Excretory System Short Notes pdf in English

By Deepak Last updated May 22, 2023

Excretory System Short Notes pdf in English

Hello Aspirants,

The excretory system, also known as the urinary system, is responsible for removing waste products and regulating the body’s fluid and electrolyte balance. Here are some key points about the function of the excretory system:

Organs of the Excretory System:

Kidneys: The kidneys are the primary organs of the excretory system. They filter waste products, excess water, and electrolytes from the blood to produce urine.

Ureters: The ureters are tubes that transport urine from the kidneys to the urinary bladder.

Urinary Bladder: The urinary bladder is a muscular sac that stores urine until it is expelled from the body.

Urethra: The urethra is a tube that carries urine from the bladder to the outside of the body.

Filtration and Urine Production:

The kidneys filter blood through millions of tiny structures called nephrons.

Nephrons consist of a glomerulus, a network of capillaries, and a renal tubule.

Filtration occurs at the glomerulus, where water, waste products, and small molecules are filtered from the blood into the renal tubule.

As the filtrate passes through the renal tubule, useful substances, such as glucose and ions, are reabsorbed into the blood, while waste products and excess water form urine.

Regulation of Water and Electrolyte Balance:

The excretory system plays a crucial role in maintaining the body’s fluid and electrolyte balance.

The kidneys adjust the reabsorption and excretion of water and electrolytes, such as sodium, potassium, calcium, and chloride, to regulate their levels in the body.

Hormones, such as antidiuretic hormone (ADH) and aldosterone, help control water reabsorption and electrolyte balance.

Removal of Waste Products:

The excretory system eliminates various waste products from the body through urine formation.

Waste products include urea, a byproduct of protein metabolism, creatinine from muscle metabolism, and excess salts and toxins.

Other waste products, such as bilirubin from the breakdown of red blood cells, are eliminated through the liver and intestines.

Maintenance of Acid-Base Balance:

The kidneys help regulate the body’s acid-base balance by controlling the excretion of hydrogen ions and the reabsorption of bicarbonate ions.

This helps maintain the pH of the blood within a narrow range.

Other Functions:

The excretory system contributes to blood pressure regulation by producing renin, an enzyme involved in controlling blood vessel constriction and fluid balance.

The kidneys also participate in the synthesis of active forms of vitamin D, which is important for calcium absorption and bone health.

The excretory system plays a vital role in maintaining homeostasis by removing waste products and regulating the body’s fluid and electrolyte balance. Proper functioning of this system is essential for overall health and the efficient functioning of other body systems.

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Excretory System

 Every living organism generates waste materials in its body and has a mechanism to expel it.

 The waste products that are produced are urea, uric acid, ammonia, carbon dioxide, water and ions like sodium, potassium, chloride, phosphates etc.

 Ammonia, urea and uric acids are the major sources of Nitrogenous Wastes.

 The most toxic substance, ammonia requires more amount of water for its elimination whereas uric acid, which is less toxic, requires less water.

 Kidney disease and kidney problems are usually treated by a nephrologist. Sometimes kidney stones are treated by a urologist.

Modes o f Excretionin Animals:

Ammonotelism:

 The process of elimination of ammonia from the body is known as ammonotelism and the organisms which exhibit this nature are called ammonotelic.

Example: bony fishes, insects etc.

 Ammonia is quite soluble, so it is excreted in the form of ammonium ions either by simple diffusion process across body surface or through the gills.

Ureotelism:

 In some mammals and amphibians, urea is excreted and are called ureotelic.

 In these organisms, ammonia that is produced is converted to urea in the “liver”

of the animals and its released in blood which is filtered and released out by the kidneys.

 It helps to maintain the “osmolality” in the body.

Ureotelism:

 The process of elimination of uric acid from body as the main nitrogenous waste material is called uricotelism.

 Animals who exhibit this kind of elimination are called ureotelic animals. Example: Reptiles, birds, snails

 Other Nitrogenous wastes are – Allantosm, creatine, creatinine and hippouric acid are some other nitrogenous waste products

excreted by mammals.

ORGANS OF HUMAN EXCRETORY SYSTEM:

Ski n:

 The skin helps in of excretion wastes by the way of sweat.

 The skin eliminates waste compounds of NaCl and some amount of urea etc.

L u n g s:

 Lungs are the primary respiratory organs and they help intake oxygen and expel carbon dioxide (CO2).

 In respiration, lungs also function to eliminate some amount of water from body in the form of vapour.

L iv e r:

The liver has an important function in excretion of wastes from body:

 Liver changes the decomposed haemoglobin of the worn out

RBCs into bile pigments bilirubin and biliverdin.

 These pigments are passed into the alimentary canal with

the bile for elimination in the faces.

 The liver also excretes cholesterol, steroid hormones, certain vitamins and through the bile.drugs

 Urea is formed in the liver by a cyclic process called as urea cycle of “Ornithine cycle”.

 The excess of amino acids in the body are deaminated by an enzyme oxidase, producing ammonia NH3. Ammonia being toxic is converted to “Urea”.

