RBSE Solutions Class 12 Biology Chapter 25 Man-Excretory System

RBSE Class 12 Biology Chapter 25 Multiple Choice Questions

Question 1. The main excretory substance in human is:
(a) Uric acid
(b) Ammonia
(c) Urea
(d) Amino acid
Answer: (c) Urea
In simple words: The main waste product that humans get rid of from their bodies is urea. Our body processes harmful substances into urea to make them safe for removal.

🎯 Exam Tip: Remember the primary nitrogenous waste product in humans is urea, which is less toxic than ammonia and requires less water for excretion.

Question 2. The main excretory organ of human is:
(a) Lungs
(b) Kidney
(c) Skin
(d) Liver
Answer: (b) Kidney
In simple words: The kidneys are the most important organs for filtering waste from our blood and making urine. They are like a cleaning machine for the body.

🎯 Exam Tip: Identify the specific function of each organ in the excretory system to understand why kidneys are the main organ for filtering blood.

Question 3. Henle's loop contains:
(a) Urine
(b) Urea
(c) Blood
(d) Glomerular filtrate
Answer: (d) Glomerular filtrate
In simple words: Henle's loop contains the liquid that has been filtered from the blood but has not yet become final urine. It's a mix of water, salts, and waste before it gets fully processed.

🎯 Exam Tip: Understand the journey of filtrate through the nephron to correctly identify its composition at each stage, especially in Henle's loop where water and salt reabsorption occurs.

Question 4. A renal column of Bertini is related to:
(a) Kidney
(b) Urinary bladder
(c) Liver
(d) Testis
Answer: (a) Kidney
In simple words: The renal columns of Bertini are parts of the kidney. They are extensions of the kidney's outer layer that go down between the kidney's inner parts.

🎯 Exam Tip: Familiarize yourself with the anatomical structures of the kidney, including the cortex, medulla, and renal columns, as these are often tested.

Question 5. Human kidneys are:
(a) Pronephric
(b) Metanephric
(c) Mesonephric
(d) All of the options
Answer: (b) Metanephric
In simple words: Human kidneys are of the metanephric type. This means they are the most developed type of kidney, allowing for efficient waste removal.

🎯 Exam Tip: Know the different types of kidneys (pronephric, mesonephric, metanephric) and which type is found in humans and other vertebrates.

Question 6. Ultrafiltration occurs in:
(a) Glomerulus
(b) Bowman's capsule
(c) Urinary bladder
(d) Ureter
Answer: (a) Glomerulus
In simple words: Ultrafiltration is the first step where blood is filtered, and it happens in the glomerulus. It's like a tiny sieve that separates waste from blood.

🎯 Exam Tip: Clearly distinguish between the glomerulus (where filtration occurs) and Bowman's capsule (which collects the filtrate). Often, these are mistakenly thought to be the same site of action.

Question 7. The glomerular filtrate is:
(a) Water, ammonia and blood corpuscles
(b) Blood without blood corpuscles and plasma protein
(c) Blood without blood corpuscles
(d) Urine
Answer: (b) Blood without blood corpuscles and plasma protein
In simple words: The fluid filtered out of the glomerulus is similar to blood plasma but does not have large things like blood cells or big proteins. It contains water, salts, glucose, and waste.

🎯 Exam Tip: Remember that large molecules like blood cells and plasma proteins are too big to pass through the filtration membrane, so they are absent in the glomerular filtrate.

Question 8. The blood vessel which brings blood into the glomerulus:
(a) Efferent arteriole
(b) Renal artery
(c) Afferent arteriole
(d) Renal vein
Answer: (c) Afferent arteriole
In simple words: The afferent arteriole is the small blood vessel that carries blood into the glomerulus for filtering. It is like an entry pipe for the blood.

🎯 Exam Tip: Differentiate between afferent (bringing blood IN) and efferent (taking blood OUT) arterioles in the kidney, as their diameter difference is crucial for filtration pressure.

RBSE Class 12 Biology Chapter 25 Very Short Answer Type Questions

Question 1. What is Excretion?
Answer: Excretion is the process by which living organisms remove metabolic waste products and harmful substances from their bodies. This keeps the body clean and healthy.
In simple words: Excretion is how bodies get rid of unwanted waste made during daily activities.

🎯 Exam Tip: Define excretion clearly, distinguishing it from egestion (removal of undigested food). Focus on metabolic waste products.

Question 2. An animal which excretes ammonia is called?
Answer: An animal that excretes ammonia as its main nitrogenous waste product is called ammonotelic. These animals usually live in water because ammonia is very toxic and needs a lot of water to be diluted and removed safely.
In simple words: Animals that get rid of ammonia are called ammonotelic.

