Class 10 Biology – Chapter 4: Urinary System

Board: Federal Board (FBISE)

Section I: Multiple Choice Questions

Q1. Nephron, the functional unit of kidney, is composed of all of the following except:

A) Bowman’s capsule
B) Loop of Henle
C) Glomerulus
D) Ureter

Correct Answer: D) Ureter

Q2. Osmoregulation involves:

A) Active transport
B) Diffusion
C) Facilitated diffusion
D) Osmosis

Correct Answer: D) Osmosis

Q3. Urine passes from the bladder to the:

A) Medulla
B) Urethra
C) Kidney
D) Ureter

Correct Answer: B) Urethra

Q4. Where is urea produced?

A) Urinary bladder
B) Blood cells
C) Kidney
D) Liver

Correct Answer: D) Liver

Q5. Which substance is present at a lower concentration in the renal artery than in the renal vein?

A) Amino acid
B) Carbon dioxide
C) Glucose
D) Urea

Correct Answer: D) Urea

Q6. In a kidney machine, what must be at the same concentration in the dialysis fluid and in the blood?

A) Glucose and salts
B) Protein
C) Urea
D) Water

Correct Answer: A) Glucose and salts

Q7. The four structures listed are part of the human excretory system (1. bladder, 2. kidney, 3. ureter, 4. urethra). In which order does a molecule of urea pass through these structures?

A) 1 → 2 → 3 → 4
B) 1 → 4 → 3 → 2
C) 2 → 1 → 3 → 4
D) 2 → 3 → 1 → 4

Correct Answer: D) 2 → 3 → 1 → 4

Q8. In a kidney machine, which of the following passes from the blood to the dialysis fluid?

A) Glucose
B) Plasma protein
C) Red blood cells
D) Urea

Correct Answer: D) Urea

Q9. Which blood vessel carries blood with the lowest concentration of urea?

A) Hepatic portal vein
B) Pulmonary vein
C) Renal vein
D) Vena cava

Correct Answer: C) Renal vein

Q10. Lithotripsy is a procedure that breaks large kidney stones into smaller ones by using:

A) X-rays
B) Microwaves
C) Sound waves
D) Ultraviolet rays

Correct Answer: C) Sound waves

Q11. Which row shows substances that are present in each of the structures of the excretory system of a healthy human?

The original text contains a duplicated and incomplete option. The complete options and table are missing, so the correct answer cannot be established from the supplied material.

Q12. The filtration of waste takes place inside the kidneys in:

A) Ureter
B) Urethra
C) Urinary bladder
D) Nephron

Correct Answer: D) Nephron

Q13. The function of glomerulus and Bowman’s capsule of the nephron is to:

A) Reabsorb water into the blood
B) Eliminate ammonia from the body
C) Reabsorb salts and amino acids
D) Filter the blood and capture the filtrate

Correct Answer: D) Filter the blood and capture the filtrate

Q14. Evidence for glomerular filtration in the kidney could be obtained by comparing the sizes of the molecules present in Bowman’s capsule with those in the:

A) Afferent blood vessel
B) Collecting duct
C) Loop of Henle
D) Proximal tubule

Correct Answer: A) Afferent blood vessel

Section II: Short Answer Questions

Q1. What is the role of the urinary system in the body?

Answer:

The primary role of the urinary system is osmoregulation and excretion. It regulates the volume and composition of body fluids (blood and tissue fluid) by removing metabolic nitrogenous wastes, such as urea, uric acid, and creatinine, and balancing water, salt, and pH levels. In this way, it maintains internal body stability (homeostasis).

Q2. Name the structures of the urinary system.

Answer:

The human urinary system consists of the following major structures:

1. A pair of kidneys (produce urine).

2. A pair of ureters (carry urine from the kidneys to the bladder).

3. Urinary bladder (temporarily stores urine).

4. Urethra (allows urine to pass out of the body).

Q3. Write the functions of kidney, ureter, urinary bladder, urethra, pelvis of kidney, capsule of kidney, and dialysis.

Answer:

• Kidney: Filters blood to remove nitrogenous wastes, excess water, and salts to form urine. It also performs osmoregulation.

