the air then urine becomes black in colour. This disease is also known as the Black Urine disease.

Q.6. What is the role of reabsorption in urine formation?

Sol: The process by which the useful substances are reabsorbed in the blood from the uriniferous tubule is known as selective reabsorption. In the formation of urine, the process of reabsorption take place in different parts of the uriniferous tubule as follows:

  • In renal tubules, 99.2 percent of the glomerular filtrate is absorbed into the blood.
  • The process of reabsorption takes place by active transport and most of the reabsorption takes place in the Proximal Convoluted Tubule (PCT). However, water is absorbed by passive transport.
  • The reabsorption of the substances is according to the renal threshold value. The maximum capacity of both the kidneys to absorb a particular substance is called a renal threshold of the substance. The renal threshold value of the substance is mainly based on their requirement by the body. The substances are divided into three types, which are based on their renal threshold value:
  1. High threshold substances:

These include substances like sugar, vitamins, amino acids, etc. which can be easily absorbed.

  1. Low threshold substances:

These include substances of low concentration like creatinine, creatine, urea, phosphate, etc.

  1. A threshold substances:

These include substances like uric acid and other substances, which cannot be absorbed.

If any of the substances exceeds its renal threshold value, it will appear in the urine. The renal threshold value of glucose is 350mg per minute, which is called TmG. The reabsorption of the substances is under the control of hormones, which are as follows:

Glucocorticoids:

They are secreted by the adrenal cortex and they control the reabsorption of sugars, amino acids, vitamins in the Proximal Convoluted Tubule (PCT).

Mineralocorticoids:

They are secreted by the adrenal cortex and they control the reabsorption of mineral ions in the Proximal Convoluted Tubule (PCT).

Calcitonin and Parathormone:

They control the reabsorption of calcium ion in the Distal Convoluted Tubule (DCT).

Vasopressin or ADH:

It is a hormone of the Pituitary gland, which controls the absorption of water in the Distal Convoluted Tubule (DCT).

Most of the water about 80 percent is absorbed in the Proximal Convoluted Tubule (PCT) along with other substances. It is called obligatory water reabsorption.

The remaining water, about 20 percent, is absorbed in the Distal Convoluted Tubule (DCT) under the control of antidiuretic hormone (ADH) according to the requirement of the body. It is called facultative water reabsorption. The excess release of the antidiuretic hormone (ADH) results in a decreased volume of urine.

Q.7. What are the advantages and disadvantages of dialysis?

Sol: Dialysis is an artificial way to eliminate waste and excess fluid from the body. This procedure helps patients with end stage renal disease to increase quantity and quality of life.

Advantages of Dialysis.

  1. Dialysis can be carried out even at home.
  2. Unlike peritoneal dialysis, hemodialysis is not carried out every day.
  3. Peritoneal dialysis is a comfortable method of dialysis that is easy to use.
  4. The equipment used in peritoneal dialysis is less bulky and easy to carry along with the patient.

Disadvantages of Dialysis.

  1. One of the most significant disadvantages of PD is that it is required to be carried out every day, which may act as an inconvenience for some.
  2. Patients undergoing dialysis are at a great risk of developing peritonitis – an infection of the abdomen.
  3. In some rare cases, patients may experience scarring and thickening of the peritoneum.
  4. Patients undergoing dialysis are at a great risk of increased fatigue and malnutrition caused by the dialysis fluid, which can lower protein levels.

Q.8. Draw a neat labelled diagram representing the different parts of the human excretory system.

Sol: The human excretory system:Human Excretory System

Q.9. What is dialysis? Explain with a neat labelled diagram.

Sol: Dialysis is an artificial way to eliminate waste and excess fluid from the body. This process is used for people with a critical kidney disorder – grave kidney damage, previously severe renal failure. It is required when the kidney loses 90% of its efficiency and has a glomerular filtration rate of less than 15. This treatment may continue for months or years since most kidney failures are irreversible. Dialysis is the process of filtering and purifying the blood with the help of a machine. This balances our fluids and electrolytes when the kidneys stop functioning. It is used to treat people suffering from kidney disorders.

Dialysis

Q.10. Brief out the structure of the human excretory system.

Sol: In humans, kidneys are the main excretory organs. Besides kidneys, urete, urinary bladder and urinary passage or urethra are also involved in the process of excretion.

Human Excretory System

Kidneys

In humans, a pair of kidneys are found and it is situated at the dorsal side of the abdominal cavity on both the sides of the vertebral column.The right kidney is anterior to the left kidney and both are attached with the dorsal wall of the abdomen.

Human kidneys are bean shaped and dark red in colour. Each kidney weighs about 10 to 11 cm in length, 5 to 6 am in width, 2.5 to 3 cm thick and 120 to 170 gm in weight.

The outer surface of the kidney is convex and the inner surface is concave.

Ureters

A narrow tube with thick muscular walls coming out from the hilum of the kidney is called ureter. Its proximal part in the kidney is wide and funnel-shaped which is called pelvis. Both the ureters, starting from the pelvis open below in the urinary bladder.

Urinary bladder

It is a muscular bag-like structure in which urine is collected and stored until micturition. Urinary bladder consists of three layers of wall.

Urinary passage or Urethra

This tube or duct arising from the urinary bladder is called urethra. It Helps to expel urine out of the body. In males, it acts as the common route for sperms and urine. Its opening is guarded by a sphincter. The male urethra is made of three parts:

  1. Prostatic or Urethral part.
  2. Membranous part.
  3. Penile part.

Q.11.Brief out the internal structure of the human kidney.

