EXCRETORY SYSTEM

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EXCRETORY SYSTEM
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Excretory System

• Metabolic wastes of the chemical reactions in the
  cell are removed from the body.
• This process is called EXCRETION.

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Function of Excretory System

1. Filtration and excretion of metabolic wastes
2. The regulation of blood content.
3. The regulation of blood pH.
4. Homeostasis.

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Excretory Substances

• The metabolic wastes of cells are
  WATER,
  CO2, NITROGENOUS
  COMPOUNDS

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WATER and CO2

• Water and CO2 are formed by means of cellular
  respiration.
• Water is excreted by lungs, sweating and kidneys.
• CO2 is excreted only by lungs.

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NITROGENOUS WASTES

• At the end of the catobolisation of aminoacids,
  AMMONIA(NH3) is formed.
• In some organisms, ammonia is removed fro body
  directly.
• But in some organisms ammonia is converted to
  other substances such as UREA and URIC ACID.

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AMMONIA (NH3)

• Ammonia is the most toxic nitrogenous waste
  material.
• It can soluble in water.
• Organisms need large amount of water for
  excretion of ammonia.
• Organisms need small amount of energy for
  formation of NH3
• Ammonia is excretory substances of freshwater
  organisms.

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UREA CO (NH2)2

• Urea is less toxic than ammonia.

• It is formed in the liver by ornithin cycle.

• Urea is excreted by the kidney.

• Urea is the excretory substances of
  amphibians,mammals,fish and human.

• Organisms use more energy in formation of urea
  than formation of ammonia.

• Living things need normal amount of water.

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URIC ACID (C5NH4O3)

• Uric Acid is least toxic nitrogenous waste.
• It is insoluble in water.
• Uric acid is excreted by with only small amount
  of water.
• Uric acid is the excretory substance of
  terrestial organisms such as INSECTS, REPTILES
  AND BIRDS.

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EXCRETION IN
LIVING THINGS
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EXCRETION IN PLANTS

• There is no special excretory system in plants.
• The STOMA, LENTICELS, HYDATHODES are used for
  excretion in plants.
• CO2 is excreted by stomata and lenticels.
• Water is excreted by hydathodes and stomata by
  TRANSPIRATION.

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excretion in invertebrates
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Excretion in
Unicellular Organisms

• Excretory structure of protista is called
  CONTRACTILE VACUOLE.
• Excess water and NH3 are pumped by contractile
  vacuole.
• Some NH3 molecules release from unicellular
  organisms by diffusion.

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• In simple animals such as Spongy and hydra
  excretory substances are excreted by diffusions.

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Excretion in Planaria (Flatworms)

• In planaria, excess water is excreted by flame
  cells.
• Flame cell take excess water from body.
• Than water pass excretory canal. And than water
  is given out of the body by excretory pore.
• CO2 and NH3 release from planaria by means of
  DIFFUSION.

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Excretion in Earthworm

• Excretory organ of earthwom is nephridium.
• Nephridium is surrounded by capillaries.
• It takes water, glucose, minerals and wastes from
  body. Than water, food and minerals are
  reabsorbed from nephridium canal by capillaries.
• And than waste materials pass into intestine.

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Excretion in Insects

• Insects have specialized excretory tubules that
  called MLPIGHIAN TUBULES.
• Wastes pass from blood into malpighian tubules
  Than malpighian tubules empty into digestive
  track.
• Finally waste materials are excreted by anus with
  undigested materials.

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GRASSHOPPER
DRAGON FLY
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excretion in
VERTEBRATES
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The excretory and reproductive system of
vertebrates are interrelated and this complex is
called UROGENITAL SYSTEM

• The kidney is the main excretory organ of
  vertebrates.