Kidneys:

 The Kidney is the main organ of the human excretory system.

 Each individual have a pair of kidneys in his body.

 The human excretory system comprises of the following structures:

2 Kidneys

2 Ureters

1 Urinary bladder

1 Urethra

Human Excretory System:

K i d n e y A n a t o m y :

 Renal Capsule – outer membrane that surrounds the kidney; it is thin but tough and fibrous.

 Renal Pelvis – basin-like area that collects urine from the nephrons, it narrows into upper end of the ureter..

 Calyx – extension of the renal pelvis; they channel urine from the pyramids to the renal pelvis.

 Cortex – the outer region of the kidney; extensions of the cortical tissue Contains about one million “blood filtering nephrons”.

 Nephron – these are the filtration units in the kidneys. It is the “Structural and Functional Unit of Kidney”.

 Medulla – inner region of the kidney contains 8-12 renal pyramids.

 The pyramids empty into the calyx.

 Medullary pyramids – formed by the collecting ducts, inner part of the kidney.

 Ureter – collects filtrate and urine from renal pelvis and takes it to the bladder for urination.

 Renal Artery – branches off of the aorta bringing waste-filled blood into the kidney for filtering in the nephrons; the renal artery is further subdivided into several branches inside the kidney.

 Each minute, the kidneys receive 20% of the blood pumped by the heart. Some arteries nourish the kidney cells themselves.

 Renal Vein – removes the filtered blood from the kidneys to the inferior vena cave.

N e p h r o n A n a t o m y :

 Renal Artery – brings waste-filled blood from the aorta to the kidney for filtering in the nephron.

 Glomerulus – each glomerulus is a cluster of blood capillaries surrounded by a Bowman’s capsule. Its main function is “Ultrafiltration”.

 The Glomerulus and Bowman’s capsule is together called as “Renal Capsule”.

 Proximal convoluted tubule (PCT)

 Loop of Henle -Thin descending limb of the loop of Henle and thick Ascending limb of the loop of Henle. The capillaries supplying the blood to

 Loop of Henle is called “Vasa Recta”.

 Distal convoluted tubule (DCT)

 Renal Vein – when filtration is complete, blood leaves the nephron to join the renal vein, which removes the filtered blood from the kidney

 Arterioles – blood is brought to and carried away from the glomerular capillaries by two very small blood vessels—the afferent and efferent arterioles.

F u n c t i o n o f N e p h r o n :

Renal Capsule:

 The blood carried by the afferent arteriole into the glomerulus, the pressure created pushes small molecules through the capillaries and into the glomerular capsule.

 This separate water, ions and small molecules from the blood, filter out wastes and toxins, and return needed molecules to the blood. This is called Ultrafiltration.

 This substance, lacking the blood cells and large molecules in the bloodstream, is known as an ultrafiltrate.

 The ultrafiltrate travels through the various loops of the nephron, where water Next, the ultrafiltrate must travel through a winding

series of tubules.

Proximal Convoluted Tubule:

 Nearest to the glomerulus.

 They have permeable cell membranes that reabsorb glucose, amino acids, metabolites and electrolytes into nearby capillaries and allow for circulation of water.

Loop of Henle:

 When the filtrate reaches the descending limb of the loop, water content has been reduced by 70%.

 The filtrate contains high levels of salts (mostly sodium).

 As the filtrate moves further through the loop, more water is removed which further concentrates the filtrate. This is called “Counter Current mechanism”.

Distal Convoluted Tubule:

 The Loop of Henle leads into the distal convoluted tubule which is where the kidney hormones cause their effect.

 And the distal convoluted tubule leads to the collecting ducts.

 The collecting ducts together form the renal pelvis through which the urine passes into the ureter and then into the urinary bladder.

 Helps regular potassium excretion.

 The kidneys collect and get rid of waste from the body in 3 steps: Glomerular filtration – Filtrate is made as the blood is filtered through a collection of capillaries in the nephron called glomeruli.

Tubular reabsorption – The tubules in the nephrons reabsorb the filtered blood in nearby blood vessels.

Tubular secretion – The filtrate passes through the tubules to the collecting ducts and then taken to the bladder.

Urine:

 Urine is made of water, urea, electrolytes, and other waste products:

 Some medicines and drugs are excreted in urine and can be found in the urine.

95% water

2% urea

0.35% sodium*

0.6% chloride*

0.15% potassium*

0.25% phosphate

0.25% sulfate

0.1% creatinine

0.05% uric acid

Kidney Disease and Disorders:

 Glomerulonephritis (nephritis) – inflammation of the glomeruli

 Hydronephrosis – water in the kidney caused by blocked urine flow

 Pyelonephritis – bacteria spreads from the bladder to the kidneys to create infection

 Kidney Stones (calculi) – usually form in the kidneys, but can form anywhere in the urinary tract

 Kidney Failure (acute and chronic)

 Kidney Tumors

 Kidney Cancer

 Nephrosis – can turn into kidney failure

 Polycystic Kidney Disease – fluid filled cysts replace healthy kidney tissues.

