Excretory/Urinary System

Overview of Excretory System• The excretory system is responsible for maintaining body

homeostasis by controlling fluid balances, and removal of waste products.

• 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 System1. 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 Organs

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 Homeostasis

• 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 Filtration• Pressure of heart contractions

filters blood by forcing water, ions and solutes from glomular capillaries into Bowman's capsule

• 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 Reabsorption

• 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 osmosis3o 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 Secretion

• 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.

References1. 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.