Excretory System
Honors Biology
Powerpoint #5
Excretory System
Function:
The excretory system eliminates nonsolid wastes from
the body.
• Nonsolid wastes are
eliminated through
lungs, skin, and kidneys.
• Lungs exhale carbon
dioxide and water vapor.
• Sweat glands in skin
release excess water
and salts.
skin
lungs
kidneys
ureters
urethra
urinary bladder
Excretory System
• The ureters are tubes that carry
urine from the pelvis of the kidneys
to the urinary bladder.
skin
lungs
• The urinary bladder temporarily
stores urine until it is released from
the body.
• The urethra is the tube that carries
urine from the urinary bladder to the
outside of the body.
• The outer end of the urethra is
controlled by a circular muscle
called a sphincter.
kidneys
ureters
urethra
urinary bladde
Excretory System
Function of the Kidney
• The principal function of the kidney is to
filter blood in order to remove cellular
waste products from the body.
• At any given time, 20 % of blood is in the
kidneys. Humans can function with one
kidney.
• If one ceases to work, the other increases
in size to handle the workload.
Excretory System
The kidneys help to maintain homeostasis by
cortex
filtering the blood.
The kidneys are fist-sized,
bean shaped structures.
– two layers: medulla and
cortex
– filtering units called
nephrons
– renal artery and renal
vein
medulla
renal
artery
renal vein
ureter
(to bladder)
Excretory System
The kidney can also excrete other waste products,
such as :
• 1) urea a nitrogenous waste produced in the liver
from the breakdown of protein. It is the main
component of urine
• 2) uric acid usually produced from breakdown of
DNA or RNA
• 3) creatinine waste product of muscle action.
Excretory System
Kidneys have three basic functions in
maintaining homeostasis.
–remove waste from blood
–help to maintain electrolyte, pH, and
fluid balances
–release key hormones
Excretory System
Nephrons clean the blood and produce urine.
• Nephrons are the
filtering units in the
kidneys.
• They clean and
rebalance the blood
to produce urine.
to body
• There
approximately 1 loop of Henle
million nephrons in
each kidney
from body
to body
from other
nephrons
Excretory System
• Nephrons clean the blood in a three-step process.
• The first step is filtration of the blood.
• Glomerulus:
Network of
capillaries
Glomerulus
1
FILTRATION
Water, electrolytes,
amino acids,
glucose, urea, and
other small
molecules diffuse
out of the blood,
creating the filtrate.
• Bowman’s
Capsule:
Encases the
glomerulus
Bowman’s capsule
• The body’s entire volume of blood is filtered every 45 min
Excretory System
• The first step is filtration of the blood.
• The second step is reabsorption of materials.
from body
to body
loop of Henle
2
REABSORPTION
As the filtrate enters
the rest of the tubule,
most of the materials
are reabsorbed into
the blood. Materials
collecting not reabsorbed make
duct
up the urine, which
flows into the loop of
Henle.
from other
nephrons
Excretory System
• The first step is filtration of the blood.
• The second step is reabsorption of materials.
• The third step is excretion of materials.
from body
3
collecting
duct
to body
loop of Henle
from other
nephrons
EXCRETION
In the loop of Henle,
water can be
reabsorbed one final
time to reduce the
volume of urine. The
remaining urine flows
into a collecting duct
that leads to the ureter.
Excretory System
Injury and disease can damage kidney functions.
• A kidney transplant can replaced damaged kidney.
– recipient and donor tissue must match
– drugs prevent tissue rejection
The daughter and son in this photo donated a kidney and
liver tissue to their mother.
Excretory System
• Dialysis can be used to filter and clean the blood.
Excretory System
Disorders of the Excretory System
UTI (Urinary Tract Infection)
• Is a very common disorder. If the bladder has
become infected, it is known as cystitis. If the
urethra is infected., it is called urethritis.
• Symptoms include painful urination burning
sensation), frequent urination (even if no urine
present) and bloody or brown urine.
• This can lead to chills, fever, nausea, vomiting and
upper abdomen tenderness.
Excretory System
NOTE :
• If left untreated, all UTI’s can lead to permanent
kidney damage and possible kidney failure.
• The general treatment is by antibiotics. A person
needs to maintain good personal hygiene when
eliminating wastes (liquid and solid forms) from
the body.
• Also, a person should drink lots of water.
Excretory System
Kidney Infections
• Result when an infection reaches the kidneys
and becomes known as pyelonephritis.
• Common causes can be infection from
elsewhere in the body or obstruction of the
prostate gland (usually in older men).
• For children, infection can be caused by the tube
that drains urine from the kidneys and the
bladder.
Excretory System
Kidney Stones
• Crystals formed from
minerals in urine.
• They can be found in
the kidney, ureter or
bladder.
• 80% of those stricken are males.
• The most common crystals are:
– Calcium Oxalates
– Uric acid
Excretory System
Kidney Stones (cont)
• Symptoms include severe back or abdomen
pain, blood in the urine, nausea and vomiting.
• Diagnosis involves a complete medical
examination, including X-rays.
• Treatment may vary from letting the stones pass
through the urinary tract to ultrasound shock (or
lithotripsy) to disintegrate the stones to a small
size that can be passed through the urinary tract.
• Real large stones require surgery for removal.
Excretory System
Kidney Stones (cont)
• Ways to avoid kidney stones:
• Increase liquid intake (more than
2l / day)
• Limit sodium intake
• Limit animal protein (link shown in
men)
• Limit foods high in oxalate
(spinach, strawberries, nuts, dark
chocolate, brewed tea)