4.3 - Overflow of Urine

Question 1

What are the 3 stages of urine formation?

Answer 1

1) filtration
2) re-absorption
3) secreation

Question 2

How does urine exit the nephron?

Answer 2

via the collecting duct

Question 3

Describe the process of filtration & where it takes place.

urine formation & urine flow

Answer 3

• from globerulus to Bowman’s capsule
• the high pressure in the glomerulus forces out H2O and other small solutes out of the capilleries and into the Bowman’s capsule
• it uses size-selective filtering. Blood cells, proteins, & other large molecues are left in the blood stream
• this solution in the nehpron is called the filtrate

Question 4

Describe the process of re-absorption & where it takes place.

urine formation & urine flow

Answer 4

• some filtrate contents move back into the blood stream
• this is due to filtration not being very precise
• its the recovery of ions (K, Na, Cl), glucose, amino acids, H2O, and other nutrients.
• this process uses passive and active transport (both uses and doesn’t use energy to transport)
• substances move through the walls of the nephron into the interstitial space and into the peritubular capilleries
• this movement causes the filtrate to be hypertonic in comparison (H2O moves out of filtrate)
• this step occurs in the PCT, LoH, DTC, and the collecting duct

Question 5

Describe the process of Secreation & where it takes place.

urine formation & urine flow

Answer 5

• from the blood stream to the filtrate
• if there is still waste in the blood stream, it has another oppritunity to move out
• can be transported out from the peritubular capilleries to the filtrate
• uses both active and passive transport
• occurs in PCT and DCT
• when the filtrate reaches the end of the tubules of the nephron, its called urine and passes throught he collecting duct to the bladder

Question 6

What is the decending limb in the nephron?

urine flow

Answer 6

• It is the downwards “U” portion of the Loop of Henle
• this is where water is reabsorbed
• it is impermeable to salt ions

Question 7

What is the ascending limb in the nephron?

urine flow

Answer 7

• It’s the upper section of the Loop of Henle
• this is where Na and Cl are reabsorbed

Question 8

Why is the Loop of Henle so long?

Answer 8

This allows for more time for water to move back into the blood stream ( to be reabsorbed).