+ Excretory System 38-3

+ By the end of this lesson on excretion you should be able to: 1) Describe the organs that make up the excretory system 2) Explain how the kidneys work to maintain homeostasis in your body 3) Explain how the lungs and the skin participate in excretion

+ Excretion: Removes the wastes produced by our cells like excess nitrogenous wastes (urea), salts, and carbon dioxide Urea – a toxic compound produced when amino acids are used for energy that is produced by the liver Major excretion organs are the skin,liver, kidneys, and lungs What waste does each organ release???

The Kidneys The size of a clenched fist Removes urea, excess water and other wastes from the blood in the renal artery Transports wastes to the urinary bladder

+ What does a kidney do? Kidneys filter the blood!!!

Parts of the Kidneys Inner part – renal medulla Outer part – renal cortex Basic functional units – nephrons 1 million per kidney Filters, reabsorbs and secretes Empties wastes into the ureter, leading to the urinary bladder

Filtration Occurs in the capillary network called the glomerulus that is surround by the Bowman ’ s capsule Filters all the blood in the body every 45 minutes Pressure pushes out the filtrate made of water, urea, glucose, salts and amino acids

+ Reabsorption Occurs in the renal tubules Materials are actively transported from the filtrate back into the blood (to stay in the body) leaving the urine - the body ’ s waste product What materials do you think should stay in the body and not leave in the filtrate as waste? Where doe the blood go next?

+ Secretion Occurs in the renal tubules Materials such as H +, K +, ammonia, and drugs are transferred from the blood to the filtrate The filtrate travels into the collecting duct as urine. What does it contain? The urine is stored in the bladder and then released through a tube called the urethra and removed from the body

+ So how do the kidneys help to maintain homeostasis??? Regulate water content of the blood Maintain blood pH Removes wastes from the blood Click here for a review video

+ SELF QUIZ: 1) What other systems work with the excretory system? 2) How is the liver involved in excretion? 3) Complete the worksheets