• Total body water content
• mean arterial pressure (MAP)
• Na+, K+, Cl-
• Body acidity (pH)
• Remove toxins
• synthesis of red blood cells

• Kidneys
• Ureter, urethra
• Bladder

Urine forming organs

(Nephron, Renal blood supply)

• surrounds capillaries.
•  Collecting duct (drains eventually into the ureter)
• Nephron allows us to make a concentrated urine or a dilute urine
• blood in capillaries (glomerular capillaries) never enters the nephrons
• instead we form filtrate: watery "extract" from the blood.

Filtrate

(in nephron)

water "extract" from the blood (glomenular capillaries)

contains:

• H₂O
• ions
• toxins
• glucose
• no cells or large proteins

is actually reabsorbed back into the body.

if all the filtrate were eliminated as urine....dehydrate

Absorption across the nephron

PROXIMAL Convoluted tubule

automatically reabsorbs..

1) ~66% of the filtered NaCl

2)~60% of H₂O

3) absorb 100% of the filter glucose

• H₂O absorption in decending limp via osmosis
• NaCl absorption in ascending limb via active transport

moves thru a gradient of osmolarity

top

=300 mOsm---> bottom:1200mOsm

• filtrate moveds thry the descending limb H₂O leaves the nephron via osmosis (~ 85% of H₂O)

• pumps enzymes
• absolutely NO H₂O absorption
• pumps remove Na⁺ (and Cl^_) fromthe filtrate
• Peritubular capillaries absorb the H₂O and some of NaCl thats removed from the filtrate
• relatively impermeable to H₂O
• active transport of Na+ (and eventually Cl- follows)=use ATP
• Contributes to osmotic gradient

178.5 L of filtrate was absorbed....

Dilute - Hypo-osmotic (hypo-tonic)