The Excretory SystemBy Eve Driver, Allegra Hu, Dylan Kantor, and Jan Nowak

Excretory System → Urinary system → Kidneys → Nephrons → Homeostasis → Cell Transport

Excretory System: Components

● Urinary system (gets rid of cell waste via urine)o Kidneys, Ureters, Urinary bladder, Urethra

● Lungs (carbon dioxide waste)● Liver (toxic substances in the blood)● Skin (sweat)Excretory refers to the word excretion: The process of eliminating or expelling waste matter (1)

Urinary System: Function● After eating, water, nutrients, and other substances →

blood → interstitial (extracellular) fluid → cells● Regulates shifts in extracellular fluid (volume and

composition) ● Removes cell waste/excess by filtering the blood and

excreting the waste via urine

(3)

The Kidneys: Structure● Contains millions of

microscopic nephrons● Bean-shaped organ located

below the rib cage in the middle of the back

(2)

Nephron: Function● To filter water and solutes from the blood and produce

urine eliminating the waste and excess products● To allow adjustments to be made in the amounts of

solute and water to be reclaimed:● Return 99% of solutes and water to the blood

o 1% of unreclaimed solutes/water = urine

(3)

Nephron: Structure● Glomerulus - filters water and solutes from the blood

o Bowman’s capsule - receives water and solutes that are filtered from the blood

o Glomerular capillaries - capillaries that increase the surface area of blood contact (2)

● Tubular system - substances added/reabsorbedo Proximal tubule - filtration of water, ions, nutrients, and wasteo Loop of Henle - reabsorbs water and nutrients from the urine and

helps control concentration of the urineo Distal tubule - regulates sodium, potassium, pH; further dilution

(3)o Collecting duct - collects the urine and final sodium regulation (3)

● Peritubular capillaries - reclaims water and solutes (3)

Nephron’s PhasesFiltration - blood pressure at the glomerulus forces water and solutes from the glomerular capillaries to the proximal tubule to be filtered Reabsorption - peritubular capillaries reabsorb water and nutrients back into the bloodstream to maintain homeostasis of water, ions and nutrients Secretion - accepts solutes and water from peritubular capillaries (bloodstream) and secretes them to the lumen to be eliminated through urine

(3)

Urine and HomeostasisWhile 99% of the water, ions, and nutrients are absorbed back into the the blood, 1% is excreted via urine in order to return the blood to homeostasis (of water, pH, solute concentrations).

For example: when you eat too much salty food, the body must return to its homeostatic sodium level

(2)

Cell Transport1 Proximal tubule -Cells pump (actively transport) some sodium out of the filtrate

-Pumping accompanied by movement of other ions-Ion movements create osmotic gradient → water leaves via osmosis-Nephron wall is highly permeable, so ⅔ of filtrate’s water is reabsorbed here

2 Descending limb of loop of Henle

-Water moves out of filtrate via osmosis, making the fluid saltier and saltier until it matches the interstitial fluid-Saltiest around turn

3.1 Ascending limb of loop of Henle (thin)

-Wall is impermeable to water (and most solutes) here-Permeable only to Na and Cl, which leave via diffusion (passive transport)

3.2 Ascending limb of loop of Henle (thick)

-Wall still impermeable to water-Sodium pumped out (active transport) → interstitial fluid gets saltier → attracts more water from the filtrate at the beginning of the loop

4 Distal tubule -Fluid is further diluted and regulates potassium, sodium, and pH levels within the urine-Water passively transports in the tubule while ions and sodium actively transports in

5 Collecting duct -Urine concentration depends on hormones-More ADH→more water reabsorption→more concentrated urine -More aldosterone→more sodium reabsorption→less concentrated urine -Excess water and urea is excreted out to the urethra via passive transport

(3)

Creative Element/Analogy● Uncooked pasta/water

○ Blood● Boiling

○ Glomerulus● Boiled pasta/water

○ Filtrate● Colander

○ Tubular system● Holes in colander

○ Transport● Drained water

○ Urine● Pasta back in the pot

○ Reclaimed solutes/nutrients

Our Sources

1) Zimmermann, Kim. "Urinary System: Facts, Functions & Diseases." LiveScience. TechMedia Network, 11 Feb. 2013. Web. 18 Nov. 2014. <http://www.livescience.com/27012-urinary-system.html>.

2) "Urinary System." InnerBody. Web. 18 Nov. 2014. <http://www.innerbody.com/image/urinov.html>.

3) Starr, Cecie, and Ralph Taggart. "The Internal Enviornment." Biology: The Unity and Diversity of Life. 6th ed. Belmont, Calif.: Wadsworth Pub., 1992. 750-754. Print.

Thank you!

http://youtu.be/lfGYd1wrTgE?t=1m5s