1- How do your kidneys work? - Emma Bryce

Source: https://www.youtube.com/watch?v=FN3MFhYPWWo

Answer: B. To filter blood and remove waste products

Explanation:
The kidneys filter the blood, remove waste, and produce urine — keeping the body’s internal environment balanced.

What is the main role of the kidneys?

A. To produce energy for the body
B. To filter blood and remove waste products
C. To help the stomach digest food
D. To store vitamins and minerals

Answer: C. 180 liters

Explanation:
Each day, the kidneys filter around 180 liters of plasma from the body’s 8 liters of blood, circulating it many times.

How many liters of blood do the kidneys filter each day?

A. 8 liters
B. 50 liters
C. 180 liters
D. 300 liters

Answer: A. Nephrons

Explanation:
Each kidney has about one million nephrons, which are the main functional units that filter blood and form urine.

What are the tiny filtering units inside each kidney called?

A. Nephrons
B. Alveoli
C. Capillaries
D. Villi

Answer: B. Glomerulus

Explanation:
The glomerulus is a small ball of capillaries that filters blood based on molecule size, allowing water and small substances to pass.

Which part of the nephron acts like a sieve to filter the blood?

A. Tubule
B. Glomerulus
C. Ureter
D. Bladder

Answer: B. Useful substances are reabsorbed and waste is secreted

Explanation:
The tubule reabsorbs water, glucose, and ions the body needs while sending waste (like urea) to the bladder as urine.

What happens in the nephron’s tubule?

A. Blood cells are destroyed
B. Useful substances are reabsorbed and waste is secreted
C. Urine is stored temporarily
D. Hormones are produced

Answer: B. Kidney → Ureter → Bladder → Urethra

Explanation:
This is the correct order of the urinary pathway.

Through which path does urine travel to leave the body?

A. Kidney → Artery → Vein
B. Kidney → Ureter → Bladder → Urethra
C. Heart → Lung → Bladder
D. Stomach → Intestine → Kidney

Answer: A. There is more urea and less water

Explanation:
When dehydrated, the kidneys conserve water, so the urine becomes more concentrated and appears darker yellow.

Why does urine appear darker when a person is dehydrated?

A. There is more urea and less water
B. The kidneys produce too much vitamin D
C. The bladder releases color pigments
D. The kidneys stop filtering blood

Answer: B. Erythropoietin

Explanation:
Erythropoietin stimulates the bone marrow to make more red blood cells, ensuring oxygen delivery to the body.

Which hormone produced by the kidney increases red blood cell production?

A. Insulin
B. Erythropoietin
C. Renin
D. ADH

Answer: B. Renin

Explanation:
Renin starts a chain reaction (the renin–angiotensin–aldosterone system) that increases blood pressure when it’s too low.

What does the kidney release to help regulate blood pressure?

A. Vitamin D
B. Renin
C. Glucose
D. Estrogen

Answer: B. The blood would fill with waste and the person could die

Explanation:
Without kidney filtration, waste like urea and toxins build up, which is deadly — dialysis or a kidney transplant would be needed.

What would happen if both kidneys stopped working?

A. The liver would take over their function
B. The blood would fill with waste and the person could die
C. The body would produce more urine
D. Nothing serious would happen

Answer: C. Antidiuretic hormone (ADH)

Explanation:
ADH, made by the hypothalamus and released by the pituitary gland, signals the kidneys to reabsorb more water and produce less urine.

What hormone helps the kidneys retain water when the body is dehydrated?

A. Insulin
B. Adrenaline
C. Antidiuretic hormone (ADH)
D. Renin

Answer: B. Vitamin D

Explanation:
The kidneys convert inactive vitamin D into its active form (calcitriol), which helps the intestines absorb calcium.

Which vitamin is activated by the kidneys?

A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin K

Answer: C. A waste product from protein breakdown

Explanation:
Urea is produced in the liver when proteins are broken down. The kidneys remove it from the blood through urine.

