1. **** Goal = homeostasis of blood volume and composition
**** Goal = homeostasis of blood volume and composition

2. Basic Principles of Urine Formation
A. Three main organic wastes ( very concentrated- avoid dehydration)
Urea- 1800mg/ day; from breakdown of amino acids
Creatinine- 150mg/day; from skeletal muscles
Uric Acid- 40mg/ day; from recycling RNA
B. Three Main Processes involved
Filtration- by size in glomerulus w/ water molecules
Reabsorption- of useful items like sugar & water
occurs in proximal convoluted tubule
selective process diffusion or active transport
Secretion- of remaining cmpds. like drugs occurs in distal convuluted tubule
Any disruption of this very delicate process can cause death within a few days if not treated!

4. C. Filtration in Glomerulus
1. openings too small for blood cells, but large enough for solutes, nutrients and ions.
2. works mainly due to conc. gradients and pressure.
3. afferent arteriole = into glomerulus; hi pressure
efferent arteriole = out of glomerulus; low pressure
4. each kidney has 6m2 of filtration surface area!
5. 125ml. of filtrate produce each min! 180L a day, but 99%of that is reabsorbed.
6. *** Tubular Reabsorbtion is VERY IMPORTANT!
7. Blood pressure has a huge effect on filtration and kidney function.

5. Watch the video linked below
What happens in the nephron?

6. 8. Control of Filtration.
Autoregulation (dilation/constriction) of blood vessesls.
Hormonalrenin ( vasoconstriction ) and adrenaline (heart rate goes up)
Autonomicsympathetic; blood flow is decreased to kidneys during exercise.
Ex. Marathon runners / distance swimmers can have wastes build up in blood
(proteinuria) or blood in urine (hematuria).
9. *Kidney Failure can’t maintain homeostasis.
a. Effects ALL systems of the body.
b. Symptoms; sleeplessness, seizures, delirium.
c. Acute renal failure due to drug overdose.
d. Chronic renal failure deteriorates gradually; problems occur overtime

8. D. Reabsorption & Secretion by...
1. facilitated diffusion, osmosis, diffusion, active transport, cotransport.
2. Reabsorbed  glucose, amino acids, proteins, viatmins, Na+, Cl-, K+, Ca+2, Mg+2, phosphate, sulfate, bicarbonate (“GOOD GUYS”)
3. Secreted  excess K+, H+, Ca+2, vitamins and, creatnine, ammonia, dopamine, histamines, drugs. water, bilirubin, and urea ( “BAD GUYS”)
4. Glycosuria = glucose in urine, occurs after a hi carb. meal, symptom of diabetes
5. Aminoaciduria = too high protein, occurs after hi protein meal
6. Proximal Convoluted Tubule
where 60 – 70 % of vol. of filtrate is reabsorbed
108 L of water reabsorbed a day!!
Coordinated by hormones

10. 7. Loop of Henle & Counter Current Exchange
a. ions in ascending & descending limbs are under diff. conc.  causes it to be filtered more efficiently
b. ascending limb removes Na+ & Cl- from filtrate
c. descending limb removes water OUT of filtrate by osmosis
d. Urea solute is now very concentrated

11. Watch the Hyperlinked video below
Urinary tract infections

12. 8. Distal Convoluted Tubule
a. more Na+/Cl- reabsorbed b. Reabsorption of WATER occurs ONLY in the presence of ADH (antidiruretic hormone) c. Secretion of any remaining dangerous cmpds. d. K+ Secretion (traded for Na+) is controlled by hormone Aldosterone e. H+ Secretion  acidifies the urine while increasing the pH of blood *** Kidneys help maintain the healthy pH of blood! 9. The Collecting System  receives Urine a. ion conc. is ultimately controlled by ADH & Aldosterone b. any last minute reabsorption occurs here

13. Summary of Renal Physiology
Step 1 = filtrate enters Glomulerus w/ lots of solutes
Step 2 = PCT removes ions / solutes which pulls water out of fluid; decrease the vol. of filtrate
Step 3 = more water moves out in PCT & descending limb of Loop of Henle
Step 4 = Na+/ Cl- pumped out in ascending limb; Urea is now the main ingredient
Step 5 = with Aldosterone’s help, DCT and collecting tube reabsorbs Na+/Cl- as needed
Step 6 = Final adjustments are made to water amts. with ADH’s help
Step 7 = Urea continues to be concentrated on “its way out”