The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The kidneys filter waste from the blood to form urine. The urine travels from the kidneys down the ureters to the urinary bladder, where it is stored until urination. During urination, the bladder contracts and the urethra carries the urine out of the body. In addition to removing waste, the urinary system regulates fluid and electrolyte balance and blood pressure.

1. URINARY SYSTEM
-By-Dr.S.Kameshwaran

2. urinary system
The urinary system is also known as the renal
system or urinary tract,
“The urinary system consists of organs, muscles,
tubes, and nerves that are responsible for
producing, transporting, and storing urine”
FUNCTIONS OF THE URINARY SYSTEM:
• Eliminate waste from the body,
• Regulates blood volume
• Regulates blood pressure,
• Control levels of electrolytes and metabolites,
• Regulates blood pH.

3. ANATOMY OF URINARY TRACT:
The urinary tract is made up of the following organs:
A pair of Kidneys – forms the urine
A pair of Ureters – Transports the urine
A urinary Bladder – stores urine
A Urethra – carries urine out side the body

5. KIDNEYS:
• It is the major organ of urinary system
• It is a bean shaped organ situated in the retro
peritoneal position in the superior lumbar region
• The right kidney present slightly lower than the left
• Mass of an adult kidney is 150gms
• It is about 12cm long and 6cm wide & 3cm thick
• The superior wall of the kidney is attached to the
adrenal gland
• They produce urine through which waste materials
such as urea & ammonium are excreted
• They also reabsorbs glucose and amino acids
• Also it performs some secretory functions
• Eg: Calcitriol, erythropoietin & renin

6. Layers of the kidney:
• Kidney is covered by three connective tissue
layers
• Renal Fascia – outer layer, made up of dense
connective tissue – Attaches kidney to
peritoneum and posterior abdominal wall
• Adipose capsule: it is the middle layer –
contains thick adipose tissue – holding the
kidney in place & protect it from physical
trauma
• Renal capsule: innermost layer – consist of thin
layer of dense irregular connective tissue –
protect kidney from infection & physical trauma

8. INTERNAL STRUCTURE OF THE KIDNEY:
• The kidney is divided in to three different zones
RENAL CORTEX
RENAL MEDULLA
RENAL PELVIS

9. RENAL CORTEX:
• This is the outer most zone
• It is light in colour
• Has granular appearance
RENAL MEDULLA:
• This zone lies beneath the cortex
• It is darker in colour
• It consist of medullary and renal pyramids - a
cone shaped tissue mass the broad bases facing
towards the cortex
• It consist of apex/ pailla – sharp base - Facing
internally

11. RENAL PELVIS:
• It is the funnel shaped tube
• Which joins the ureter at the hilum
• The branches emerging from pelvis form two or
three major calyces
• Which further divided in to cup shaped minor
calyces
• Urine is collected by the calyces & continuously
drained from the papillae
• Emptied in to renal pelvis – ureter and finally in to
the bladder for storage
• The walls of the calyces, pelvis & ureter are smooth
muscles
• These smooth muscles undergoes rhythmic
contraction to propel urine.

13. FUNCTIONS OF THE KIDNEY:
Regulate the concentration of Na+, K+, Ca2+, Cl- in
the blood
Regulation of blood pH
Regulation of blood volume
Regulation blood pressure
Regulation blood osmolarity
Production of hormones
Regulation blood glucose level
Excretion of waste and foreign substances

14. NEPHRONS:
It is the basic structural and functional unit of the
kidney
It filters the waste products from the blood
Reabsorbs the required nutrients in to the body
Excrete the remaining things in the urine
Thereby it regulates the water and sodium salt
concentration in the blood
Types of Nephron:
Cortical Nephrons: renal corpuscles present near
the renal cortex
Juxtamedullary Nephrons: Renal corpuscles
present near the renal medulla

15. • Nephrons are made up of
– RENAL / MALPIGHIAN CORPUSCLES &
– RENAL TUBULES
RENAL / MALPIGHIAN CORPUSCLES
• Filtration of larger waste solute molecules out
of the body takes place
RENAL TUBULES
• Reabsorption of water and small waste solute
molecules and secretion of waste material takes
place

