4.6 control systems co-ordination and regulation of processes
TRANSCRIPT
4.6 Control SystemsCo-ordination and Regulation of Processes
HomeostasisWhat is homeostasis?
Mechanisms by which a constant internal environment is maintained.
The urinary system
Kidney
Ureter
Aorta
Renal vein
Bladder
Renal arteryVena cava
Urethra
© 2008 Paul Billiet ODWS
4
Kidney – structure and function
Biological principles in action
Deamination in Liver produces Urea…
5
Human kidney
ureter renal artery renal vein attached here
1 – Filtration by the Kidney
Renal artery
Ureter
Renal vein
•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
cortex
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 nephronBowman’s capsule
Glomerulus
proximal (1st) convoluted tubuleCapillary
Loop of Henlé
Collecting duct
Distal (2nd) convoluted tubule
Branch of renal vein
Branch of renal artery
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 asthey are TOO BIG!!!!)
Blood from renal artery enters wide capillary
Blood travels through narrow capillary towards renal veinGlomerul
ar filtrate
Filtration
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
Variable permeability to
water
Impermeable to water
Freely permeable to
water
The nephron osmoregulation
Variable permeability to
water
Impermeable to water
Freely permeable to
water
Na+ Na+ Na+
Active reabsorption
H2O H2O
Passive osmosis
80% of water
reabsorbed
Ultrafiltration under pressure
Variable permeability to
water
Impermeable to water
Freely permeable to
water
The nephron osmoregulationM
ore
an
d m
ore
salty
H2O
H2O
H2O
H2O
H2O
H2O
Colle
ctin
g
du
ct
Loop of
Henlé
H2O
H2O
Na+
Na+
Na+
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 osmoregulationThe 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
Proteins 0 0
© 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 waterAll of the glucoseAll of the amino acidsBlood pH is regulatedBlood salt levels are regulatedUrea is left behind and even secreted
into the tubules Reabsorbed molecules pass into the
surrounding capillaries
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