The Excretory System

Waste Products of Metabolism

Protein

Amimo Acids

Ammonia

Ammonia Uric Acid Urea(Fish) (Insects, Reptiles, Birds) (Mammals)

The Urinary SystemAnd

Excretion

Vena cava

Aorta

Renal vein

renal

Renal Cortex

Medulla

Peritubular Capillary

Proximal Tubule

Distil Tubule

Nephron Loop

Collecting Duct

Gradient of Increasing S

odium C

oncentration

------- ---- ---- -------------------Cortex

Medulla

Renal Artery

Glomerulus

Nephron Capsule

Gradient of Increasing S

odium C

oncentration

------- ---- ---- -------------------Cortex

Medulla

13

14

15

Gradient of Increasing S

odium C

oncentration

------- ---- ---- -------------------Cortex

Medulla

11

12

1. Glomerularfiltration

2. Tubularreabsorption

3. Tubular secretion

Peritubular capillary

RenalArtery

Glomerulus

NephronCapsule

PeritubularCapillary

Proximal Tubule1. 70% Na+ actively reabsorbed2. 70% Cl- passively follows Na+

3. H2O passively follows NaCl4. Glucose is 100% actively

reabsorbedDistilTubule

CollectingDuct

Nephron Loop

--------- ---- ---- ---------------------Cortex

Medulla

Gradient of Increasing S

odium C

oncentration

300 mOsm 300mOsm

1200 1200mOsm

Urine

600mOsm

400mOsm300

500

700 800mOsm

900 1000mOsm

Water Balance

Input = Output

Water Balance in K-Rats

• Input– Drinking– Food– Metabolic Water

(C6H12O6 + 6O6 6CO2 + 6H2O + E)

• Output– Urine– Feces– Evaporation

• Via skin• Via respiration

Water Balance in Kangaroo Rats

Table of Water Balance (149)

• Input (in milliliters)– Drinking 0– Metabolic water 54– Food 6**

– Total 60

**At 20% relative humidity 100g of barley contains 6ml of water

• Output (ml)– Urine 13.5– Feces 2.6– Evaporation 43.9*

– Total 60

*Respiration is responsible for significant evaporative water loss

Water Balance in Kangaroo Rats

The Three Process InUrine Formation

1. Glomerular filtration• Small substances are

forced by blood pressurethrough the glomerulusinto the nephron capsule

2. Tubular Reabsorption• Water, salt, and glucose

are reabsorbed into theblood stream. Most ofthe reabsorption takesplace in the proximaltubule

3. Tubular Secretion• Substances are secreted

from the bloodstreaminto the distil tubule

Glomerulus