16. MALPIGHIAN CORPUSCLES
• It is also known as Malpighian body / Renal corpuscle
• It involved in the Initial filtering of components
Each Malpighian corpuscle is made up of
1.Glomerulus &
2.Bowman’s/
Glomerular Capsule

17. GLOMERULUS:
It is a mass of capillaries which is supplied with
blood by an afferent arteries of the renal
circulation.
Blood pressure with in the glomerulus provides the
driving force for water and solutes to be filtered
out of the blood and reach the Bowman’s capsule.
The remaining blood passes into the efferent
arteriole(narrower than the afferent arteriole )
blood along with reabsorbed substances reaches
the vasa recta (collecting capillaries attached tothe
convoluted tubules).
The vasa recta and the efferent venules coming
from other nephrons combine to join the renal vein
and the main blood circulation .

19. BOWMAN’S OR GLOMERULAR CAPSULE:
It is the capsule surrounds the glomerulus
It is made up of
visceral inner layer - contains specialized cells
called podocytes &
parietal outer layer - contain single layer of
flat cells called simple squamous epithelium.
Fluids from the glomerulus blood for filter
through the podocytes
The glomerular filtrate is then processed
along the nephron to form urine .

20. RENAL TUBULE :
This 3cm long tubule exits the glomerular
capsule
A renal tubule is made up of :
PROXIMAL CONVOLUTED TUBULE (PCT):
LOOP OF HENLE
DISTAL CONVOLUTED TUBULE
COLLECTING DUCT

22. PROXIMAL CONVOLUTED TUBULE (PCT):
• It is the initial and longest sub-division of the renal tubule
through which the glomerular filtrate flows.
• It is made up of SIMPLE CUBOIDAL EPITHELIAL CELLS
• They have prominent microvilli projecting into the lumen
of the proximal tubule.
• These microvilli forms brush border - which increases the
surface area.
LOOP OF HENLE:
• This loop receives the remaining glomerular filtrate.
• It is the only part of the renal tubule which dips into the
renal medulla.
• The loop of henle is sub divided into the following two
limbs:
Descending loop of Henle
Ascending loop of Henle

23. DESCENDING LOOP OF HENLE:
• This loop travels towards the renal medulla
and turns 180 degree to become the
ascending loop,
• descending loop contains simple squamous
epithelium - named as the thin descending
loop.
ASCENDING LIMB OF LOOP OF HENLE:
• It is made up of thicker simple cuboidal
epithelium; thus is referred to as the thick
ascending loop.

24. DISTAL CONVOLUTED TUBULE(DCT):
It is the final sub-division of the renal tubule
Through which the golmerular filtrate flows.
It contains simple cuboidal epithelium; but lacks the
brush border.
COLLECTING DUCT:
Each collecting duct travels through the medullary
pyramids ,
The collecting tubules after receiving glomerular
filtrate from many nephrons , approach the renal pelvis
where they fuse together and empty urine into the
minor calyces via papillae of the pyramids .

25. FUNCTIONS OF NEPHRON:
The bowman’s capsule and the glomerulus of the nephrons act
as a filtration unit .
glomerular filtrate that enters the tubule – where reabsorption
takes place
This process of the glomerular filtration produces the tubular
fluid which secreted across the epithelial cells of the tubule wall .
Other function includes
1) They undergo GLOMERULAR FILTRATION in which the water
and solutes from the blood plasma enter the nephron via wall of
glomerular capillarioes into glomerular capsule .
2) They undergo TUBULAR SECRETION in which the substances
are transported to the lumen.
3) They also undergo TUBULAR REABSORPTION in which water
or solutes are transported from the tubular lumen into the kidney.

26. URETERS
• Ureters are PAIRED TUBES through which the urine
flows from the kidney to the urinary bladder.
• Both the tubes begin from the sinus of the
corresponding kidney as CALYCES surrounding the
renal papillae.
• One minor calyx contains more than one papillae
• The minor calyces combine with each other to form
major calyces
• which further combine to form RENAL PELVIS
• It is a funnel-shaped dilatation with wide above
and narrow below , and situated partially inside
and partially outside the RENAL SINUS .

