complete solved exercise for Chapter 14

Chapter 14 – Human Urinary System

Solved Exercise

SECTION 1: MULTIPLE CHOICE QUESTIONS

1. Which one of these is not a part of a single nephron? (a) Distal convoluted tubule (b) Collecting duct (c) Bowman’s capsule (d) Loop of Henle

Answer: (b) Collecting duct Explanation: Collecting duct is shared by many nephrons.

2. In a healthy person, glucose is present in blood but not in urine because glucose molecules are: (a) Reabsorbed from the proximal convoluted tubule to blood (b) Oxidised in kidneys (c) Stored in kidneys (d) Too large to enter Bowman’s capsule

Answer: (a)

3. The sizes of molecules present in Bowman’s capsule are smaller than the sizes of molecules present in: (a) Afferent renal arteriole (b) Collecting duct (c) Loop of Henle (d) Proximal tubule

Answer: (a)

4. If a drug reduces mitochondrial activity in nephrons, which chemical will be present in increased amounts in the urine? (a) Ammonia (b) Glucose (c) Uric acid (d) Urea

Answer: (b) Glucose Explanation: Active transport of glucose needs energy. Less energy → less reabsorption of glucose.

5. The water content of blood is regulated by ADH. In which part of the nephron does this regulation occur? (a) Bowman’s capsule (b) Proximal convoluted tubule (c) Loop of Henle (d) Collecting duct

Answer: (d) Collecting duct

6. Where is glucose reabsorbed into blood? (a) Bowman’s capsule (b) Glomerulus (c) Proximal convoluted tubule (d) Collecting duct

Answer: (c)

7. In normal conditions, which one is completely reabsorbed? (a) Urea (b) Water (c) Salts (d) Glucose

Answer: (d) Glucose

8. If the loops of Henle are absent in all nephrons, what would happen? (a) No urine formation (b) Formation of urine with normal concentration (c) Formation of concentrated urine (d) Formation of dilute urine

Answer: (d) Formation of dilute urine

9. In peritoneal dialysis, the lining of which part acts as a filter? (a) Stomach (b) Intestine (c) Lungs (d) Abdomen

Answer: (d) Abdomen

10. Patients are prescribed immunosuppressant drugs during: (a) Lithotripsy (b) Haemodialysis (c) Kidney transplant (d) Peritoneal dialysis

Answer: (c) Kidney transplant

SECTION 2: SHORT QUESTIONS

1. Justify the functioning of kidneys as both excretion and osmoregulation.

Kidneys remove nitrogenous wastes (urea), excess salts and toxins → Excretion. At the same time, they control the amount of water and salts reabsorbed according to body needs → Osmoregulation. When body is dehydrated → concentrated urine is produced. When excess water is present → dilute urine is produced.

2. List the organs of the urinary system.

Two kidneys, two ureters, one urinary bladder and one urethra.

3. Define glomerular filtration.

It is the first step of urine formation in which high pressure in the glomerulus forces water, urea, glucose, amino acids and salts into the Bowman’s capsule. This fluid is called glomerular filtrate.

4. Compare glomerular capillaries and peritubular capillaries.

Feature	Glomerular Capillaries	Peritubular Capillaries
Location	Inside Bowman’s capsule	Around renal tubules
Pressure	High	Low
Function	Filtration	Reabsorption & Secretion

5. What are the three main processes of urine formation?

Glomerular filtration
Selective reabsorption
Tubular secretion

6. What are the causes of kidney failure?

Chronic: Diabetes, high blood pressure, chronic infections. Acute: Infection, blockage by stones, certain medicines, blood clots.

7. Why do blood and dialysate flow in opposite directions?

To maintain a continuous concentration gradient so that maximum wastes can diffuse from blood into the dialysate.

8. Differentiate between the following:

Afferent vs Efferent Arteriole

Feature	Afferent Arteriole	Efferent Arteriole
Function	Brings blood into glomerulus	Takes blood out of glomerulus
Diameter	Wider	Narrower

Chronic vs Acute Renal Failure

Feature	Chronic	Acute
Onset	Slow	Sudden
Reversibility	Usually irreversible	Often reversible

Haemodialysis vs Peritoneal Dialysis

Feature	Haemodialysis	Peritoneal Dialysis
Filter	Artificial dialyzer	Peritoneal membrane
Location	Outside the body	Inside the abdomen

SECTION 3: LONG QUESTIONS

1. Describe the structure of kidney and relate it with its function.

Kidney is a bean-shaped organ covered by a fibrous capsule. Internally it has:

Cortex (outer) → filtration and most reabsorption
Medulla (inner) → contains pyramids and helps in concentrating urine
Pelvis → collects urine and passes it to ureter

The structure is perfectly designed for filtration, reabsorption and concentration of urine.

2. Explain the detailed structure of nephron.

Nephron is the functional unit of kidney. It consists of:

Renal Corpuscle

Glomerulus
Bowman’s capsule

Renal Tubule

Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct

There are two types: Cortical nephrons (short loops) and Juxtamedullary nephrons (long loops).

3. Explain the main processes in kidney functioning.

Glomerular Filtration – High pressure forces small molecules into Bowman’s capsule.
Selective Reabsorption – Useful substances (glucose, amino acids, water, salts) are taken back into blood.
Tubular Secretion – Unwanted substances (H⁺, K⁺, toxins) are added into the filtrate.

4. Explain that concentration of urine is regulated by counter-current and hormonal mechanisms.

Counter-current Mechanism: Descending limb is permeable to water, ascending limb pumps out salts. This creates a hypertonic medulla. Water is then reabsorbed from collecting duct.

Hormonal Control:

ADH → increases water reabsorption from collecting duct
Aldosterone → increases sodium (and water) reabsorption

5. Explain the causes and treatments of kidney stones.

Causes: High calcium/oxalate, high uric acid, dehydration.

Treatment:

ESWL (shock waves from outside)
PNL (for larger stones)

6. Explain in detail the mechanism and problems related to dialysis.

Haemodialysis: Blood is cleaned outside the body by a dialyzer. Peritoneal Dialysis: Dialysate is put into abdomen; peritoneal membrane acts as filter.

Problems: Infection, low blood pressure, muscle cramps, anaemia, emotional stress.

7. Describe the principles and the problems associated with kidney transplant.

A healthy kidney from a donor is surgically placed in the recipient.

Problems: