Water

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HUAMAN URINARY SYSTEM
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Human Urinary System
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Human Urinary System
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Structure of Mammalian Kidney

• made up of three parts
  -cortex - a
  light outer region
• -medulla - a dark inner region
• -pelvis - a whitish central region leads to
  ureter
• contains numerous tiny tubules called nephrons

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Structure of Mammalian Kidney
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Structure of Nephron
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Nephron
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How does a nephron work ?
By two ways, one is ultrafiltration and the other
is reabsorption
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Ultrafiltration

• diameter of tiny artery leading to the glomerulus
  is larger than the one leaving, so a pressure is
  set up as blood tries to force its way out of the
  smaller tube
• the high hydrostatic pressure forces small
  molecules through the walls of capillaries and
  Bowmans capsule into the capsular space

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• fluid which filtered into the nephron is called
  glomerular filtrate

• glomerular filtrate has the same composition as
  that of blood except that it does not contain
  blood cells, blood proteins blood platelets

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Reabsorption

• reabsorption is the process of absorbing useful
  substances into capillaries which wrapped around
  tubule
• as in glomerular filtrate, some substances like
  glucose and amino acid are useful to human so
  they are absorbed back while fluid travels along
  the tubule

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• those urea which remains in the fluid pass the
  whole nephron and finally drains into collecting
  duct which leads to pelvis and form urine

• urine contains mostly water, with urea and excess
  mineral salts

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• reabsorption of all the glucose and amino acids
  and some salts begins in the first convolution
  and finished when the fluid reaches loop of Henle

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• useful substances are reabsorbed by diffusion
  down the concentration gradient and active
  transport against concentration gradient

• in collecting duct, water is mainly reabsorbed by
  osmosis but the first convolution actually
  reabsorbs the largest amount of water

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Functions of Kidney

• kidney mainly has three functions
• osmoregulation
• removal of excess salt
• excretion

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Functions of Kidney -
Osmoregulation
drink a lot of water
Amount of water in blood CONSTANT
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Functions of Kidney -
Osmoregulation
after sweating
Amount of water in blood CONSTANT
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Functions of Kidney -
Removal of Excess Salt
after eating a salty meal
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Functions of Kidney -
Excretion

• amino acids are broken down in liver to form
  urea by deamination
• Urea is carried by blood to the kidneys which
  excrete them from the body in the form of urine

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Kidney Failure and Artificial Kidney

• some kidney diseases can lead to kidney failure
  and the kidneys can no longer function properly
• toxic substances will accumulate in blood and
  patient will die

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KIDNEY FAILURE

• Caused by
• Bacterial infection
• External mechanical damage
• High blood pressure

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Dialysis fluid in
Air trap
Air trap
clean blood

Blood carrying waste
Dialysis fluid out
pump
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• artificial kidney is a bulky machine attached to
  patient which is used to filter and clean
  patients blood

• artificial kidney make use of the principle of
  dialysis. It has a filter made of cellophane
  which acts as a selectively permeable membrane

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• along one side of the membrane is the patients
  blood while the other side is dialysis fluid
  which has the same contain as plasma except urea

• only urea diffuses from patients blood into
  dialysis fluid through cellophane filter
• blood without urea will return to patient through
  his vein

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• dialysis fluid flows in direction opposite to
  that of blood flow to increase the efficiency of
  diffusion of urea into dialysis fluid

• other than using artificial kidney, kidney
  transplant is another possible method but only
  few people are willing to donate their kidneys
  after death

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KIDNEY MACHINE
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