EXCRETION — NEAT NOTES
1. EXCRETION
Excretion: A process of removal of nitrogenous waste from our body through metabolism.
Metabolism: The sum of all the chemical reactions that occur within a living organism.
NITROGENOUS WASTE
The major nitrogenous wastes are: Ammonia, Urea and Uric Acid.
1. AMMONIA
Ammonia (NH₃) is the waste material that is released by aquatic organisms.
The organisms which release ammonia are known as ammonotelic organisms.
Ammonia is the most toxic waste, so a large amount of water is needed to release it.
Note: Tadpoles (babies of frogs) release ammonia.
Ammonia is formed by protein metabolism.
2. UREA
Urea is the waste material that is released by land animals.
Examples: Animals, humans, land animals, etc.
The organisms which release urea are known as ureotelic organisms.
Urea — Important Points
Urea is less toxic as compared to ammonia.
Note: Adult frogs release urea.
Important note: Liver converts the toxic ammonia into less toxic urea in land organisms.
Examples: Mammals and amphibians.
Amphibians: Animals which can survive both on land and in water.
3. URIC ACID
Uric acid is the waste material that is released by birds.
The organisms which release uric acid are known as uricotelic organisms.
Uric acid is the least toxic waste material.
EXCRETION IN UNICELLULAR ORGANISMS
Unicellular organisms remove metabolic waste directly through their cell membrane into the surrounding
environment by simple diffusion or specialised structures called contractile vacuoles.
PORIFERA
Porifera → Phylum
Poro → Hole
Phera → Bearing
Osculum → One
Ostia → Many
Excretion Notes
, Examples: Sponge, Amoeba.
Amoeba does not have bones.
It changes its shape according to the food it consumes.
They do not have kidneys.
PC₂ → Porifera
C → Coelenterata
C → Ctenophora
These organisms release waste materials through the body membrane.
EXCRETION IN HUMAN BEING
PATHWAY OF URINE
Kidney → Ureter → Urinary bladder → Urethra
Ureter: It is a tube that collects urine from the kidney and transports it to the urinary bladder.
Urinary bladder: It is a muscular sac that stores urine until it leaves the body.
Urethra: It is a tube that carries urine from the urinary bladder to outside the body.
KIDNEY
Kidney is the primary and a vital excretory organ.
Kidney is bean-shaped and reddish-brown in colour.
Kidney is located between thoracic and lumbar regions (T12–L3).
Right kidney is slightly inferior to the left kidney because of the presence of the liver.
SIZE OF THE KIDNEY
Length → 10–12 cm
Breadth → 2–3 cm
Width → 5–7 cm
WEIGHT OF THE KIDNEY
125–170 g
PARTS OF SPINAL COLUMN
Cervical = 7
Thoracic = 12
Lumbar = 5
Sacral = 1
Coccyx = 1
There are a total of 26 vertebrae in the spinal column.
RENAL CAPSULE
Kidneys are lined or covered by a tough fibrous connective tissue called renal capsule.
Convex → Lateral side of outer portion
Concave → Inner portion
Excretion Notes
1. EXCRETION
Excretion: A process of removal of nitrogenous waste from our body through metabolism.
Metabolism: The sum of all the chemical reactions that occur within a living organism.
NITROGENOUS WASTE
The major nitrogenous wastes are: Ammonia, Urea and Uric Acid.
1. AMMONIA
Ammonia (NH₃) is the waste material that is released by aquatic organisms.
The organisms which release ammonia are known as ammonotelic organisms.
Ammonia is the most toxic waste, so a large amount of water is needed to release it.
Note: Tadpoles (babies of frogs) release ammonia.
Ammonia is formed by protein metabolism.
2. UREA
Urea is the waste material that is released by land animals.
Examples: Animals, humans, land animals, etc.
The organisms which release urea are known as ureotelic organisms.
Urea — Important Points
Urea is less toxic as compared to ammonia.
Note: Adult frogs release urea.
Important note: Liver converts the toxic ammonia into less toxic urea in land organisms.
Examples: Mammals and amphibians.
Amphibians: Animals which can survive both on land and in water.
3. URIC ACID
Uric acid is the waste material that is released by birds.
The organisms which release uric acid are known as uricotelic organisms.
Uric acid is the least toxic waste material.
EXCRETION IN UNICELLULAR ORGANISMS
Unicellular organisms remove metabolic waste directly through their cell membrane into the surrounding
environment by simple diffusion or specialised structures called contractile vacuoles.
PORIFERA
Porifera → Phylum
Poro → Hole
Phera → Bearing
Osculum → One
Ostia → Many
Excretion Notes
, Examples: Sponge, Amoeba.
Amoeba does not have bones.
It changes its shape according to the food it consumes.
They do not have kidneys.
PC₂ → Porifera
C → Coelenterata
C → Ctenophora
These organisms release waste materials through the body membrane.
EXCRETION IN HUMAN BEING
PATHWAY OF URINE
Kidney → Ureter → Urinary bladder → Urethra
Ureter: It is a tube that collects urine from the kidney and transports it to the urinary bladder.
Urinary bladder: It is a muscular sac that stores urine until it leaves the body.
Urethra: It is a tube that carries urine from the urinary bladder to outside the body.
KIDNEY
Kidney is the primary and a vital excretory organ.
Kidney is bean-shaped and reddish-brown in colour.
Kidney is located between thoracic and lumbar regions (T12–L3).
Right kidney is slightly inferior to the left kidney because of the presence of the liver.
SIZE OF THE KIDNEY
Length → 10–12 cm
Breadth → 2–3 cm
Width → 5–7 cm
WEIGHT OF THE KIDNEY
125–170 g
PARTS OF SPINAL COLUMN
Cervical = 7
Thoracic = 12
Lumbar = 5
Sacral = 1
Coccyx = 1
There are a total of 26 vertebrae in the spinal column.
RENAL CAPSULE
Kidneys are lined or covered by a tough fibrous connective tissue called renal capsule.
Convex → Lateral side of outer portion
Concave → Inner portion
Excretion Notes