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TYPES OF KIDNEYS

• There are three types of Kidneys
• Pronephros kidney
• Mesonephros kidney
• Metanephros kidney

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PRONEPHROS KIDNEY

• Pronephros kidney is found in the embryonic stage
  of fish and amphibia and in adult form of shark.
• Pronephros kidneys contain many nephridia.
• Nephridia have ciliary funnels that is connected
  to ball of capillaries or glomerulus by ciliary
  funnels.
• Than wastes pass wolf channel for transport to
  the cloaca.

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MESONEPHROS KIDNEY

• Mesonephros kidney is found in embryonic stage of
  reptiles, birds an mammals and adutlt stage of
  fish and amphibia.
• In mesonephros kidney, ciliary funnels are
  replaced with Bowmans capsules.
• A glomerulus is located in Bowmans capsule.
  Waste materials pass to Bowmans capsule from
  glomerulus.
• Than wastes flow the wolf channel. And than they
  are expelled through cloaca.

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METANEPHROS KIDNEY

• Metanephros kidney is found in adult reptiles,
  birds, mammals and human.
• Each kidney contains a millions of nephrons.

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CLOACA

• In fish, amphibians, reptiles and birds
  excretory substances, unigested materials and
  reproductive cells are expelled through the same
  channel or openin that called CLOACA.

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HUMAN
EXCRETORY SYSTEM
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PARTS OF HUMAN EXCRETORY SYSTEM

1. Kidneys
2. Ureter
3. Urinary bladder
4. Urethra

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KIDNEY

• Kidneys are bean shaped organs that filtere 180
  lt. blood in a day.
• Blood is come into kidney by renal artery.
• Filtered blood leaves from kidney by renal vein.

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Functions of Kidneys

1. They remove wastes of cellular metabolism from
   the blood.
2. They control concentration of various substances
   found in the body fluid.

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Structure of Kidneys

1. Renal Capsule It surrounds and protects the
   kidneys.
2. Cortex It contains glomerulus and Bowmans
   capsules.
3. MedullaIt is located under the cortex and has
   malphigian pyramids. Malphigian pyramids contains
   urine collecting canal and loop of henle.
4. Pelvis It is innermost part of kidney. The urine
   is collected in pelvis.

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NEPHRONS

• They are structural unit of kidneys.
• A nephron begins with a glomerulus.
• Glomerulus is surrounded by a Bowmans capsule.
• Each glomerulus is formed by capillaries from a
  branch of renal arteriole.

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• The complex of Bowmans capsule and glomerulus is
  called malpighian body. Bowmans capsule is
  connected with long tubule that is called Loop of
  Henle.
• Loop of Henle is joined with collecting duct.

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URINE FORMATION

• There are three steps during urine formation.
• Filtration
• Reabsorbtion
• Secretion

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Filtration

• During filtration, substances pass from the blood
  into the Bowmans capsule.
• Under pressure, water and many small molecules
  such as salts, urea, glucose and aminoacids pass
  from glomerulus into Bowmans capsule.

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Reabsorbtion

• The absorbtion of needed materials such as
  glucose, amino acids and water from nephrons to
  blood capillaries is called reabsorbtion.
• Water is reabsorbed passively by osmosis. But
  reabsorbtion of glucose, aminoacids and salt ions
  occurs by active transport.

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• All glucose, aminoacids and many salt ions are
  reabsorb during reabsorption.
• Most reabsorbtion takes places in loop of henle.
• Antidiuretic hormone (ADH or Vasopressin)
  regulates concentration of water in blood.
• It increases water permeablity of the cells of
  the distal tubules.

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Secretion

• The cells of distal tubule excrete molecules such
  as penicilin, ammonia, potassium and excess
  acids. This process is called secretion.
• After secretion, the fluid remaining in the
  nephrons is called urine.
• Urine contains urea, uric acid, sodium,
  potassium, calcium, chlorine, phosphorus, water
  and small amount of cells.

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• Urine flows from the tubules into the collecting
  ducts and it is stored temporary in pelvis.
• Than urine is transported into the urinary
  bladder by the urether of each kidney.
• And than it is expelled through the urethra.