Formation of Urine & Water Balance 7.5, 7.6

First, some review…

What is this?

quizlet.com Remember this website? terms-flash-cards/ this is a set of Homeostasis flashcards

How is urine formed?

Urine Formation (Image on previous slide from: 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 HCO 3 - (charge attraction), etc.

Secretion nitrogen-containing wastes (such as NH 3, urea, uric acid), H + ions, and K + ions are secreted in the distal tubule Simple animation on urine formation with no narration:

Review This interactive animation has a nice feature where you can track the movement of various substances: Narrated animation on urine formation: rcise=NephronFiltration&title=Nephron%20Filtrationhttp://davisplus.fadavis.com/scanlon6e/Animations/animations.cfm?exe rcise=NephronFiltration&title=Nephron%20Filtration Narrated animation of structure & function; quite detailed:

7.6 - Water Balance

Water Balance (Image on next slide from: 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:

pH balance cellular respiration produces CO 2 as a waste product CO 2 dissolved in the blood becomes H 2 CO 3 (carbonic acid) carbonic acid dissociates into H + (acidic) and HCO 3 - (basic)

pH balance

peritubular capillaries actively transport CO 2 to the tubules generates H + and HCO 3 - ions HCO 3 - 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: ogenital.htm Kidney: Nephron (colour): diagram-labeled.html Nephron (unlabelled): _08.htm