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The Excretory System
By Leigh Berndsen, Harry Yao, and
Josh Silver
The Urinary system
• It is made of two kidneys, Ureters, bladder, and
Urethra.
• The Kidneys produce urine.
• The urine passaess though the urerter into the
urinary bladder.
• It is stored in the bladder, and excreted though
the urethra.
• The kidneys remove watses from cellular
resperation and reglulate the blood
concentrations
Kidneys
• Kidneys is located against the mussles of the
back just below the diaphrgme, and are 10 cm
long.
• Kidney is made of three parts, outer cortex,
mudulla, pelvis.
• the blood is filleted in the cortex, the mudula is
made of collecting ducts, and the pelvis is a
cavity connected to the ureter.
• The collecting ducts carry the fillrate to the
pelvis.
Nephrons
• Fillisters the waste from the blood.
• Each kidney has 1.25 million nephrons.
• some nephrons are in the cortex, but the majority are in the
medulla.
• Part of a nephron is a glomerulus, which is a group of capillaries.
• Bowman’s capsule is a double walled surrounding of the
glomerulus.
• The blood in the glomerulus is filleted into the Bowman’s
capsule.
• The filtrate exits the Bowman's capsule though the renal tubule.
• The center section of the renal tubule is the loop of henle, which
goes to the medulla
• Slight reabsorption happens int eh loop of henle
• Cortical nephrons have reduced loops of Henle and
jutamedullary nephrons have long loops which extend to the
inner medulla.
Nephron
Blood in the Kidneys
• Blood enters through the renal arteries and exits through the
renal veins.
• Nephrons have arteriole, which carry the blood from the renal
arteries to the nephron.
• Prior to leaving the Bowman's capsule the capillaries join into an
arteriole.
• The Bowman's capsule receves filtrate from the blood.
• These arterioles subdivide into into a second capillary network
aroun the renal tubule.
• Those caperlarses merge into a venule.
• The golmerulus is a ball of capcapillieraies from the Bowman's
capsule.
• Afferent artiole is a renal artery that supplies blood to the
nephrons.
• Efferent artiole is when the capillaries converge and leave the
capsule.
• After the Efferent artiole, the network of capillaries subdivide into
the peritubular capillaries.
Renal tubules
• There are three main section to this tubule: Proximal convoluted
tubule, the loop of Henle, and the distal convoluted tubule.
• The fillterate is emptied into the collecting ducts from the renal
tubules.
Urine formation
• Formation of urine is in the nephrons during two
processes.
• Filtration and reabsorption.
• Filtration is a process of removing the wates
from the blood. Useful substances can be
removed from the blood.
• Reabsorption is when the useful substances
reenter the blood.
Filtration
• Filtration takes place in the glomeruli and Bowman’s
capsules.
• The blood in the glomerulus is under pressure.
• The pressure causes the filtrate which is water, urea,
glucose, amino acids, and salts though the permeable
walls of the glomerulus into the Bowman's capsule.
• Blood cell and proteins are two big to pass though the
walls of glomerulus
• Kidneys form around 180 liters of filtrate in a day
• Only about 1-1.5 liters of urine are produced, this is
because if all the filtrate is excreted, the body will lose too
much water.
Reabsorbtion
• Reabsorbtion occurs in the renal tubule.
• Reabsorbtion reduceses volume of the filtrate, and resumite important
molecues into the blood.
• When the filtrate goes though the renal tubes of the nephron, almost all
the water, guloces, amino acids and salts are reaborbted.
• They enter though the caperallierys around the tubales.
• The reabsorbtion of water is essentral to mammals, due to the fact of
Hemostasis.
• While osmosis occures, guloce, amino acids, and salts use active tranport
and ATP is supplyed by the mytocondria in the renal tubuales. The
tubuales have microvilli which increses the surface area in order to
absorb.
Reabsorption
• Kidney threshold level, is when the concentration is too high
the is can not be absorbed.
• The excess substances that were not reabsorbed remains in
the urine and is excreted from the body
• urine flows from the tubules to the collecting ducts. then the
kidneys, then the ureters t the bladder, which is disposed of
through the urethra
• Crystallization in the urine is called a kidney stone
Transport in the renal tubule
• proximal convoluted tubule (cortex):
• plays a role in homeostasis by altering volume and
composition of filtrate through reaborbtion and secreation
• regulates the pH throughout body fluids by secreating
hydrogen ions
• nutrients such as glucose, amino acids, and potassium are
actively tranported into the interstitial fluid and then blood
• microvilli on epithical cells compose the brush border allow
for reabsorbtion of nutrients such as NaCl and water
• both active and passive transportation occur
• water enters the capillaries through osmosis becasue the
solution in hypotonic compared to the cell
Descending Limb of Loop of Henle
• Epithelium is permeable to water and not permeable to salt
and other small solutes
• The interstitial fluid surrounding the tubule is hyperosmotic
compared to the filtrate
• Water departs filtrate through osmosis (passive transport)
Ascending limp of loop of Henle
• epithelia relativley impermable to water
• Thin segment:
o permeable to NaCl
o NaCl diffuses out of tubule and into interstitial fluid via
passive transport
o allows for high osmolarity in kidney
• Thick segment:
o loses NaCl to interstitial fluid through active transport
without giving up water
o filtrate is more diluted as it moves up cortex
Distal Convoluted Tubule
• It is a region of controlled reabsorption and secretion.
• Contributes to pH regulation by quantitative secretion of H+
and reabsorption of bicarbonate (buffer in blood and
intestitial fluid).
• It controls the K+ and Na+ homeostasis .
• In order to control K+, it controls the the amount secreted
into the filtrate.
• As for Na+, it does so though reabsorption.
Collecting Duct
• The collecting ducts carries the filtrate back in the direction
of the medulla and renal pelvis.
• The epithelium of duct is permeable to H2O, not salt.
• The filtrate becomes more concentrated because of the loss
of water though the process of osmosis (because of a
hypertonic fluid outside the duct).
• Passive transport
• The bottom of the duct epithelium is permeable to urea
(which will be explained in the next slide), thus using passive
transport.
• Due to the bodies need to keep homeostasis when a
substance has a high concentration some of the urea
diffuses from the duct
Nitrogenous wastes
• Due to the metabolism of the body, nitrogenous wastes are
formed. They generally takes the form of ammonia (NH3)
and are extremely toxic to the body therefore creating a
need for the body to expel it.
• The human body does this though a detoxification process
which results in a type of waste called Urea. This is more
efficient then just ammonia exreaction via water (which it is
extremely soluble to) because it allows a conservation of
water and therefore helps the human body to retain
homeostasis.
• Kidney has high osmolarity
Figue of the nephron.
Bibliogrpahy
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