🎯 Exam Tip: Remember that ammonotelic animals are typically aquatic, as ammonia requires large amounts of water for its excretion due to its high toxicity.

Question 3. Animals which excrete uric acid are called?
Answer: Animals that excrete uric acid as their main nitrogenous waste product are called uricotelic. Uric acid is the least toxic and requires very little water for excretion, making it suitable for animals living in dry conditions.
In simple words: Animals that get rid of uric acid are called uricotelic.

🎯 Exam Tip: Connect the type of excretory product (ammonia, urea, uric acid) with the animal's habitat and water availability for efficient waste removal.

Question 5. Write the name of the excretory unit in the kidney.
Answer: The excretory unit in the kidney is called a nephron, also known as a uriniferous tubule. Each kidney contains millions of these tiny filtering units.
In simple words: The working part of the kidney that cleans blood is called a nephron.

🎯 Exam Tip: State both common names (nephron, uriniferous tubule) to ensure full marks and show complete knowledge.

Question 6. Name the blood vessel coming out of the glomerulus.
Answer: The blood vessel coming out of the glomerulus is called the efferent arteriole. This vessel carries filtered blood away from the glomerulus.
In simple words: The efferent arteriole takes blood away from the glomerulus.

🎯 Exam Tip: Distinguish the efferent arteriole (exit) from the afferent arteriole (entry) of the glomerulus, noting their difference in diameter.

Question 7. What is the term used for pain at the time of micturition?
Answer: The term used for pain at the time of micturition (the act of urinating) is dysuria. This symptom can indicate various urinary tract issues.
In simple words: Pain when peeing is called dysuria.

🎯 Exam Tip: Learn common medical terms associated with the excretory system, as they are often used in clinical contexts and exams.

Question 8. Where the glomerulus is found? What is its role?
Answer: The glomerulus is found inside Bowman's capsule, which is part of the nephron in the kidney. Its main role is to perform ultrafiltration, which means filtering blood to produce glomerular filtrate.
In simple words: The glomerulus is inside Bowman's capsule and filters blood.

🎯 Exam Tip: Clearly state both the location and the primary function (ultrafiltration) of the glomerulus to answer comprehensively.

Question 9. What is the malpighian body?
Answer: The Malpighian body, also known as the renal corpuscle, is the anterior part of the nephron. It includes both the glomerulus and the Bowman's capsule, where the initial filtering of blood takes place.
In simple words: The Malpighian body is the first part of the nephron, made of the glomerulus and Bowman's capsule.

🎯 Exam Tip: Remember that the Malpighian body is a combined structure, not just the glomerulus or Bowman's capsule alone.

Question 10. Where the Henle's loop is found?
Answer: Henle's loop is a U-shaped part of the nephron. It extends from the renal cortex down into the renal medulla and then back up to the cortex, playing a crucial role in concentrating urine.
In simple words: Henle's loop is a U-shaped tube in the kidney's filtering unit.

🎯 Exam Tip: Note the characteristic U-shape and its location spanning both the cortex and medulla, which is vital for its function.

Question 12. What is the main role of kidneys in the body?
Answer: The main role of kidneys in the body is to remove nitrogenous waste products, like urea, from the blood. They also help maintain the body's water and salt balance.
In simple words: Kidneys mostly remove waste like urea from blood and balance water in the body.

🎯 Exam Tip: Focus on the primary role of filtering nitrogenous waste, but also briefly mention their role in osmoregulation (water and electrolyte balance).

Question 13. What is haemodialysis?
Answer: Haemodialysis is a medical procedure that removes urea and other waste products from the blood using an artificial kidney machine (dialyzer). This is done when a person's kidneys can no longer function properly.
In simple words: Haemodialysis uses a machine to clean a person's blood when their kidneys fail.

🎯 Exam Tip: Clearly explain that haemodialysis is a treatment that mimics kidney function, specifically mentioning the artificial kidney or dialyzer.

Question 14. Presence of Urea in the blood is called?
Answer: The presence of urea in the blood is called uremia. High levels of urea in the blood can be very harmful and indicate kidney dysfunction.
In simple words: Too much urea in the blood is called uremia.

🎯 Exam Tip: Learn the correct medical term for conditions related to abnormal levels of waste products in the blood.

Question 15. What is glycosuria?
Answer: Glycosuria is the condition where glucose is present in the urine. Normally, the kidneys reabsorb all glucose back into the blood, so its presence in urine usually suggests high blood sugar levels, as seen in diabetes.
In simple words: Glycosuria means there is sugar (glucose) in the urine.

