Homeostasis- The Kidneys

Question 1

What is one of the main functions of the kidneys?

Answer 1

To excrete waste products such as urea

Question 2

What do the kidneys regulate?

Answer 2

The water potential of the blood

Question 3

What is ultrafiltration?

Answer 3

As blood passes through capillaries in the cortex of the kidneys, substances are filtered out of the blood and into long tubules that surround the capillaries

Question 4

What is selective reabsorption?

Answer 4

Useful substances (such as glucose and the right amount of water) are then reabsorbed back into the blood

Question 5

What happens to the remaining unwanted substances?

Answer 5

They pass along to the bladder and are excreted as urine

Question 6

What are the nephrons?

Answer 6

Long tubules along with the bundle of capillaries where blood is filtered

Question 7

How many nephrons are in each kidney?

Answer 7

Around a million

Question 8

How does blood enter the kidney?

Answer 8

From the renal artery enters smaller arterioles in the cortex of the kidney

Question 9

What does each arteriole split into?

Answer 9

A structure called a glomerulus

Question 10

What is a glomerulus?

Answer 10

A bundle of capillaries looped inside a hollow ball called a Bowman’s capsule

Question 11

Where does ultrafiltration take place?

Answer 11

The glomerulus

Question 12

What is the afferent arteriole?

Answer 12

The arteriole that takes blood into each glomerulus

Question 13

What is the efferent arteriole?

Answer 13

The arteriole that takes the filtered blood away from the glomerulus

Question 14

Why is the blood in the glomerulus under high pressure?

Answer 14

Because the efferent arteriole is smaller in diameter than the afferent arteriole

Question 15

What does the high pressure mean?

Answer 15

It forces liquid and small molecules in the blood out of the capillary and into the Bowman’s capsule

Question 16

What three layers do the liquid and small molecules pass through to get into the Bowman’s capsule and enter the nephron tubules?

Answer 16

The capillary wall, a membrane (basement membrane) and the epithelium of the Bowman’s capsule

Question 17

Why do larger molecules like proteins and blood cells stay in the blood?

Answer 17

They can’t pass through

Question 18

What are the substances that enter the Bowman’s capsule known as?

Answer 18

The glomerular filtrate

Question 19

How does the glomerular filtrate pass out the kidney?

Answer 19

Along the rest of the nephron and useful substances are reabsorbed along the way —> flows through the collecting duct —> passes out of kidney along ureter

Question 20

When does selective reabsorption take place?

Answer 20

As the glomerular filtrate flows along the proximal convoluted tubule, through the loop of Henle, and along the distal convoluted tubule

Question 21

What do useful substances do?

Answer 21

They leave the tubules of nephrons and enter the capillary network that’s wrapped around them

Question 22

Why does the epithelium of the wall of the PCT have microvilli?

Answer 22

To provide a large surface area for the reabsorption of useful materials from the glomerular filtrate into the blood

Question 23

What happens to useful solutes like glucose?

Answer 23

The are reabsorbed along the PCT by active transport and facilitated diffusion

Question 24

Why does water enter the blood by osmosis?

Answer 24

Because the water potential of the blood is lower than that of the filtrate- water is reabsorbed from the PCT, loop of Henle, DCT and the collecting duct

Question 25

What is the filtrate that remains?

Answer 25

Urine which passes along the ureter to the bladder

Question 26

What is urine usually made up of?

Answer 26

Water and dissolved salts, urea, other substances such as hormones and excess vitamins

Question 27

What does urine not usually contain?

Answer 27

Proteins and blood cells as they’re too big to be filtered out of the blood, glucose because it’s actively reabsorbed back into the blood