Sol: Structure of the Human Kidney:

Structure of the Human Kidney

In humans each kidney is covered with a firm, fibrous connective tissue, which is called a renal capsule. Inside the renal capsule, the kidney is differentiated into two main parts:

Cortex

The outer part of the kidney is called the cortex. It is situated near the capsule and is granular in structure because of Malpighian bodies.

Medulla

The inner part of the kidney is called the medulla. In this region, Henle’s loop and collecting tubules are found. They consist of pyramids which are situated in a cup shaped cavity which is called calyx. The calyx joins together and opens into a pelvis, which is funnel shaped and which later opens in the ureter.

Q.12. Define Hemodialysis and Peritoneal dialysis. How are they different from each other?

Sol: Hemodialysis dialysis

It is the method, in which the patient’s blood is passed through the dialysis machine where it is purified and returned to the patient’s body.

Peritoneal dialysis

It is the surgical method, in which the catheter is implanted into the stomach of the patient. A cleaning fluid (dialysate) is then circulated throughout the catheter that absorbs the waste materials from the blood vessels in the walls of the stomach. It is then drawn out and discarded. Peritoneal dialysis is considered to be more versatile and convenient than hemodialysis.

Difference between Hemodialysis and Peritoneal dialysis

Hemodialysis – In hemodialysis, the blood is pumped out of the body, filtered through a machine and returned to the body through the tubes that connect the patient to the machine.

Peritoneal dialysis- In peritoneal dialysis, a catheter is implanted in the patient’s stomach through which the dialysate is circulated. This dialysate absorbs all the waste from the body.

Q.13. Brief out the structure of nephrons.

Sol: The tubular structures called nephrons, also called the uriniferous tubule are the unit of the kidney.

The Structure of Nephrons.

The Structure of Nephrons

  • Nephrons, formed independently, are located inside the kidneys and are called the structural and functional unit of the kidney.
  • It comprises an anteriormost part called Malpighian body, which includes a cup like Bowman’s capsule and a glomerulus.
  • The glomerulus is a branch of blood capillaries. It functions by receiving the blood through an afferent arteriole and the blood comes out through the efferent arteriole. The diameter of the afferent is comparatively more.
  • The Bowman’s capsule opens into a proximal convoluted tubule (PCT) through a short and straight neck.
  • The anterior part of the proximal convoluted tubules (PCT) is more coiled, compared to its posterior part, which is almost straight. The proximal convoluted tubules (PCT) opens into a Henle’s loop.
  • The Henle’s loop is a U shaped structure, which has a distinct descending limb and an ascending limb.
  • The ascending limb opens into the distal convoluted tubules (DCT), which is a coiled duct.
  • Many of the distal convoluted tubules (DCT) unite to form a collecting duct.
  • The collecting ducts of one pyramid unite to form a duct of bellini, which lead into the pelvis part.
  • The Malpighian body and a part of the Proximal convoluted tubule ( CT) and Distal convoluted tubules (DCT) are situated in the cortex.
  • The parts of the Proximal convoluted tubule (PCT), Distal convoluted tubules (DCT), Henle’s loop and collecting ducts are found in the medulla.
  • The efferent arteriole forms a per-tubular capillary network around the Proximal convoluted tubule (PCT), Distal convoluted tubules (DCT), Henle’s loop, which is called Vasa recta.
  • The capillaries of Vasa recta join to form venules, which finally open into the renal vein.

Q.14. What is Peritoneal Dialysis?

Sol: It is the surgical method performed for patients suffering from kidney disease. In this procedure the catheter is implanted into the stomach of the patient.

In this process of dialysis:

  • The catheter is implanted into the stomach of the patient.
  • The implanted catheter helps in filtering the blood through the peritoneum, which is a membrane in your abdomen.
  • During peritoneal dialysis, a special fluid called dialysate flows into the peritoneum by absorbing all the wastes and it is transported through a tube in the abdomen.
  • Once the dialysate is completed, it is flushed out when the patient is sleeping in the night time.

Types of Peritoneal Dialysis

There are two types of Peritoneal Dialysis

  1. Automated Peritoneal Dialysis (APD)
  2. Continuous Ambulatory Peritoneal Dialysis (CAPD)

Complication of Peritoneal Dialysis:

  1. The main complication of this process is infections caused due to the presence of a permanent tube.
  2. The catheter must be cleaned properly before each infusion and flow in and out of the abdomen.
  3. Two to three litres of dialysis fluid is supplied to the abdomen for around ten to fifteen minutes.

Q.15. Explain the Principle of Dialysis.

Sol: Dialysis is an artificial way to eliminate waste and excess fluid from the body.

Dialysis functions on the ultrafiltration of fluid through a semipermeable membrane and the concept of the dissipation of solutes. Diffusion is a characteristic of materials in water that has the tendency to flow against a concentration gradient.

Blood runs on one flank of the semi-permeable film, and dialysate or distinct dialysis fluids flow on the opposite flank.

A selectively permeable layer is a skinny membrane of material that comprises pores of different sizes or holes.

Minor solutes and fluids flow through the layer, but the membrane stops the path of bigger substances (for instance, large proteins, red blood cells).

This imitates the filtering procedure that happens in the kidneys when the blood moves into the kidneys and the bigger substances are divided from the minor ones in the glomerulus.

However, dialysis is not a permanent solution, instead, it should be seen as a temporary alternative to substitute the kidney’s function until the kidney can repair itself.

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