Excretory System

• Metabolic wastes of the chemical reactions in the cell are removed from the body.

• This process is called EXCRETION.

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.

Excretory Substances The metabolic wastes of cells are;

WATER, CO2, NITROGENOUS COMPOUNDS

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.

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.

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.

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.

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.

• There is no special excretory system in plants.

• The STOMA, LENTICELS, HYDRATHODES are used for excretion in plants.

• CO2 is excreted by stomata and lenticels.• Water is excreted by hydrathodes and

stomata by TRANSPIRATION.

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.

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

Excretion in Planaria (Flatworms)

• In planaria, excess water is excreted by flame cells.

• Flame cell take ewcess 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.

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.

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.

GRASSHOPPER

DRAGON FLY

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.

TYPES OF KIDNEYSThere are three types of Kidneys;

a) Pronephros kidney

b) Mesonephros kidney

c) Metanephros kidney

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.

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 Bowman’s capsules.

• A glomerulus is located in Bowman’s capsule. Waste materials pass to Bowman’s capsule from glomerulus.

• Than wastes flow the wolf channel. And than they are expelled through cloaca.

METANEPHROS KIDNEY

• Metanephros kidney is found in adult reptiles, birds, mammals and human.

• Each kidney contains a millions of nephrons.

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.

PARTS OF HUMAN EXCRETORY SYSTEM

1. Kidneys

2. Ureter

3. Urinary bladder

4. Urethra

• 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.

1. They remove wastes of cellular metabolism from the blood.

2. They control concentration of various substances found in the body fluid.

Structure of Kidneys1.Renal Capsule: It surrounds and protects the kidneys.

2.Cortex: It contains glomerulus and Bowman’s capsules.

3.Medulla:It 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

Bowman’s capsule.• Each glomerulus is formed by

capillaries from a branch of renal arteriole.

• The complex of Bowman’s capsule and glomerulus is called malpighian body. Bowman’s 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.

1. Filtration

2. Reabsorbtion

3. SecretionClick

Filtration

• During filtration, substances pass from the blood into the Bowman’s capsule.

• Under pressure, water and many small molecules such as salts, urea, glucose and aminoacids pass from glomerulus into Bowman’s capsule.

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.

• 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.

• 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.

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