1. 16
Part One: The Urinary
System: Filtration and
Fluid Balance

3. Introduction
 Urinary system acts as
purification plant,
cleaning blood of
waste materials
 Liver does some
purification, but
urinary system
controls electrolyte
and fluid balances for
body

4. Introduction
 Kidneys filter
blood, reabsorb
and secrete ions,
and produce urine
 Without this
important
function you
would die in a few
days

5. System Overview
 Urinary system
consists of two
kidneys, beanshaped organs
located in superior
dorsal abdominal
cavity that filter
blood and make
urine, as well as
accessory
structures

6. System Overview
 Ureter is tube that
carries urine from
each kidney to single
urinary bladder,
located in inferior
ventral pelvic cavity
 Urinary bladder is
basically expandable
sac that holds urine

7. System Overview
 Job of urinary system
is to make urine, thus
controlling body's fluid
and electrolyte
balance and
eliminating waste
products

8. http://www.youtube.com/watch?v=lfGYd1wrTgE

9. 3 Processes to Make Urine

10. Function of the Urinary System
 Filtration involves
passing substances in
blood through walls of
glomerular capillaries
that are dotted with
pores to create
filtrate; contains
various substances
that can either be

11. Function of the Urinary System
 Reabsorbed from
tubules to capillaries
or
 Secreted from
capillaries to tubules
and removed in the urine
 Part of filtrate is
reabsorbed and sent
back into bloodstream,
some is secreted into
tubules and eliminated
from body

12. Figure 16-1
Anatomy of the urinary
system.

13. Anatomy of the urinary system
 Kidney covered
by fibrous layer
of connective
tissue called
renal capsule
 Indentation that
gives kidney
bean-shaped
called renal
hilum
External
Anatomy of
the Kidney

14. Anatomy of the urinary system
 At hilum, renal
arteries bring blood
to kidneys to be
filtered; blood
leaves kidney via
renal vein
 Ureter also
attached to
transport urine
from kidney to
bladder
External
Anatomy of
the Kidney

15. Anatomy of the urinary system
 Renal cortex:
outer layer,
grainy in
appearance;
little obvious
structure to
naked eye;
where blood
filtration occurs
Internal
Anatomy of
the Kidney

16. Anatomy of the urinary system
◦ Renal medulla:
Contains number
of triangleshaped, striped
areas called
renal pyramids
Internal
Anatomy of
the Kidney

17. Anatomy of the urinary system
◦ Renal
medulla:
◦ Renal pyramids
composed of
collecting
tubules for
urine formed in
kidney
Internal
Anatomy of
the Kidney

18. Anatomy of the urinary system
 Renal pelvis
 Funnel, divided
into two or three
large collecting
tubes called
major calyces
Internal
Anatomy of
the Kidney

19. Anatomy of the urinary system
 Renal pelvis
 Each calyx divided into
several minor calyces,
forming cup-shaped
areas around tips of
pyramids to collect
urine that continually
drains through
pyramids
Internal
Anatomy of
the Kidney

20. Filtration and Collection System

21. Figure 16-2
The internal and external
anatomy of the kidney

22. Figure 16-3
Renal blood vessels and the pathway of blood
through the renal system.

23. The NephronFunctional Unit of Kidney
 Consisting of millions
of microscopic
funnels and tubules
 Divided into two
distinct parts:
 Renal corpuscle
 Renal tubule

24. The NephronFunctional Unit of Kidney
 Blood flows through
afferent arteriole
and into the
glomerulus, a
capillary ball
 Walls of glomerular
capillaries dotted
with pores

25. The NephronFunctional Unit of Kidney
 Surrounding
glomerulus is a
double-layered
membrane
called
glomerular
capsule
(Bowman's
capsule)

26. The NephronFunctional Unit of Kidney
 Blood flows into
glomerulus and blood
cells and few large
molecules, mainly
plasma protein, remain
in blood.
 Water and small solutes
allowed to pass through
pores in capillaries
across filter and into
glomerular capsule
The NephronFiltration

