Excretory System
by Drew Buzzell, Eirik Somerville,
Alex Pernokas, Oliver Saffery, and
Sam Morrow
Overview of Excretory System3
• The excretory system is responsible for maintaining body
homeostasis by controlling fluid balances, and removal of waste
products.3
• When cells break down proteins they create nitrogenous waste
called Urea; the excretory system removes this waste and other
wastes created as a byproduct of digestion.
Urinary System
1. After the blood gets pumped to the kidney, water and other solutes are filtered
through the nephrons.
2. Then the filtered waste and excess water reconvenes as Urine in the Ureter.
3. After traveling through the Ureter it is stored in the Bladder.
4. When the Bladder is full it is then expelled by the Urethra.
3.NIDDK scientists and outside experts, . "Your Urinary System and How it Works." Kidney and Urologic Diseases A to Z(2007): 1-4. Web. 14 Nov 2010.
<http://kidney.niddk.nih.gov/kudiseases/pubs/yoururinary/>.
Major Organs Involved
Purpose of Major Organs3
Kidney - Filters water and all solutes except proteins from
blood; reclaims water and solutes as the body requires.
Excretes the remainder, as urine.
Ureter - Channel for urine to flow from kidney to urinary
bladder.
Urinary Bladder - Stretchable container for temporarily storing
urine.
Urethra - Channel for urine to flow from the urinary bladder to
the body surface.
3. Starr, Cecie. Biology: the unity and diversity of life. 11th ed. Australia: Thomson Brooks/Cole, 2006. Print.
Relation to Homeostasis2
• The kidney removes water, vitamins, and minerals when
they are in excess within the bloodstream, but reclaims them
when they are too scarce. In this sense, the kidney is a
major organ for homeostasis because it maintains an
equilibrium.
2. "The Kidneys." RCN D.C. Metro | High-Speed Internet, Digital Cable TV & Phone Service Provider. N.p., n.d. Web. 9 Nov. 2010.
<http://users.rcn.com/jkimball.ma.ultranet/ BiologyPages/K/Kidney.html#TubularSecretion>.
Purpose of Nephron
• Millions of nephrons located inside of each kidneys
• Responsible for filtration and purification of blood
• Creates urine
Parts of a Nephron
Nephron Overview Video
Glomular Filtration3
• Pressure of heart contractions
filters blood by forcing water,
ions and solutes from glomular
capillaries into Bowman's
capsule3
• Leaves behind blood cells and
proteins
• First step in urine formation
• Osmosis and active filtration
• Substances that passes through
become filtrate
3. Starr, Cecie. Biology: the unity and diversity of life. 11th ed. Australia: Thomson Brooks/Cole, 2006. Print.
Tubular Reabsorption3
• Variety of substances (water, ions, and selected solutes)
leak out of the nephron, diffuse through interstitial fluid, and
then enter a peritubular capillary3
• Occurs along a nephron's tubular parts
• Returns most of filtrate back to blood
• Water is transported via osmosis3
o High to low concentration
• Passive and active transportation (tubule → capillary)
3. Starr, Cecie. Biology: the unity and diversity of life. 11th ed. Australia: Thomson Brooks/Cole, 2006. Print.
Tubular Secretion3
• Transporters move urea, H+, and K+, (wastes) from the
capillaries into the nephron for excretion1
• Continues along nephron's tubular parts
• Active transportation (capillary → tubule)
3. Starr, Cecie. Biology: the unity and diversity of life. 11th ed. Australia: Thomson Brooks/Cole, 2006. Print.
References
1. NIDDK scientists and outside experts. "Your Urinary System and How
it Works." Kidney and Urologic Diseases A to Z(2007): 1-4. Web. 14 Nov
2010. <http://kidney.niddk.nih.gov/kudiseases/pubs/yoururinary/>.
2. "The Kidneys." RCN D.C. Metro | High-Speed Internet, Digital Cable
TV & Phone Service Provider. N.p., n.d. Web. 9 Nov. 2010.
<http://users.rcn.com/jkimball.ma.ultranet/
BiologyPages/K/Kidney.html#TubularSecretion>.
3. Starr, Cecie. Biology: the unity and diversity of life. 11th ed. Australia:
Thomson Brooks/Cole, 2006. Print.