1. The Good, The Bad and the Wasted
Excretory System
The Good, The Bad and the Wasted

2. Maintaining the internal water balance in the body is important for biological function
OSMOREGULATION is used to keep this balance
OSMOREGULATION:
the process of actively regulating the osmotic pressure of bodily fluids and cells
the pressure that is created by the difference in solute concentrations between two sides of a semi-permeable membrane is called OSMOTIC PRESSURE
Water Regulation

3. Water will move through the membrane to the side that has the highest concentration of solute until the two solutions are isosmotic
Cells must regulate their pH, osmotic and ionic balance thus certain ions and toxins must be eliminated
Since most wastes products are water soluble excretion and osmoregulation are closely tied processes
Water Regulation

4. The excretory system eliminates nonsolid wastes from the body
Nonsolid wastes are eliminated through lungs, skin, and kidneys.
Lungs exhale carbon dioxide and water vapor.
Sweat glands in skin release excess water and salts.
Kidneys filter Nitrogen Waste & clean the blood to produce urine.
The Excretory System

5. Kidneys Kidneys help to maintain homeostasis by filtering the blood
cortex
medulla
Kidneys help to maintain homeostasis by filtering the blood
Kidneys are a pair of bean-shaped organs.
two layers: medulla and cortex
filtering units called nephrons
renal artery and renal vein
renal artery
renal vein
ureter
(to bladder)

6. Kidneys Kidneys have three basic functions in maintaining homeostasis.
remove waste from blood
help to maintain electrolyte, pH, fluid balances
release key hormones

7. Kidneys: Nephrons Nephrons are tiny tubuals in the kidney
Nephrons are the filtering units in the kidneys.
They clean and rebalance the blood to produce urine.
from body
to body
loop of Henle
to body
Kidneys: Nephrons

8. Kidney: Nephrons Nephrons clean the blood in a three-step process.
The First step is Filtration 1
FILTRATION
Water, electrolytes, amino acids, glucose, urea, and other small molecules diffuse out of the blood, creating the filtrate.
Glomerulus
Bowman’s capsule
Kidney: Nephrons

9. Kidneys: Nephron The second step is reabsorption of materials.
The third step is excretion of materials.
REABSORPTION
As the filtrate enters the rest of the tubule ,most of the materials are reabsorbed into the blood. Materials not reabsorbed make up the urine, which flows into the loop of Henle. 2
from body
Collecting duct
to body
loop of Henle
from other nephrons
EXCRETION
In the loop of Henle, water can be reabsorbed one final time to reduce the volume of urine. The remaining urine flows into a collecting duct that leads to the ureter. 3
Kidneys: Nephron