1. The Human Excretory System
The function of the excretory system is the excrete (get rid of) wastes that are not helpful to the body.

2. EXCRETION

3. Excretion is: removal of metabolic wastes removal of excess heat
Main Excretory organs involved are:
kidneys
liver
lungs
skin

4. A Note About Metabolism
This is the series of activities that cells do in order to keep the organism alive.
Cellular activities usually involve chemical reactions that produce products necessary for life and bi-products (wastes) that are often toxic to cells.
Example: Cellular Respiration produces ATP energy for the cells but it also produces Carbon Dioxide, which is very harmful to the cells.

5. Cellular Waste
Wastes that are removed include carbon dioxide, water, salt, urea and uric acid.
All excreted wastes travel at some time in the blood.

6. Major Metabolic wastes:
carbon dioxide, water
CO2 and H2O are from cellular respiration
certain nitrogen compounds
Breakdown of amino acids from proteins produces nitrogen compounds
Urea
Ammonia
Uric acid
Mineral salts from metabolism
Sodium chloride (NaCl)
Potassium sulfate K2SO4

7. Structures of the Excretory System
Skin
Lungs
Liver
Urinary System
Large Intestine
Can you guess how these structures are a part of the excretory system? What makes the Large Intestine different from the rest?

8. Large Intestine
The large intestine removes solid, undigested food from the body after it passes through the digestive system.
Waste is stored in rectum until it is excreted from the body as solid waste. NOTE: This is NOT waste produced by the cells (cellular waste) as a part of your metabolism!!!!!

9. Skin
Wastes such as excess water, salt, urea and uric acid are removed from the body in sweat.

10. Skin Small amounts of urea and salts in sweat
2. Excretion-
Small amounts of urea and salts in sweat
Removal of excess heat (Major Function)
Blood vessels dilate bringing more warm blood to skin surface
Sweat is produced by sweat glands
Sweat absorbs body heat and evaporates to water vapor and body heat leaves the body in the water vapor
Body cools as a result of the evaporation

12. Lungs
Excess carbon dioxide waste is removed from the body when we exhale.
CO2

13. Liver
The liver is a part of what other system? The digestive system
Liver

14. The liver has many functions, including (but not limited to):
to produce substances that break down fats
produce urea (the main substance of urine)
make certain amino acids (the building blocks of proteins)
filter harmful substances from the blood (such as alcohol)
The liver is also responsible for producing cholesterol. It produces about 80% of the cholesterol in your body.

15. The Liver and Waste Liver
The liver produces urea and uric acid as a by-product of the breakdown of proteins
Urea and uric acid are sent to the kidneys to be processed
Liver

16. Formation of Urea in Liver:
Amino acids are broken down.
amino group, NH2→ changed to ammonia, NH3 → changed to urea (less poisonous)
Finally: Urea diffuses back into bloodstream and is filtered out by the kidneys.

17. Human Excretion Liver’s role Detoxification-
changes harmful substances into inactive or less poisonous substances
These inactive substances are returned to blood and are filtered by kidneys.

18. The urinary system
The kidneys filter the blood to form urine, which is excess water, salt, urea and uric acid

19. Urinary System Kidneys 2 main functions
Kidneys-> ureter-> urinary bladder-> urethra
Kidneys
2 main functions
1. Remove wastes from cellular metabolism
2. Regulate the concentrations of substances found in the body fluids
*****If kidneys cannot perform these functions a person will die.*****

21. Kidney structure 3 layers of the kidney
Cortex- outer layer blood is filtered to remove waste and excess substances
Medulla- middle layer made up of tubes called collecting ducts that carry the filtered substances (filtrate) to the innermost layer of the kidney
Pelvis- cavity that collects the filtrate and connects the kidney to the ureter which exits the kidney

23. Nephron
Nephron- waste filtering unit of the kidney found in the cortex and the medulla
1.25 million nephrons in each kidney

24. Filtration in Nephron Blood enters kidney through renal artery,
Small substances (water, salts and minerals) and wastes (urea) diffuse from the capillaries into the nephron of the kidneys.
Urea, excess water and excess substances travel to the renal pelvis to form urine.
Water and some dissolved substances are reabsorbed into the blood through the capillaries.
Clean blood leaves the kidney through the renal vein.

25. Urine- final waste fluid excreted
Made up of water, urea and various salts.
1-1.5 liters of urine are produced every 24 hours
Structures Involved in Getting Rid of Urine!
Ureter- tube connects kidney to urinary bladder
Function –conducts urine from kidney to bladder
Urinary Bladder- collects and stores urine for
Excretion
Urethra- during urination urine travels from the bladder to the outside of the body