3.6 - The excretory system in animals

Question 1

Define excretion.

Answer 1

Excretion is the removal of toxic metabolic waste products and substances in excess from an organism.

Question 2

What is the function of the kidneys in the human excretory system?

Answer 2

The kidneys produce urine to remove nitrogen-containing metabolic wastes and maintain the balance of water and salts in the blood.

Question 3

What is the function of the ureter?

Answer 3

The ureter transports urine from the kidneys to the bladder.

Question 4

What is the role of the bladder?

Answer 4

The bladder stores urine until it is excreted through urination.

Question 5

What is the function of the urethra?

Answer 5

The urethra excretes urin during urination.

Question 6

What is the structure and function of a nephron?

Answer 6

The nephron is the structural and functional unit of the kidney. It consists of Bowman’s capsule, glomerulus, and a long renal tubule. It filters blood, removes wastes, and reabsorbs useful substances.

Question 7

What is filtration in the kidneys?

Answer 7

Filtration is the process where blood is filtered under high pressure in the glomerulus, and small molecules like water, glucose, amino acids, salts, and urea enter the Bowman’s capsule, forming the glomerular filtrate.

Question 8

What is selective reabsorption?

Answer 8

Selective reabsorption is the process where useful substances such as glucose, amino acids, and water are reabsorbed from the filtrate back into the blood along the renal tubule and collecting duct.

Question 9

Why is filtration important in the excretory system?

Answer 9

Filtration allows the removal of metabolic waste products and excess substances from the blood, contributing to the formation of urine.

Question 10

What is the importance of reabsorption in the kidneys?

Answer 10

Reabsorption ensures that useful substances like glucose, amino acids, and water are returned to the bloodstream, preventing their loss in urine and maintaining homeostasis.

Question 11

What is the role of antidiuretic hormone (ADH) in osmoregulation?

Answer 11

ADH regulates water balance by increasing the permeability of the collecting ducts to water, promoting more water reabsorption when the body is dehydrated.

Question 12

What are the main components of the renal artery and renal vein?

Answer 12

The renal artery carries blood to the kidneys, while the renal vein carries filtered blood away from the kidneys back to the heart.

Question 13

What is the function of the renal cortex and medulla in the kidneys?

Answer 13

The renal cortex is the outer region of the kidney, where blood filtration begins, and the renal medulla is the inner region, where the renal tubules and collecting ducts are located.

Question 14

What is the role of the glomerulus in the nephron?

Answer 14

The glomerulus is a cluster of capillaries that filters blood under high pressure, allowing small molecules like water, glucose, and urea to enter the Bowman’s capsule.

Question 15

What is the function of the proximal tubule?

Answer 15

The proximal tubule reabsorbs essential substances like glucose and amino acids, along with some salts and water.

Question 16

What is the role of the Loop of Henle?

Answer 16

The Loop of Henle reabsorbs water and salts, helping maintain the osmotic balance of the blood.

Question 17

What is the function of the distal tubule?

Answer 17

The distal tubule is involved in the reabsorption of water and salts and the regulation of potassium and pH levels.

Question 18

What is the function of the collecting duct in the nephron?

Answer 18

The collecting duct transports urine toward the ureter and reabsorbs water, depending on the body’s hydration status, influenced by ADH.

Question 19

What is glomerular filtrate?

Answer 19

Glomerular filtrate is the liquid that passes into the Bowman’s capsule, containing water, glucose, amino acids, urea, and salts, but not blood cells or large proteins.

Question 20

What is osmoregulation?

Answer 20

Osmoregulation is the process of maintaining the balance of water and salts (osmotic balance) in the blood to ensure proper bodily function and homeostasis.

Question 21

How does ADH influence the kidneys?

Answer 21

ADH increases the permeability of the collecting ducts to water, promoting water reabsorption into the blood and reducing urine volume during dehydration.

Question 22

What is homeostasis in the context of the excretory system?

Answer 22

Homeostasis refers to maintaining a stable internal environment, such as maintaining a consistent water and salt balance, which is critical for proper kidney function and overall body health.

Question 23

What is a diuretic?

Answer 23

A diuretic is a substance that increases urine production. Examples include alcohol and caffeine, which inhibit ADH release and promote water excretion.

Question 24

What is the role of the renal artery in the excretory system?

Answer 24

The renal artery carries oxygenated blood containing metabolic waste products into the kidneys for filtration.

Question 25

What is the role of the renal vein in the excretory system?

Answer 25

The renal vein carries filtered blood, now free of waste products, from the kidneys back to the heart.

Question 26

What is the difference between proximal and distal tubule?

Answer 26

The proximal tubule reabsorbs most of the important substances like glucose and water. The distal tubule helps balance water, salts, and pH.

Question 27

What is the role of nephron in filtration?

