The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The kidneys filter waste from the blood to form urine. Each kidney contains over 1 million nephrons, the basic functional units that filter blood and form urine. Urine travels from the kidneys through the ureters to the urinary bladder, where it is stored until micturition. During micturition, muscles contract to expel urine through the urethra and out of the body. Precise regulation of urine production, composition, and excretion helps maintain fluid and electrolyte balance in the body.

1. URINARY SYSTEM
S.S.MOORTHY SEMENCHALAM
M.Sc. Comm Health (Occ Health) UKM
B.HSc. Nursing (Aust)
Dip Med Sc. (Moh)

2. Learning objectives
At the end of the lesson, students will be able to:
1.State the main components of urinary system
2.Lists the functions of kidney
3.State the path of blood flow through the kidney
4.State the structure of nephrones
5.State and describe 3 main processes in urine formation
6.State the compositions of urine
7.State the structure and specific functions of ureter,
urinary bladder and urethra
8.Discuss the process of micturition

4. Urinary system consists of:
• 2 kidneys ; urine
formation takes
place
• 2 ureters; carry
urine from kidney to
urinary bladder
• 1 urinary bladder;
storage of urine
• 1 urethra; carries
urine from bladder
out from body

5. Function of the Kidney
1. Eliminates waste products – urea, creatinine
etc
2. Regulates blood pressure by secreting renin
(juxtaglomerular cells)
3. Maintains water & electrolyte balance
4. Synthesis of prostaglandins & erythropoitein

6. Structure of kidney
• Retroperitoneal
• Superior lumbar region
• Right kidney slightly
lower than left
• Bean-shaped,
indentation: hilus
• Adrenal gland on top

7. Three layers of supportive tissue
• Renal capsule: fibrous
connective tissue that
enclosed kidney
• Renal fat pad: adipose
tissue around renal
capsule; protects kidney
from mechanical shock
• Renal fascia: connective
tissue that anchor kidney
to abdominal wall

8. Longitudinal section of
kidney
 cortex- outer,
made of bowman’s
capsule enclosing
glomerulus
 medulla- inner,
tubules responsible
for urine formation

9. • Within medulla,
triangular shaped
structures; renal
pyramids
• Base: open into
cortex
• Apex: point to apex
base
centre; renal papilla

10. • Renal cortex & renal
pyramids- form the
functional portion of
kidney
• Each renal cortex &
medulla; is made of 1
million nephrons
• Each nephron is the
basic unit of urine
formation. When
nephrons are damaged
they are not replaced

11. • Urine formed by
nephron, drains into
large ducts- papillary
ducts
• Papillary ducts drain
their contents into
minor calyces
• Papillary ducts: 8-18
per kidney

12. • Contents of minor
calyces drain into
major calyces
• Major calyces: 2-3 per
kidney
• From major calyces,
urine drains into renal
pelvis
• From renal pelvis it
drains into the ureters

13. Route taken by the urine in the kidney after its
formation:
Nephrons
Papillary ducts (renal pyramid)
Minor calyx
Major calyx
Renal pelvis
Ureters

14. Renal medulla ureter urinary bladder urethra
ureter
Urinary bladder
urethra

15. Nephron: The basic functional unit of kidney
• Each kidney made of
millions of nephron
• Tubule; closed at one
end, other end
opening to collecting
tubule

16. Nephron
Closed-end
- indented to form cup-shaped glomerular capsule
(Bowman’s capsule)
- enclosed arterial capillaries network (glomerulus)
Remainder:
i. Proximal convoluted tubule (PCT)
ii. Loop of Henle
ii. Distal convoluted tubule (DCT)

17. Nephrons: functional units of kidney

18. Renal artery (at hilum):
• from abdominal aorta,
enters renal sinus
• Branches to form
afferent arterioles
• Supply oxygenated
blood to glomerular
capillaries of renal
corpuscles