28. ANATOMY OF URETERS
Ureters are 20-30 cm long ,
They are thick – walled , narrow cylindrical tubes .
They begin near the lower end of the kidney - run downward
enter the pelvic cavity and terminate in the fundus of the urinary
bladder.
Ureter contains three coats –
FIBROUS COAT OR TUNICA ADVENTITIA
 MUSCULAR COAT OR TUNICA MUSCULARIS
MUCOUS COAT OR TUNICA MUCOSA
FUNCTION
They transport urine from the renal pelvis of the kidney to
urinary bladder
During urination when pressure in the bladder is high the uterus
are compressed and back flow of urine is prevented . Otherwise,
cystitis – inflammation of ureter - which may lead to kidney
infection .

29. URINARY BLADDER
Urinary bladder is a hollow muscular, and distensible (or elastic)
organ,
Which rests on the pelvic floor .
It receives urine from the kidneys via the Ureters - stores it
within , and expels it during urination via Urethra.
It is a RESERVOIR, WHERE URINE IS STORED TEMPORARILY.
The bladder is some what spherical in shape,
Its shape and size vary from individual to individual and also
depends on the urine volume is stores.
An empty bladder is about the size and shape of a pear.
The normal capacity of the bladder is 400-600ml

30. ANATOMY
Urinary bladder is made up of three layers
MUCOUS MEMBRANE- inner lining - transitional epithelium
SUBMUCOSA - second layer - connective tissue with elastic fibres
MUSCULARIS - outer layer smooth muscle having fibres
interwoven - collectively termed detrusor muscle - This muscle
contracts to expel urine from the bladder .
A triangular area , called TRIGONE
three opening is present on the urinary bladder floor.
The trigone base is formed by two opening from the ureters,
These openings are covered by small flaps of mucosa which act
as valves to allow the entry of urine into the bladder and to
prevent its back-flow into the ureters.
The trigone apex is formed by the third opening into the urethra.
This opening is covered with detrusor muscles which form an
internal urethral sphincter

31. FUNCTIONS OF URINARY BLADDER:
Urinary bladder performs the following functions:
1)It is a reservoir for urine.
2)It expels urine via urethra.
A urinary bladder filled with urine becomes distended.

Urine stimulates the starch receptors on the bladder wall,

which in turn trigger a reflex contraction of the bladder wall
muscle and relax the internal sphincter (a wall which
remains close so that the urine remains in the bladder till
urination).

Soon the external sphincter relaxes and the bladder expels the
urine .

32. URETHRA
 Urethra is tube like structure which transports urine from
the urinary bladder to the exterior of the body.
 It forms the “exit tube” of the body for liquid wastes.
 It is closed by the urethral sphincter(a muscular structure )
which keeps the urine in the bladder till urination.
 Mucous membranes form the inner lining of the urethra,
and muscular layer forms the outer layer.
ANATOMY
 Urethra is made up of two separate urethral sphincter
muscles.
 The internal urethral sphincter muscle consists of
involuntary smooth muscles,
 The external sphincter muscle consists of lower voluntary
muscles.

33. The characteristic features of Female urethra:
 It is 4cm long and opens to the exterior via urethral orifice,
 located in the vestibule in the labia minora between the
clitoris and the vaginal orifice .
 Female urethra transports urine from the bladder to the out
side at the time of urination.
The characteristic features of male urethra:
 It is 20cm long
 S-shaped to follow the line of the penis.
 It transports urine(during urination) and semen(during
ejaculation) to the out side.

34. FUNCTION
Urethra perform the following functions:
1) It is the passageway through which urine is
expelled out of the body.
2) In males, it is also the passageway through
which semen is ejaculated.

