What is the primary function of the excretory system? — Electrical Engineering MCQ

B. Removal of metabolic waste products from the body to maintain homeostasis — The excretory system is responsible for eliminating metabolic waste products - substances produced during normal body metabolism that are toxic if allowed to accumulate. Key waste products excreted: Urea (from protein metabolism), Carbon dioxide (from cellular respiration), Water (from metabolic reactions), Salts/ions (excess minerals), Bile pigments (from haemoglobin breakdown). Organs of excretion: Kidneys (urea, salts, water), Lungs (CO2, water), Skin (salts, water - sweat), Liver (bile pigments). The excretory system also helps maintain homeostasis - stable internal environment.

What are the primary organs of the excretory system in humans? — Electrical Engineering MCQ

B. Kidneys — The kidneys are the primary organs of excretion in humans. They are a pair of bean-shaped organs located in the retroperitoneal space (behind the peritoneum) in the abdominal cavity, on either side of the vertebral column at the level of T12-L3 vertebrae. The right kidney is slightly lower than the left (due to the liver above it). Each kidney is approximately 10-12 cm long, 5-6 cm wide, and weighs about 150 g. Together, the kidneys filter approximately 180 litres of blood per day, producing about 1.5 litres of urine.

What is the functional unit of the kidney? — Electrical Engineering MCQ

B. Nephron — The Nephron is the structural and functional unit of the kidney. Each kidney contains approximately 1-1.3 million nephrons. Each nephron consists of: Renal corpuscle (Bowman's capsule + Glomerulus), Proximal Convoluted Tubule (PCT), Loop of Henle (descending and ascending limbs), Distal Convoluted Tubule (DCT), and Collecting Duct. Types of nephrons: Cortical nephrons (85% - short loop of Henle, located mainly in cortex) and Juxtamedullary nephrons (15% - long loop of Henle, important for urine concentration).

What is the Bowman's capsule? — Electrical Engineering MCQ

B. A cup-shaped structure surrounding the glomerulus where filtration begins — Bowman's Capsule (Glomerular capsule) is the cup-shaped, double-walled structure at the beginning of each nephron that completely surrounds the glomerulus. Together, the Bowman's capsule and glomerulus form the Renal Corpuscle - the filtration unit of the nephron. Blood is filtered from the glomerular capillaries into the Bowman's space (between the two layers of the capsule), forming the glomerular filtrate (primary urine). Named after Sir William Bowman (1842). The inner layer contains specialised cells called podocytes that form filtration slits.

A. A tubule in the kidney that reabsorbs water

C. A blood vessel in the kidney

D. The outer covering of the kidney

What is the glomerulus? — Electrical Engineering MCQ

B. A network of capillaries inside the Bowman's capsule where blood filtration occurs — The Glomerulus is a tiny ball-shaped network (tuft) of capillaries located inside the Bowman's capsule. It receives blood from the afferent arteriole and drains into the efferent arteriole. The glomerulus is the site of ultrafiltration - blood pressure forces small molecules (water, glucose, urea, salts, amino acids) out of the blood into the Bowman's capsule. Large molecules like proteins and blood cells are retained in the blood. The glomerular filtration rate (GFR) is approximately 125 mL/min or 180 L/day in healthy adults - the gold standard measure of kidney function.

A. The tube that carries urine to the bladder

C. The muscular wall of the urinary bladder

D. The collecting duct of the nephron

What is urine primarily composed of? — Electrical Engineering MCQ

B. Water, urea, salts, and other waste products — Normal urine composition: Water (~95%), Urea (main nitrogenous waste ~2% - product of protein catabolism), Creatinine (waste product of muscle metabolism), Uric acid (from nucleic acid metabolism), Salts (ions) - Sodium, potassium, chloride, phosphates, sulphates, and Ammonia (small amount). Normal urine is pale yellow (due to urochrome pigment from bilirubin breakdown), slightly acidic (pH 4.6-8.0, average 6.0), specific gravity 1.001-1.035. Abnormal findings: Glucose (glucosuria) = diabetes, Protein (proteinuria) = kidney disease, Blood (haematuria) = kidney stones/infection/cancer.

What is the process by which the kidneys filter blood called? — Electrical Engineering MCQ

C. Glomerular filtration — Glomerular Filtration is the first step in urine formation. It is a non-selective, passive process driven by blood pressure (hydrostatic pressure) in the glomerular capillaries. The filtration barrier consists of: Capillary endothelium (fenestrated - porous), Basement membrane (main filter - blocks proteins and cells), and Podocyte filtration slits (slit diaphragm - further filtration). Everything in blood except large proteins and blood cells passes into the filtrate. The filtrate is identical to plasma minus proteins. The GFR (Glomerular Filtration Rate) = ~125 mL/min. Normal GFR indicates healthy kidneys; reduced GFR indicates Chronic Kidney Disease (CKD).

What is tubular reabsorption? — Electrical Engineering MCQ

B. The process by which useful substances from the filtrate are returned to the blood — Tubular Reabsorption is the second step in urine formation - the process by which useful substances from the glomerular filtrate are selectively transported back into the peritubular capillaries (blood). Substances reabsorbed: All glucose (in PCT - by active transport with Na+), All amino acids (in PCT), Most water (~99% - in PCT, loop of Henle, DCT, collecting duct), Most Na+, K+, Cl- (various tubule segments), and Bicarbonate (HCO3-) in PCT. Of 180 L/day filtered, only 1-1.5 L/day becomes urine - meaning ~99% is reabsorbed.