19. • Efferent arterioles arise
from glomerular capillaries
& carry blood away from
glomeruli
• These gives rise to plexus
of capillaries around PCT &
DCT
• a.k.a peritubular capillary
system
• Join to form renal vein
• Renal vein: drains
deoxygenated blood into
inferior vena cava

20. Afferent arteriole - brings blood to the glomerulus
Efferent arteriole - brings blood away from the glomerulus

21. Bowman’s capsule:
• externally layered
with squamous
epithelium
• Internal viscera:
specialized epithelial
cells (podocytes)
• Basement
membranes: separate
endothelial calls of
glomerular capillaries
& podocytes

22. • Capillary
endothelium
*
• Basement
membrane
• Podocytes
* Made of filtrate
membrane; major
role in the first step
of urine formation

23. The renal corpuscle opens into:
• Proximal convulated tubule
(PCT)
- lined with microvilli in lumen
- cuboidal epithelium
- absorption & secretion
- opens into nephron loop

24. • Distal convulated tubule (DCT), further end of
the nephron
- cuboidal epithelium with fewer microvilli
- surrounded by smooth muscles of the space
to form juxta glomerular apparatus
PCT, renal corpuscle & DCT: placed in outer
kidney cortex

26. i. nephron loop connect PCT & DCT
ii. collecting tubule receives contents from DCT
iii. squamous epithelium protect the tubules against
abrasion
iv. cuboidal epithelium: reabsorption of water & ions in
the process of urine formation
v. nephron loop, collecting ducts & DCT placed in
medulla
vi. The DCT opens into collecting tubule carrying urine
into calyces
•DCT < microvilli than PCT

27. Urine production:
In nephron
• 3 processes
 Glomerular
Filtration
 Tubular
Reabsorption
 Tubular Secretion

28. Filtration
• Occurs in Bowman’s
capsule by filtrate or
hydrostatic pressure
from glomerular
capillaries
• Due to smaller
diameter of efferent
arterioles than
afferent arterioles

29. Filtration Cont.
• Pressure exerted by plasma & osmotic pressure in
glomerulus (filteration pressure) -forces substances out of
glomerulus
• The portion of the plasma entering the nephron is called
-Filtrate
• Generally, small molecule:
- diameter <40,000 daltons/ 7nM
- e.g. water, sugar, ions, aminoacids, ammonia, urea,
creatine able to pass through
• Large molecules:
- exit into glomerulus
- transported through blood into efferent arterioles

30. Tubular Reabsorption:
• The filtrate leaves
Bowman’s capsule &
flow through proximal
tubule, nephron loop
& DCT
• Substances needed in
filtrate are reabsorbed
back into blood
- to maintain fluid &
electrolyte, pH
• Active transport

31. • These include water, important amino acids,
nutrients, hormones etc.
a. Water is reabsorbed by osmosis in PCT
b. Amino acids, ions(Na+) are reabsorbed by active
transport in the PCT
c. limit to glucose reabsorbtion: up to 100
mg/100ml, then all is reabsorbed (no glucose in
urine)

32. d. above 150 mg/100ml glucose, then glucose
present in urine
e. active ion reabsoption:
sodium, potassium, calcium,
magnesium,bicarbonate, phosphate, and sulfate ions
actively resorbed (selective reabsorption)
f. The small volume of filterate forming a part of
urine are urea, creatine, toxic substances and K+.

33. Secretion
• Substances that is not required & foreign
material (e.g. drugs); secreted into tubules to
be excreted out from body (in urine)
• Tubular secretion: secrete H+ to maintain
homeostasis of blood pH

34. • Ammonia is secreted by the epithelial cells of
nephron and secreted into lumen of nephron by
passive transport.
• Substances that are toxic to body include drugs,
hydrogen ions, K+ ions are secreted into PCT, DCT
by active transport.
• Though the filtrate that enters the proximal
convoluted tubule is 180 lts,
• only 1% is ultimately removed as urine and
• 99% is reabsorbed along the different regions of
the nephron