35. FUNCTIONS OF URINARY SYSTEM
 The organs of urinary system eliminate the waster products
produced by the body cells.
 Bilirubin obtained from haemoglobin breakdown,
 uric acid from nucleic acid in cells,
 creatinine from creatine phosphate in muscle,
 urea and ammonia from amino acid metabolism are the organic
waste products presents in the extravascular fluid.
 It involves in nutrients preservation by eliminating only the
unwanted products from the body.
 Regulates the osmolarity , volume and pressure of blood by
altering the volume of water lost with urine.
 The body levels of Na+, K+, Cl-, Ca+, and other ions are also
balanced by monitoring the quantity excreted via urine.

36.  It maintains the body pH at an optimum level by monitoring the
blood hydrogen level
Organs of the urinary tract perform the following functions
1) Role of kidneys:
They regulate the blood volume, pressure and composition; assist
in glucose synthesis; release erythropoietin; assist in vitaminD
synthesis; and excrete wastes via urine.
2) Role of Ureters:
They carry urine from the kidneys to the urinary bladder.
3) Role of Urinary bladder:
It acts as a temporary storage area for the urine.
4) Role of Urethra:
It transports urine out of the body in males and females both;
while in males it also forms a passageway for the excretion of
semen.

37. PHYSIOLOGY OF URINE FORMATION
 The cells of the body produce nitrogenous wastes,
 which are transported via blood to the kidneys.
where they are converted into urine by the following three process:
1) ULTRAFILTRATION OR GLOMERULAR FILTRATION
2) TUBULAR REABSORPTION,
3) TUBULAR SECRETION( AUGMENTATION)

38. Ultrafiltration / Glomerular filtration:
It is a passive process involving hydrostatic pressure
to force fluids and solutes across a membrane.
Glomerular filters wastes more efficiently (because
its filtration membrane is of larger surface area and
is thousand times more permeable to solutes in
comparison to the other capillary beds)
molecules having < 3nm diameter size like Water,
glucose, amino acids and nitrogenous wastes can
easily move into glomerular capsule from the blood
Molecules of 3-5 nm diameter enter the glomerular
capsule with much difficulty:
while those of >5nm diameters are prevented from
entering the tubule.

39. Filtration membrane:
 Glomerular capsules inner part is made up of 3 layers (collectively called the
filtration membrane) acting as barriers or filters.
The Filtration membrane consist of
 Fenestrated glomerular capillary endothelial cells:
 Basal Lamina
 Podocytes
1) Fenestrated glomerular capillary endothelial cells:
 The glomerular endothelial cells are fenestrated, i.e, they have
perforations, thus making them leakier than the other capillariers.
 These cells have gaps of 70-100nm between them but still prevent the exit
of blood cells and platelets form the capillaries.
2) Basal Lamina:
 It is a thin layer of extra cellular matrix gel, separating the glomerular
endothelial cells from the podocytes .
 The basal lamina consist of collagen fibres which form a meshwork and
function like a sieve to prevent the entry of substances having >8 nm
diameter into the capsular space.
 As a result, most of the plasma proteins are barred from entering the
capsule.

40. 3) Podocytes:
 These cells form the visceral layer of the glomerular capsule.
 Podocytes are the 3rd and finest filter of the filtration membrane.
 The finger-like pedicels of podocytes wrap around the glomerular capillaries
and interlock to form narrow filtration slits,
 which allow the entry of substance having <6-7nm diameter into the capsular
space.

41. Net Filtration Pressure(NFP):
“NFP is the total pressure gradient which drives
water across the filtration membrane to reach
the capsular space”
It is responsible forming filtrate and involves three
main forces which act on the glomerular bed:
Glomerular Hydrostatic Pressure(GHP):
The value of GHP is usually 50mmHg.
Capsular Hydrostatic Pressure(CHP):
CHP pressure is usually of 10mmHg.
Glomerular Colloid Osmotic Pressure(GCOP):
The average value of GCOP in glomerular
capillaries is 30mmHg.

42. Glomerular Filtration Rate(GFR):
“IT IS THE AMOUNT OF FILTRATE PRODUCED BY BOTH
THE KIDNEY’S IN A MINUTE”
 filtrate is formed very rapidly at a rate of about 125ml
/min.
 The kidney’s form around 180 liters of filtrate in a single
day.
 Since the body contains only 3 liters of plasma, the
kidney’s filter this entire volume around 60 times each
days.

