Biology 449 - Animal Physiology April 14, 2008

Lecture 31 - Renal Physiology II

Nephrons (cont'd)

Urine formation

Proximal tubule (review)

Loop of Henle & initial distal tubule

End distal tubule & collecting duct

Mechanisms of reabsorption and secretion

Counter-current multipliers

Summary of nephron function

Summary of Nephron Function

Location Transported*/
Diffused Out 		Impermeable to Final Osmolarity
(mOsm) 		Final Volume
(ml / min)
Bowman’s — — 300 120
Proximal Tubule NaCl, glucose, a.a.,
H2O, some urea 		Less permeable to urea 300 40
Descending limb H2O NaCl 1200 15
Thin ascending NaCl H2O – –
Thick ascending NaCl H2O 100 15
Distal tubule Some NaCl
H2O varies 		H2O permeability varies Varies
(100-300) 		Varies
(10-15)
Collecting duct Some NaCl, some urea
H2O varies 		H2O permeability varies Varies
(100-1400) 		Varies
(0.25 – 15,
average = 1)

* Items in bold are actively transported.

Values given for osmolarity and volume are those seen as the urine reaches the end of that segment.

 

Terms to Know

Proximal tubule
Loop of Henle
Descending limb
Thin ascending limb
Thick ascending limb
Distal tubule
Collecting duct

Glomerular filtration
Glomerular filtration rate (GFR)
Secretion
Reabsorption

Tubular lumen
Apical or luminal membrane
Basolateral membrane

Counter-current multiplier

Readings

Lectures 30-32: Chapter 12, pages 521-563
Lecture 33: Chapter 13, pages 588-609