27. http://www.youtube.com/watch?v=Hlg7oh2OcOc

28. The NephronFunctional Unit of Kidney
 Blood then exits the
glomerulus through
the efferent arteriole
and the small blood
vessels become part
of the peritubular
capillaries that
surround the renal
tubules

29. The NephronFunctional Unit of Kidney
 Material filtered
from blood into
glomerular capsule
is called the
glomerular filtrate
 If blood or protein
leaks into urine,
this can indicate
kidney filtration
problem
The NephronFiltration

30. The
NephronFunctional Unit of Kidney
 The rest of nephron is
series of tubes known
as renal tubules
 Glomerular filtrate
travels from
glomerular capsule
into first part of renal
tubule called the
proximal tubule
 Wall of proximal tubule
made cells with
microvilli
The Nephron

31. The NephronFunctional Unit of Kidney
 From proximal tubule,
glomerular filtrate flows
into nephron loop
(Loop of Henle)
 Nephron loop consists
of:
 Descending loop
(similar in structure to
proximal tubule) and
Ascending loop
The Nephron

32. http://www.youtube.com/watch?v=_CnhwhHsWLI&list=PL315

33. The NephronFunctional Unit of Kidney
 Glomerular filtrate
then flows into
distal tubule
 From distal tubule,
glomerular filtrate
flows into one of
several collecting
ducts,

34. Flow of Urine to
External Kidney
 Collecting ducts lead
to
 1) minor calyces,
then to
 2)major calyces,
 3)renal pelvis,
 4) ureter
At this point,
glomerular filtrate is
urine

35. Figure 16-5
A functional renal
unit.

36. Urine Formation-3 Processes
 Kidney controls fluid and electrolyte balance by
controlling urine volume and composition
 In order to form urine, nephron must perform
three processes:

37. Urine Formation at
Level of the Nephron
the

38. Urine Formation at the Level
of the Nephron
Urine
Formation

39. Urine Formation at the
Level of the Nephron
 Filtration moves
fluid and chemicals
into nephron from
blood
 Reabsorption and
secretion control
concentration of
chemicals and
volume of urine
Urine
FormationSummary

40. Urine Formation at the Level
of the Nephron
 Due to the action of
reabsorption and secretion,
the urine is chemically very
different that the original
glomerular filtrate.
 In other words, what starts
out looking very similar to
blood, changes after
passing through the
tubules
Urine
FormationSummary

41. Figure 16-7
The processes involved
in urine formation

42. Figure 16-8
Filter selectivity
Only when filter is damaged, do blood and
Only when filter is damaged, do blood and
protein pass through
protein pass through
 Control of filtration
(amount and
composition of fluid
filtered) is
determined by size
of pores in the
walls of the renal
corpuscle
 Like a coffee filter,
it is selective as to
what it let’s pass
through

43.  If GFR controls rate of
urine formation
then….
 Tubular reabsorption
and secretion control
chemistry and volume
of urine
Control of
Tubular
Reabsorption
and Secretion

44.  REMEMBER:
 Substances that are
reabsorbed move
from tubule back to
bloodstream via
peritubular
capillaries and stay
in body
 Substances that are
secreted stay in
tubule and
eventually leave
body via urine
Control of
Tubular
Reabsorption
and Secretion

45. Control of Tubular
Reabsorption and
Secretion
 IMPORTANT:
 Anything that affects
reabsorption and
secretion affects
urine chemistry
and/or composition
and volume

46.  First thing that
affects tubular
reabsorption and
secretion is tubule
permeability
 Each portion of
tubule can
reabsorb and
secrete different
substances
Control of
Tubular
Reabsorption
and Secretion

47. Control of Tubular
Reabsorption and
Secretion
 Molecules move across
membranes through
several different
methods (diffusion,
osmosis, active or
passive transport)

48. Control of Tubular Reabsorption
and Secretion
 Differences in
tubular
permeability result
in dramatic
differences in
which molecules
are reabsorbed or
secreted in each
part of tubule

