1. Co-ordination and Regulation of Processes
4.6 Control Systems
Co-ordination and Regulation of Processes

2. Homeostasis What is homeostasis?
Mechanisms by which a constant internal environment is maintained.

3. 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

4. Kidney – structure and function
Deamination in Liver produces Urea…
Kidney – structure and function
Biological principles in action

5. Human kidney
ureter renal artery renal vein attached here

6. 1 – Filtration by the Kidney
cortex
Supplied with blood from renal artery
Inside it splits into many fine capillaries
Each capillary supplies blood to hundreds of thousands of tiny filtration units called nephrons
Renal artery
Renal vein
Ureter
Medulla

7. The blood supply

8. The cortex (view x100)
Tubule
(Malpighian) renal corpuscles

9. The corpuscle (view x400) Glomerulus – a ball of capillaries
Bowman’s capsule

10. Medulla (view x400)
Tubules
Capillaries

12. The nephron
In the cortex
In the medulla

13. The nephron Bowman’s capsule Branch of renal artery Glomerulus
Branch of renal vein
Branch of renal artery
proximal (1st) convoluted tubule
Capillary
Distal (2nd) convoluted tubule
Collecting duct
Loop of Henlé

14. 2. Liquid filtered from blood under pressure (filtration)
Glomerulus brings a large surface area of blood capillaries in close contact with Bowman’s capsule
2. Liquid filtered from blood under pressure (filtration)
Glomerular filtrate produced containing:
-water
-glucose
-salts
-urea
(Protein molecules and red blood
cells do not pass into tubule as
they are TOO BIG!!!!)
Blood from renal artery enters wide capillary
Blood travels through narrow capillary towards renal vein
Filtration
Glomerular filtrate
The blood plasma is filtered at about 150 litres per day

15. 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

16. The nephron functions Freely permeable to water Impermeable to water
Variable permeability to water

17. 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

18. 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

19. 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

20. 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

21. 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

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

23. The afferent 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

24. Summary of kidney function

25. Controlling Water Concentration
Blood
-important part of internal environment
-constantly changing water concentration
-e.g. exercising
drinking lots of water
The body uses negative feedback control to regulate water content of the blood

26. How does it work?

27. Control of Water animation