43. REGULATION OF GFR:
GFR is regulated by intrinsic controls (acting locally within the
kidney to maintain GFR) and extrinsic controls(acting by the
nervous and endocrine systems to maintain blood pressure).
1) Intrinsic controls (Renal Auto – Regulation)
Myogenic Mechanism
Tubuloglomerular Feedback Mechanism
2) Extrinsic Controls( Neural and Hormonal Mechanism)
Sympathetic Nervous System Controls
Renin-Angiotensin Mechanism

44. TUBULAR REABSORPTION:
It is a selecting transepithelial process initiates when the filtrate enters the
proxmial tube.
The reabsorption substance enter the blood via:
TRANSCELLULAR ROUTE:
 The substance (water and solutes) pass through the luminal membrane
 Then they diffuse across the cytosol
 Then they pass through the basolateral membrane of the tubule cell(often
the solutes are transported across the lateral intracellular spaces via the
membrane transporters),
 Finally, the substance enter the endothelium of peritubular blood capillaries.
PARACELLULAR ROUTE
 movement of substances between the tubule cells connected by tight
junctions
 thus the movement occurs in a restricted manner. But these tight junctions
are leaky in the proximal nephron,
 thus allowing the passage of some essential ions (Ca2+, Mg2+, K+, and some
Na+) through the paracellular route

46.  Tubular reabsorption is either a passive ( ATP is not required)
or an active(at least one step requires ATP directly or
indirectly) process depending on the substance being
transported.
SODIUM REABSORPTION
 Glomerular filtrate contains Na+ ions most abundantly, and
80% of the energy is utilized for active reabsorption of Na+
ions by the transcellular route.
The active reabsorption of Na+ ions – 2 processes
1)A Na+ -K+ ATP ase pump (present in the basolateral
membrane) involves in primary active transport Na+ ions out
of the tubule cells - Bulk flow of water and solutes.
2) The Na+ ions from the tubule cells are actively pumped by the
secondary active transport carries or by faciliated diffusion

47. REABSORPTION OF NUTRIENTS, WATER AND IONS
 Water. Glucose, Amino acid, Lactate, Vitamins are
reabsorbed by secondary active transport & Osmosis
 Transporter proteins helps in the transport of nutrients
 A large number of transporters (high Tm values) (Tm –
Transport Maximun) are available for substance
essential for body (like glucose) ;
 while a few or no transporters are available for
substances not required by the body.

49. TUBULAR SECRETION:
• The plasma is cleared from unwanted substances
by tubular secretion
• The H+, K+, NH4+, Creatinine and certain organic
acids are secreted in to the tubules/ pass through
the tubule cells
• The urine contains both filtered and secreted
substances
• The PCT is the major secretion site
Tubular secretions involved in
• Disposing of substances Eg: Some drugs
• Eliminating end products Eg: Urea, Uric acid
• Eliminating Excess K+ Ions
• Controlling blood pH

51. ROLE OF RENIN ANGIOTENSIN SYSTEM(RAS) IN KIDNEYS:
 The RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM (RAAS) is
essentially required for the regulation of cardiac output and
arterial pressure.
 Renin is a proteolytic enzyme released by the kidney into the
blood circulation -facilitate angiotensin to be formed in the blood
and tissue,
 Which further facilitates aldosterone to be released from the
adrenal cortex

52. STIMULATION OF RENIN RELEASE:
Incresed sympathetic / Decreased Pressure/ Decreased Na+ Delivery to Distal tubule
↓
Renin is released from the juxtaglomerular (JG) cells linked with the afferent arteriols of
the renal glomerulus
↓
Released renin enters in the blood circulation
↓
Converts the Angiotensinogen in to Angiotensin- I
↓
Angiotensin- I is converted in to Angiotensin –II by ACE (Angiotensin Converting Enzyme)
↓
 It increases arteriole pressure by constricting blood vessels .
 It increases the sodium and water retention in the body by stimulating
sodium reabsorption at various sites on a renal tubule.
 It stimulates the release of aldosterone from the adrenal cortex, which in
turn acts on the kidneys to aid sodium and fluid retention
 It stimulates the release of anti-diuretic hormone from the posterior
pituitary gland to increase the fluid retention by the kidneys
 It stimulates the thirst centers in the brain

