Transcript The Excretory System

The Excretory
System
Purpose
Contributes to homeostasis
 Regulates internal environment by
eliminating metabolic waste products:

 Volume
 Electrolyte
 pH
composition
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 Organs
Kidneys
 Lungs
 Skin

1. Kidneys
Main organs of excretion.
 Remove excess water, urea & other
excess mineral wastes from the body.

 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.
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.

3. Skin

Excretes excess
water, salts, and
small amounts of
urea through
sweating.
The Urinary System

Made up of:
 Left
and right kidneys
 Ureters
 Bladder
 Urethra


Removes wastes and toxins from the blood and
produces urine.
Urine: made of water, excess salts, & urea
Kidney Structure




Bean shaped
Either side of the spinal
column, near lower back
Size of your fist
Each are attached to a
renal artery & a renal
vein
10
10
Renal Vessels

Renal artery – blood from aorta
 unfiltered

and full of bodily wastes
Renal vein – filtered blood
http://www.yoursurgery.com/ProcedureDetails.cfm?BR=1&Proc=69
Ureters and Bladder



Ureter leaves each kidney with fluid containing
excess water, salts, urea & other waste products
Ureters lead to the bladder; liquid wastes are
deposited/stored here
Expulsion of wastes controlled by specific
sphincter muscles – voluntary control.
http://www.etsy.com/listing/70476539/kidneys-crochet-plush-with-uretersand
http://www.emedicinehealth.com/prolapsed_bladder/page17_em.htm
Kidney Regions

2 distinct regions:
1.
2.
Inner Part: Renal Medulla
Outer Part: Renal Cortex
Nephrons
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.agefotostock.com/age/ingles/enam01b.asp?foto=13173541&key1=&foto_clave=BSI-3555309&famp=1
FYI
The kidneys receive approximately 10% of
the blood that is pumped out of our heart
every minute.
 Adult kidneys filter approx. 180L of blood
daily.

Filtration-Reabsorption-Secretion-Excretion
1. Filtration - Bowman’s Capsule (BC)

-Hollow bulb surrounding ball of capillaries
(Glomerulus)
http://www.pitt.edu/~anat/Abdomen/Kidneys/Kidneys.htm
http://www.as.miami.edu/chemistry/2086/chap26/chapter%2026-new_part1.htm
Filtration (cont’d)
Blood enters via renal artery
 Blood filters through
permeable walls under
pressure
 Filtered materials (urea,
glucose, salts, & some
vitamins) are called
filtrates.

http://physrev.physiology.org/content/88/2/451
Filtration (cont’d)
Platelets, red and white blood cells remain in
the blood (too large to pass)
 Adult kidneys filter approx. 180L of blood
daily.

Filtration-Reabsorption-Secretion-Excretion
2. Re-Absorption - Tubules

Some filtrates reabsorbed by active
transport
 valuable

& can’t be lost
Water returns to blood through osmosis
 99%
of the water that is filtered out of BC is
reabsorbed into your blood
Filtration-Reabsorption-Secretion-Excretion
3. Secretion - Tubules

Excess fluid leaves BC & enters tubules
 URINE.

First part – Proximal Convoluted Tubule
(PCT).
 carries
(LH).
fluid down into the Loop of Henle
3. Secretion - Tubules

Urine concentrated in the tubule at the LH.
 i.e.water

reabsorbed
Urine moves up Distal Convoluted Tubule
(DCT) & meets ureter
Filtration-Reabsorption-Secretion-Excretion
4. Excretion
Purified blood returns to the body through
the renal vein, which runs to the Inferior
Vena Cava
 Urine moves from the nephrons to ureters
and goes to the bladder for storage
 Once urine is ready to leave the body, the
urine will be expelled through the urethra.

 Stretch
receptors in bladder
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
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)