Excretory System

1
Excretory System
2
Where are the kidneys located?

• What is the function of the kidneys
• Maintain salt balance
• Maintain pH balance
• Waste excretion (especially nitrogen waste)
• Maintain blood pressure

3
Kidney business

• _____ of blood flow through the kidneys per day.
• That makes _______ circuits per day.
• 700L/ 200

4
Kidney terms

• Find definitions for the major kidney structures
• Nephron
• Glomerulus
• Renal tubule
• Bowmans capsule
• Locate these on your diagram.

5
Kidney terms

• Find definitions for the major kidney structures
• Nephron- structural and functional unit of kidney
  which forms the urine
• Glomerulus- structural part of nephron forming a
  knot where circulatory system meets kidney.
• Renal tubule-ducts in which formed urine collects
  (proximal and distal parts)
• Bowmans capsule- cup into which blood filtrate
  enters renal tubule (like a funnel)

6
Kidney processes

• The two main transport mechanisms that produce
  urine in the proper concentration of salts and
  water are
• Osmosis
• Active Transport
• How are these different?

7
Kidney processes

• Three overall processes occur
• Filtration
• Reabsorption
• Secretion

8
Filtration

• Water and small molecules (most of plasma
  including glucose, salts, urea) forced into
  Bowmans capsule from blood capillaries by force
  of blood pressure.
• Draw a red arrow on your diagram to represent
  filtration (page 1054)

9
Reabsorption

• While 180 liters of water flow through the
  kidneys, some of this and other valuable
  molecules (glucose, amino acids) are returned to
  the blood. (Natural recycling)
• Urea- a nitrogen waste product of cellular
  metabolism -is poorly reabsorbed

10
reabsorption

• Reabsorption depends on active transport of
  molecules, and water follows passively by
  osmosis. (See Fig 49.19)
• Yellow color of urine comes from bile pigments
  that were released into blood.
• Draw an blue arrow showing reabsorption.

11
Secretion

• Substances can still enter renal tubule.
• Hydrogen, potassium, some drugs and poisons are
  secreted.
• Helps maintain blood pH and rid the body of
  toxins.
• Draw a green arrow showing secretion

12
Osmoregulatory Organs

• Nephridiaduct with openings to coelom and
  outside the body (in earthworms and some other
  invertebrates)
• Malpighian Tubuleextension of the digestive
  system, waste actively transported in (in
  insects)
• NephronVertebrates

13
Development of Kidneys

• As embryos, we develop 3 pairs of kidneys.
• First are non-functional and fish-like, then they
  degenerate
• Second may function for several days, then they
  also degenerate.
• Third set are the form that will stick with us.

14
Nitrogenous Waste Fig 49.15

• Fish produce the least processed, most toxic
  waste- ammonia
• (requires a lot of water because it must be
  dilute)
• Mammals convert ammonia to urea, which is less
  toxic at higher concentration.
• Uric acid--Most processed but least toxic waste
  that conserves water and protects enclosed eggs.
  (reptiles and some birds)

15
Hormonal Regulation in Kidneys

• Antidiuretic hormone-ADH
• Reduces urination to maintain blood pressure
• (Diuresis means flow of urine from kidney
• Aldosterone- Increases Na reuptake by renal
  tubule. Also maintains blood pressure.

16

• What happens after you give a urine sample? What
  are they looking for?