54. MICTURITION (URINATION) REFLEX
When 300-400ml of urine has been collected in a urinary bladder
↓
Afferent autonomic nerve fibres send the impulse to the brain
↓
Brain send the efferent impulse to the bladder
↓
Relaxation of the urethral sphincter - bladder muscles to tightens
↓
Squeezing urine out of the bladder.

55. ROLE OF KIDNEYS IN ACID-BASE BALANCE
 An acid donates protons, while base accepts it.
 Physiologically, acids are categorized into two important
groups:
10.Carbonic or Volatile Acid:
It is derived from aldehyde (CHO) and fat metabolism
It producing 15,000 mmol of Co2 per day.
The equation of carbonic is Co2 +H20 ↔ H2Co3 .
Carbonic acid metabolism is regulated by respiration.
2) Non-Carbonic or Non-Volatile Acid;
It is derived from the protein metabolism,
It producing 1.0-1.5 mmol of H+ per day per Kg .
The released H+ is captured in the form of H2So4, H2Po4, etc.,
It is excreted by the kidney

56. TYPES OF ACID-BASE BALANCE:
Acid-Base Balance divided into :
1) Normal Acid-Base balance:
i) normal plasma pH= 7.4( Range: 7.35-7.45)
Co2 + H20 ↔ H2Co3 ↔ HCo3 + H+
ii) using the Henderson-Hasselsbach equation,
pH= 7.4= pka + log {[ A-]/[HA]}= 6.1+log{[HCo3-]/[0.03pCO2]}
iii) In order to keep the pH of blood at 7.4 , and given pKa =6.1 for bicarbonate ,
the ratio of bicarbonate to 0.03 pCO2 should remain constant.
2) Abnormal Acid-Base Balance: An imbalance in Acid-Base is termed as acidosis
or alkalosis
i) acidosis is an increased state of H+ ions
ii) Acidemia occurs when blood pH becomes less than 7.35
iii) Alkalosis is an increased state of HCO3 – ions .
iv) Alkalemia occurs when blood pH becomes greater than 7.45
Acid-Base disturbance is termed as an metabolic disorder

57. FACTORS AFFECTING ACID-BASE BALANCE PROCESSESS;
 Increase acid load
 Volume contraction
 Increased pCO2
 Decreased intracellular K+
 Increase the Aldosterone
The final urine should not contain any HCo3 – ions .
Urine pH is less than 5.8 is an indication of being free from HCo3 –ions.
REGULATION OF ACID-BASE BALANCE
Acid-Base balance should be regulated by the following ways.
i) chemical buffering by intracellular and extracellular buffers
ii) control of pCO2 by normal respiratory functions , and
iii) Control of HCO3 –ions concentration and acid excretion by the kidneys

58. DISORDERS OF KIDNEY
The following disorders of kidney are discussed below:
1) Renal calculi (kidney stones) – accumulation of calcium oxalate in inner lining
of kidney
2) Urinary tract infections – Bacteria – E.coli - Enters through urethra – affect
any part of urinary system
3) Glomerulonephritis – due to change in the body immune system – affect
glomerulus
4) Diabetic nephropathy – in diabetic patients – kidney fails to remove waste
products & excessive fluids from body
5) Renal failure - kidney permanently fails to function
6) Polycystic Kidney Disease(PKD) – genetic disease – formation of cluster of
cyst
7) Nephroblastoma (Wilm’s tumour) – cancer disease in kidney
8) Hydronephrosis – Inflammation of kidney
9) Urithritis - Inflammation and Irritation in urethra
10) Urinary Bladder cancer – cancer in the bladder

59. THANK U