The human excretory system removes waste from the body through four main organs. The lungs exhale carbon dioxide, while the skin sweats out water, salts, and urea. The liver converts nitrogenous wastes to urea and excretes bile, and the kidneys filter wastes like urea, salts, and water from the blood to produce urine for excretion. Together, these organs maintain homeostasis by removing harmful cellular wastes that could otherwise build up to toxic levels.

1. Human Excretory SystemHuman Excretory System
Name: ___________________Name: ___________________
Date: __________________Date: __________________

2. Excretory SystemExcretory System
Excretion – removes cellular waste
The process that collects & removes
harmful or useless substances that
form in the body or are taken into the
body from the blood, tissues, and cells.

3. Excretory SystemExcretory System
Although the urinary system has a major role in
excretion, other organs contribute to the excretory
function.

4. Four Organs of the Excretory SystemFour Organs of the Excretory System
•The lungs in the respiratory system excrete some
waste products, such as carbon dioxide and water.
•The skin is another excretory organ that rids the
body of wastes through the sweat glands.
•The liver (via the intestines) excretes bile pigments
that result from the destruction of hemoglobin. It
also converts nitrogenous waste from the break
down of proteins into urea.
•The major task of excretion still belongs to the
kidneys, the major organ in the urinary system. If it
fails the other organs cannot take over and
compensate adequately.

5. Cellular WasteCellular Waste
Heat
Water
Salts
CO2
Urea
W/O excretion poisonous wastes build
up in blood, cells, and tissues.
Could lead to serious illness &
eventually DEATH!

6. Liver – Some FunctionsLiver – Some Functions
Functions in ExcretionFunctions in Excretion
– Detoxifies BloodDetoxifies Blood
Filters Bacteria, alcohol, drugs, toxicFilters Bacteria, alcohol, drugs, toxic
substancessubstances
Changes them into inactive or less toxicChanges them into inactive or less toxic
forms.forms.
Excretes Bile
 Contains
 Worn-out RBC
 Bile salts
 Cholesterol

7. Liver Produces UreaLiver Produces UreaFunctions in ExcretionFunctions in Excretion
– FormsForms UreaUrea
Changes toxic wastes (ammonia – from breakChanges toxic wastes (ammonia – from break
down of amino acids) to Urea.down of amino acids) to Urea.
UreaUrea  BloodBlood  KidneysKidneys
Filtered out & excreted in UrinFiltered out & excreted in Urinee

8. Lungs –Main FunctionLungs –Main Function
Alveoli - Exchange O2 & CO2 between air and
blood (through process of diffusion)
Lungs excrete CO2 when you EXHALE

9. SkinSkin
Sweat GlandsSweat Glands
– Help cool body: Heat escapes throughHelp cool body: Heat escapes through
millions of pores in skin surfacemillions of pores in skin surface
– Excrete perspiration (evap. cooling)Excrete perspiration (evap. cooling)
99% H99% H22OO
Mineral SaltsMineral Salts
UreaUrea

10. Kidneys & Urinary SystemKidneys & Urinary System
Urinary System –Urinary System – excretes waste andexcretes waste and
maintains homeostasismaintains homeostasis of body fluidsof body fluids..
– KidneysKidneys (main organ of the system)(main organ of the system)
– UretersUreters
– BladderBladder
– UrethraUrethra

11. Kidneys & Urinary SystemKidneys & Urinary System
KidneysKidneys
– TwoTwo
– Fist sizedFist sized
– Bean shapedBean shaped

12. Kidneys-Kidneys- Functional Units & ProductFunctional Units & Product
NephronNephron (about one million per kidney)(about one million per kidney)
– Microscopic units thatMicroscopic units that filterfilter blood of wastes.blood of wastes.
– HH22O and waste taken from blood into nephronO and waste taken from blood into nephron
Form URINEForm URINE
 Glomerulus (clump of capillaries)
 At end of each nephron
 Network of coiled tubes – diffusion of wastes -
while useful substances & water are reabsorbed
 Urine
 Pale yellow solution
 Urea, H20, salts, other trace solutions (toxins…)

13. Urinary System - continuedUrinary System - continued
UretersUreters
– Narrow muscular tubesNarrow muscular tubes
– Connect KidneyConnect Kidney  BladderBladder
 Bladder
 Muscular sac
 Stores Urine
 Expand to fill
 Muscle relaxes
 Urine squeezed into Urethra

14. Urinary System - endpointUrinary System - endpoint
UrethraUrethra
– Tube leading from BladderTube leading from Bladder  outside of bodyoutside of body

15. Failures of HomeostasisFailures of Homeostasis
Bladder & Kidney InfectionsBladder & Kidney Infections caused bycaused by
bacteria from colon/rectum entering urethra.bacteria from colon/rectum entering urethra.
Kidney StonesKidney Stones - crystallization of mineral salts- crystallization of mineral salts
& uric acid that block passage of urine& uric acid that block passage of urine
Kidney DiseaseKidney Disease - caused by long term- caused by long term
diabetes, infections, & chemical poisoningdiabetes, infections, & chemical poisoning
GoutGout – form of arthritis where excess– form of arthritis where excess
production of uric acid leads to deposits ofproduction of uric acid leads to deposits of
crystals in joints (esp. toes)crystals in joints (esp. toes)