Excretory System

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FunctionThe 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.

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• The ureters are tubes that carry urine from the
  pelvis of the kidneys to the urinary bladder.
• 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.

urethra
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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.

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The kidneys help to maintain homeostasis by
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

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• 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.

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Kidneys have three basic functions in maintaining
homeostasis.

• remove waste from blood
• help to maintain electrolyte, pH, and fluid
  balances
• release key hormones

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Nephrons clean the blood and produce urine.

• Nephrons are the filtering units in the kidneys.
• They clean and rebalance the blood to produce
  urine.
• There approximately 1 million nephrons in each
  kidney

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• Nephrons clean the blood in a three-step process.

• The first step is filtration of the blood.

• Glomerulus Network of capillaries
• Bowmans Capsule Encases the glomerulus

• The bodys entire volume of blood is filtered
  every 45 min

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• The first step is filtration of the blood.

• The second step is reabsorption of materials.

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• The first step is filtration of the blood.

• The second step is reabsorption of materials.

• The third step is excretion of materials.

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Injury and disease can damage kidney functions.

• A kidney transplant can replace a damaged kidney.

• recipient and donor tissue must match
• drugs prevent tissue rejection

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• Dialysis can be used to filter and clean the
  blood.

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UTI (Urinary Tract Infection)

• Disorders of the Excretory System

• 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.

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NOTE

• If left untreated, all UTIs 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.

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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.

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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

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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.

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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)