The Excretory System

The Excretory System
Waste Products of Metabolism
Protein
Amimo Acids
Ammonia
Ammonia
(Fish)
Uric Acid
(Insects, Reptiles, Birds)
Urea
(Mammals)
Renal
vein
Vena cava
The Urinary System
And
Excretion
Aorta
Renal Cortex
renal
Medulla
Peritubular Capillary
Distil Tubule
Proximal Tubule
-------
----
Renal Artery
----
Cortex
------------------Medulla
Collecting Duct
Nephron Capsule
Nephron Loop
Gradient of Increasing Sodium Concentration
Glomerulus
----
----
------------------Medulla
Gradient of Increasing Sodium Concentration
-------
Cortex
14
13
------11
----
----
Cortex
------------------Medulla
15
Gradient of Increasing Sodium Concentration
12
Peritubular capillary
1. Glomerular
filtration
2. Tubular
reabsorption
3. Tubular
secretion
Proximal Tubule
1. 70% Na+ actively reabsorbed
2. 70% Cl- passively follows Na+
3. H2O passively follows NaCl
4. Glucose is 100% actively
reabsorbed
Peritubular
Capillary
Distil
Tubule
--------Renal
Artery
----
300 mOsm
300mOsm
----
--------------------Medulla
Cortex
300
Nephron
Capsule
500
400mOsm
600mOsm
Collecting
Duct
Nephron Loop
700
800mOsm
900
1000mOsm
1200
1200mOsm
Urine
Gradient of Increasing Sodium Concentration
Glomerulus
Water Balance
Input = Output
Water Balance in K-Rats
• Output
• Input
– Drinking
– Food
– Metabolic Water
(C6H12O6 + 6O6
6CO2 + 6H2O + E)
– Urine
– Feces
– Evaporation
• Via skin
• Via respiration
Water Balance in Kangaroo Rats
Table of Water Balance (149)
• Output (ml)
• Input (in milliliters)
– Drinking
– Metabolic water
– Food
0
54
6**
– Urine
– Feces
– Evaporation
13.5
2.6
43.9*
– Total
60
– Total
60
**At 20% relative humidity
100g of barley contains
6ml of water
*Respiration is responsible
for significant evaporative
water loss
Water Balance in Kangaroo Rats
The Three Process In
Urine Formation
1. Glomerular filtration
•
Small substances are
forced by blood pressure
through the glomerulus
into the nephron capsule
2. Tubular Reabsorption
Glomerulus
•
Water, salt, and glucose
are reabsorbed into the
blood stream. Most of
the reabsorption takes
place in the proximal
tubule
3. Tubular Secretion
•
Substances are secreted
from the bloodstream
into the distil tubule