Excretion - DOC

							                            Excretion
Excretory Organs
  • Metabolic wastes
  • Skin, kidneys, lungs, intestine, liver
Urinary System
  • Anatomy and physiology of urinary system
  • Anatomy and physiology of the nephron
  • Water and solute concentration in the nephron
  • ADH and aldosterone
  • Diuretics
  • Kidney dialysis

                     The Excretory System
Excretion is defined as the removal of metabolic wastes,
 especially nitrogen-containing waste products of metabolism.

Many substances produced by the body as waste products can be
 reused or recycled by the body – others have to be removed
 from the body as they are toxic.

                       Excretory Organs
Metabolic wastes:
• these are only wastes that have entered the body cells, so do not
  include the waste products from digestion (feces)
• The most important metabolic wastes are:
   – carbon dioxide (from cellular respiration)
   – water (from CR and dehydration synthesis)
   – mineral salts (sodium chloride, potassium sulphate – from
     metabolism)
   – nitrogen compounds (ammonia, urea, uric acid – from the
     breakdown of proteins and amino acids)
  –   excess heat
                 Organs involved in Excretion
Skin, Lungs, Intestine, Liver, Kidneys
• Skin
One of the functions of the skin is the excretion of wastes:
• Excretes a small amount of urea and salts in sweat, which is 99
  percent water
• Major role of skin in excretion is the removal of excess heat
• Excess heat is removed in 2 ways:
Removal of Heat through the Skin
  1. Blood vessels in the skin open wider (dilate)
  • increases blood flow through the skin’s capillaries allowing

    more heat to be given off to the air

  2. Sweat begins to evaporate
  • evaporation of sweat cools the body by using , and removing,

    some of its heat

Skin also keeps heat in when the body is too cool:
   blood vessels narrow slightly (constrict), body sweats less
   can produce heat by muscle tension and shivering
Note: remember this is a type of homeostasis
Lungs
  considered part of the excretory system because they rid the
   body of carbon dioxide and water (as vapor) – both end
   products of cellular respiration

Liver
  Major function is detoxification
  – removes harmful substances, such as bacteria, certain drugs,
    and hormones, from the blood
  – these substances are changed into inactive or less poisonous
    forms (detoxified)
  – inactive substances are returned to the blood and then
    excreted through the kidneys
Intestines
   metabolic wastes (such as bile) that were secreted by the
     body to aid in digestion are removed with the other solid
     wastes that never entered body cells

Kidneys
   Part of the urinary system that produces urine
   Excretes nitrogenous wastes resulting from protein
    metabolism (urea, poisons, water, mineral salts)
Urinary System
Anatomy and Physiology of the Urinary System
   Organs of the Urinary System include:
  – 2 kidneys, 2 ureters, 1 urinary bladder, 1 urethra

  Other structures of the system include:
  – Renal arteries and renal veins, nephrons



Describe the structure and the function of each of the organs and
 tubes listed above.
Draw and label a diagram of the urinary system. Enlarge one of
 the kidneys and draw and label its structures as they would
 appear in a longitudinal section. Include: renal vein, renal
 artery, inferior vena cava, aorta, kidney, ureter, urinary
 bladder, urethra, medulla, cortex, fibrous capsule, renal pelvis,
 location of nephrons
Complete this on plain white paper with all the labels horizontal
  and to the right where possible.
Title your drawing.
Water and solute concentration in the nephron
Using the information in your textbook, answer the following
  questions:
• Why does plasma pass through the capillaries in the glomerulus

  and then into the Bowman’s capsule?
• What substances are in the plasma that filtered through the

  Bowman’s capsule that are still needed by the body?
• What do the capillaries around the proximal tubule reabsorb

  from the plasma?
• Why is an input of energy required to get needed sodium ions

  out of the tubules and into the body cells?
• What do the chlorine ions that follow the sodium ions form?

  Why is salt needed? (think osmosis)
• What happens in the distal tubule?

• What happens to the reabsorbed substances needed by the

  body? What happens to the urine that has been produced?

ADH and Aldosterone
ADH
– produced by the hypothalamus

– stored and released from the pituitary gland

– released into bloodstream

– affects permeability of collecting tubules

– controls amount of water being reabsorbed (blood-water

  concentration)
– low body water = high ADH = high permeability in the distal

  and collecting tubules = more water reabsorbed from the
    tubules back to the capillaries (blood) {this is homeostasis!)

 Diuretics
– Diuretics change the body's natural balance of fluids and salts

  (electrolytes) and can lead to dehydration. {This loss of water
  may allow an athlete to compete in a lighter weight class, which
  many athletes prefer. Diuretics also help athletes pass drug tests
  by diluting their urine.}

–   Diuretics are commonly used to treat high blood pressure and
    conditions that cause fluid retention (edema), such as
    congestive heart failure. When taken in small amounts, they
    have relatively few side effects, although electrolyte
    disturbances can occur.
    {When taken at the higher doses preferred by some athletes,
    however, the adverse effects may be significant. Using diuretics
    to achieve weight loss may cause muscle cramps, exhaustion,
    decreased ability to regulate body temperature, potassium
    deficiency and heart arrhythmias.}

•   alcohol inhibits the release of ADH = high urine output =
    dehydration and hangover
•   caffeine is also a diuretic that affects the production of ADH


Dialysis
Using your textbook, answer the following questions:
• Dialysis machines are often referred to as
  . When are these needed?
• From what vessel does the blood leave the body to enter the
  machine? through which vessel does it return?
•   What is used for the filtering of the blood?
•   Briefly describe some of the features of the semipermeable
    membrane.
•   What is the purpose of the dialyzing solution?
•   How long does dialysis take and how often is it usually done?