• Ureter: Transports urine from the renal pelvis of each kidney to the urinary bladder through rhythmic muscular contractions called peristalsis.

• Urinary bladder: A muscular sac that temporarily stores urine until it is released from the body.

• Urethra: Carries urine from the urinary bladder to the outside of the body during micturition (urination).

• Pelvis of kidney: Acts as a funnel-shaped collecting space that gathers urine from the major calyces and channels it into the ureter.

• Capsule of kidney (renal capsule): A tough, fibrous outer covering that protects the delicate functional tissues of the kidney.

• Dialysis: An artificial medical procedure (haemodialysis or peritoneal dialysis) used to filter and purify blood when the kidneys cannot function properly.

Q4. What materials are returned to the blood?

Answer:

During tubular reabsorption in the nephron, useful components filtered out during glomerular filtration are reabsorbed into the blood through the peritubular capillaries. These include:

• Water (approximately 99% of the filtered water).

• Essential salts and ions, such as sodium, potassium, chloride, and bicarbonate.

• Glucose.

• Amino acids.

Q5. What materials leave the body in urine?

Answer:

Materials excreted from the body through urine include:

• Excess water.

• Nitrogenous metabolic wastes, primarily urea, along with uric acid and creatinine.

• Excess mineral salts and ions, such as sodium, potassium, and phosphates.

• Toxins, drugs, and metabolic by-products.

Q6. Name the disorders of the kidney.

Answer:

• Kidney Stones (Renal Calculi): Hard mineral and salt deposits formed inside the kidneys.

• Kidney Failure (Renal Failure): A condition in which the kidneys progressively or suddenly lose their ability to filter blood properly.

Q7. Write the causes of formation of kidney stones.

Answer:

Kidney stones form due to a combination of genetic and environmental factors that promote the precipitation and crystallization of salts in urine. Major causes include:

• High concentrations of calcium, oxalate, and uric acid in urine.

• Dehydration or inadequate fluid intake.

• Urinary tract infections (UTIs) and metabolic abnormalities.

• A diet high in animal protein, sodium, or oxalate-rich foods.

Q8. Name the structures in the urinary system of humans that are associated with each of the following:

a. Urea formation: Liver. Urea is produced here through the urea cycle and transported by blood to the kidneys.

b. Urine formation: Nephrons (inside the kidneys).

c. Filtration: Glomerulus (within the renal corpuscle of the nephron).

d. Reabsorption: Renal tubules, including the proximal convoluted tubule, loop of Henle, and distal convoluted tubule.

e. Tubular secretion: Renal tubules, particularly the proximal and distal convoluted tubules.

f. Temporary storage of urine: Urinary bladder.

g. Conduction of urine out of the body: Urethra.

Q9. The given diagram shows the structure of a human nephron. Trace the pathway of blood with the help of arrows (→) in the given diagram. (Note: Do NOT show the pathway of the filtrate.)

Answer:

The pathway of blood flow through the nephron’s vascular network is:

Renal Artery → Afferent Arteriole → Glomerulus → Efferent Arteriole → Peritubular Capillaries / Vasa Recta → Renal Vein

Q10. Describe kidney transplant.

Answer:

• Definition: Kidney transplant is a surgical procedure in which a healthy kidney from a living or deceased donor is implanted into a patient with end-stage renal failure (chronic kidney failure).

• Procedure: The failed kidneys are generally left in place unless they cause complications such as infection, high blood pressure, or pain. The donor kidney is placed in the lower abdomen, and its blood vessels (renal artery and vein) are connected to the recipient’s iliac blood vessels. The donor ureter is connected directly to the urinary bladder.

• Complications and Success: The recipient’s immune system may recognize the new kidney as foreign and attempt to reject it. Therefore, immunosuppressive drugs must be taken for the rest of the patient’s life to prevent organ rejection.

Q11. What are kidney failure and dialysis?

Answer:

Kidney Failure:

Kidney failure is a medical condition in which both kidneys lose their ability to filter metabolic wastes, regulate fluid balance, and maintain electrolyte balance effectively. It can be acute (sudden) or chronic (long-term).

