The Excretory System

Chapter 30 Section 4

What is excretion and why do we do it?

• Excretion is the removal of chemical waste product from the body

• We excrete this waste to help maintain homeostasis

• How does this help maintain homeostasis?

What organs excrete?

• Skin– Water, salts, small amounts of urea

• Lungs– Carbon dioxide, water vapor

• Liver– urea

• Kidneys– Excess water, urea, and other metabolic wastes

What is urea?

• Urea is a less toxic version of ammonia• Ammonia is created when proteins are broken

down.

Get to know your kidneys!

Kidney and surrounding structures

• A few structures work with your kidney to rid your body of urine.

• Ureters transport urine from kidneys to urinary bladder.

• Urinary bladder stores urine until it is ready to be released.

• Urethra is the tube from the urinary bladder to the outside of your body.

Blood Scrubbers! How do kidneys clean the blood?

• Kidneys remove urea, excess water and minerals, and other metabolic wastes.

• The nephrons, or kidney cells, do most of this work.

• Two major processes: filtration and reabsorption.

Filtration

• Filter coffee: how does it work?

• In kidney filtration, the blood is passed through a filter to remove wastes.

Filtration• Takes place in the glomerulus

part of the nephron (small ball of capillaries) inside the Bowman’s capsule.

• Blood is under pressure, and the fluid leaks out of the capillaries into the Bowman’s capsule.

• This fluid contains water, urea, glucose, salts, amino acids, and vitamins. This is called FILTRATE.

• Blood cells and proteins are too big, so they don’t go through the walls.

• Is all of that stuff waste, though?

Reabsorption

• Dumpster diver: one who goes through garbage to find items that he or she wants.

• How is the kidney like a dumpster diver?

Reabsorption: Kidney dumpster diving!

• 180 L of filtrate passes through nephron tubules daily. Chances are you don’t urinate 180 L per day. So what happens to that fluid filtrate?

• Much of the filtrate is reabsorbed back into the blood.

• Active transport is used to reabsorb salts, vitamins, amino acids, fats, and glucose.

• Osmosis is used to reabsorb water.

Loop of Henle: condensation and reabsorption

• The Loop of Henle is responsible for water conservation and condensing the filtrate. Water and other substances are reabsorbed by the capillary network.

• Urine goes to collecting duct, then ureter

Cellular transport involved?

• Where is ATP needed in this process?– Reabsorption: Good stuff is pulled out of the Loop of

Henle via active transport, leaving the filtrate behind.• Where is osmosis occurring?– Filtration (water into Bowman’s capsule) and

reabsorption (water out of Loop of Henle back into blood supply)

• Passive transport?– Filtration (all materials are pushed out of the blood

from the glomerulus into the Bowman’s capsule.

Kidneys and Homeostasis

• Kidneys respond to blood composition– Excess salt in diet?– Blood too acidic?– Too much glucose?– Not enough water today?

• The composition of your urine can tell your doctor a lot about your health. This is why we often have “pee tests” at the doctor for our regular check-ups.

• What other info can urine tests give?

Kidney Problems

• Kidney Problems

• Kidney Damage

• Kidney Failure

Kidney Stones

• Kidney stones– Crystalized

calcium, magnesium, uric acid salts

– SUPER PAINFUL, especially for guys. Ouch.

– Pulverized with sound waves! Cool!

Kidney Damage

• Injury (don’t get kicked in the kidneys—could cause blood in urine or function problems!)

• High Blood pressure—damages the filter!• Diabetes—causes overuse of the filter!• Eventually, this could cause kidney failure.

Kidney Failure

• This is when the kidneys can no longer help the body maintain blood homeostasis. It is a medical diagnosis.

• People need to have a machine clean the blood. This is called having “kidney dialysis.”

• http://youtu.be/IQKQ4eoKfTg• This is painless, but takes a lot of time. 3-4 hours, 3 times a

week!• Also they have to change their diet to be nice to their kidneys. • Some people get a kidney transplant. Sometimes it works,

sometimes it doesn’t.• Did you know that you can live with only one kidney?

Kidney Cartoon Project

• These are the characters in your cartoon: red blood cell, white blood cell, protein, urea, glucose, salt, and water.

• Your characters must travel through the nephron (through the filtration and reabsorption processes.) The actions in your cartoon must demonstrate that you understand how both processes work.

• Your cartoon may be for a healthy, normal person, a person who ate WAY TOO MUCH SALT, a pregnant lady, or a person with diabetes. Your cartoon must specify which type of person and have the correct actions happening to the characters for whichever type of person you choose.

• Due Thursday Feb 20. Groups of 1 or 2. Poster or A4 paper. Have fun!