Download 1/9/2015 1 The Excretory System Function **Urea

1/9/2015
The Excretory System
Biology 11
Function
y
The excretory system eliminates non-solid
wastes from the body.
y Included are:
1. Lungs (CO2
2.
3.
4.
and water vapor from
respiration)
i ti )
Skin (loses some salt, urea**, and water
through pores/perspiration)
Large Intestine (bile and wastes like
cellulose and fiber)
Renal System (nitrogenous wastes from
metabolism)
**Urea
Amino acids contain the functional group
“amino,” NH2.
y When proteins are broken down, excess
amino acids cannot be stored by the body
and
d are removed
d (d
(deamination)
i i ) by
b the
h
liver.
y The amino group is converted into
ammonia, which is converted into a less
toxic substance, urea, through a series of
enzyme-catalyzed reactions.
y
1
1/9/2015
Urea
y
Kidneys will transport the urea from
blood to urine.
Renal System
aka urinary system or urinary tract
Made up of:
1. Kidneys –
y
y
◦
bean-shaped organs that control concentrations
off substances
bt
in
i the
th body
b d and
d filters
filt
metabolic
t b li
wastes.
Ureters –
1.
◦
two, 25-30 cm, tube-like structures (one for
each kidney) that carry urine from the kidneys
to…
Urinary Tract (continued)
(Urinary) Bladder
3.
◦
◦
Temporary storage site for urine
Can hold anywhere from 300 mL to 400 mL,
person dependent, due to the elastic-like
muscle.
Urethra
4.
◦
tube to carry urine and excrete outside of
body.
2
1/9/2015
1. Kidney - Function
The principal function of the kidney is
to filter blood in order to remove
cellular waste products from the body.
y At any given time, 20 % of blood is in
the kidneys. Humans can function with
one kidney.
y If one ceases to work, the other
increases in size to handle the
workload.
y
y
y
The kidneys help to
maintain homeostasis
by filtering the blood.
The kidneys are fistsized, bean shaped
structures.
– two layers: medulla
and
d cortex
– filtering units called
nephrons
– renal artery and
renal vein
cortex
medulla
renal
artery
renal vein
ureter
(to bladder)
capsule
3
1/9/2015
The kidney can also excrete other waste
products, such as :
y
1) urea a nitrogenous waste produced in the
liver from the breakdown of p
protein. It is the
main component of urine
y
2) uric acid usually produced from
breakdown of DNA or RNA
y
3) creatinine waste product of muscle action.
Kidney Function
y
3 basic functions in maintaining
homeostasis:
1. remove waste from blood
2 help
2.
h l to maintain
i i electrolyte,
l
l
pH,
H
and fluid balances
3. release key hormones
4
1/9/2015
y
y
y
y
Because most of our diet is acidic, the
kidney help produce ammonia which help to
neutralize.
Every 24 hours, about 180 L of blood is
filtered.
filtered
Much of the filtered fluid is reabsorbed while
approx. 1.5 L of urine is produced each day.
Sometimes essential substances are filtered
out of the body; these can be detected in
urine to help diagnose disease or illness.
from body
Nephrons
•
•
•
Nephrons are the
filtering units in the
kidneys.
They clean and
rebalance
b l
the
h bl
blood
d to body
to produce urine.
loop of Henle
There are
approximately 1million nephrons in
each kidney
to body
from other
nephrons
from body
t body
to
b d
to body
loop of Henle
from other
nephrons
5
1/9/2015
Nephron
y
Each nephron is made up of cup-shaped
structure called the Bowman’s capsule.
• This narrows into a
long coiled tubule.
tubule
• In the center of
each capsule is a
mass of capillaries
called the
glomerulus.
Bowman’s capsule
6