Dialysis:

Dialysis is an artificial method of filtering blood to remove toxins, excess fluids, and waste products when the kidneys fail. There are two primary types:

1. Haemodialysis: Blood is pumped out of the body through an artificial machine containing a dialyzer (artificial kidney) with a semi-permeable membrane. Waste products diffuse out of the blood, and purified blood is returned to the body.

2. Peritoneal Dialysis: Dialysis fluid is introduced into the patient’s abdominal cavity (peritoneal cavity), where the peritoneum acts as a natural semi-permeable membrane. Waste products pass from the blood into the dialysis fluid, which is then drained out.

Section III: Extensive Answer Questions

Q1. Describe the human urinary system.

Introduction

The human urinary system (excretory system) is responsible for filtering metabolic waste products from the blood and maintaining osmotic balance (water and electrolyte balance) in the body.

Organs of the Human Urinary System

The human urinary system consists of four main components:

1. A pair of kidneys.

2. A pair of ureters.

3. Urinary bladder.

4. Urethra.

Detailed Description of Components

1. Kidneys

• Location and Structure: Kidneys are dark red, bean-shaped organs located against the back wall of the abdominal cavity, on either side of the vertebral column. They are protected by the lower rib cage.

• Dimensions: Each kidney is about 10 cm long, 5 cm wide, and 4 cm thick.

• Hilum: The concave inner side of each kidney contains a depression called the hilum. The ureter, renal artery, renal vein, nerves, and lymphatic vessels enter or leave the kidney through it.

• Function: Kidneys filter blood, remove nitrogenous wastes such as urea and uric acid, regulate blood pressure, and perform osmoregulation.

2. Ureters

• Structure: Ureters are muscular tubes that arise from the renal pelvis of each kidney and extend downward to open into the urinary bladder.

• Function: They transport urine from the kidneys to the urinary bladder through rhythmic peristaltic contractions of their muscular walls.

3. Urinary Bladder

• Structure: The urinary bladder is a smooth, collapsible, hollow muscular sac located in the pelvic cavity.

• Function: It temporarily stores urine. Its elastic muscular wall (detrusor muscle) expands as it fills. A sphincter muscle at the bladder outlet helps control the release of urine.

4. Urethra

• Structure: The urethra is a tube leading from the urinary bladder to the exterior of the body.

• Function: It carries urine out of the body during urination (micturition). In males, it also carries seminal fluid.

Q2. Relate the structure of the kidney with its function.

Introduction

The functional structure of the kidney is divided into three distinct anatomical regions: the renal cortex, renal medulla, and renal pelvis. Each region contains specialized structures that perform filtration, reabsorption, secretion, and urine collection.

Detailed Structural-Functional Relationship

Q3. Describe the structure of the nephron.

Introduction

The nephron is the structural and functional unit of the kidney. Each human kidney contains approximately one million nephrons.

A nephron consists of two main parts:

1. Renal Corpuscle (Malpighian Body).

2. Renal Tubule.

Detailed Components of Nephron

1. Renal Corpuscle

The renal corpuscle is located in the renal cortex and performs ultrafiltration.

• Glomerulus: A dense network of high-pressure capillaries branching from the afferent arteriole and merging into the efferent arteriole.

• Bowman’s Capsule: A double-walled, cup-shaped sac surrounding the glomerulus. Its inner layer contains specialized epithelial cells called podocytes, which have filtration slits.

2. Renal Tubule

The renal tubule is a long, coiled tube extending from Bowman’s capsule. It consists of the following parts:

• Proximal Convoluted Tubule (PCT): Located in the cortex and lined with microvilli (brush border) to maximize surface area for selective reabsorption.

• Loop of Henle: A U-shaped hairpin loop extending down into the medulla.

• Descending Limb: Has a thin wall and is highly permeable to water but relatively impermeable to solutes.

• Ascending Limb: Reabsorbs sodium and chloride ions and is impermeable to water.

• Distal Convoluted Tubule (DCT): Located in the renal cortex. It performs selective secretion and hormonally controlled salt and water reabsorption.

• Collecting Duct: Receives fluid from the distal tubules of several nephrons, passes through the renal medulla, and ultimately drains into the renal pelvis.

