1. Removes cellular wastes from the body
Excretory System
Removes cellular wastes from the body

2. Excretion is: the removal of metabolic wastes
Main Excretory organs involved are:
kidneys
liver
lungs
skin

3. Major metabolic wastes:
carbon dioxide and 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)

4. Liver
Detoxification
changes harmful substances into inactive or less poisonous substances
These inactive substances are returned to blood and are filtered by kidneys.
liver

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

6. Urinary System
Kidneys ureter urinary bladder urethra

7. Kidneys Two main functions:
1. Filters the blood (removes wastes from cellular metabolism)
2. Reabsorbs water
***If kidneys cannot perform these functions a person will die due to toxins building up.

8. 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

9. Nephrons
waste filtering unit of the kidney found in the cortex and the medulla
1.25 million nephrons in each kidney
Contains glomerulus, Bowman’s capsule and a renal tubule

10. Filtration in Nephrons
Blood enters kidney through renal artery,
Small substances and wastes diffuse from the glomerulus capillaries into the Bowman’s capsule collecting cup and into the renal tubule of the pelvis,
Water and some dissolved substances are reabsorbed into the blood through the capillary
Clean blood leaves the kidney through the renal vein

11. So where does the waste go???
Urine- final waste fluid excreted
made up of water, urea and various salts
1-1.5 liters of urine are produced every 24 hours
Ureter- tube connects kidney to urinary bladder; urine travels 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

12. Skin Excretion- Small amounts of urea and salts in sweat
Removal of excess heat
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

13. Lungs
Excretion-
Removes CO2 and water from cellular respiration

14. Excretion Disorders
Renal Failure- kidneys stop filtering the blood and wastes and fluid build up in the body and death can result
Treatment- dialysis- artificial machine filters and cleans the blood (works because of diffusion)
*Presence of protein, sugar, or other needed substances indicates other conditions such as diabetes or cardiovascular disease