Urine Formation

Question 1

What is the function of the Nephron in urine formation?

Answer 1

1. glomerular filtration
2. selective reabsorption
3. tubular secretion

Question 2

What is glomerular filtration?

Answer 2

most substances (filtrate) are pushed into the proximal convoluted tubule

Question 3

What is selective reabsorption?

Answer 3

reabsorbs all the substances the body still wants back into the blood

Question 4

What is tubular secretion?

Answer 4

actively putting anything the blood doesn’t need back into the tubule

Question 5

Where does glomerular filtration take place?

Answer 5

takes place in renal corpuscle

Question 6

What does the difference in size of afferent and efferent arterioles achieve?

Answer 6

• the afferent has a larger diameter
• this causes a difference in pressure
• Because the efferent arteriole is smaller it increases resistance to the flow of the blood, increasing pressure in the glomerulus
• forces filtrate to be pushed into the glomerular capsule

Question 7

What is filtrate composed of?

Answer 7

• water
• salts, minerals m amino acids, fatty acids, glucose
• urea, uric acid, creatinine
• hormones, toxins
• ions like K+, Na+, and H+

Question 8

What are some materials that are selectively reabsorbed?

Answer 8

• water, glucose, amino acids
• ions like: Na+, K+, Ca+, and Cl-
• urea

Question 9

What does tubular secretion do?

Answer 9

• removes substances from the filtrate to the blood
• adds materials to the filtrate from the blood

Question 10

What are the 2 main effects of tubular secretion? + example

Answer 10

1. maintain blood pH
   e.g. diets usually contain acid producing foods that lower pH, therefore kidneys remove H+ and NH3 ions
2. Maintain urine pH
   e.g. H+ and NH3 ions make the urine slightly acidic

Question 11

What is urine composed of?

Answer 11

• 96% water
• 2% urea
• 1.5% various ions
• 0.5% glucose, uric acid and creatinine