🎯 Exam Tip: Relate glycosuria to conditions like diabetes mellitus, explaining the link between high blood glucose and glucose in urine.

RBSE Class 12 Biology Chapter 25 Short Answer Type Questions

Question 1. Describe the excretory organ in the human body other than kidneys.
Answer: Other Excretory Organs in Man:
1. **Skin:** The human skin has sweat glands that release sweat. This sweat contains water, salts, and a small amount of nitrogenous waste products. So, skin helps in getting rid of some wastes.
2. **Lungs:** During cellular respiration, the lungs release carbon dioxide (\( \text{CO}_2 \)) as a waste product. This \( \text{CO}_2 \) is then breathed out of the body.
3. **Liver:** Liver cells convert the nitrogenous part of amino acids into ammonia, which is then changed into urea. This urea is released into the blood and then filtered by the kidneys. The liver also creates bile pigments, which are removed from the body along with bile through the intestines.
In simple words: Besides kidneys, skin releases sweat, lungs exhale carbon dioxide, and the liver makes urea and bile pigments for removal.

🎯 Exam Tip: When describing accessory excretory organs, list each organ separately and clearly state the specific waste product it helps to excrete.

Question 2. What is Gout disease?
Answer: Gout is a genetic disease where the level of uric acid in the blood increases. This excess uric acid then forms crystals that get deposited in the joints (causing pain and swelling) and in kidney tissues. Factors like dehydration, fasting, and increased urination can trigger or worsen gout.
In simple words: Gout is a disease where too much uric acid builds up in the blood and forms crystals in joints and kidneys.

🎯 Exam Tip: Remember gout is linked to increased uric acid, often affecting joints and kidneys, and has a hereditary component.

Question 3. Explain Bright's disease.
Answer: Bright's disease, also known as Nephritis, is an inflammation of the glomeruli in the kidneys, typically caused by a bacterial infection like Streptococci. This inflammation makes the glomerular membranes more permeable, allowing red blood cells and proteins to leak into the filtrate. If not treated, this can lead to fluid buildup in the body, causing swollen legs, a condition called Edema or Dropsy.
In simple words: Bright's disease is kidney inflammation caused by infection, making the filters leaky and causing swelling in the body.

🎯 Exam Tip: Highlight the key features: inflammation of glomeruli, bacterial cause (Streptococci), leakage of RBCs and proteins, and potential complication of edema.

Question 4. What is the role of ultrafiltration and selective reabsorption in urine formation?
Answer: Urine formation involves two main processes: ultrafiltration and selective reabsorption.
**Ultrafiltration:** This is a passive process that occurs in the glomerulus. Blood pressure forces water and small solutes from the blood into Bowman's capsule, forming glomerular filtrate. The glomerular epithelium has many tiny pores (about \( 0.1\mu \) in diameter) that allow fast filtration. This process happens because the blood pressure in the glomerulus is higher due to the difference in the sizes of the afferent (wider) and efferent (narrower) arterioles. Almost all components of blood are filtered, except for blood corpuscles and large plasma proteins. The glomerular filtrate is essentially plasma without plasma protein.
**Selective Reabsorption:** After filtration, the useful substances from the glomerular filtrate (like glucose, amino acids, and some salts) are reabsorbed back into the blood capillaries surrounding the nephron tubules. This process is selective, meaning the body only takes back what it needs. This reabsorption can be active or passive and ensures that essential nutrients are not lost in the urine. The process helps in creating a concentrated urine by removing excess water and retaining necessary salts. About 180 liters of filtrate are formed daily, but only about 1.5 liters of urine are produced, showing how much is reabsorbed.
In simple words: Ultrafiltration cleans blood by pushing fluids and small particles into the kidney tubules. Selective reabsorption then takes back useful things from this fluid into the blood, making sure only waste leaves the body as urine.

🎯 Exam Tip: For this type of question, define each process clearly, mention where it occurs, and explain its significance in forming the final urine.