A. The process of filtering blood in the glomerulus

C. The addition of waste products into the tubule from blood

D. The formation of urine in the collecting duct

What is tubular secretion? — Electrical Engineering MCQ

B. The process by which additional waste substances are actively transported from blood into the renal tubule — Tubular Secretion is the third step in urine formation - substances are actively transported from peritubular capillaries INTO the tubular fluid. This allows the kidney to eliminate substances not filtered by the glomerulus or to increase elimination of certain wastes. Substances secreted: H+ ions (acid secretion - regulates blood pH), K+ ions (regulated by aldosterone), Creatinine, Drugs and toxins (penicillin, aspirin, morphine), and Ammonia (NH3). Tubular secretion is important for acid-base balance and drug elimination. Together, filtration + reabsorption + secretion = final urine composition.

A. The process of urine leaving the bladder

C. The production of hormones by the kidney

D. The filtration of blood in the glomerulus

What is the normal volume of urine produced by an adult per day? — Electrical Engineering MCQ

C. 1-1.5 litres — A healthy adult produces approximately 1-1.5 litres (1000-1500 mL) of urine per day under normal conditions. Urine output terminology: Normal = 1-1.5 L/day (or 0.5-1 mL/kg/hour), Polyuria = excess urine production (>2.5 L/day) - diabetes mellitus, diabetes insipidus, excessive fluid intake, Oliguria = reduced urine output (<400 mL/day or <0.5 mL/kg/hour) - dehydration, kidney failure, Anuria = no urine output (<100 mL/day) - severe kidney failure, urinary obstruction, and Nocturia = excessive urination at night - heart failure, diabetes, prostate enlargement.

What is the role of the Loop of Henle? — Electrical Engineering MCQ

B. Creates a concentration gradient in the kidney medulla to concentrate urine and conserve water — The Loop of Henle is a U-shaped tubule that dips into the renal medulla. It is responsible for creating a hyperosmotic concentration gradient in the medullary interstitium through the countercurrent multiplier mechanism: Descending limb (permeable to water not solutes - water leaves by osmosis - filtrate becomes concentrated) and Ascending limb (permeable to solutes not water - NaCl actively pumped out - filtrate becomes dilute). This gradient allows the collecting duct to concentrate urine under the influence of ADH (Antidiuretic Hormone). Juxtamedullary nephrons with long loops are most efficient at concentrating urine.

A. Filters blood from the glomerulus

C. Secretes hormones to regulate kidney function

D. Carries urine from the kidney to the bladder

What is the glomerular filtration rate (GFR)? — Electrical Engineering MCQ

B. The volume of plasma filtered by the glomeruli per minute - approximately 125 mL/min in healthy adults — Glomerular Filtration Rate (GFR) is the volume of plasma filtered by all the glomeruli per minute. It is the best measure of kidney function. Normal GFR: ~125 mL/min (180 L/day). GFR is estimated clinically using serum creatinine (eGFR formula) or creatinine clearance. GFR staging (CKD): G1 = >=90 mL/min (normal), G2 = 60-89 (mildly reduced), G3 = 30-59 (moderately reduced), G4 = 15-29 (severely reduced), G5 = <15 (kidney failure - dialysis/transplant needed). GFR decreases with age (~1 mL/min/year after age 30).

A. The rate at which urine is produced per hour

C. The rate of tubular reabsorption

D. The blood pressure in the renal artery

What is urea and how is it formed? — Electrical Engineering MCQ

B. The main nitrogenous waste product formed in the liver from the breakdown of amino acids (urea cycle) — Urea (CO(NH2)2) is the primary nitrogenous waste product in humans, formed in the liver through the Urea Cycle (Ornithine Cycle): Amino acids are deaminated (amino group -NH2 removed), the -NH2 group becomes ammonia (NH3) - highly toxic, ammonia is converted to urea in the liver - much less toxic, water-soluble, urea is transported in blood to the kidneys and excreted in urine. Normal blood urea: 7-25 mg/dL. Elevated blood urea = Uraemia (kidney failure). The urea cycle involves: Ornithine > Citrulline > Argininosuccinate > Arginine > Ornithine + Urea.

A. A salt formed from sodium and chloride

C. A hormone produced by the kidneys

D. A product of carbohydrate metabolism

What are the parts of the urinary system? — Electrical Engineering MCQ

B. Kidneys, ureters, urinary bladder, and urethra — The Urinary System consists of: Kidneys (x2 - filter blood and produce urine), Ureters (x2 - muscular tubes ~25-30 cm long that carry urine from each kidney to the bladder by peristalsis), Urinary Bladder (x1 - muscular sac that stores urine, capacity ~400-600 mL, lined with transitional epithelium/urothelium), and Urethra (x1 - tube that carries urine from the bladder to outside the body, length ~4 cm in females, ~20 cm in males - passes through prostate gland and penis). This is why UTIs (urinary tract infections) are more common in females - shorter urethra.

