The document summarizes key aspects of the human excretory system. It describes the major organs that make up the system - the kidneys, ureters, bladder, and urethra. It explains their functions and roles in filtering waste from the blood and excreting it from the body in urine. Furthermore, it provides details on urine formation within the nephron structural units of the kidneys and how concentration of urine is achieved in the kidney medulla.

2. Excretory Products and their Elimination
• Elimination of metabolic waste products from the animal body to regulate the
composition of body fluids and tissue is called as excretion. These waste products
include ammonia, uric acid, carbon dioxide and ions like na+,k+and cl- and phosphates
and sulphate
• Ammonia is the most toxic and uric acid is the least toxic. The process of removing
ammonia is called ammonotelism and organisms that excrete ammonia are
called ammonotelic (bony fishes, aquatic amphibians and insects).
• The organism that release urea as nitrogenous wastes are called ureotelic (mammals,
terrestrial amphibians). The organism that excretes uric acids is
called uricotelic (reptiles, birds and land snails). Animals Excretory organs
Flat worms, some annelids
and cephalochordates.
Protonephridia or flame
cells.
Earthworms and annelids Nephridia
Insects including
cockroaches
Malpighian tubules
Mammals Kidney

3. The Human Excretory System
The function of excretory
system is the excrete (get
rid of) waste that are not
helpful to the body.
STRUCTURE OF THE EXCRETORY SYSTEM
 T h i s s y s t e m c o n s i s t s o f s p e c i a l i z e d s t r u c t u r e s a n d c a p i l l a r y
n e t w o r k s t h a t a s s i s t i n t h e e x c r e t o r y p r o c e s s .
 T h e h u m a n e x c r e t o r y s y s t e m i n c l u d e s t h e k i d n e y a n d i t s
f u n c t i o n a l u n i t n e p h r o n .
 T h e e x c r e t o r y a c t i v i t i e s o f t h e k i d n e y i s c h a n g e d b y
s p e c i a l i z e d h o r m o n e s t h a t r e g u l a t e t h e a m o u n t o f a b s o r p t i o n
w i t h i n t h e n e p h r o n
EXCRETORY SYSTEM
EXCRETORY
SYSTEM
KIDNEYS
URETERS
BLADDER
URETHRA
MEATUS

4. Human Excretory System
Human excretory system consists
of:
1.A pair of kidneys
2.A pair of ureters
3.A urinary bladder
4.A urethra

5. THE KIDNEYS
•Kidneys are reddish brown bean shaped structure situated
between last thoracic and lumber vertebra. Each kidney has a
notch on its inner side called hilum through which ureter, blood
vessels and nerves enter.
•Inside the hilum has broad funnel shaped space called renal
pelvis with projection called calyces.
•Cortex extends between medullary pyramids as renal column
called Columns of Bertini.
•The functional unit of kidney is nephron. Each kidney
contains about one million nephrons.
•Each nephron has two parts- the glomerulus and renal tubules.
Glomerulus is the tuft of capillaries formed by afferent arteriole.
Blood from glomerulus is carried away by efferent arteriole.
•Renal tubules starts with Bowman’s capsule continue with
tubular parts divided into Proximal Convoluted tubules, Henle’s
loop and Distal Convoluted tubule.
•The malpighian tubules, PCT and DCT of nephron are situated in
cortical region where as loops of Henle’s into medulla.

6. Juxta medullary Nephrons Cortical Nephrons
a. Loop of Henle’s is short and extend only a little into
medulla.
a. Loop of Henle’s are very long and extend deep into
medulla.
b. The glomeruli lie close to the inner margin of the cortex. b. The glomeruli lie in the outer cortex.
A DIAGRAMMTIC
REPRESENTATION OF A
NEPHRON SHOWIN BLOOD
VESSELS,DUCT AND TUBULE :