Q4. Explain the process of urine formation in humans.

Introduction

Urine formation takes place in the nephron through three main processes:

1. Pressure Filtration (Ultrafiltration).

2. Selective Reabsorption.

3. Tubular Secretion.

Detailed Steps

1. Glomerular Filtration (Ultrafiltration)

• Site: Glomerulus and Bowman’s capsule.

• Mechanism: Blood enters the glomerulus under high hydrostatic pressure through the wider afferent arteriole and exits through the narrower efferent arteriole.

• Outcome: Water, glucose, amino acids, urea, uric acid, and mineral salts pass across the filtration barrier into Bowman’s capsule, forming glomerular filtrate. Blood cells and large plasma proteins remain in the blood capillaries.

2. Selective Reabsorption

• Site: Proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.

• Mechanism: About 99% of the glomerular filtrate volume is reabsorbed into the peritubular capillaries.

The process occurs as follows:

• PCT: Nearly all glucose and amino acids are normally reabsorbed. A large proportion of water and sodium ions is also reabsorbed through active transport and osmosis.

• Loop of Henle: Creates a hypertonic medullary interstitium. The descending limb reabsorbs water, while the ascending limb reabsorbs sodium and chloride ions.

• DCT and Collecting Duct: Water reabsorption is regulated by Anti-Diuretic Hormone (ADH), while sodium reabsorption is regulated by aldosterone.

3. Tubular Secretion

• Site: Proximal and distal convoluted tubules.

• Mechanism: Epithelial cells of the tubules transport certain substances directly from the peritubular capillaries into the tubular fluid.

Substances secreted include:

• Hydrogen ions (H⁺).

• Potassium ions (K⁺).

• Ammonium ions (NH₄⁺).

• Creatinine.

• Drug metabolites.

Function: Tubular secretion helps maintain normal blood pH (approximately 7.35–7.45) and electrolyte balance.

Q5. Describe the osmoregulatory function of the kidney.

Introduction

Osmoregulation is the maintenance of an optimal balance of water and solute (salt) concentrations in body fluids. The kidneys regulate urine concentration according to the hydration status of the body.

Mechanisms of Osmoregulation

1. When Water is in Excess (Overhydration)

• Blood plasma osmotic pressure decreases, and the blood becomes relatively dilute.

• Osmoreceptors in the hypothalamus detect the change and signal the posterior pituitary gland to reduce ADH release.

• The walls of the distal tubules and collecting ducts become less permeable to water.

• Less water is reabsorbed back into the blood.

• Result: A large volume of dilute urine is produced.

2. When Water is Scarce (Dehydration or Sweating)

• Blood plasma osmotic pressure increases, and the blood becomes more concentrated.

• The hypothalamus stimulates the posterior pituitary gland to release ADH (vasopressin) into the blood.

• ADH increases the permeability of the collecting ducts to water by promoting the insertion of aquaporin channels.

• More water is reabsorbed back into the blood.

• Result: A small volume of concentrated urine is produced.

Q6. Discuss kidney stones and their treatment.

1. Definition

Kidney stones (renal calculi) are hard, insoluble crystalline deposits of minerals and salts that form inside the renal pelvis or calyces when dissolved substances crystallize out of urine.

2. Causes and Risk Factors

• Hypercalcemia and Hyperoxaluria: High levels of calcium or oxalate in blood or urine.

• Dehydration: Inadequate fluid consumption leads to concentrated urine.

• Dietary Factors: Excessive consumption of animal protein, sodium, or oxalate-rich foods.

• Infections: Recurrent urinary tract infections (UTIs).

3. Symptoms

• Severe, sharp back or flank pain below the ribs (renal colic), which may radiate to the lower abdomen and groin.

• Painful or burning urination (dysuria).

• Blood in urine (hematuria).

• Nausea and vomiting.

• Fever and chills, particularly when an infection is present.

4. Treatments

A. Non-Surgical Treatments

• High Fluid Intake: Adequate water intake helps flush out small stones. The required amount depends on the patient’s condition and medical advice.

• Medications: Painkillers (analgesics) and alpha-blockers may be used to relieve pain and help certain stones pass through the ureter.