C. Kidneys, liver, pancreas, colon

D. Nephrons, glomerulus, alveoli, skin

What is the hormone ADH (Antidiuretic Hormone) and what does it do? — Electrical Engineering MCQ

B. A hormone produced by the posterior pituitary that increases water reabsorption in the collecting duct, producing concentrated urine — ADH (Antidiuretic Hormone / Vasopressin) is produced by the hypothalamus and released from the posterior pituitary gland. It acts on the collecting ducts and distal tubules of the nephron: ADH increases = collecting duct becomes more permeable to water = more water reabsorbed = concentrated urine (small volume). ADH decreases = less water reabsorbed = dilute urine (large volume). ADH is released when: blood osmolarity increases (dehydration), blood volume drops, stress. Diabetes Insipidus: ADH deficiency = massive production of dilute urine (polyuria up to 20 L/day), excessive thirst (polydipsia).

A. A hormone produced by the kidneys that increases blood pressure

C. A hormone that stimulates urine production

D. A hormone that regulates sodium excretion only

What is aldosterone and what is its role in kidney function? — Electrical Engineering MCQ

B. A steroid hormone from the adrenal cortex that increases sodium reabsorption and potassium secretion in the distal tubule and collecting duct — Aldosterone is a mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex. It acts on the DCT and collecting duct: Increases Na+ reabsorption (water follows - increases blood volume and pressure), Increases K+ secretion (into urine), and Increases H+ secretion (alkalinising effect). Stimulated by: Angiotensin II (RAAS system), high blood K+, low blood Na+. Conn's syndrome (primary hyperaldosteronism) = excess aldosterone - hypertension, hypokalaemia. Addison's disease = aldosterone deficiency - low BP, hyperkalaemia.

A. A hormone from the anterior pituitary that controls water reabsorption

C. A hormone that reduces blood pressure

D. An enzyme that converts angiotensin I to angiotensin II

What is the RAAS (Renin-Angiotensin-Aldosterone System)? — Electrical Engineering MCQ

B. A hormonal cascade that regulates blood pressure and fluid balance through renin, angiotensin, and aldosterone — The RAAS is a critical hormonal system for blood pressure and fluid regulation: Low blood pressure/volume > Juxtaglomerular (JG) cells of kidney secrete Renin > Renin converts Angiotensinogen (liver) to Angiotensin I > ACE (Angiotensin Converting Enzyme) in lungs converts Angiotensin I to Angiotensin II > Angiotensin II causes: Vasoconstriction (increases BP), Stimulates Aldosterone release (Na+/water retention), Stimulates ADH release (water retention), and Stimulates thirst. ACE inhibitors (e.g., ramipril) and ARBs (e.g., losartan) block this system to treat hypertension.

C. A system that controls respiratory rate

D. A system that regulates blood glucose

What is the ureter? — Electrical Engineering MCQ

A. The tube connecting the kidney pelvis to the urinary bladder — The Ureter is a muscular tube (~25-30 cm long, 3-4 mm diameter) that connects each renal pelvis (of the kidney) to the urinary bladder. There are two ureters - one for each kidney. Structure: three layers - inner mucosa (transitional epithelium), middle muscularis (smooth muscle), outer adventitia (fibrous). Function: carries urine from the kidney to the bladder by peristaltic contractions (wave-like muscular movements). The ureter enters the bladder at the ureterovesical junction (UVJ) - a common site for kidney stones (renal calculi) to get stuck.

B. The tube connecting the bladder to outside the body

C. The tube inside the kidney that collects urine from nephrons

D. A blood vessel supplying the kidney

What is the urinary bladder? — Electrical Engineering MCQ

B. A hollow, muscular organ that stores urine until it is expelled — The Urinary Bladder is a hollow, distensible (stretchable) muscular organ located in the pelvis that stores urine. Key features: Capacity = 400-600 mL (urge to urinate at ~300 mL), Wall = Detrusor muscle (smooth muscle - three layers) contracts during urination, Lining = Transitional epithelium (urothelium) - can stretch without tearing, Trigone = triangular area at the base of the bladder formed by the two ureteral openings and internal urethral orifice (most sensitive area; common site of infection), and Micturition (urination) = voluntary control via external urethral sphincter (skeletal muscle); involuntary via internal urethral sphincter (smooth muscle).

A. A gland that produces hormones

C. The tube that carries urine outside the body

D. A filter membrane in the kidney

What is micturition? — Electrical Engineering MCQ

B. The process of urination - expulsion of urine from the bladder — Micturition (Urination/Voiding) is the process of expelling urine from the bladder through the urethra. The micturition reflex: Bladder fills (~300 mL) - stretch receptors in bladder wall activated - Signals sent to sacral spinal cord (S2-S4) - Parasympathetic stimulation - detrusor muscle contracts, internal sphincter relaxes - Somatic nerve - voluntary relaxation of external urethral sphincter - Urine expelled. Voluntary control is learned during childhood (toilet training). Loss of bladder control = Urinary incontinence. Inability to urinate = Urinary retention (common in prostate enlargement in men).

A. Filtration of blood in the glomerulus

C. Production of urine in the nephron

D. Reabsorption of water in the collecting duct

What is the difference between the urethra in males and females? — Electrical Engineering MCQ

B. Male urethra is longer (~20 cm, passes through prostate and penis); female urethra is shorter (~4 cm) — Urethra differences between sexes: Female urethra = ~3-4 cm long, carries urine only, opens between clitoris and vaginal opening. Short length = higher risk of UTIs (Urinary Tract Infections) - bacteria from anal region easily reach bladder. Male urethra = ~18-20 cm long, divided into Prostatic (passes through prostate), Membranous (shortest, passes through urogenital diaphragm), and Spongy/Penile (longest, passes through penis). Carries both urine and semen (but not simultaneously). The male's longer urethra is protective against ascending UTIs.

