THE
EXCRETORY
SYSTEM
Section 11.3
(pages 374 – 381)
 How does the excretory system
maintain homeostasis?
 The excretory system maintains safe
and fairly unchanging levels of many
substances inside of us by removing
(excreting) extra amounts of things
(referred to as waste) from our body.
Excretion’s Cast of Characters
1. Skin : Removes _______as_____
2. Lungs: Remove _____________
3. Kidneys: Remove waste and extra water
from the blood and produce _______
4. Liver: Changes toxic substances in the
blood into other less toxic substances
Human Urinary System
Human Urinary System
PARTS OF THE URINARY SYSTEM
1. Kidneys: _____ pea shaped
organs located on each side of
our back that filter waste from
the blood to produce urine.
2. Ureters: two tubes that carry
urine from the kidneys to the
___________
3. Bladder: stores urine. (can hold
about ____ liters max)
4. Urethra: tube that carries urine
from________________________.
KUBU
Why are Kidneys Important?
The kidneys play several important roles in the
human body:
1. Filter cellular wastes from our bloodstream
2. Control the water levels in our bodies
3. Regulate pH of the blood
4. Regulate the concentration of ions in blood
5. Secrete a hormone that causes production of
red blood cells. (erythropoietin)
6. Helps with Vitamin D production
7. Help to control blood pressure.
Why are Kidneys Important?
We lose lots of water each day.
1 L from lungs, 100mL in feces,
1.5 L in kidneys, up to 10 L through the
skin.
The kidneys limit water lost when
getting rid of body wastes.
Wastes Filtered Out of the Blood
by the Kidneys
1.Urea – formed in the liver by combining
ammonia (waste from protein use)
with CO2
2. Creatinine – formed by our muscles
3. Uric Acid – a waste product made from
the breakdown of (DNA and
RNA)
Wastes Filtered Out of the Blood
by the Kidneys
4. Hydrogen ions
5. Potassium ions
6. Drugs and medicines
7. Poisons processed in the liver
BLOOD Supply for the Kidneys
 Renal Arteries: carry “dirty” blood
into the kidneys. They branch off of
the aorta.
 Renal Veins: carry “cleaned” blood
away from the kidneys and return it
back into circulation. They connect to
the inferior vena cava.
Human Urinary System
How much of blood in your
body is in your kidneys now?
Or now?
Or now?
Or now?
20% of the total amount
of blood in your body is in
your kidneys being cleaned.
KIDNEYS ( a closer look)
Human Kidneys can be divided into three areas
- Cortex: the outer kidney area
- Medulla: the middle kidney area
-Renal Pelvis: the inner kidney area
where urine piles up
The Human Kidney
The Human Kidney
What kidney part does the filtering?
The nephron.
!!!!!!!!!
Each kidney contains
1 to 1.25 million nephrons. !!!!!!!!!
Lets play a game. It’s
called Draw the
Nephron!!
Each nephron has
5 main parts:
Yes, you draw it now
for practise! Include the i)Bowman’s capsule,
following parts in the
ii)Proximal
tubule,
list to the right.
iii)Loop of Henle,
iv)Distal tubule
v)Collecting duct
How Nephrons make Urine (4 stages)
1. Filtration: (Waste first enters the nephron)
The glomerulus is a bunch of capillaries
connected to the renal arteries and renal
veins.
As blood is pushed through the
glomerulus, small particles and some
liquid in the blood get pushed into
Bowman’s Capsule part of the nephron.
--Nephrons process180 L of filtrate per day
--The material that enters the
Bowman’s Capsule is called
filtrate.
-- The
filtrate contains: water,
urea, uric acid, salt, glucose,
amino acids, ions and vitamins.
Some good stuff and some
waste.
http://www.nephron.com/htkw.html
2. Re-absorption: (Getting the Good Stuff Back):
 Occurs in the Proximal tubule and Distal
tubule, the Loop of Henle and the
Collecting duct.
 Sugars, vitamins, amino acids, water and
ions are taken from the filtrate inside the
nephron and put back into the blood.
 Reabsorption occurs using osmosis,
diffusion and active transport.
Reabsorption (in detail)
Nephron Part
Stuff Reabsorbed into blood
Proximal Tubule
Potassium, nutrients,
NaCl and water
Descending
Loop of Henle
Water (not salt)
Ascending
Loop of Henle
Sodium, Chloride and
Bicarbonate
(not water)
Collecting Duct
Some Urea and Water
 Why don’t salts leave the nephron at
the descending loop of Henle ?
-- The membrane of each cell in this
area is able to block salts from
crossing the cell.
Why doesn't water leave the nephron at
the ascending loop of Henle ?
-- The membrane of each cell in this
area is able to block water from
crossing the cell.
3. Secretion: (Moving all the waste from the
blood and into the nephron)
--Occurs in the distal tubule
--_________ transport moves substances
--Moves :hydrogen ions
:potassium ions
:creatinine
:drugs
:ammonia
:poisons processed in the liver
4. Elimination: (Urine Leaves Kidney)
The yellowy liquid that enters the
collecting duct is called ________.
Urine flows from the collecting duct
through the pelvis and into the ureter,
then on to the bladder and out through
the urethra.
Controlling the Kidneys
1.ADH (anti-diuretic hormone)
-- hormone made by the hypothalamus that
causes water to be taken out of the nephron
and put into the blood
-- Makes Pee have less water in it.
-- The more water we drink the less ADH our
brain makes.
-- Caffeine and Alcohol block ADH release so
we pee more.
-- helps raise blood pressure
Controlling the Kidneys
2. Aldosterone
-- hormone made by the adrenal
glands that causes sodium to
be taken out of the nephron
and put into the blood
-- helps raise blood pressure
Controlling the Kidneys
3. Atrial Natriuretic Protein (ANP)
-- hormone released by the heart's
atrium wall
-- lowers the amount of sodium
taken out of the nephron and
put into the blood
-- helps lower blood pressure.
When Kidneys Fail (Dialysis)
 Kidney dialysis replaces a person’s
kidneys.
 Blood is removed from the body , a
machine removes waste products
from the blood using osmosis and
diffusion and the “clean” blood is
returned to the body.
When Kidneys Fail (Dialysis)
 Dialysis is not a long term solution
because the kidneys work all the time
and tightly control what is in the blood.
Dialysis only works while the person is
hooked up to the machine. When the
person is not hooked up to the
machine their body is slowly being
damaged by the waste in their blood.
Eventually this slow damage is fatal.