HS 20 - Weir
The Excretory (Urinary) System
Functions of the Excretory System:
 The cells of our body obtain energy by converting complex organic compounds into
simpler compounds
 Some of these simpler compounds can be ___________________ to the body
 Therefore our body must __________________ these waste products
MAIN FUNCTION: Removes various ________________ from the blood and ___________
those wastes from the body
 Wastes are produced by 2 main processes in the body: digestion and metabolic processes
MAIN PARTS OF EXCRETORY SYSTEM:
 ________________________ (main organ)
 _________________
 _________________
 _________________
 As we know our body breaks down the nutrients we take in
 ________________________  the breakdown of proteins
 A byproduct of deamination is _________________ (NH4)
 Ammonia comes from breaking down proteins and is ______________
 Humans convert ammonia into ____________
 Urea is produced in the liver
 Urea is much less toxic than ammonia and your blood can dissolve it.
 However urea still needs to be expelled from the body
 Another waste product produced in the body is __________________.
 Uric acid is a byproduct of your body’s ____________________.
 This is another waste that needs to be expelled from the body
HS 20 - Weir
So how do we get these wastes out of our blood and eventually out of our body?
 Through the ______________
The Kidneys
 The excretory system _____________ with the kidneys
 Paired, bean-shaped, size of fist
The kidneys have a few functions:
 Removing ______________
 Filtering the _____________
 Maintaining _____________ balance
Remember:
_____________ = relating to the kidneys

A cross section of a kidney shows 3 sections:
 Outer layer of connective tissue = ______________
 Inner layer = _____________
 Hollow chamber = ____________________ (joins kidney with the ureter)
HS 20 - Weir
 All the ___________ in our body passes through the _______________ several times a
day.
 As the kidneys filter blood they will remove any unwanted wastes
 Those wastes will eventually be turned into ____________
 ___________________________ branch from the aorta (in the heart) and carry blood to
the paired kidneys
 Each kidney is supplied with blood from a single renal artery.
 The kidneys remove waste from the body by _____________________ the blood
 However a lot of what the kidneys filtered out ends up being ______________________.
**Note: If the kidneys did not reabsorb materials we would produce 120L of urine every minute.
If this were the case you would have to consume 1 L of fluids every 10 minutes to maintain
homeostasis.
Homeostasis = __________________ (we always want our body to maintain homeostasis)
Nephrons
 Kidneys are made up of slender tubules called ________________
 These are the ____________________ units of the kidneys.
 Nephrons are like small ______________ – each kidney has about 1 million nephrons
 Smaller branches from the renal arteries called afferent arterioles supply the nephrons
with blood.
Nephron Diagram
HS 20 - Weir
Glomerulus (Filtration)
 The afferent arterioles branch into a capillary bed called the ____________________
 The glomerulus is the ______________________ of a nephron
 It is a high pressure capillary bed where the blood is filtered(clusters of capillaries in the
kidney)
 The pressure squeezes some of the fluid out of the blood and into
cup-like sac that surrounds the glomerulus…..
The Bowman’s Capsule
 Bowman’s capsule  __________________ the glomerulus
 This capsule ________________ the wastes that are filtered out of the blood
 The fluid that is filtered from the blood into the bowman’s capsule is now called
__________________ – and eventually forms the urine
 Filtrate is made up of water, urea, smaller ions and molecules.
 Now the filtrate is ready to be processed and reabsorbed so it exits into the
________________ portion of the nephron
 Filtrate enters a thin tubule called the _________________ convoluted tubule
 There are different tubule sections of the nephron – each section performs different types
of ______________________ – where substances are transferred back to the blood
Loop of Henle (Reabsorption)
 From the proximal convoluted tubule the filtrate (urine) is carried to the
_______________________________
 This is where _________ of the reabsorption occurs.
 Some things that are reabsorbed into the blood include:
Glucose, Amino acids, Ions, Minerals, Sodium, Chlorine, Water
HS 20 - Weir
 Dissolved waste materials such as urea are not returned to the blood stream.
 About 160 liters of water per day soak into the tubules of the nephron
 The body cannot afford to lose this much fluid so almost ________ of water filtering
through the nephrons is reabsorbed into the blood
 The remaining _______ together with other wastes is turned into urine.
Collecting Ducts (Secretion)
 Filtrate then moves into the distal convoluted tubule - which regulates levels of minerals
 Filtrate then moves into the ___________________________ –this joins with several
collecting ducts to collect the filtrate (urine) – by this point the urine is mainly made up
of water, urea and other metabolic waste. Now it is _______________ urine.
 The collecting ducts collect urine from many nephrons.
 Urine is a form of waste therefore our body needs to get rid of it.
Ureters
 From the kidneys the urine is transported by 2 thin tubes called
_____________.
 These are approximately 25 – 30cm long in adults
Bladder
 The ureters carry the urine to the bladder – a balloon-like structure
 A sphincter ______________ at the base of the bladder acts as a valve allowing the
________________ of urine.
 This muscle is what allows you to hold in urine until you reach the washroom
HS 20 - Weir
Urethra
 When the bladder is full the urine is then excreted (removed) from the body through the
____________
 In the male the urethra also transports semen.
URINE FORMATION:
Depends on 3 functions: **Before urine is created our waste goes through these 3 steps
1) ________________________  Completed by the movement of fluids from the blood
into the glomerulus and Bowman’s capsule
2) ________________________  Involves the absorption of molecules, ions and water
from the nephron back to the blood (occurs in tubule portion of nephron – mostly the
loop of henle)
3) ________________________  Involves the transfer of materials from the blood to the
collecting duct.
Complete Excretory System Diagram