Excretory System Practice Questions
19 free Excretory System practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What is the basic functional and structural unit of the human kidney?
- A Neuron
- B Nephron
- C Alveolus
- D Ureter
Correct answer: Nephron
Each kidney contains approximately one million nephrons. These microscopic structures perform the essential tasks of filtering blood and forming urine.
In which part of the nephron does the majority of selective reabsorption of glucose and amino acids occur?
- A Glomerulus
- B Descending limb of the Loop of Henle
- C Distal Convoluted Tubule (DCT)
- D Proximal Convoluted Tubule (PCT)
Correct answer: Proximal Convoluted Tubule (PCT)
The PCT is lined with microvilli that increase surface area for reabsorption. Nearly all essential nutrients, like glucose and amino acids, are actively transported back into the blood here.
Which nitrogenous waste product is primarily excreted by the human urinary system?
- A Ammonia
- B Uric acid
- C Guanine
- D Urea
Correct answer: Urea
Humans are ureotelic organisms, meaning we convert highly toxic ammonia into less toxic urea in the liver. This urea is then transported via the blood to the kidneys for excretion.
What is the name of the cluster of capillaries where blood filtration begins in the kidney?
- A Glomerulus
- B Bowman's capsule
- C Renal pelvis
- D Vasa recta
Correct answer: Glomerulus
The glomerulus is a high-pressure capillary network. It acts as a mechanical filter, allowing water and small solutes to pass into the nephron while retaining blood cells and large proteins.
The presence of which substance in a urine sample is a clinical indicator of potential kidney damage or disease?
- A Urea
- B Creatinine
- C Sodium chloride
- D Albumin
Correct answer: Albumin
Albumin is a large plasma protein that should not normally pass through the glomerular filter. Its presence in urine suggests that the filtration membrane has been damaged.
Which vessel carries oxygenated, unfiltered blood into the kidney?
- A Renal artery
- B Renal vein
- C Hepatic portal vein
- D Inferior vena cava
Correct answer: Renal artery
The renal artery branches directly from the abdominal aorta. It delivers blood under high pressure, which is necessary for the filtration process in the glomeruli.
Which structure connects the kidneys to the urinary bladder?
- A Ureter
- B Urethra
- C Nephron
- D Hilum
Correct answer: Ureter
The ureters are thin muscular tubes that move urine from the renal pelvis to the bladder. They use peristaltic contractions to ensure urine flows in one direction.
The cup-shaped structure that surrounds the glomerulus and collects the filtrate is called:
- A Loop of Henle
- B Cortical collecting duct
- C Renal calyx
- D Bowman's capsule
Correct answer: Bowman's capsule
Bowman's capsule is the double-walled start of the nephron. It receives the 'glomerular filtrate' which contains water, salts, glucose, and urea.
Which process involves the movement of substances like hydrogen ions and drugs from the blood into the tubular fluid?
- A Ultrafiltration
- B Tubular reabsorption
- C Micturition
- D Tubular secretion
Correct answer: Tubular secretion
Tubular secretion is the active transfer of materials from peritubular capillaries into the nephron. It helps regulate blood pH and eliminate metabolic byproducts or toxins.
What is the physiological term for the act of emptying the urinary bladder?
- A Micturition
- B Defecation
- C Dialysis
- D Ultrafiltration
Correct answer: Micturition
Micturition is a reflex action controlled by both the autonomic and somatic nervous systems. It involves the contraction of the detrusor muscle and the relaxation of the urethral sphincters.
Where are the kidneys located in the human body?
- A Inside the pelvis
- B Behind the peritoneum
- C Within the pleural cavity
- D Directly behind the sternum
Correct answer: Behind the peritoneum
The kidneys lie against the posterior abdominal wall, outside and behind the peritoneal cavity, a position described as retroperitoneal. They normally sit between the T12 and L3 vertebral levels.
Which part of the kidney contains the renal pyramids?
- A Renal cortex
- B Renal medulla
- C Renal pelvis
- D Renal capsule
Correct answer: Renal medulla
The renal medulla is the inner region of the kidney. It is divided into several cone-shaped sections called renal pyramids, which contain the loops of Henle and collecting ducts.
What is the primary function of the Loop of Henle?
- A Filtration of blood cells
- B Production of the hormone erythropoietin
- C Creation of the medullary osmotic gradient
- D Temporary storage of urine prior to excretion
Correct answer: Creation of the medullary osmotic gradient
The Loop of Henle works as a countercurrent multiplier that makes the medullary interstitium increasingly salty. That osmotic gradient is what allows water to be reabsorbed from the collecting ducts to concentrate urine.
Aldosterone, a hormone that increases sodium reabsorption, is secreted by which gland?
- A Pituitary gland
- B Adrenal gland
- C Thyroid gland
- D Pancreas
Correct answer: Adrenal gland
Aldosterone is a mineralocorticoid made in the cortex of the adrenal glands, which sit on top of the kidneys. By retaining sodium the body also retains water, which raises blood volume and blood pressure.
Which enzyme is released by the kidneys to help regulate blood pressure when it falls too low?
- A Pepsin
- B Renin
- C Amylase
- D Lipase
Correct answer: Renin
Renin is secreted by the juxtaglomerular apparatus. It initiates the renin-angiotensin-aldosterone system (RAAS), which leads to vasoconstriction and water retention to raise blood pressure.
What is the involuntary muscle found in the wall of the urinary bladder?
- A Rectus abdominis
- B Detrusor muscle
- C Psoas major
- D Cremaster muscle
Correct answer: Detrusor muscle
The bladder wall is formed by the detrusor, a layer of smooth and therefore involuntary muscle. It stays relaxed while the bladder fills and contracts during micturition to expel urine.
Glycosuria, or the presence of glucose in the urine, is a classic sign of which condition?
- A Hypertension
- B Diabetes mellitus
- C Kidney stones
- D Urinary tract infection
Correct answer: Diabetes mellitus
In diabetes mellitus the blood glucose level rises above the renal threshold, so the proximal convoluted tubule cannot reabsorb all of the glucose that has been filtered. The surplus glucose passes on and appears in the urine.
Kidney stones (Renal calculi) are most commonly composed of which substance?
- A Cholesterol
- B Bilirubin
- C Potassium chloride
- D Calcium oxalate
Correct answer: Calcium oxalate
Most kidney stones form when minerals like calcium and oxalate become highly concentrated in the urine and crystallize. They can cause severe pain if they obstruct the flow of urine in the ureters.
What is the medical procedure used to filter waste products from the blood when the kidneys fail?
- A Angioplasty
- B Plasmapheresis
- C Hemodialysis
- D Laparoscopy
Correct answer: Hemodialysis
Hemodialysis passes blood across an artificial membrane inside a dialyzer, which takes over the filtering job of the nephrons. It removes metabolic wastes and excess fluid from patients whose kidneys have failed.