 Renal Hypertension – if kidneys don’t get enough blood, they set off a series of events leading to high blood pressure.

 Renal Infarction – similar to a heart attack, but in the kidney, caused by blockage of kidney vessels.

 Renal Vein clot – clot in the vein that carries blood from the kidney, can be fatal. Some Important previous years Questions:

Q-1. The functional unit of Kidney is–

(a) Aron (b) Urinary Bladder

Q-2. Which of the following is responsible for water balance in human body?

(a) Heart (b) Liver

Q-3. Medicine which increases the urine secretion–

(a) Adernalin (b) Monouretie

Q-4. Which of the following to the abnormal component of Urine–

(a) Kitone body (b) Urea

Q-5. In following Organ, which excrete water, fat and different waste (catabolic)–

(a) Kidney (b) Skin

Q-6. Nephron is related to which of the following system of human body?

(a) Circulatory system (b) Excretory system

Q-7. Which of the following function is performed by the kidneys in the human body?

(a) Excretion (b) Respiration

Q-8. Uric acid is chief nitrogenous waste of which of the following?

(a) Human (b) Frogs

Q-9. Where is urine stored in human body?

(a) Kidneys (b) Nephron

Q-10. Which one of the following substances is normally found in urine?

(a) Blood proteins (b) Creatinine

Q-11. Which is the organ that excretes water, fat and various catabolic wastes?

(a) Kidney (b) Skin

Q-12. All of the following are excretory (waste) products of animals, except

(a) Uric Acid (b) Ammonia

Q-13. Which of the following is an excretory organ of cockroach?

(a) Malphigian Tubules (b) Nephridia

Q-14. In mammals, an important role of excretion is played by_______

(a) Large intestine (b) Kidneys

Q-15. The excretory products of mammalian embryo are eliminated out by–

(a) Placenta (b) Amniotic fluid

Excretory System:

Every living organism generates waste materials in its body and has a mechanism to expel it.

The waste products that are produced are urea, uric acid, ammonia, carbon dioxide, water, and ions like sodium, potassium, chloride, phosphates, etc.

Ammonia, urea, and uric acids are the major sources of Nitrogenous Wastes.

The most toxic substance, ammonia requires more amount of water for its elimination whereas uric acid, which is less toxic, requires less water.

Kidney disease and kidney problems are usually treated by a nephrologist. Sometimes kidney stones are treated by a urologist.

Modes of Excretion in Animals:

Ammonotelism:

The process of elimination of ammonia from the body is known as ammonotelism and the organisms which exhibit this nature are called ammonotelic. Example: bony fishes, insects, etc.

Ammonia is quite soluble, so it is excreted in the form of ammonium ions either by a simple diffusion process across the body surface or through the gills.

Ureotelism:

In some mammals and amphibians, urea is excreted and is called ureotelic.

In these organisms, ammonia that is produced is converted to urea in the liver of the animals and it’s released in the blood which is filtered and released out by the kidneys.

It helps to maintain the osmolality in the body.

Ureotelism:

The process of elimination of uric acid from the body as the main nitrogenous waste material is called uricotelism.

Animals who exhibit this kind of elimination are called ureotelic animals. Example: Reptiles, birds, snails

Other Nitrogenous wastes are – Allantosm, creatine, creatinine and hippuric acid are some other nitrogenous waste products excreted by mammals.

ORGANS OF HUMAN EXCRETORY SYSTEM:

Skin:

The skin helps in excretion wastes by the way of sweat.

It eliminates waste compounds of NaCl and some amount of urea etc.

Lungs:

Lungs are the primary respiratory organs and they help intake oxygen and expel carbon dioxide (CO2).

In respiration, lungs also function to eliminate some amount of water from the body in the form of vapor.

Liver:

The liver has an important function in the excretion of wastes from the body.

It changes the decomposed hemoglobin of the worn-out RBCs into bile pigments bilirubin and biliverdin.

These pigments are passed into the alimentary canal with the bile for elimination in the faces.

The liver also excretes cholesterol, steroid hormones, certain vitamins, and through the bile. drugs

Urea is formed in the liver by a cyclic process called a urea cycle of the Ornithine cycle.

The excess of amino acids in the body is deaminated by an enzyme oxidase, producing ammonia NH3. Ammonia being toxic is converted to Urea.

Kidneys:

The Kidney is the main organ of the human excretory system.

Each individual has a pair of kidneys in his body.

The human “excretory system” comprises of the following the structures:

2 Kidneys

2 Ureters

1 Urinary bladder

1 Urethra

Urine:

Urine is made of water, urea, electrolytes, and other waste products:

Some medicines and drugs are excreted in urine and can be found in the urine.

95% water

2% urea

0.35% sodium*

0.6% chloride*

0.15% potassium*

0.25% phosphate

0.25% sulfate

0.1% creatinine

0.05% uric acid

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