RBSE Class 12 Biology Chapter 25 Essay Type Questions

Question 1. Explain the excretory system in man by giving a suitable diagram.
Answer: The human excretory system is responsible for removing waste products from the body. It mainly consists of a pair of kidneys, a pair of ureters, a urinary bladder, and a urethra. (A diagram illustrating these parts, such as Fig. 25.1 Excretory System of Man, would typically be included here to show the anatomical arrangement.)
**Kidney:** Kidneys are the primary excretory organs, dark red and bean-shaped. They are metanephric, meaning they are highly developed. They are located on the dorsal side of the middle part of the coelom and are retroperitoneal, meaning they are behind the peritoneum. The right kidney is slightly lower than the left. Each kidney weighs around 120-170 grams and measures approximately 4" x 2.5" x 1". The concave inner side is called the hilus, where the renal artery enters, the renal vein exits, and the ureter also emerges. An adrenal gland sits like a cap on top of each kidney.
**Ureters:** These are tubes that carry urine from the kidneys to the urinary bladder.
**Urinary Bladder:** This is a bag-like structure made of smooth, involuntary muscles. Its inner lining has transitional epithelium, which allows it to stretch and store urine. The bladder's opening into the urethra is controlled by a sphincter made of voluntary muscles, which relaxes during urination (micturition).
**Urethra:** The urethra is the tube through which urine exits the body. In males, it passes through the penis and is divided into three parts: the prostatic part (receives prostate gland, urinary bladder, and vas deferens), the membranous part (receives Cowper's glands), and the penile part (about 15 cm long, inside the corpus spongiosum of the penis). In females, the urethra is much shorter and opens directly outside through the urinary orifice.
The basic functional unit of the kidney is the nephron (uriniferous tubule). Each kidney has millions of these units, where urine is formed. The Malpighian body (glomerulus and Bowman's capsule) filters the blood. The filtered fluid then passes through various tubules (PCT, Henle's loop, DCT, collecting duct) where reabsorption and secretion occur to produce final urine. Vasa recta, a network of capillaries, surrounds these tubules and helps in the exchange of substances.
In simple words: The excretory system has kidneys to filter blood, ureters to carry urine, a bladder to store it, and a urethra to release it. Kidneys are bean-shaped, and their main job is to clean the blood and remove waste.

🎯 Exam Tip: For essay questions, always provide a clear introduction and conclusion. Describe each component of the system, mentioning its structure, location, and specific function, and include a simple, labeled diagram if allowed.

Question 4. Describe various diseases associated with the excretory system.
Answer: Irregularities in the excretory system can lead to various diseases:
1. **Uremia:** This condition occurs when the amount of urea in the blood becomes too high (more than 10-30 mg/100 ml). Excess urea is toxic and can be fatal if not treated.
2. **Gout:** A hereditary disease where high levels of uric acid build up in the blood. Uric acid crystals deposit in synovial joints and kidney tissues, causing pain. Dehydration, fasting, and diuresis can worsen it.
3. **Kidney stones (Renal Calculi):** These are hard deposits of crystals like calcium oxalate, phosphate, or uric acid that form in the renal pelvis. They cause severe pain and difficulty in urinating.
4. **Bright's disease (Nephritis):** This is an inflammation of the kidney's glomeruli, often caused by Streptococci bacteria. It makes the glomerular membrane leaky, allowing red blood cells and proteins to enter the filtrate. Untreated nephritis can lead to fluid accumulation (edema).
5. **Glycosuria:** This is the presence or excretion of glucose in the urine. It typically results from a deficiency of insulin hormone, leading to diabetes mellitus.
6. **Dysuria:** Refers to painful urination, which can be a symptom of various urinary tract infections or conditions.
7. **Polyurea:** An increased volume of urine output due to reduced water reabsorption by the kidneys.
8. **Cystitis:** This is the swelling or inflammation of the urinary bladder. It can be caused by bacterial infections, chemical irritants, or mechanical damage.
9. **Diabetes Insipidus:** Caused by low secretion of antidiuretic hormone (ADH). This leads to decreased water reabsorption in the distal convoluted tubules and collecting tubules, resulting in a large volume of dilute urine and frequent, excessive urination.
10. **Oliguria:** This refers to the formation of a less than normal quantity of urine.
11. **Proteinuria:** This is the presence of protein in the urine.
12. **Jaundice:** The presence of a large amount of bile pigments in the urine is a symptom of jaundice. It often occurs due to hepatitis or blockage of the bile duct.
13. **Alkaptonuria:** This condition is characterized by the presence of alkaline or homogentisic acid in the urine. When urine containing alcapton comes into contact with air, it turns black, earning it the name "Black urine disease."
In simple words: Many diseases can affect the excretory system, like uremia (too much urea in blood), gout (uric acid in joints), kidney stones, nephritis (inflamed kidney filters), glycosuria (sugar in urine), and diabetes insipidus (excessive urination). Each disease involves problems with waste removal or fluid balance.

🎯 Exam Tip: For each disease, briefly state its cause (if known), its main symptom, and how it relates to excretory system function. Grouping similar diseases can help with recall.