C. Female urethra is longer than male

D. Male urethra only carries urine; female urethra carries both urine and reproductive fluids

What is kidney stone (Renal Calculi)? — Electrical Engineering MCQ

B. Hard deposits of minerals and salts that form inside the kidney or urinary tract — Kidney Stones (Renal Calculi / Nephrolithiasis) are hard, crystalline deposits that form in the kidneys or urinary tract when urine becomes supersaturated with certain minerals. Types: Calcium oxalate (most common - ~80%), Calcium phosphate, Uric acid stones (in gout patients), Struvite stones (infection-related - Proteus bacteria), and Cystine stones (rare - genetic). Symptoms: severe colicky flank pain (renal colic), haematuria, nausea, vomiting. Diagnosis: CT scan (gold standard), ultrasound. Treatment: hydration, pain relief, lithotripsy (sound waves to break stones), surgery. Prevention: high fluid intake.

D. Protein deposits in the glomerulus

What is dialysis? — Electrical Engineering MCQ

B. A medical procedure that artificially performs the kidney's function of filtering waste from the blood when the kidneys have failed — Dialysis is a life-saving treatment for patients with End Stage Renal Disease (ESRD) or acute kidney failure. Two main types: Haemodialysis (HD) - blood is drawn out, filtered through an artificial kidney machine (dialyser - semipermeable membrane), and returned to the body. Typically 3-4 hours, 3 times/week. Requires arteriovenous (AV) fistula access. Peritoneal Dialysis (PD) - dialysis fluid (dialysate) is infused into the peritoneal cavity; the peritoneal membrane acts as the filter. Can be done at home. Dialysis removes waste products (urea, creatinine), excess fluid, and corrects electrolyte imbalances. It does NOT restore other kidney functions (hormone production, etc.).

A. A surgical removal of a kidney

C. A medication that increases urine output

What is the role of the skin as an excretory organ? — Electrical Engineering MCQ

B. The skin excretes water, salts (NaCl), small amounts of urea, and lactic acid through sweat glands — The skin acts as an accessory excretory organ through sweat glands (sudoriferous glands): Eccrine sweat glands (most numerous, found all over body) = produce watery sweat for thermoregulation. Apocrine sweat glands (axilla, groin) = produce thicker sweat (body odour when broken down by bacteria). Sweat composition: Water (~99%), NaCl, urea, lactic acid, ammonia, small amount of glucose. Primary role of sweating = thermoregulation (cooling the body). Secondary role = excretion (minor). In kidney failure, urea accumulation causes uraemic frost - white crystalline deposits of urea on skin.

A. Kidneys only excrete waste; skin has no excretory function

C. The skin only produces vitamin D

What is the role of the liver as an excretory organ? — Electrical Engineering MCQ

B. The liver produces bile, which excretes bile pigments (bilirubin and biliverdin) from haemoglobin breakdown — The Liver plays an important excretory role: Bile production (liver cells/hepatocytes produce bile containing bile pigments - bilirubin and biliverdin - breakdown products of haemoglobin from old red blood cells), Bile excretion (bile is stored in the gallbladder and released into the duodenum - bile pigments are eventually excreted in faeces - giving faeces its brown colour), Urea synthesis (converts toxic ammonia to urea for kidney excretion), and Detoxification (metabolises drugs, alcohol, and other toxins for excretion). Jaundice = yellowing of skin/eyes due to accumulation of bilirubin when liver function is impaired or bile duct is blocked.

A. The liver only produces digestive enzymes

C. The liver filters urea from blood

What is jaundice? — Electrical Engineering MCQ

B. Yellowing of skin and eyes caused by accumulation of bilirubin in the blood — Jaundice (Icterus) is a yellowish discolouration of the skin, mucous membranes, and whites of the eyes (scleral icterus) caused by hyperbilirubinaemia (elevated bilirubin in blood). Three types: Pre-hepatic (Haemolytic) = excess RBC breakdown - too much bilirubin produced (e.g., malaria, sickle cell anaemia, haemolytic anaemia). Hepatic (Hepatocellular) = Liver damage - cannot process bilirubin (e.g., hepatitis, cirrhosis). Post-hepatic (Obstructive) = Bile duct blockage - bilirubin cannot be excreted (e.g., gallstones, pancreatic cancer). Neonatal jaundice is common in newborns (immature liver) - treated with phototherapy (blue light).

A. A kidney disease causing protein in urine

What is the juxtaglomerular apparatus (JGA)? — Electrical Engineering MCQ

B. A specialised structure near the glomerulus that regulates GFR and releases renin — The Juxtaglomerular Apparatus (JGA) is a specialised structure located at the junction of the afferent arteriole and the distal convoluted tubule (DCT). It consists of: Juxtaglomerular (JG) cells (in afferent arteriole wall) - secrete renin when blood pressure falls, Macula densa cells (in DCT wall) - sense NaCl concentration in tubular fluid - if low, stimulate renin release, and Mesangial cells (supporting cells). The JGA is critical for the RAAS (Renin-Angiotensin-Aldosterone System) and autoregulation of GFR. It maintains kidney blood flow and filtration within a normal range despite changes in systemic blood pressure.

