The urinary system includes the kidneys, ureters, urinary bladder, and urethra. The kidneys filter waste from the blood and regulate fluid and electrolyte balance. They remove wastes via nephrons that filter blood and form urine which drains through the ureters into the bladder. The bladder stores urine which is then emptied via the urethra. Together these organs regulate waste elimination, fluid balance, and blood pressure.

1. URINARY SYSTEM
By Abebaw D.

2. Introduction
Excretion
• is the process of separating wastes from the
body fluids and eliminating them from the
body
• It is carried out by the respiratory,
integumentary, digestive, and urinary
systems

3. Introduction…
Several organs contribute to the job of waste
elimination from the body
• kidneys- excrete water, waste from protein
catabolism , some bacterial toxin ,H+,
inorganic salts , heat and carbon dioxide
• Lungs- excrete carbon dioxide, heat and little
water
• Skin (sweat glands) –excrete heat ,water, CO2,
salt and urea
• GIT- eliminates solid ,undigested food ,water,
,salts and heat

4. Urinary system…
• The primary function of the urinary system is
to regulate the concentration and volume of
blood by removing selected amounts of water
and solutes.
• The branch of medicine that deals with the
structure, function, diseases of the male and
female urinary systems and the male
reproductive system is known as nephrology

5. Urinary system…
• Nephrology is the scientific study of the anatomy,
physiology, and pathology of the kidneys.
• The branch of medicine that deals with the male and
female urinary systems and the male reproductive
system is called urology
• A physician who specializes in this branch of medicine
is called a urologist

7. Organs of the urinary system
• Organs of the urinary
system are:-
• Two kidneys
• Two ureters
• One urinary bladder
and
• One urethra

8. The urinary system includes the kidneys, ureters, urinary
bladder, and urethra. Notice the relationship of these
structures to the major blood vessels.

9. kidneys
• Bean shaped
• Retroperitoneal organs
attached to the posterior
abdominal wall.
• Each kidney is enclosed in
renal capsule
• left kidney is a longer and
more slender organ than
the right kidney, and
nearer to the midline.
• Right kidney is lower than
left kidney.

10. kidneys

11. Kidneys…
• Kidneys are reddish brown in color and
• Are located b/n the levels of the last thoracic & third
lumbar vertebrae which means just above the waist.
• They are found b/n the parietal peritoneum and
posterior wall of the abdomen.
• Are partially protected by the eleventh and twelfth
pairs of ribs.
• Since their position is behind the peritoneum they said
to be retroperitoneal organ.
• Other organs include under retroperitoneal organs are
called adrenal gland

12. Kidneys…
• A notch near the center
of the medial concave
border is called the hilus.
• The hilus is:
– The passage through which
the ureter leaves the
kidney.
– Blood & lymphatic vessel &
nerves enter & exit the
kidney.
• The entrance to cavity in
the kidney called the
renal sinus

13. Kidneys…
The kidney are surrounded by three layers
1. Renal capsule
• The inner most layer
• Is a thin transparent fibrous membrane
• It is continuous with the outer coat of the ureter at the hillus.
2. Adipose capsule
• The middle layer
• It is a mass of a fatty tissue
3. Renal facia
• The outer most layer
• Is a thin layer of dense irregular C.T.
• Attach kidney to the surrounding structures and the abdominal
wall

14. Kidneys…
• The kidney itself has the
internal medulla and
external cortex.
• The medulla consists of pale
cone-shaped structured
called renal pyramid.
• The base of the pyramid
face the cortex and their
apexes are known as renal
papillae.
• The renal cortex is
subcapsular, arching over
the bases of the pyramids
and extending b/n them
toward the renal sinus as
renal columns

15. Kidneys…
• The functional portion
(parenchyma) of the
kidney is the cortex and
renal pyramids.
• The parenchyma of each
kidney consists of about
1 million microscopic
structures called
nephrons
• A large cavity in the renal
sinus is called renal pelvis

16. Kidneys…
• The edged of the pelvis
contains cup like
extension called major
and minor calyces.
• There are 2 to 3 major
calyces and 8 to 18
minor calyces.

17. Kidneys…
– Each minor calyx
receives urine from
collecting ducts of one
pyramid & delivers urine
to major calyces.
– From the major calyces,
the urine drains in to the
renal pelvis &out
through the ureter to
the urinary bladder

18. Kidneys…
Path of urine drainage
Nephrons
collecting ducts
papillary ducts
minor calyx-major calyx-renal pelvis-
ureter
urinary bladder
urethra

19. Kidneys…
Function of kidneys
• Regulation of blood volume and composition
• Regulation of blood pressure
• Contribution to metabolism

20. Function of kidneys….
• The kidneys filter blood plasma, separate
wastes from useful chemicals
• regulate blood volume and pressure
• secrete renin and erythropoietin
• regulate blood pH,
• synthesize calcitriol
• detoxify free radicals and drugs, and
• Generate glucose in times of starvation.

21. Kidneys…
Metabolic wastes removed by kidney are :-
• Wastes produced by the body, such as CO2
and nitrogenous wastes
• The main human nitrogenous wastes are
urea, uric acid, and creatinine.