What is urea?

A. A hormone that lowers blood pressure
B. A sugar that fuels kidney cells
C. A waste product from protein breakdown
D. A mineral stored in bones

Answer: A. Renal artery

Explanation:
The renal artery carries oxygen-rich blood from the heart into each kidney to be filtered.

Where does blood enter the kidney?

A. Renal artery
B. Renal vein
C. Ureter
D. Glomerulus

Answer: B. Renal vein

Explanation:
After filtration and reabsorption, clean blood leaves the kidney through the renal vein and returns to circulation.

What structure carries filtered blood out of the kidney?

A. Ureter
B. Renal vein
C. Loop of Henle
D. Collecting duct

Answer: B. Glucose

Explanation:
Glucose should be reabsorbed in the nephron. Its presence in urine may indicate diabetes or kidney damage.

Which of the following is NOT normally found in urine?

A. Water
B. Glucose
C. Urea
D. Salts

Answer: B. Controls water and salt reabsorption

Explanation:
The Loop of Henle creates a salt gradient that allows the kidney to concentrate or dilute urine as needed.

What is the role of the Loop of Henle in the nephron?

A. Filters blood cells
B. Controls water and salt reabsorption
C. Produces hormones
D. Stores urine

Answer: C. By releasing renin, which triggers constriction of blood vessels

Explanation:
Renin activates a cascade that narrows blood vessels and increases sodium and water reabsorption, raising blood pressure.

How do the kidneys help regulate blood pressure?

A. By increasing heart rate
B. By producing insulin
C. By releasing renin, which triggers constriction of blood vessels
D. By storing extra water

Answer: A. They release erythropoietin

Explanation:
Erythropoietin stimulates the bone marrow to produce more red blood cells, increasing oxygen-carrying capacity.

What happens when the kidneys detect low oxygen levels in the blood?

A. They release erythropoietin
B. They increase urine production
C. They stop filtering blood
D. They release vitamin D

Answer: C. Accumulation of toxins and fluid in the body

Explanation:
Without proper filtration, waste products and excess fluid build up, causing serious complications and requiring dialysis.

What would be the immediate effect of losing kidney function?

A. Increase in energy levels
B. Decrease in blood sugar
C. Accumulation of toxins and fluid in the body
D. Thinner blood

Answer: B. Tubes that carry urine from the kidneys to the bladder

Explanation:
Each ureter is a muscular tube that transports urine using rhythmic contractions called peristalsis.

What are ureters?

A. Filters inside the kidneys
B. Tubes that carry urine from the kidneys to the bladder
C. Muscles that contract the bladder
D. Blood vessels near the kidney

Answer: C. Reabsorption

Explanation:
Reabsorption occurs mainly in the tubules, where water, glucose, and ions are taken back into the bloodstream.

Which term describes the process of returning useful substances from the filtrate back to the blood?

A. Filtration
B. Secretion
C. Reabsorption
D. Diffusion

Answer: C. Collecting duct

Explanation:
The collecting duct gathers urine from several nephrons and delivers it to the renal pelvis, leading to the ureter.

What part of the nephron collects the final urine before it exits the kidney?

A. Glomerulus
B. Proximal tubule
C. Collecting duct
D. Renal artery

Answer: B. By removing or reabsorbing hydrogen and bicarbonate ions

Explanation:
The kidneys regulate blood pH by controlling how much acid (H⁺) or base (HCO₃⁻) they excrete or reabsorb.

How do kidneys help maintain acid-base balance in the body?

A. By producing stomach acid
B. By removing or reabsorbing hydrogen and bicarbonate ions
C. By storing alkaline minerals
D. By releasing insulin

Answer: C. Lighter when hydrated, darker when dehydrated

Explanation:
Diluted urine (more water) looks pale, while concentrated urine (less water, more urea) looks darker yellow.

Which of the following correctly describes the color change of urine when hydrated vs. dehydrated?