A. The site of urine collection in the kidney

C. The outer layer of the kidney

D. The blood vessel supplying the glomerulus

What is the renal cortex? — Electrical Engineering MCQ

B. The outer region of the kidney that contains the glomeruli and convoluted tubules — The kidney has two distinct regions: Renal Cortex (outer region) = contains glomeruli, Bowman's capsules, PCT, DCT, site of filtration and most reabsorption, reddish-brown in colour due to rich blood supply, contains cortical nephrons (85%). Renal Medulla (inner region) = contains loops of Henle and collecting ducts, organised into renal pyramids (8-18 triangular structures), tips of pyramids = renal papillae - drain urine into minor calyces, site of urine concentration. Renal Pelvis = funnel-shaped structure that collects urine from calyces and drains into the ureter.

A. The inner part of the kidney that contains the loop of Henle

C. The funnel-shaped structure that collects urine

D. The fibrous capsule surrounding the kidney

What is nephritis? — Electrical Engineering MCQ

B. Inflammation of the kidney (nephrons), particularly the glomeruli — Nephritis is inflammation of the kidneys, most commonly affecting the glomeruli (glomerulonephritis). Types: Acute Glomerulonephritis (often follows Group A Streptococcal throat or skin infection - post-streptococcal glomerulonephritis. Symptoms: haematuria - cola-coloured urine, proteinuria, oedema, hypertension, reduced urine output), Chronic Glomerulonephritis (progressive destruction of glomeruli - CKD), Nephrotic Syndrome (massive proteinuria >3.5g/day, hypoalbuminaemia, oedema, hyperlipidaemia), and Interstitial Nephritis (inflammation of renal tubules and interstitium - drug reactions, infections). Diagnosis: urine analysis, renal biopsy. Treatment: immunosuppressants, blood pressure control.

What is creatinine and why is it important clinically? — Electrical Engineering MCQ

B. A waste product of muscle metabolism used as a marker of kidney function - elevated levels indicate impaired kidney function — Creatinine is a waste product formed from the breakdown of creatine phosphate in muscle tissue. It is produced at a constant rate proportional to muscle mass and is freely filtered by the glomerulus and not reabsorbed - making it an excellent marker of GFR. Normal serum creatinine: Males = 0.7-1.2 mg/dL, Females = 0.5-1.0 mg/dL (lower due to less muscle mass). Elevated creatinine = impaired kidney function (CKD, acute kidney injury). Creatinine clearance is approximately equal to GFR - calculated using Cockcroft-Gault formula. eGFR (estimated GFR) is calculated from serum creatinine, age, sex, and race - used to stage CKD.

A. A hormone produced by the kidneys

C. A protein found in urine during kidney disease

D. An enzyme that converts urea in the blood

What is the colour of normal urine and what gives it that colour? — Electrical Engineering MCQ

B. Pale yellow - due to urochrome pigment (from bilirubin/urobilinogen breakdown) — Normal urine is pale to deep yellow in colour. The yellow colour is primarily due to Urochrome (Urobilin) - a pigment produced from the breakdown of urobilinogen (itself a product of bilirubin metabolism from haemoglobin breakdown). Urine colour variations: Colourless (dilute urine - high fluid intake, diabetes insipidus), Dark yellow/amber (concentrated urine - dehydration), Orange (dehydration, certain drugs - rifampicin, liver disease), Red/Pink (blood/haematuria, beetroot ingestion, rifampicin), Brown/Cola (glomerulonephritis, myoglobinuria - muscle breakdown), Green (Pseudomonas infection, certain medications), and Foamy (excess protein - proteinuria).

A. Colourless - no pigment present

C. Dark brown - due to high urea content

What is the role of erythropoietin (EPO) produced by the kidneys? — Electrical Engineering MCQ

B. Stimulates the bone marrow to produce red blood cells (RBCs) — Erythropoietin (EPO) is a glycoprotein hormone produced by peritubular cells of the renal cortex in response to low oxygen levels (hypoxia) in the blood. EPO stimulates the bone marrow to produce more red blood cells (erythropoiesis), increasing oxygen-carrying capacity. Clinical significance: In Chronic Kidney Disease (CKD) - reduced EPO production - anaemia of chronic disease - treated with recombinant EPO (epoetin). EPO doping - illicitly used by athletes (cyclists, runners) to boost RBC count and endurance. People at high altitude naturally produce more EPO - polycythaemia (more RBCs) - part of acclimatisation.

A. Regulates blood pressure only

C. Controls water reabsorption in the collecting duct

D. Regulates sodium levels in blood

What is the countercurrent mechanism in the kidney? — Electrical Engineering MCQ

B. A mechanism involving the loop of Henle and vasa recta that creates an osmotic gradient to concentrate urine — The Countercurrent Mechanism allows the kidney to produce urine more concentrated than plasma. Two components: 1) Countercurrent Multiplier (Loop of Henle) - The descending and ascending limbs run in opposite directions, establishing an increasing osmolarity gradient in the medullary interstitium (from ~300 mOsm in cortex to ~1200 mOsm in deep medulla). 2) Countercurrent Exchanger (Vasa Recta) - The capillaries surrounding the loop of Henle also flow in opposite directions, maintaining the medullary gradient without washing it away. Under ADH influence, the collecting duct becomes permeable to water - water moves out into concentrated medulla - concentrated urine is produced.

