Excretion of Liquid Waste

Chapter 49
By: Kayla Nida
This system is needed to allow for removal of impurities and
waste from the body.
Helps maintain homeostasis in the body
◦ Regulating Body temperature
◦ Regulating Blood glucose
◦ Oxygen
◦ pH concentrations
Contain Nephridia,
which are similar to
the human kidney.
Obtain fluid from the
body through the
filtration system called
◦ Removes salt through
active transport
◦ Forms urine
Have Malpighian
◦ Urine is not formed by
◦ Waste molecules and
potassium are secreted
into the tubules trough
active transport
◦ Most of the potassium
and water is reabsorbed
into the circulatory
system through the hind
Kidneys first developed among bony fish
◦ Body fluids are hypotonic to surrounding sea water so
water leaves their body by osmosis through the gills and
◦ Drink large amounts of sea water to compensate
◦ Kidney is needed to get rid of the divalent ions, such as
Cartilaginous Fish
Kidney helps to reabsorb urea from the nephron
tubule and maintain a blood urea concentration a 100
times higher than mammals
Urea makes the blood isotonic to the sea water,
preventing water loss
Kidney in Amphibians: first terrestrial vertebrate
◦ Identical to fresh water fish
◦ Makes sense because they stay in moist places
◦ Transport sodium across their skin from surrounding
Fresh water reptiles have similar kidneys to
Marine reptiles tend to lose water and obtain a lot of
Process similar to bony fish; eliminate excess salt
through salt glands
Only ones able to produce urine with a higher
osmotic concentration than their body fluid
 Can excrete waste in small amounts so that more
water can be retained in the body
 Human kidneys can produce urine that is more than
4.2 times concentrated as blood plasma
 Only ones to have loop of Henle that produces the
hypertonic urine
 Kangaroo rat kidneys
are so efficient that it never
has to drink water!
Nitrogen containing by-products that must
be removed from the body though urine
◦ Ammonia- toxic to cells and only safe in very dilute
◦ Urea- mammals excrete ammonia in this form
 water soluble and can be excreted in large amounts
through urine
◦ Uric acid- Humans, Apes, and Dalmatians lack
enzyme uricase, which converts uric acid into a
more soluble derivative and must
excrete the uric acid
Fist sized organ located in
the lower back
◦ Juxtamedullary nephrons- long
loops that go deeply
Receives blood from a
renal artery from which
urine is produced
Ureter: where urine drains
and carries it to the
urinary bladder
Renal pelvis: mouth of the
ureter when flared up
◦ Has cup-shaped extensions
that receive urine from renal
◦ Tissue is split into an outer
renal cortex and inner renal
Each kidney contains 1
million nephrons
into the medulla
◦ Cortical nephrons – shorter
Each nephron consists of
a long tubule and small
blood vessels
Glomerulus- a group of
capillaries in the renal
Capillaries filter the blood
Filtrate enters the first
region of the nephron
tubule= Bowman’s Capsule
Proximal convoluted
Tubule- sends filtrate to
the loop of Henle
Fluid is then sent to the
Distal Tubule, which drains
into the collecting duct
All the collecting ducts
merge in the medulla to
empty the urine
Driven by active
transport and
secondary active
Reabsorbs glucose,
amino acids, and other
molecules needed by
the body
Moves out of tubules
and into the blood
Moves from the blood
and into the tubule to
be excreted
Involves the transport
of molecules across
the capillaries and
kidney tubules into the
Elimination of nitrogenous wastes,
potassium, and other ions
Urin’s high hydrogen concentration helps
maintain the acid base balance of the blood
from 7.35-7.45
Maintains blood volume and pressure
because of the excretion of water
◦ More water excreted means lower blood volume
and visa-versa
Important for homeostasis
Include volume of blood, blood
pressure, and osmolality of blood
Antidiuretic Hormone (ADH)
◦ Produced by hypothalamus and
secreted by pituitary gland
◦ Secreted when a person is dehydrated
or eats salty food, making you thirsty
◦ Causes walls of distal tubules and
collecting ducts to become more
permeable to water= conserving
Aldosterone- secreted by the adrenal cortex
◦ Stimulated by the drop in blood sodium concentration
◦ Stimulates the distal convoluted tubules and collecting
ducts to reabsorb sodium, decreasing the excretion of
sodium in the urine
◦ Promotes secretion of potassium to help regulate the
potassium concentrations in the blood
Atrial Natriuretic Hormone (ANH)
◦ Secreted by the right atrium of the heart in response
to an increase in blood volume
◦ Promotes excretion of salt and water into the blood to
lower the blood volume
The Kidneys maintain a constant internal
When affected by disease, a rise in the blood
concentration of waste products,
disturbances of electrolyte balance, and
failure of blood pressure regulation occur
This causes other systems to develop
problems because the homeostasis is thrown
Kidney disease- gradual and permanent
loss of kidney over time.
◦ Five stages of severity
◦ Cured by replacing the kidney, watching your
diet, some antibiotics
Gout- build up of uric acid in the body
because the kidneys cannot process it
Causes joint pain and kidney stones
Diet change and antibiotics are used to help
clear it
Nephritis- inflammation of the nephron
Can suffer permanent damage= chronic
Most can be cured but severe cases have
lead to death

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