36. Urine composition
• Colour: clear - Light yellow (presence of
urobilin)
• Normal volume 1 to 1.5L/day
• pH ≈ 6 (4.5-8) but mostly acidic
• Normal specific gravity- 1.003 to 1.040

37. Major nitrogen-containing wastes
a. Urea: most abundant organic waste product
(21g/day), d/t breakdown of amino acids
b. Uric acid: results from breakdown of nucleic
acids (0.5g/day)
c. Creatinine: generated in muscle tissue from
breakdown of creatine phosphate (1.8g/day:
amount depend on muscle mass)
d. Ammonia salt: small amount filtered into
Bowman’s capsule

38. Water balance & urine output
• Regulation of urine formation – regulates
homeostasis of fluids in the body
• Hormones:
i. Antidiuretic hormone (ADH)
ii. Aldosterone
iii. Antinatriuretic hormone (ANH)

39. a. When water concentration is low……….
Aldosterone released
Stimulates gene expression of those proteins that involved in Na+ active
transport
Na+ ion concentration in blood (K+ eliminate)
Water reabsorbed & conserved
Urine formation
i. Maintain water levels in blood
ii. Maintain blood pressure

40. b. When water concentration is high………
Release of aldosterone is inhibited
Stopping gene expression of those proteins that involved in
Na+ active transport
Na+ ion concentration in blood (reduce ion Na+ uptake)
Water excretion increases
Urine formation
i. Maintain water levels in blood
ii. Maintain blood pressure

41. Ureters
• Tubes; convey urine from
kidney to urinary bladder
• Continuous with renal
pelvis; passes obliquely
through the posterior
wall of bladder
• Urine accumulates –
pressure in bladder –
ureters compressed –
opening occluded
- to prevent urine reflux
back

42. Ureters: structure & function
• 3 layers of tissue:
i. fibrous tissue – outer covering
ii. muscular layer – middle
iii. Mucosa – inner, transitional epithelium
• Function: propel urine from kidney into
bladder by peristaltic contraction of the
smooth muscle

43. Urinary bladder
• Reservoir for urine
• Situated in pelvic cavity – size & position
vary depends on the amount of urine contain
• Structure:
- pear-shaped – oval (filled with urine)
- 3 surface: anterior, superior & posterior (base)
- opens into urethra at the lowest point (neck)
- have folds/ rugae
- 3 orifices; form trigone (2: posterior wall – opening of ureters & 1:
lower – origin of urethra)

44. Urinary bladder: structure & function
• 3 layers of bladder wall
i. outer: loose connective tissue (blood, lymph
vessels & nerves)
ii. middle: smooth muscle & elastic tissue;
dextrusor muscle
iii. inner: mucosa, transitional epithelium

46. Urethra
• Urethra opens to out side by external
sphincter made of skeletal muscles.
• ♂ - opens into penis
• ♀ - opens into vestibule in vagina.
• By parasympathetic stimulation , muscles of
bladder expel urine.

47. Male urethra
• 18-20cm long
• 2 curvatures – s-
shaped
• Extend from internal
urethral orifice at the
neck of bladder to
external urethral
orrifice at tip of penis

48. Female Urethra
• Narrow membranous
about 4cm long
• Extend from internal
to external urethral
orifice directly in front
of the vaginal opening
• Place behind the
symphysis pubis in the
anterior wall of vagina

49. MICTURITION
• The reflex center for urination is present in the spinal
cord
• Reflex center respond to stretch receptors of urinary
bladder
• Initiates urge to urinate

50. • Process of urination requires
i. relaxation of external urethral sphincter,
ii. contraction detrusor muscles
iii. the muscles of abdominal wall and pelvis
• Detrusor is a smooth muscle under
parasympathic control
• Where as
• Muscles of abdomen and pelvis and
external urethral sphincter are skeletal
muscles under voluntary control

51. Muscle involved in micturition

53. Thank you….
Questions please!!