A. The process of blood filtration in the glomerulus

C. The movement of glucose from tubule back to blood

D. The secretion of H+ ions in the DCT

What is acute kidney injury (AKI)? — Electrical Engineering MCQ

B. A sudden (within hours to days) deterioration in kidney function causing accumulation of waste products — Acute Kidney Injury (AKI) (previously called Acute Renal Failure - ARF) is a sudden deterioration in kidney function occurring over hours to days, leading to accumulation of waste products and fluid/electrolyte imbalances. Causes classified as: Pre-renal (most common, ~55%) - reduced blood flow to kidneys (dehydration, shock, heart failure, haemorrhage). Renal (Intrinsic) - direct kidney damage (glomerulonephritis, ATN - acute tubular necrosis - most common intrinsic, nephrotoxic drugs). Post-renal - obstruction to urine outflow (kidney stones, enlarged prostate, tumours). AKI is potentially reversible with treatment. Diagnosis: rising serum creatinine, reduced urine output. Treatment: treat underlying cause, fluid management, dialysis if severe.

A. A genetic disorder of the kidneys

C. A chronic progressive loss of kidney function over years

What is chronic kidney disease (CKD)? — Electrical Engineering MCQ

B. A progressive, irreversible loss of kidney function over months to years, classified in 5 stages by GFR — Chronic Kidney Disease (CKD) is a progressive, irreversible deterioration of kidney function lasting >3 months. The most common causes are: Diabetes mellitus (diabetic nephropathy - leading cause worldwide), Hypertension (hypertensive nephrosclerosis - second most common), Glomerulonephritis, Polycystic kidney disease, recurrent UTIs. CKD stages by GFR (G1-G5). Stage 5 = End Stage Renal Disease (ESRD) - requires dialysis or kidney transplant. Complications: anaemia (reduced EPO), hypertension, bone disease, cardiovascular disease, hyperkalaemia. Early detection: urine albumin:creatinine ratio (ACR), eGFR.

A. A sudden loss of kidney function

What is osmoregulation? — Electrical Engineering MCQ

B. The process by which the body maintains a constant osmotic concentration of body fluids — Osmoregulation is the homeostatic regulation of the osmotic pressure (solute concentration) of body fluids. The kidneys are the primary osmoregulatory organs. Key mechanisms: When blood osmolarity rises (too concentrated - dehydration) = Osmoreceptors in hypothalamus detect change > ADH released > water reabsorbed > thirst stimulated > dilute blood. When blood osmolarity falls (too dilute - overhydration) = ADH suppressed > water excreted > concentrated blood. The hypothalamus acts as the osmoreceptor centre and controls ADH release. Normal plasma osmolarity = 280-295 mOsm/kg. This ensures cells neither shrink nor swell due to osmotic imbalances.

C. Regulation of body temperature

D. The process of breaking down proteins

What is the renal threshold for glucose? — Electrical Engineering MCQ

B. The plasma glucose concentration above which glucose begins to appear in urine (approximately 180 mg/dL) — The Renal Threshold for Glucose is the plasma glucose concentration above which the tubular maximum (Tm) for glucose reabsorption is exceeded and glucose spills into urine (glucosuria). Normally: All filtered glucose is reabsorbed in the PCT via SGLT2 (sodium-glucose cotransporter 2) active transport. Renal threshold = ~180 mg/dL (10 mmol/L). When blood glucose exceeds 180 mg/dL (as in uncontrolled diabetes mellitus): SGLT2 transporters are saturated, glucose appears in urine (glucosuria), glucose in tubule draws water with it (osmotic diuresis) causing polyuria and polydipsia. SGLT2 inhibitors (e.g., empagliflozin, dapagliflozin) lower blood glucose by blocking glucose reabsorption - used in diabetes treatment.

A. The amount of glucose filtered per day

C. The minimum blood glucose level needed for kidney function

D. The glucose level in the glomerular filtrate

What is proteinuria and what does it indicate? — Electrical Engineering MCQ

B. Abnormal presence of protein in urine - indicates kidney damage (glomerular injury) — Proteinuria is the abnormal presence of protein (mainly albumin) in urine, indicating that the glomerular filtration barrier is damaged. Normally, the glomerulus prevents large proteins from passing into the filtrate. Normal urine protein 3.5g/day), Diabetic nephropathy (microalbuminuria = earliest sign of diabetic kidney disease - 30-300 mg/day), Glomerulonephritis, and Hypertensive nephropathy. Proteinuria causes: Hypoalbuminaemia > reduced oncotic pressure > oedema (pitting oedema of legs, face, ascites - due to low oncotic pressure). Diagnosis: Dipstick urinalysis, 24-hour urine collection, ACR (albumin:creatinine ratio).

What is haematuria? — Electrical Engineering MCQ

B. Presence of blood (red blood cells) in urine — Haematuria is the presence of blood (red blood cells) in urine. Two types: Macroscopic (Gross) Haematuria (visible red/pink/brown urine - alarming to patient) and Microscopic Haematuria (red blood cells visible only under microscope - >3 RBCs/high power field). Important causes: Kidney stones (renal colic + haematuria - most common benign cause), UTI (infection - most common cause overall), Glomerulonephritis (cola-coloured urine), Kidney/bladder/prostate cancer (painless haematuria in elderly = cancer until proven otherwise), and Trauma. Haematuria always requires investigation: urine culture, ultrasound, CT scan, cystoscopy (bladder examination).