7. Urine Formation
• G l o m e r u l a r c a p i l l a r i e s b l o o d p re s s u re c a u s e f i l t ra t i o n o f b l o o d t h ro u g h 3 l ay e rs
( e n d o t h e l i u m o f g l o m e r u l a r b l o o d v e s s e l s , e p i t h e l i u m o f B o w m a n ’s c a p s u l e a n d
b a s e m e n t l ay e r b e t w e e n t w o m e m b ra n e s a s u l t ra - f i l t ra t i o n .
• T h e a m o u n t o f f i l t ra t e fo r m e d b y k i d n e y s p e r m i n u t e i s c a l l e d g l o m e r u l a r f i l t ra t i o n
ra t e ( G F R ) w h i c h i s 1 2 5 m l / m i n u t e .
• G l o m e r u l a r F i l t ra t i o n ra te i s c o n t ro l l e d b y J u x ta g l o m e r u l a r a p p a ra t u s ( J G A ) .
• 9 9 % o f f i l t ra t e h a s t o b e re a b s o r b e d b y re n a l t u b u l e s c a l l e d re a b s o r p t i o n .

8. Function of Tubules
1.Proximal Convoluted Tubules (PCT) – all the
important nutrients, 70-80% electrolytes and water are
reabsorbed.
2.Henle’s Loop– maintains high osmolarity of medullary
interstitial fluid.
3.Distal Convoluted Tubules (DCT) – conditional
reabsorption of Na+ and water. Maintains pH and sodium-
potassium balance.
4.Collecting Duct– large amount of water is reabsorbed
to produce concentrated urine.

9. Mechanism of concentration of urine
• The flow of filtrate in two limbs
of Henle’s loop is in opposite
direction to form counter
current. The flow of blood in
two limbs of vasa recta
increase the osmolarity towards
the inner medullary interstitium
in the inner medulla.
• The transport of substance
facilitated by special
arrangement of Henle’s loop
and vasa recta is
called counter current

10. Regulation of kidney
function–
•Functioning of kidney is monitored by hormonal feedback mechanism of hypothalamus and
JGA. Change in blood volume, body fluid and ion concentration activates the osmoreceptors
in the body that stimulate the hypothalamus to release ADH or vasopressin hormones. The
ADH facilitates water absorption in tubules.
•Decrease in glomerular blood pressure activate JG cells to release renin which converts
angiotensinogen to angiotensin I and II that increase the glomerular blood pressure and
release of aldosterone that increase absorption of Na+ ions and water.
Micturition
• The process of expulsion of urine from the urinary bladder is called micturition. The
neural mechanism that causes it is called micturition reflex. Urine formed in
nephron is stored in urinary bladder till a voluntary signal is given by CNS. This
initiates the contraction of smooth muscles of the bladder and simultaneous
relaxation of the urethral sphincter causing the release of urine.
• Lungs, liver and skin also play important role in process of excretion. Lungs remove
CO2 and water, liver eliminates bile containing substances like bilirubin, biliverdin.
Sweat glands remove NaCl, small amount of urea and lactic acid. Sebaceous
glands excrete sterol, hydrocarbons and waxes.

11. *Uremia– there is high concentration of non-protein nitrogen (urea, uric acid,
creatinine). Urea can be removed by hemodialysis.
•Renal failure– also known as kidney failure where glomerular filtration is
ceased and both kidney stops working. Kidney transplant is the ultimate
method in correction of acute kidney failure.
•Renal Calculi– formation of stone or insoluble mass of crystallized salts
formed within the kidney.
•Glomerulonephritis (Bright’s Disease)-inflammation of glomeruli of kidney due
to entry of protein or red blood corpuscles in to filtrate due to injury.
Disorders of Excretory System

12. Oh no! my stomach hurts so
bad,it feels like kidney
stones!how will I ever get into my
grandma’s
House?
Mwahaha!this man will never be able to
go to hermione’s now! he’ll be stuck at
the hospital!
He and the other residents of
Excretown will be stuck with their
kidney stones just in time for me
to finish my master plan:complete
kidney domination
This looks like
the work of
Dr.Stones
….
excretion
Wow thanks guys!! you
saved the day and just in
time for Hermione
Granger’s magic