8- How do the Kidneys work? Renal Physiology and Filtration Explained for Beginners | Corporis (Not finished yet)

Source: https://www.youtube.com/watch?v=hfKDA5kbL5o

Which organs are primarily responsible for detoxifying the body?

A. Stomach and liver
B. Liver and kidneys
C. Lungs and pancreas
D. Spleen and intestines

Answer: B. Liver and kidneys

Explanation: The liver metabolizes and neutralizes toxins, while the kidneys filter waste products and excess ions from the blood.

Where are the kidneys located in the body?

A. In front of the abdominal cavity
B. Behind the abdominal cavity
C. Inside the thoracic cavity
D. Below the pelvic cavity

Answer: B. Behind the abdominal cavity

Explanation: The kidneys are retroperitoneal, meaning they lie behind the peritoneum that lines the abdominal cavity.

Each kidney is approximately the size of a:

A. Tennis ball
B. Closed fist
C. Large orange
D. Open hand

Answer: B. Closed fist

Explanation: On average, each kidney is about 10–12 cm long—roughly the size of your closed fist.

What is the function of the adrenal glands sitting atop each kidney?

A. Filter blood
B. Produce urine
C. Secrete hormones like adrenaline
D. Absorb water

Answer: C. Secrete hormones like adrenaline

Explanation: The adrenal (suprarenal) glands release hormones such as adrenaline, cortisol, and aldosterone.

The correct path of urine flow from the kidneys is:

A. Urethra → bladder → ureters
B. Bladder → urethra → kidneys
C. Kidneys → ureters → bladder → urethra
D. Kidneys → bladder → ureters → urethra

Answer: C. Kidneys → ureters → bladder → urethra

Explanation: Urine is produced by the kidneys, travels through the ureters to the bladder, and exits the body via the urethra.

Which structure is the outermost layer of the kidney?

A. Renal pelvis
B. Medulla
C. Cortex
D. Pyramids

Answer: C. Cortex

Explanation: The renal cortex is the outermost layer of the kidney, containing most of the nephrons’ filtering components.

What is the functional unit of the kidney?

A. Glomerulus
B. Nephron
C. Renal corpuscle
D. Loop of Henle

Answer: B. Nephron

Explanation: Each nephron filters blood and produces urine; there are about a million per kidney.

Which structure brings blood into the nephron for filtration?

A. Renal vein
B. Efferent arteriole
C. Afferent arteriole
D. Collecting duct

Answer: C. Afferent arteriole

Explanation: Blood enters the nephron through the afferent arteriole, which leads into the glomerulus.

What is Bowman’s capsule?

A. A hormone secreted by the kidney
B. The cup-like structure surrounding the glomerulus
C. The looped region of the nephron in the medulla
D. The duct that collects urine from multiple nephrons

Answer: B. The cup-like structure surrounding the glomerulus

Explanation: Bowman’s capsule encloses the glomerulus and captures the filtrate that passes through its capillaries.

Which of the following substances does not normally pass through the glomerular filtration barrier?

A. Water
B. Glucose
C. Sodium ions
D. Red blood cells

Answer: D. Red blood cells

Explanation: The glomerular capillaries are fenestrated, allowing small molecules to pass but retaining large cells and proteins.

What happens in the proximal convoluted tubule (PCT)?

A. Only secretion
B. Reabsorption of water, ions, and nutrients
C. Production of hormones
D. Filtration of blood

Answer: B. Reabsorption of water, ions, and nutrients

Explanation: The PCT reabsorbs about 65% of water and sodium, and nearly 100% of glucose and amino acids under normal conditions.

In the Loop of Henle, which limb is permeable to water?

A. Descending limb
B. Ascending limb
C. Both limbs
D. Neither limb

Answer: A. Descending limb

Explanation: The descending limb allows water to leave but not ions, while the ascending limb allows ions out but not water.

Which process moves substances from the blood back into the tubules for excretion?

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

Answer: C. Secretion

Explanation: Tubular secretion transports waste and excess ions (like H⁺, K⁺, and drugs) from blood into the tubules.

What is the approximate daily volume of filtrate produced by both kidneys?

A. 1.5 liters
B. 18 liters
C. 180 liters
D. 500 liters

Answer: C. 180 liters

Explanation: The kidneys filter about 180 liters of plasma per day, but reabsorb most of it, producing ~1.5 liters of urine.

What is the primary purpose of the kidneys’ filtration and reabsorption processes?

A. To maintain blood pH, volume, and composition
B. To digest food
C. To increase blood sugar
D. To pump oxygen

Answer: A. To maintain blood pH, volume, and composition

Explanation: The kidneys maintain homeostasis by controlling ion balance, fluid levels, and pH while removing metabolic wastes.

Which of the following correctly lists the three main regions of the kidney from outermost to innermost?

A. Medulla → Cortex → Renal pelvis
B. Cortex → Medulla → Renal pelvis
C. Renal pelvis → Cortex → Medulla
D. Medulla → Renal pelvis → Cortex

Answer: B. Cortex → Medulla → Renal pelvis

Explanation: The outer cortex surrounds the medulla, which leads into the renal pelvis, where urine collects.

What is the correct order of blood flow through the kidney?