What is the role of the proximal convoluted tubule (PCT)? — Electrical Engineering MCQ

B. It reabsorbs ~65% of filtered water, all glucose, all amino acids, and most electrolytes from the filtrate — The Proximal Convoluted Tubule (PCT) is the most active site of reabsorption in the nephron: ~65% of filtered water reabsorbed (obligatory - follows solutes), 100% of glucose reabsorbed (via SGLT2 and SGLT1 co-transporters), 100% of amino acids reabsorbed, ~65-70% Na+, Cl-, K+, HCO3- reabsorbed, Uric acid (mostly reabsorbed, some secreted), and Drugs and toxins secreted (penicillin, aspirin). The PCT has brush border (microvilli) on its luminal surface - increases surface area for reabsorption. The PCT is highly metabolically active and is the segment most vulnerable to ischaemia (ATN - Acute Tubular Necrosis).

A. It filters blood from the glomerulus

C. It secretes ADH into the filtrate

D. It concentrates urine by creating an osmotic gradient

What is the function of the distal convoluted tubule (DCT)? — Electrical Engineering MCQ

B. It fine-tunes reabsorption of Na+, water, and secretion of K+ and H+ under hormonal control (aldosterone, ADH) — The Distal Convoluted Tubule (DCT) is the segment between the ascending Loop of Henle and the collecting duct. Its key functions: Aldosterone-regulated Na+ reabsorption and K+ secretion (via ENaC channels), PTH-regulated Ca2+ reabsorption (parathyroid hormone stimulates calcium reabsorption), H+ secretion (acid-base regulation), and fine-tuning of electrolyte balance. The DCT connects to the collecting duct, which is the final site of water regulation (ADH-dependent). Thiazide diuretics act on the DCT to block Na+-Cl- cotransporter - increased Na+ and water excretion - reduced blood pressure.

A. It filters blood from the glomerulus

C. It creates the osmotic gradient in the medulla

D. It carries urine to the bladder

Excretory System MCQ [ Free PDF Download ] for RRB & SSC and other Competitive exams

Excretory System MCQ for RRB & SSC and other Competitive exams

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What is the medical term for painful urination?

✓ Answer: C Dysuria

Dysuria is the medical term for painful, burning, or uncomfortable urination. It is a common symptom of: Urinary Tract Infection (UTI) - most common cause, Cystitis (bladder infection), Urethritis (urethral infection - STIs like gonorrhoea, chlamydia), Pyelonephritis (kidney infection), Kidney stones (as they pass through the ureter/urethra), and Interstitial cystitis (chronic bladder inflammation). Other urinary symptoms: Frequency (urinating often), Urgency (sudden urge), Nocturia (urinating at night), Haematuria (blood in urine), Polyuria (excess urine), Oliguria (reduced urine). Dysuria always warrants urine dipstick and culture.

What is the significance of glucosuria in urine?

✓ Answer: B Abnormal presence of glucose in urine - most commonly indicates diabetes mellitus when blood glucose exceeds the renal threshold (~180 mg/dL)

Glucosuria (Glycosuria) is the abnormal presence of glucose in urine. Causes: Diabetes Mellitus (most common) - blood glucose > renal threshold (~180 mg/dL) - SGLT2 transporters saturated - glucose in urine - osmotic diuresis - polyuria/polydipsia. Renal Glucosuria - normal blood glucose but low renal threshold - due to SGLT2 genetic defect or PCT dysfunction (Fanconi syndrome) - glucose in urine despite normal blood glucose. Pregnancy - reduced renal threshold - mild glucosuria in normal pregnancy. Glucosuria causes osmotic diuresis - large volumes of dilute, sweet-smelling urine. Historically diagnosed by testing if urine tasted sweet (before modern tests). Now detected by urine dipstick (glucose oxidase reaction).

What is SIADH (Syndrome of Inappropriate Antidiuretic Hormone Secretion)?

✓ Answer: B Excessive ADH secretion causing water retention, hyponatraemia, and concentrated urine despite low plasma osmolality

SIADH is caused by excessive, unregulated ADH secretion independent of plasma osmolality, leading to water retention and dilutional hyponatraemia (low blood sodium - most common electrolyte disorder in hospitalised patients). Features: Hyponatraemia (Na+ <135 mmol/L), Low plasma osmolality (100, usually >300 mOsm/kg), Urine Na+ >20 mmol/L (kidneys excreting sodium inappropriately), and No oedema (euvolaemic - total body water up, sodium normal). Causes: Malignancy (small cell lung cancer - most common), CNS disease (meningitis, head injury), Drugs (SSRIs, carbamazepine, cyclophosphamide), and Pulmonary disease (pneumonia, TB). Treatment: Fluid restriction, hypertonic saline (severe), Tolvaptan (vasopressin antagonist).

What is meant by tubular maximum (Tm)?

✓ Answer: B The maximum rate at which a substance can be reabsorbed (or secreted) by the renal tubules - beyond this, excess appears in urine

Tubular Maximum (Tm) is the maximum transport capacity of the renal tubules for a particular substance - determined by the number of carrier proteins available. When plasma concentration of a substance exceeds the Tm: Carrier proteins become saturated (transport maximum reached) and excess substance cannot be reabsorbed - appears in urine. Classic example: Glucose Tm = ~320 mg/min. Normal filtered glucose = ~125 mg/min (all reabsorbed). When blood glucose > 180 mg/dL (renal threshold) - filtered load exceeds Tm - glucosuria. Tm also applies to tubular secretion (e.g., penicillin, PAH - para-aminohippuric acid - used to measure tubular secretion capacity). The Tm concept explains why certain substances appear in urine only when plasma levels are elevated.

What is Fanconi syndrome?

