The Excretory System

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The Excretory System
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Purpose

• Contributes to homeostasis by helping regulate
  the volume, electrolyte composition, pH of
  internal environment and by eliminating metabolic
  waste products.

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Waste Products

• Some are metabolic
• E.g. Water, salts, CO2, and urea
• Urea is a toxic compound that is produced when
  amino acids are used for energy (contain
  nitrogen).

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Three Main Organs of Excretion

• 1.) Kidneys
• These are the main organs of excretion. They are
  responsible for removing excess water, urea
  other excess mineral wastes from the body.
• The kidneys act as filters to remove wastes that
  are collected and transported by the blood.
• E.g. Surplus in water or electrolyte (salt) in
  blood kidneys excrete in the urine.

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Three Main Organs of Excretion

• 2.)Lungs
• Every time we exhale, we get rid of small amounts
  of water vapor and CO2.
• CO2 is the waste product of cells that must be
  removed from the body so you can take in oxygen.

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Three Main Organs of Excretion

• 3.) Skin
• Excretes excess water, salts, and small amounts
  of urea through sweating.

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The Urinary System

• Made up of the
• Left and right kidneys
• Ureters
• Bladder
• Urethra
• Removes wastes and toxins from the blood and
  produces urine.
• Urine made of water, excess salts, urea

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How is this different from the excretory system?
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Structure of Kidney

• 2 bean shaped kidneys
• Located on either side of the spinal column, near
  the lower back
• Each kidney is about the size of your fist
• Each are attached to a renal artery a renal
  vein

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Structure of Kidney

• Each are attached to a renal artery a renal
  vein
• Renal artery carries blood from the hearts
  aorta, this blood is unfiltered and full of
  wastes collected from the whole body!!
• The renal vein carries blood that has been
  filtered out of the kidney

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Structure of Kidney

• A ureter leaves each kidney with fluid that
  contains excess water, salts, urea other waste
  products
• Ureters lead to the bladder, where liquid wastes
  are deposited/stored until released as urine from
  the body.
• Expulsion of wastes from bladder is controlled by
  specific sphincter muscles voluntary control.

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Anatomy of a Kidney

• If you cut a kidney in half you will find 2
  distinct regions
• Inner Part Renal Medulla
• Outer Part Renal Cortex

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Anatomy of a Kidney

• Nephrons
• Found in the renal cortex
• Working parts of the kidney
• Each acts as an individual unit of filtration
• About 1 million nephrons per kidney

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http//www.pitt.edu/anat/Abdomen/Kidneys/Kidneys.
htm
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Nephrons

• A. Filtration
• The nephron begins with Bowmans Capsule (BC)
• BC is a hollow bulb that surrounds a ball of
  capillaries known as the glomerulus
• BLOOD ENTERS BC via the renal artery
• Walls of the BC are permeable so blood is
  filtered through
• Filtered materials (urea, glucose, salts, some
  vitamins) are called filtrates.

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Nephrons

• Filtration Contd
• Platelets, red and white blood cells are too
  large to pass, so they remain in the blood
• Filtration of blood occurs in the Glomerulus BC
• Adult kidneys filter approx. 180L of blood daily.

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Nephrons

• Re-Absorption
• Some filtrates are valuable
  cant be lost, so the body reabsorbs them.
• Capillaries in the blood reabsorb valuable
  materials through active transport.
• Water returns to blood through osmosis, 99 of
  the water that is filtered out of BC is
  reabsorbed into your blood
• Takes place in the tubules of the nephron
• Excess fluid leaves the BC, enters the tubules
  and is called URINE.

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Nephrons

• Re-absorption Contd
• First part of tubule is the Proximal Convoluted
  Tubule (PCT).
• The PCT carries fluid down into the Loop of Henle
  (LH).
• Urine is concentrated at the LH.
• The urine then moves up the Distal Convoluted
  Tubule where it eventually meets the ureter

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Nephrons

• Re-absorption Contd
• Purified blood returns to the body through the
  renal vein, which runs to the Inferior Vena Cava
• The urine then moves from the nephrons to the
  ureters and goes to the bladder where it is
  stored
• Once urine is ready to leave the body, the urine
  will be expelled through the urethra.

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Recap

• http//www.as.miami.edu/chemistry/2086/chap26/chap
  ter2026-new_part1.htm

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• http//www.ask.com/wiki/Proximal_convoluted_tubule

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• http//www.colorado.edu/intphys/iphy3410saul/outli
  nes08fall/nephron.gif

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http//www.agefotostock.com/age/ingles/enam01b.asp
?foto13173541key1foto_claveBSI-3555309famp1
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Kidney Failure

• You have two kidneys in the body located on
  either side of the spine and extend a little
  below the ribs.
• Your kidneys are bean-shaped organs and is about
  the size of a fist.
• The kidneys receive approximately 10 of the
  blood that is pumped out of our heart every
  minute.

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• Your kidneys are responsible for the following
• Regulate fluids
• Balance chemicals
• Remove wastes
• Secrete hormones

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Condition Explanation

• Progressive in nature
• Anemia possible lack of iron
• Malnutrition (lack of appetite)
• Decrease well-being
• Increased risk for heart disease

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• Toxins build up in blood
• Weight gain (excess fluids, swollen ankles,
  puffiness)
• Fluid imbalances dizziness nausea

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Treatment Options

• General
• Limit fluid intake, high carb, low protein, low
  potassium diet
• Too much potassium can cause irregular heartbeat

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• Haemodialysis
• Most common method
• Use of a machine (size of dishwasher) blood
  flow through special filter to remove and filter
  wastes
• Clean blood returned to body
• Strict schedule 3 times a week for 3 to 5 hours
  each time

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• Side effects
• Less energy
• Loss of time
• Once a month blood is tested to see how effective
  dialysis is may not work forever!

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• Peritoneal Dialysis
• Removes extra water, wastes, and chemicals
• Cleansing solution passed through catheter into
  abdomen
• After a couple of hours the solution is drained
• Does not require a machine
• Strict diet
• More recent advances, more flexibility (done at
  home)

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• Kidney Transplantation
• Receive a healthy kidney from a living donor or a
  recently deceased donor
• When effective recovers quality of health AND
  life
• Yields longer life expectancy
• Could be long waiting lists (shortage of donors)
• Typical Surgery Risks (bleeding, infection, etc.)
• Anti-rejection medications after surgery may
  weaken immune system
• Risk of rejection (body doesnt accept kidney)