Formation of Urine & Water
Balance
7.5, 7.6
First, some review…
What is this?
quizlet.com
• Remember this website?
http://quizlet.com/1644286/homeostasisterms-flash-cards/
• this is a set of Homeostasis flashcards
How is urine formed?
Urine Formation
(Image on previous slide from: http://www.mountainside-medical.com/products/Urine-Specimen-Cup,-Sterile.html)
• filtration
• reabsorption
• secretion
Filtration
• glomerulus high pressure: 65mm Hg
• smaller dissolved molecules can move
through the walls of the glomerulus
• 600mL of blood flows through the
kidneys each minute; 120mL is filtered
Reabsorption
• 119mL of every 120mL of glomerular
filtrate is reabsorbed (phew!)
• 3 main substances reabsorbed:
– water (passive)
– all glucose (active)
– Na+ (active)
• also amino acids (active), Cl- and HCO3(charge attraction), etc.
Secretion
• nitrogen-containing wastes (such as
NH3, urea, uric acid), H+ ions, and K+
ions are secreted in the distal tubule
• Simple animation on urine formation
with no narration:
•
http://www.kidneypatientguide.org.uk/site/HKWanim.php
Review
• This interactive animation has a nice feature
where you can track the movement of various
substances:
•
http://www.biologymad.com/resources/kidney.swf
• Narrated animation on urine formation:
•
http://davisplus.fadavis.com/scanlon6e/Animations/animations.cfm?exe
rcise=NephronFiltration&title=Nephron%20Filtration
• Narrated animation of structure & function;
quite detailed:
•
http://bcs.whfreeman.com/thelifewire/content/chp51/51020.html
7.6 - Water Balance
Water Balance
(Image on next slide from: http://knight.noble-hs.sad60.k12.me.us/content/exploringLife/text/chapter32/concept32.2.html)
• water balance (i.e. amount of water in
the blood) is regulated by the
hypothalamus
• osmoreceptors detect changes in
blood solute concentration
• release of ADH (anti-diuretic hormone)
increases water reabsorption
Blood Pressure Regulation
• blood pressure receptors in the
juxtaglomerular apparatus release
renin, which activates angiotensinogen
• angiotensin causes the adrenal glands
to release aldosterone
• aldosterone is a hormone that acts on
nephrons to increase Na+ reabsorption
in the distal tubule and collecting duct
(Image from: http://www.colorado.edu/intphys/Class/IPHY3430-200/017kidneys.htm)
pH balance
• cellular respiration produces CO2 as a
waste product
• CO2 dissolved in the blood becomes
H2CO3 (carbonic acid)
• carbonic acid dissociates into H+
(acidic) and HCO3- (basic)
pH balance
pH balance
• peritubular capillaries actively transport
CO2 to the tubules
• generates H+ and HCO3- ions
• HCO3- ions diffuse back into blood
• H+ ions combine with phosphate ions or
ammonia and are removed by the
kidneys
Images in Slides #3,4,5
Excretory system:
• http://faculty.ccri.edu/kamontgomery/anatomy%20lab_13%20uro
genital.htm
Kidney:
• http://www.dorenarode.com/anatomy/openlab.htm
Nephron (colour):
• http://movies-ciarancolegage.blogspot.com/2011/03/kidneydiagram-labeled.html
Nephron (unlabelled):
• http://kenpitts.net/hbio/46skel_musc_integ_systems/ch46_sched
_08.htm