✓ Answer: B A generalised dysfunction of the PCT causing failure to reabsorb glucose, amino acids, phosphate, uric acid, and bicarbonate - leading to multiple substances in urine

Fanconi Syndrome is a disorder of generalised PCT dysfunction - the PCT fails to reabsorb multiple substances normally: Glucosuria (with normal blood glucose), Aminoaciduria (amino acids in urine), Phosphaturia - hypophosphataemia - rickets/osteomalacia, Uricosuria (uric acid in urine - low serum uric acid), Bicarbonate wasting - proximal RTA (renal tubular acidosis type 2), and Potassium wasting - hypokalaemia. Causes: Wilson's disease (copper accumulation), Cystinosis (most common in children), Lead poisoning, Multiple myeloma, Tenofovir (HIV medication), and Hereditary fructose intolerance. Treatment: treat underlying cause, supplement lost substances.

What is the effect of diuretics on kidney function?

✓ Answer: B Diuretics increase urine production by reducing tubular reabsorption of sodium and water at various sites in the nephron

Diuretics are drugs that increase urine output by reducing Na+ (and therefore water) reabsorption. Classification by site of action: Loop diuretics (furosemide/frusemide) - block Na+-K+-2Cl- co-transporter in thick ascending Loop of Henle - most potent - used in heart failure/pulmonary oedema. Thiazides (hydrochlorothiazide) - block Na+-Cl- co-transporter in DCT - used in hypertension/calcium stones. K+-sparing diuretics (spironolactone = aldosterone antagonist; amiloride = ENaC blocker) - acting on DCT/collecting duct - prevent potassium loss - used in heart failure/hyperaldosteronism. Carbonic anhydrase inhibitors (acetazolamide) - act on PCT - used in altitude sickness/glaucoma. Osmotic diuretics (mannitol) - act throughout tubule - used in raised ICP/AKI prevention.

What is the function of podocytes in the kidney?

✓ Answer: B Specialised epithelial cells that form filtration slits in the glomerular filtration barrier, preventing large proteins from entering the filtrate

Podocytes are highly specialised visceral epithelial cells that form the innermost layer of the Bowman's capsule. Key features: Have octopus-like foot processes (pedicels) that wrap around the glomerular capillaries. The gaps between foot processes = Filtration slits (slit diaphragms). Slit diaphragm protein = Nephrin (encoded by NPHS1 gene) - critical for maintaining the filtration barrier. Podocyte injury/damage > filtration slit effacement > proteinuria. Minimal Change Disease (most common nephrotic syndrome in children): Podocyte foot process effacement - only visible on electron microscopy. Podocytes cannot regenerate well - persistent podocyte injury causes permanent scarring (FSGS).

What is renal tubular acidosis (RTA)?

✓ Answer: B A group of disorders where the kidney tubules fail to acidify urine properly, causing metabolic acidosis with a normal anion gap

Renal Tubular Acidosis (RTA) is a group of disorders where kidney tubules fail to properly acidify the urine, causing metabolic acidosis (normal anion gap). Type 1 (Distal RTA): DCT/collecting duct fails to secrete H+ - urine pH always >5.5 despite acidosis - nephrocalcinosis, kidney stones (calcium phosphate). Causes: Sjogren's syndrome, SLE, amphotericin B toxicity. Type 2 (Proximal RTA): PCT fails to reabsorb HCO3- - bicarbonate lost in urine. Often part of Fanconi syndrome. Type 4 (Hyperkalaemic RTA): Aldosterone deficiency/resistance - reduced H+ and K+ secretion - hyperkalaemia + acidosis. Common in diabetic nephropathy. All types treated with bicarbonate supplementation.

What is meant by renal autoregulation?

✓ Answer: B The intrinsic ability of the kidney to maintain relatively constant GFR and renal blood flow despite changes in systemic blood pressure (between 80-180 mmHg)

Renal Autoregulation is the ability of the kidney to maintain constant GFR and renal blood flow over a wide range of systemic blood pressures (approximately 80-180 mmHg) through intrinsic mechanisms: 1) Myogenic mechanism = Rise in blood pressure - afferent arteriole smooth muscle stretches - reflexively constricts - reduces blood flow to maintain constant GFR. 2) Tubuloglomerular Feedback (TGF) = Increased GFR - increased NaCl delivery to macula densa - signals afferent arteriole to constrict - GFR returns to normal. These mechanisms operate independently of nerves and hormones. Outside the autoregulatory range (180 mmHg) - GFR changes with BP. In severe hypotension - oliguria/anuria. Neonates and transplanted kidneys have impaired autoregulation.

What is the Bowman's capsule filtration pressure?

✓ Answer: B Net filtration pressure = Glomerular hydrostatic pressure minus Capsular hydrostatic pressure minus Blood colloid osmotic pressure

Net Filtration Pressure (NFP) determines the rate of glomerular filtration: NFP = GHP - CHP - BCOP. GHP (Glomerular Hydrostatic Pressure) = ~55 mmHg (pushes fluid OUT of capillaries INTO Bowman's capsule - promotes filtration). CHP (Capsular Hydrostatic Pressure) = ~15 mmHg (pushes back AGAINST filtration - opposes). BCOP (Blood Colloid Osmotic Pressure) = ~30 mmHg (proteins in blood pull water back - opposes filtration). NFP = 55 - 15 - 30 = +10 mmHg (net force favouring filtration). Any condition that reduces GHP (shock, dehydration) or increases CHP (obstruction) reduces filtration and reduces urine output.

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