Download The Excretory System

The Excretory
System
Purpose

Contributes to homeostasis by helping
regulate the volume, electrolyte
composition, pH of internal environment
and by eliminating metabolic waste
products.
Waste Products

Some are metabolic
 E.g.
Water, salts, CO2, and urea
 Urea is a toxic compound that is produced
when amino acids are used for energy
(contain nitrogen).
Three Main Organs of Excretion

1.) Kidneys
These are the main organs of excretion. They are
responsible for removing excess water, urea &
other excess mineral wastes from the body.
 The kidneys act as filters to remove wastes that
are collected and transported by the blood.
 E.g. Surplus in water or electrolyte (salt) in blood =
kidneys excrete in the urine.

Three Main Organs of Excretion

2.)Lungs
Every time we exhale, we get rid of small amounts
of water vapor and CO2.
 CO2 is the waste product of cells that must be
removed from the body so you can take in oxygen.

Three Main Organs of Excretion

3.) Skin:

Excretes excess
water, salts, and
small amounts of
urea through
sweating.
The Urinary System

Made up of the:
 Left
and right kidneys
 Ureters
 Bladder
 Urethra


Removes wastes and toxins from the blood and
produces urine.
Urine: made of water, excess salts, & urea
How is this different from
the excretory system?
Structure of Kidney




2 bean shaped kidneys
Located on either side
of the spinal column,
near the lower back
Each kidney is about the
size of your fist
Each are attached to a
renal artery & a renal
vein
Structure of Kidney
Each are attached to a renal artery & a
renal vein
 Renal artery carries blood from the
heart’s aorta, this blood is unfiltered
and full of wastes collected from the
whole body!!
 The renal vein carries blood that has been
filtered out of the kidney

Structure of Kidney



A ureter leaves each kidney with fluid that
contains excess water, salts, urea & other waste
products
Ureters lead to the bladder, where liquid wastes
are deposited/stored until released as urine from
the body.
Expulsion of wastes from bladder is controlled
by specific sphincter muscles – voluntary
control.
Anatomy of a Kidney

If you cut a kidney in half you will find 2
distinct regions:
1.
2.
Inner Part: Renal Medulla
Outer Part: Renal Cortex
Anatomy of a Kidney

Nephrons
 Found
in the renal
cortex
 Working parts of the
kidney
 Each acts as an
individual unit of
filtration
 About 1 million
nephrons per kidney
http://www.pitt.edu/~anat/Abdomen/Kidneys/Kidneys.htm
http://www.as.miami.edu/chemistry/2086/chap26/chapter%2026-new_part1.htm
Nephrons

A. Filtration
nephron begins with Bowman’s Capsule
(BC)
 BC is a hollow bulb that surrounds a ball of
capillaries known as the glomerulus
 BLOOD ENTERS BC via the renal artery
 Walls of the BC are permeable so blood is
filtered through
 Filtered materials (urea, glucose, salts, &
some vitamins) are called filtrates.
 The
Nephrons

Filtration Cont’d
 Platelets,
red and white
blood cells are too large
to pass, so they remain
in the blood
 Filtration of blood occurs
in the Glomerulus & BC
 Adult kidneys filter
approx. 180L of blood
daily.
Nephrons

Re-Absorption
 Some
filtrates are valuable &
can’t be lost, so the body reabsorbs them.
 Capillaries in the blood reabsorb valuable
materials through active transport.
 Water returns to blood through osmosis, 99%
of the water that is filtered out of BC is
reabsorbed into your blood
 Takes place in the tubules of the nephron
 Excess fluid leaves the BC, enters the tubules
and is called URINE.
Nephrons

Re-absorption Cont’d
 First
part of tubule is the Proximal Convoluted
Tubule (PCT).
 The PCT carries fluid down into the Loop of
Henle (LH).
 Urine is concentrated at the LH.
 The urine then moves up the Distal
Convoluted Tubule where it eventually meets
the ureter
Nephrons

Re-absorption Cont’d
 Purified
blood returns to the body through the
renal vein, which runs to the Inferior Vena
Cava
 The urine then moves from the nephrons to
the ureters and goes to the bladder where it is
stored
 Once urine is ready to leave the body, the
urine will be expelled through the urethra.
Recap:

http://www.as.miami.edu/chemistry/2086/chap26/chapter%2026-new_part1.htm
http://www.ask.com/wiki/Proximal_convoluted_tubule
http://www.colorado.edu/intphys/iphy3410saul/outlines08fall/nephron.gif
http://www.agefotostock.com/age/ingles/enam01b.asp?foto=13173541&key1=&foto_clave=BSI-3555309&famp=1
Kidney Failure
You have two kidneys in the body located
on either side of the spine and extend a
little below the ribs.
 Your kidneys are bean-shaped organs and
is about the size of a fist.
 The kidneys receive approximately 10% of
the blood that is pumped out of our heart
every minute.


Your kidneys are responsible for the
following:
 Regulate
fluids
 Balance chemicals
 Remove wastes
 Secrete hormones
Condition Explanation:
Progressive in nature
 Anemia possible – lack of iron
 Malnutrition (lack of appetite)
 Decrease well-being
 Increased risk for heart disease

Toxins build up in blood
 Weight gain (excess fluids, swollen ankles,
puffiness)
 Fluid imbalances – dizziness – nausea

Treatment Options:

General
 Limit
fluid intake, high carb, low protein, low
potassium diet
 Too much potassium can cause irregular
heartbeat

Haemodialysis
 Most
common method
 Use of a machine (size of dishwasher) –
blood flow through special filter to remove and
filter wastes
 Clean blood returned to body
 Strict schedule – 3 times a week for 3 to 5
hours each time
 Side
effects
Less energy
 Loss of time

 Once
a month blood is tested to see how
effective dialysis is – may not work forever!

Peritoneal Dialysis
 Removes
extra water, wastes, and chemicals
 Cleansing solution passed through catheter
into abdomen
 After a couple of hours the solution is drained
 Does not require a machine
 Strict diet
 More recent advances, more flexibility (done
at home)

Kidney Transplantation
 Receive
a healthy kidney from a living donor
or a recently deceased donor
 When effective recovers quality of health AND
life
 Yields longer life expectancy
 Could be long waiting lists (shortage of
donors)
 Typical Surgery Risks (bleeding, infection,
etc.)
 Anti-rejection medications after surgery – may
weaken immune system
 Risk of rejection (body doesn’t accept kidney)