Answer 27

The nephron filters blood in the kidneys by removing waste products and excess substances, such as water, salts, glucose, and urea, from the blood and forming glomerular filtrate in the Bowman's capsule.

Question 28

What substances are involved in reabsorption from the tubule?

Answer 28

Substances involved in reabsorption from the renal tubule include glucose, amino acids, water, sodium, and other essential ions.

Question 29

Which factors may influence the final concentration of the urine?

Answer 29

Factors that influence the final concentration of urine include hydration status (controlled by ADH), the reabsorption of water and salts in the renal tubule, and the presence of diuretics.

Question 30

What is metabolism?

Answer 30

All the biochemical reactions carried out by a living thing are collectively called metabolism.

Question 31

What substances are not reabsorbed and are excreted in urine?

Answer 31

Urea, excess water, salts, and other metabolic waste products.

Question 32

Why is the structure of the nephron important for its function?

Answer 32

The nephron's long, folded tubules and close contact with capillaries increase surface area for efficient filtration and reabsorption.

Question 33

How is the glomerulus adapted for filtration?

Answer 33

It has thin, leaky capillary walls and high blood pressure, allowing small molecules to be pushed into the Bowman's capsule.

Question 34

What is the importance of maintaining osmotic balance?

Answer 34

It ensures cells don't shrink or swell, maintains blood pressure, and keeps internal conditions stable (homeostasis).

Question 35

What is the function of the renal pelvis?

Answer 35

The renal pelvis collects urine from the collecting ducts and channels it into the ureter.

Question 36

What would happen if reabsorption didn’t occur?

Answer 36

The body would lose essential substances like glucose, amino acids, and water, leading to dehydration and nutrient loss.

Question 37

Where is glucose reabsorbed in the nephron, and how much is reabsorbed under normal conditions?

Answer 37

100% Glucose is reabsorbed in the proximal tubule by active transport under normal conditions.

Question 38

Where is amino acids reabsorbed in the nephron, and how much is reabsorbed under normal conditions?

Answer 38

100& Amino acids are reabsorbed in the proximal tubule via active transport under normal conditions.

Question 39

Where is water reabsorbed in the nephron, and how much is reabsorbed under normal conditions?

Answer 39

99% of water is reabsorbed by osmosis, mainly in the proximal tubule, Loop of Henle, distal tubule, and collecting duct (regulated by ADH) under normal conditions.

Question 40

Where is sodium reabsorbed in the nephron, and how much is reabsorbed under normal conditions?

Answer 40

99% Sodium is reabsorbed in the proximal tubule, Loop of Henle, distal tubule, and collecting duct by active transport under normal conditions.

Question 41

Where is urea reabsorbed in the nephron, and how much is reabsorbed under normal conditions?

Answer 41

50% Urea is reabsorbed in the proximal tubule, distal tubule and collecting duct.

Question 42

What role does the Loop of Henle play in reabsorption?

Answer 42

The descending limb reabsorbs water (osmosis); the ascending limb reabsorbs salts (active transport), helping establish a concentration gradient for water reabsorption.

Question 43

What controls water reabsorption in the collecting duct?

Answer 43

ADH (antidiuretic hormone) increases water reabsorption by making the collecting duct more permeable to water.

Question 44

What is the role of aldosterone in the nephron?

Answer 44

Aldosterone increases sodium reabsorption and potassium excretion in the distal tubule, helping maintain blood pressure and fluid balance.

Question 45

What is aldosterone?

Answer 45

Aldosterone is a hormone produced by the adrenal glands that regulates sodium and potassium balance in the kidneys. It increases sodium reabsorption and potassium excretion, helping maintain blood pressure and fluid balance.

Question 46

What are the three main stages of urine formation?

Answer 46

Filtration, selective reabsorption, and secretion.

Question 47

How do alcohol and caffeine affect the excretory system?

Answer 47

They act as diuretics by reducing ADH release, leading to decreased water reabsorption and increased urine output.

Question 48

What is the Pituitary Gland and its role?

Answer 48

The pituitary gland is a small gland at the base of the brain and releases ADH (antidiuretic hormone)

Question 49

What is kidney disease and how does it affect the excretory system?

Answer 49

Kidney disease is a condition where the kidneys lose their ability to effectively filter waste and maintain fluid and electrolyte balance. This can lead to the buildup of toxins in the blood, fluid retention, and disrupted homeostasis. Severe cases may require dialysis or a kidney transplant.

Question 50

What factors can change the composition of urine?

Answer 50

Hydration Level: More water is reabsorbed when dehydrated, leading to concentrated urine. Diet: High-protein diets increase urea in urine, while high-salt diets affect sodium levels. Medications/Diuretics: Increase urine production and alter its composition. Hormones (e.g., ADH): Influence water reabsorption, affecting urine volume and concentration.