A. Renal artery → Glomerulus → Afferent arteriole → Efferent arteriole → Renal vein
B. Renal artery → Afferent arteriole → Glomerulus → Efferent arteriole → Renal vein
C. Renal vein → Glomerulus → Renal artery → Efferent arteriole
D. Afferent arteriole → Efferent arteriole → Renal artery → Renal vein

Answer: B. Renal artery → Afferent arteriole → Glomerulus → Efferent arteriole → Renal vein

Explanation: Blood enters through the renal artery, passes the glomerulus for filtration, and leaves via the renal vein.

What is the purpose of the fenestrated (windowed) capillaries in the glomerulus?

A. To allow only red blood cells through
B. To prevent all substances from leaving the blood
C. To allow water and small solutes to pass while blocking larger molecules
D. To increase blood pressure

Answer: C. To allow water and small solutes to pass while blocking larger molecules

Explanation: Fenestrations (tiny pores) permit filtration of small molecules but prevent large proteins and cells from escaping.

Which structure immediately surrounds the glomerulus?

A. Renal pelvis
B. Bowman’s capsule
C. Loop of Henle
D. Collecting duct

Answer: B. Bowman’s capsule

Explanation: Bowman’s capsule encases the glomerulus and collects the filtrate that passes through its capillary walls.

What term describes the combination of the glomerulus and Bowman’s capsule?

A. Nephron loop
B. Renal corpuscle
C. Collecting duct
D. Renal hilum

Answer: B. Renal corpuscle

Explanation: The renal corpuscle (glomerulus + Bowman’s capsule) is the initial filtration site of the nephron.

The Loop of Henle plays a key role in:

A. Maintaining the kidney’s salt concentration gradient
B. Filtering blood
C. Producing hormones
D. Preventing urine formation

Answer: A. Maintaining the kidney’s salt concentration gradient

Explanation: The countercurrent mechanism in the Loop of Henle establishes a concentration gradient crucial for water reabsorption.

The term vasa recta refers to:

A. Capillaries surrounding the convoluted tubules
B. Capillaries surrounding the Loop of Henle
C. The collecting ducts
D. The renal pyramids

Answer: B. Capillaries surrounding the Loop of Henle

Explanation: The vasa recta are straight capillaries that follow the Loop of Henle in the medulla and maintain osmotic balance.

Which process primarily occurs in the distal convoluted tubule (DCT)?

A. Filtration of plasma
B. Reabsorption of sodium and secretion of potassium
C. Collection of urine
D. Formation of glucose

Answer: B. Reabsorption of sodium and secretion of potassium

Explanation: The DCT fine-tunes ion balance under hormonal control, especially sodium and potassium exchange.

What does tubular secretion accomplish?

A. It reabsorbs needed substances
B. It removes additional wastes like hydrogen ions and drugs from the blood
C. It stores urine in the bladder
D. It filters blood cells

Answer: B. It removes additional wastes like hydrogen ions and drugs from the blood

Explanation: Tubular secretion actively transports unwanted substances into the tubules for excretion.

Which of the following helps maintain blood pH?

A. Reabsorption of glucose
B. Secretion of hydrogen ions into the tubules
C. Reabsorption of urea
D. Secretion of water

Answer: B. Secretion of hydrogen ions into the tubules

Explanation: The kidneys help regulate acid-base balance by secreting H⁺ ions, making blood less acidic.

Why does urea appear in urine even though some is reabsorbed?

A. It is constantly secreted and reabsorbed to maintain an osmotic gradient
B. It cannot pass through any membranes
C. It is too large to be reabsorbed
D. It is produced in the lungs

Answer: A. It is constantly secreted and reabsorbed to maintain an osmotic gradient

Explanation: Urea recycling between the tubules and capillaries helps maintain medullary concentration, but excess urea is excreted.

Which structure collects urine from several nephrons before passing it to the renal pelvis?

A. Collecting duct
B. Distal tubule
C. Glomerulus
D. Loop of Henle

Answer: A. Collecting duct

Explanation: Each collecting duct receives filtrate from multiple nephrons and directs it toward the renal pelvis.

Approximately how much of the body’s cardiac output goes to the kidneys?

A. 5%
B. 10%
C. 20%
D. 50%

Answer: C. 20%

Explanation: About one-fifth of total cardiac output flows through the kidneys to support continuous filtration.

Why do people with shorter urethras experience urinary tract infections (UTIs) more often?

A. They have smaller bladders
B. Bacteria have a shorter distance to travel to the bladder
C. They produce less urine
D. Their kidneys are closer to the bladder

Answer: B. Bacteria have a shorter distance to travel to the bladder

Explanation: A shorter urethra allows easier bacterial access to the bladder, increasing UTI risk.

Which of the following best summarizes the kidney’s role in homeostasis?

A. Produces red blood cells directly
B. Regulates blood volume, ion concentration, and pH while removing wastes
C. Creates digestive enzymes
D. Controls skeletal muscle movement

Answer: B. Regulates blood volume, ion concentration, and pH while removing wastes

Explanation: The kidneys maintain homeostasis by filtering blood, balancing fluids and electrolytes, and excreting metabolic wastes.