A. Darker when hydrated, lighter when dehydrated
B. Always the same color
C. Lighter when hydrated, darker when dehydrated
D. Turns red when dehydrated

Answer: B. Because the ingredients in the blood keep changing as we eat and drink

Explanation:
Every time we eat or drink, new nutrients and waste enter the blood. The kidneys must constantly adjust and filter to keep blood composition stable.

Why do the kidneys work continuously throughout the day?

A. Because they produce energy for the body
B. Because the ingredients in the blood keep changing as we eat and drink
C. Because the heart stops at night
D. Because they store urine

Answer: C. 20–25 times

Explanation:
All 8 liters of blood circulate through the kidneys around 20–25 times daily, totaling about 180 liters filtered every 24 hours.

About how many times does the body’s blood pass through the kidneys each day?

A. 2–3 times
B. 10 times
C. 20–25 times
D. 50 times

Answer: B. Sensors in the nephron tubules that detect substances in the blood

Explanation:
Nephron tubules act like detectors, sensing what the body needs to keep (like ions and water) and what to excrete (like urea).

What allows the kidneys to sense what the body needs and adjust urine production?

A. Brain cells in the hypothalamus
B. Sensors in the nephron tubules that detect substances in the blood
C. The heart’s electrical signals
D. The stomach’s digestion rate

Answer: B. The kidneys send the extra liquid to the bladder to be removed

Explanation:
When water levels rise, the kidneys excrete the extra fluid as urine to maintain balance in the bloodstream.

When you drink several glasses of water at once, what happens?

A. The kidneys store the extra water
B. The kidneys send the extra liquid to the bladder to be removed
C. The kidneys stop filtering temporarily
D. The bladder absorbs the water

Answer: B. The kidneys release water back into the bloodstream

Explanation:
During dehydration, the kidneys conserve water by reabsorbing more into the blood, producing less but darker urine.

What happens when the body’s water level is too low?

A. The kidneys remove more water
B. The kidneys release water back into the bloodstream
C. The kidneys stop filtering blood
D. The bladder stores more urine

Answer: B. There’s more urea and less water in it

Explanation:
When dehydrated, less water is excreted, so urea concentration increases — making urine darker yellow.

Why does urine appear yellower when a person is dehydrated?

A. The kidney adds pigment
B. There’s more urea and less water in it
C. The bladder changes its color
D. Blood mixes with urine

Answer: C. If one fails, the other can still filter blood and keep you alive

Explanation:
Most people can survive with one healthy kidney because both perform the same filtering function independently.

Why is having two kidneys beneficial?

A. One makes urine, and the other stores it
B. They help the lungs breathe
C. If one fails, the other can still filter blood and keep you alive
D. It helps you digest food faster

Answer: B. The person would need dialysis or a kidney transplant

Explanation:
Without kidneys, waste builds up rapidly. Dialysis or transplantation is required to artificially clean the blood.

What would likely happen if both kidneys stopped working completely?

A. The liver would take over filtration
B. The person would need dialysis or a kidney transplant
C. The bladder would replace the kidneys
D. The body would produce more hormones to fix it

Answer: B. Kidneys remove waste and balance water, salts, and minerals in blood

Explanation:
The kidneys are constantly fine-tuning the blood’s content to maintain homeostasis — the body’s internal balance.

What is the relationship between the kidneys and blood composition?

A. Kidneys add nutrients to the blood
B. Kidneys remove waste and balance water, salts, and minerals in blood
C. Kidneys only control red blood cells
D. Kidneys keep blood warm

Answer: A. Because they detect waste and adjust how much water and salts are kept or removed

Explanation:
Kidneys “sense” changes in blood composition and respond immediately — filtering waste, conserving water, or reabsorbing needed minerals.

Why are the kidneys described as “fine-tuned internal sensors”?

A. Because they detect waste and adjust how much water and salts are kept or removed
B. Because they measure body temperature
C. Because they control heart rate
D. Because they detect brain activity