22. Kidneys…
• The level of nitrogenous wastes in the blood
is often expressed as blood urea nitrogen
(BUN)
• An elevated BUN is called azotemia, and may
progress to a serious syndrome called uremia

23. Kidneys…
• Nephrons are functional unit of kidneys
• Nephrons consist of renal corpuscle and renal
tuble
• Blood enters the kidneys through the renal
artery and leaves through the renal vein.
• A single large renal artery, a lateral branch of
the abdominal aorta, supplies each kidney.
• Renal arteries deliver about 25% of resting
COP to the kidney

24. Kidneys…
• Nephron types
1.cortical nephrons.
- About 80–85% of the nephrons
-Their renal corpuscles lie in the outer portion of the renal cortex,
-they have short loops of Henle
2. juxtamedullary nephrons.
- The other 15–20% of the nephrons
-Their renal corpusles lie deep in the cortex,
- They have a long loop of Henle that extends into the deepest
region of the medulla

25. 25
Nephron: types
Cortical nephron (85%)
has peritubular capillaries
Juxtamedullary nephron
(15%) has vasa recta
2.6 million nephrons

26. 26
Nephron: Components
Types:Cortical, Juxta-medullary
Abundance (2 - 2.6 millions)
Components: Glomerulus:

27. (a) A single Nephron.
(b) A renal pyramid containing nephrons.
(c) Longitudinal section of a kidney

31. Kidneys…
• The microscope structure
• i. Nephron: which elaborate urine
• Ii. Collecting tubules
i. Nephron:- comprises a
– Renal corpuscles: concerned with filtration of
plasma and
– Rental tubule: concerned selective restoration
from the glomerular filtrate to form the urine.

32. Kidneys…
ii. Collecting tubules: - carry fluid from several
renal tubules to a terminal papillary duct.
• Opening in to a minor calyx at the apex of
renal papilla.
• Renal corpuses are small rounded masses that
are visible in the renal cortex and columns.

33. Renal corpuscles are two
components
• The glomerulus and
glomerular capsule or
bowman’s capsule
i. The glomerulus: a tuff
of capillary loops that
are supplied by an
efferent arteriole.
Afferent
arteriole
Efferent
arteriole
Glomerulus
Glomerular
capsule
Proximal
convoluted tubule

34. Kidneys…
ii. The glomerulus capsule (of bowman):
• is a double walled epithelial cup that
surrounds the glomerulus.
• It is an expanded end of renal tubule (the
proximal convoluted tubule )
• Capsular (bowman’s) space is a space b/n the
outer wall (parietal) and inner wall (visceral
layer) of the glomerular capsule.

35. Kidneys…
• As blood flows through the glomerular
capillaries water and most kinds of solutes
filter from blood plasma into the capsular
space.
• From the capsular space, filtered fluid passes
in to the renal tubule

36. Kidneys…
36
:
• The renal tubule
consists of a
I. Proximal convulated
tubule (PCT)
II. Loop of henle
(nephron loop)
III. Distal convoluted
tubules

37. Kidneys…
• The wall of the entire renal
tubule consists of a single
layer of epithelial cells and a
basement membrane.
• The renal tubule empties
it’s consist to collecting
ducts.
• collecting ducts then merge
to papillary duct which
drain in to a minor calyx
which inurn empty to major
calyx to the renal pelvis and
then to Ureters that carry
urine to urinary bladder.

38. Kidney…
Clinical Condition
Renal Failure
• Renal failure is a decrease or cessation of glomerular
filtration.
• In acute renal failure (ARF), the kidneys abruptly stop working
entirely (or almost entirely).
• The main feature of ARF is the suppression of urine flow,
usually characterized either by oliguria (daily urine output
between 50 mL and 250 mL), or by anuria (daily urine output
less than 50 mL).

39. Ureters
• There are two ureters one for each kidney.
• It is an extension of the pelvis of the kidney and
stretches to the urinary bladder
• Each of the two ureters transports urine from the
renal pelvis of one kidney to the urinary bladder.
• The ureters are 25–30 cm (10–12 in.) long and are
thick walled, narrow tubes that vary in diameter
from 1 mm to 10 mm along their course

40. Ureters…
• Even though there is no anatomical valve at
the opening of each ureter into the urinary
bladder, a physiological one is quite effective.
• When this physiological valve is not operating
properly, it is possible for microbes to travel
up the ureters from the urinary bladder to
infect one or both kidneys
• Ureters are retroperitoneal organs.

41. Ureters…
• The wall of the ureters is composed of three
layers
– An external adventitia,
– A middle non striated muscles and
– An inner muscular layer

43. Urinary bladder
• Is a hollow muscular organ situated retroperitoneal,
posterior to the pubic symphysis
• In the male, it is directly anterior to the rectum.
• In the female, it is anterior to the vagina and inferior to
the uterus.
• Is freely movable and held in position by folds of
peritoneum.
• When slightly distended due to the accumulation of
urine, the urinary bladder is spherical. When it is
empty, it collapses. As urine volume increases, it
becomes pear-shaped and rises into the abdominal
cavity

44. Urinary bladder…
• In females, the capacity is smaller b/c the
uterus occupies the space just above the
bladder.
• The urinary bladder consists of a mucous, a
muscular and a serous coat.
• The average capacity is 700 to 800ml

46. Urethra
• Is small tube leading from the floor of the
urinary bladder to the exterior of the body.
• In both males and females, the urethra is the
terminal portion of the urinary system and the
passageway for discharging urine from the
body.
• In males, it discharges semen (fluid that
contains sperm) as well.

47. Urethra…
• In females, the urethra lies directly posterior to
the pubic symphysis, and has a length of 4 cm
(1.5 in.)
• The male urethra first passes through the
prostate, then through the deep muscles of the
perineum, and finally through the penis, a
distance of about 20 cm (8 in.).
• The wall comprises an outer muscle and an inner
mucous membrane (which is continuously with
that of the urinary bladder)

48. Urethra…
Parts of male urethra
1. Prostatic urethra
2. Membranous urethra
3. Penile urethra
• The urethral orifice is on
the glans penis.

50. Path of Urine in Urinary System
Glomerulus Proximal convoluted tubule  Loop of
Henle  Distal convoluted tubule Collecting duct 
Renal pyramid  Minor calyx  Major calyx  Renal
pelvis  Ureter Bladder  Urethra Out of the body