The Excretory System

What Does Excretion Mean?

• ExcretionExcretion means getting rid of wastesgetting rid of wastes that could harm or poison the body

• The three main wastes are Carbon Dioxide, undigested food (like fibre) and Urea

How Do We Get Rid Of Wastes?

• The three mains ways are:1. Urination :1. Urination : Urea is made into to urine Urea is made into to urine (http://health.howstuffworks.com/adam-200032.htm )(http://health.howstuffworks.com/adam-200032.htm )

2. Breathing:2. Breathing: Carbon DioxideCarbon Dioxide is breathed out by the is breathed out by the lungslungs3. Defecation 3. Defecation We We egestegest food that we cannot digest through food that we cannot digest through((http://lgfl.skoool.co.uk/content/keystage3/biology/pc/learningsteps/EGSLC/http://lgfl.skoool.co.uk/content/keystage3/biology/pc/learningsteps/EGSLC/

launch.html )launch.html )

Excretory Organs

• The kidneys are responsible for filtering the blood

• The large intestine begins the egestion of waste food

The Kidneys• You have two kidneys, but can survive

with one

• They look like kidney beans

The Kidneys• Each Kidney gets it’s blood from the renal

artery

The Nephron

• The Nephron: there are millions found inside the kidney. They absorb useful water and salts from the blood

• ADH (anti- diuretic hormone) is produced when it is a hot day and you are dehydrated. It makes your urine less watery and more concentrated

The Kidneys

• How they work?• http://www.kidneypatientguide.org.uk/site/HKWanim.php (basic)

• http://www.biologymad.com/resources/kidney.swf (excellent)

Other Excretory Organs

• The lungs breathe out Carbon Dioxide, which can acidify the blood

• Your skin can remove salt and water as sweat

Weird Facts

• Your blood passes through the kidneys 300 times a day.

• The nephrons clean all your blood in 45 minutes. 

• Every day the nephrons send about six cups of urine to the bladder.

• If you eat lots of beetroot your urine will turn beetroot red

Questions

• What are the three main wastes made by the body?• Urea, Carbon Dioxide, undigested food• What are the three main ways wastes are removed from

the body?• Breathing, defecation and urination• Which organ filters the blood?• The kidneys• What is the most important part inside the kidney?• The Nephron• What does the kidney reabsorb into the blood?• Water and glucose