1. Organ of osmoregulation and excretion
THE KIDNEY
Organ of osmoregulation and excretion
© 2008 Paul Billiet ODWS

2. The urinary system Aorta Renal vein Kidney Renal artery Vena cava
Ureter
Aorta
Renal vein
Bladder
Renal artery
Vena cava
Urethra
© 2008 Paul Billiet ODWS

3. The Kidney Outer membrane Renal artery Nephrons Renal Vein (2 million)
Pelvis
Cortex
Medulla organised in pyramids
Ureter
Urine
© 2008 Paul Billiet ODWS

4. The blood supply
© 2008 Paul Billiet ODWS

5. The cortex (view x100) Tubule Malpighian or renal corpuscles
© 2008 Paul Billiet ODWS

6. The Malpighian corpuscle (view x400)
Glomerulus – a ball of capillaries
Bowman’s capsule
© 2008 Paul Billiet ODWS

7. Medulla (view x400)
Tubules
Capillaries
© 2008 Paul Billiet ODWS

8. The nephron
In the cortex
In the medulla
© 2008 Paul Billiet ODWS

9. The nephron Bowman’s capsule Branch of renal artery Glomerulus
Branch of renal vein
Branch of renal artery
Proximal convoluted tubule
Capillary
Distil convoluted tubule
Collecting duct
Loop of Henlé
© 2008 Paul Billiet ODWS

10. Filtration in the glomerulus
Blood enters the glomerulus from a branch of the renal artery
This blood is under high pressure
The capillary walls are one cell thick
They are pierced with openings (fenestrations)
The plasma filters though the membrane under pressure
Proteins do not pass
Southern Illinois School of Medicine
© 2008 Paul Billiet ODWS

11. Filtration in the glomerulus
A membrane surrounds each capillary of the glomerulus
The blood plasma is filtered at about 150 litres per day
Southern Illinois School of Medicine
© 2008 Paul Billiet ODWS

12. Filtration in the glomerulus
Southern Illinois School of Medicine
Auer Lab Life Sci Div Lawrence Berkley National Lab
The filtration membrane is held in place by specialised podocytes
© 2008 Paul Billiet ODWS

13. Blood plasma v Filtrate
Component
Plasma
/ mg 100cm-3
Filtrate
Urea
0.03
Glucose
0.10
Amino acids
0.05
Salts
0.72
Proteins
8.00
© 2008 Paul Billiet ODWS

14. The nephron functions Freely permeable to water Impermeable to water
Variable permeability to water
© 2008 Paul Billiet ODWS

15. The nephron osmoregulation
Active reabsorption
Variable permeability to water
Impermeable to water
Freely permeable to water
Na+ Na+ Na+
H2O H2O
Passive osmosis
Ultrafiltration under pressure
80% of water reabsorbed
© 2008 Paul Billiet ODWS

16. The nephron osmoregulation
Variable permeability to water
Impermeable to water
Freely permeable to water
Collecting duct
More and more salty
Loop of Henlé
Na+
H2O
H2O
© 2008 Paul Billiet ODWS

17. The nephron osmoregulation
The blood concentration is monitored by osmoreceptors in the hypothalamus
If the concentration rises the hypothalamus releases ADH
ADH makes the collecting duct walls more permeable
More water is reabsorbed from the filtrate as the ducts pass through the salty tissues of the medulla
© 2008 Paul Billiet ODWS

18. The nephron osmoregulation
The urine released into the pelvis is more or less concentrated depending upon the blood concentration
Excessive sweating and eating salty food will produce concentrated urine
Drinking and cold weather will produce dilute urine
© 2008 Paul Billiet ODWS

19. Kidney reabsorption Component Filtrate / mg 100cm-3 Urine Urea 0.03
2.00
Glucose
0.10
Amino acids
0.05
Salts
0.72
1.50
Proteins
© 2008 Paul Billiet ODWS

20. Reabsorption Microvilli on cuboidal epithelial cells
Dr Millet USC Med schooll
Kidney tubule with brush border
© 2008 Paul Billiet ODWS

21. The proximal tubules reabsorb:
80% of water
All of the glucose
All of the amino acids
Blood pH is regulated
Blood salt levels are regulated
Urea is left behind and even secreted into the tubules
Reabsorbed molecules pass into the surrounding capillaries
© 2008 Paul Billiet ODWS