B. Lithotripsy (Extracorporeal Shock Wave Lithotripsy – ESWL)

• High-energy sound or shock waves are focused from outside the body onto the kidney stone.

• The shock waves break the stone into smaller particles.

• The fragments can then pass out naturally through urine.

C. Surgical Treatments

• Percutaneous Nephrolithotomy (PCNL): A small incision is made in the back to insert a scope and break or remove large stones.

• Ureteroscopy: A thin scope is passed through the urethra and bladder into the ureter to remove stones.

• Open Surgery: Rarely performed for very large or complex stones.

Q7. Describe the following two types of dialysis:

a. Haemodialysis

b. Peritoneal Dialysis

Introduction

Dialysis is an artificial technique used to remove waste products and excess fluids from the blood when the kidneys can no longer perform their functions properly.

a. Haemodialysis

– Mechanism: Blood is pumped outside the body through an artificial machine containing a dialyzer (artificial kidney).

Procedure:

1. Blood is taken from the patient’s blood vessels through a suitable vascular access, such as an arteriovenous fistula or graft.

2. Blood flows through long, thin, semi-permeable tubes inside the dialyzer.

3. Dialysis fluid (dialysate) contains suitable concentrations of glucose and essential salts but normally does not contain urea.

4. Waste products, such as urea and creatinine, move out of the blood into the dialysis fluid by diffusion.

5. The cleaned blood is returned to the patient’s body.

– Frequency: It is commonly performed at a dialysis centre three times a week, with each session taking approximately 3–5 hours. The schedule may vary according to the patient’s needs.

b. Peritoneal Dialysis

– Mechanism: This method uses the patient’s own peritoneum (abdominal lining) as a natural semi-permeable membrane.

Procedure:

1. A soft plastic tube (catheter) is placed into the lower abdominal cavity (peritoneal cavity).

2. Dialysis fluid is introduced through the catheter into the peritoneal cavity.

3. Waste products and excess fluid pass from the blood vessels lining the peritoneum into the dialysis fluid.

4. After a period of time, the fluid is drained out and replaced with fresh dialysis fluid.

– Frequency: It can be performed at home daily, either manually several times a day or automatically overnight using a special machine.

Q8. Outline the causes of kidney failure and its treatment.

1. Causes of Kidney Failure

Kidney failure occurs due to the progressive decline or sudden loss of kidney function. Major causes include:

• Diabetes Mellitus: Diabetic nephropathy damages the glomeruli due to chronically high blood sugar levels.

• Hypertension (High Blood Pressure): Uncontrolled high blood pressure damages small blood vessels in the kidneys.

• Glomerulonephritis: Inflammation of the glomeruli caused by autoimmune reactions or infections.

• Long-Term Drug Toxicity: Prolonged or inappropriate use of certain medicines, including some non-steroidal anti-inflammatory drugs (NSAIDs) and antibiotics, can damage the kidneys.

• Polycystic Kidney Disease (PKD): A genetic disorder that causes fluid-filled cysts to develop in the kidneys and damage kidney tissue.

• Urinary Tract Obstructions: Prolonged blockage caused by large kidney stones or an enlarged prostate can damage the kidneys.

2. Treatments for Kidney Failure

Option A: Dialysis (Artificial Support)

• Haemodialysis: Removes waste products from the blood through an artificial filtration machine, commonly three times per week.

• Peritoneal Dialysis: Removes waste products using fluid exchange in the peritoneal cavity, often performed daily.

• Note: Dialysis replaces some of the functions of the kidneys but does not cure the underlying kidney disease.

Option B: Kidney Transplantation

• Definition: A surgical procedure in which a failed kidney is replaced with a healthy, functioning kidney from a living or deceased donor.

• Matching: Donor and recipient blood groups and tissue (HLA) compatibility are assessed to reduce the risk of rejection.

• Procedure: The donor kidney is placed in the lower abdomen. Its renal artery and vein are connected to the recipient’s iliac blood vessels, and the donor ureter is connected to the urinary bladder.

• Post-Operative Care: The recipient must take immunosuppressive drugs, usually for life, to prevent the immune system from rejecting the transplanted kidney.

Notes by Sir Dilawar
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