The Excretory System By 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/reabsorbed o Proximal tubule - filtration of water, ions, nutrients, and waste o Loop of Henle - reabsorbs water and nutrients from the urine and helps control concentration of the urine o 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 Phases Filtration - 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 Homeostasis While 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 Transport 1Proximal 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 2Descending 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 3.1Ascending 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) 3.2Ascending 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 4Distal 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 5Collecting 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 Web. 18 Nov )"Urinary System." InnerBody. Web. 18 Nov )Starr, Cecie, and Ralph Taggart. "The Internal Enviornment." Biology: The Unity and Diversity of Life. 6th ed. Belmont, Calif.: Wadsworth Pub., Print.

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