Transcript 4.6 Kidneys - Dr Rob's A

4.6 Control Systems
Co-ordination and Regulation of Processes
Homeostasis

What is homeostasis?

Mechanisms by which a constant internal
environment is maintained.
The urinary
system
Aorta
Renal vein
Kidney
Renal artery
Vena cava
Ureter
Bladder
Urethra
© 2008 Paul Billiet ODWS
Deamination in Liver produces Urea…
Kidney – structure and function
Biological principles in action
4
Human kidney
ureter renal artery
renal vein attached here
5
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
The blood supply
The cortex (view x100)
Tubule
(Malpighian) renal corpuscles
The corpuscle (view x400)
Glomerulus
– a ball of
capillaries
Bowman’s capsule
Medulla (view x400)
Tubules
Capillaries
The nephron
In the cortex
In the medulla
The nephron
Branch of renal
artery
Branch of renal
vein
Distal (2nd)
convoluted tubule
Bowman’s capsule
Glomerulus
proximal (1st)
convoluted tubule
Capillary
Collecting duct
Loop of Henlé
1.
Glomerulus brings a large
surface area of blood
capillaries in close contact with
Bowman’s capsule
2.
Liquid filtered from blood under
pressure (filtration)
3.
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
Filtration
Glomerular
filtrate
Blood travels
through
narrow
capillary
towards rena
vein
The blood plasma is filtered at
about 150 litres per day
Blood plasma v Filtrate
Component
Plasma
/ mg 100cm-3
Filtrate
/ mg 100cm-3
Urea
0.03
0.03
Glucose
0.10
0.10
Amino acids
0.05
0.05
Salts
0.72
0.72
Proteins
8.00
0
The nephron functions
Freely permeable
to water
Impermeable Variable permeability to
to water
water
The nephron osmoregulation
Active reabsorption
Na+ Na+ Na+
H2O H2O
Passive
osmosis
Ultrafiltration
under pressure
80% of water
reabsorbed
Freely permeable
to water
Impermeable Variable permeability to
to water
water
The nephron osmoregulation
H2O
Na+
Na+
Na
+
H2O
Freely permeable
to water
H2O
H2O
H2O
H2O
H2O
H2O
Impermeable Variable permeability to
to water
water
More and more salty
Collecting duct
Loop
of
Henlé
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

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

Kidney reabsorption
Component
Filtrate
/ mg 100cm-3
Urine
/ mg 100cm-3
Urea
0.03
2.00
Glucose
0.10
0
Amino acids
0.05
0
Salts
0.72
1.50
0
0
Proteins
© 2008 Paul Billiet ODWS
Reabsorption
Microvilli on cuboidal epithelial cells
Kidney tubule with brush border
Dr Millet USC Med schooll
© 2008 Paul Billiet ODWS
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


Summary of kidney function
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
How does it work?

Control of Water animation