49. Table 16-2
Individual Tubule
Functions
Most of important substances reabsorbed or secreted
Most of important substances reabsorbed or secreted
in PROXIMAL TUBULE
in PROXIMAL TUBULE
90% of water reabsorbed in descending loop
90% of water reabsorbed in descending loop

50. Balancing
H20 & IONS
 Filtrate flows
into descending
loop,
reabsorbing
water and
increasing
concentration of
ions

51. Balancing H20
& IONS
 As filtrate enters
ascending loop, fluid is
concentrated because
of water loss,
membrane is
permeable to only ions,
so ions are reabsorbed
from ascending loop

52. Figure 16-11
Sites of tubular reabsorption and
secretion

53. Figure 16-11
Sites of tubular
reabsorption and
secretion
Use handout and
Use handout and
follow along
follow along

54. Complete worksheets using your notes from Power
Complete worksheets using your notes from Power
Point Presentation notes and textbook on
Point Presentation notes and textbook on
••TheNephron (page 457 and slides 22-30)
The Nephron (page 457 and slides 22-30)
••GlomerularFiltration (page 458 and PPP)
Glomerular Filtration (page 458 and PPP)

55. 16
Part Two:The Urinary
System: Filtration and
Fluid Balance

56. Pressure Affects
Glomerular Filtration
 Higher pressure in
glomerulus increases
filtration, while lower
pressure decreases
filtration
 Glomerulus protected
from minor changes
in blood pressure by
mechanism called
autoregulation
Filtration
RateAmount of
Filtered
Fluid

57. BP and Formation of
Urine-GFR*
 As systemic BP
increases, afferent
arterioles leading into
glomerulus constrict,
thereby decreasing
amount of blood
getting into
glomerulus
*glomerular filtration rate
Autoregulation
of GFR*

58. BP and Formation of UrineGlomerular Filtration
 Autoregulation can be
overridden when BP
must be regulated.
 Kidney controls fluid
volume, so when BP or
blood volume drops,
(extreme blood loss)
GFR decreases to
conserve fluid volume
Autoregulation
of GFR

59. BP and Formation of UrineGlomerular Filtration
 Glomerular filtration
rate can decrease to
conserve fluid when
blood pressure falls, or
increase filtration if
blood pressure rises
Autoregulation
of GFR

60. ADH-Hormone that controls
Reabsorption and Secretion
 ADH is a hormone that regulates blood pressure
 Made by hypothalamus and secreted from
posterior pituitary when BP decreases or
ionic concentration increases

61. ADH-Hormone that controls
Reabsorption and Secretion
 Increases permeability of distal tubule and
collecting duct; more water reabsorbed, increasing
blood volume and blood pressure, and diluting
ionic concentration

62. ADH-Hormone that
controls Reabsorption
and Secretion
 Less urine is produced
 Alcohol inhibits ADH production, increasing
urine production

63. The Urinary Bladder –
Next Stop for the Urine

64. The Urinary Bladder
and Urination Reflex
 Urinary bladder: small,
hollow organ
 Lined with
transitional
epithelium, which is
the only epithelium
stretchy enough to
expand as bladder
fills

65. The Urinary Bladder
and Urination Reflex
 Ability to stretch enhanced by series of pleats
called rugae
 Has muscular wall consisting of circular and
longitudinal smooth muscle
 Muscle layer known as detrusor muscle

66. Figure 16-14
The urinary
bladder.

67. Figure 16-15
Control of
urination
As urine accumulates, bladder fills and stretches
Stretch triggers urinary reflex and need to void to
empty bladder

68. Figure 16-15
Control of urination
Urination had been thought to be
Urination had been thought to be
spinal reflex; new research
spinal reflex; new research
indicates controlled by brain
indicates controlled by brain
When bladder is full,
signals sent from
bladder to spinal cord
to pons, then
Pons sends
parasympathetic
signals down spinal
cord, causing
contraction of
muscular walls of
bladder, and bladder
empties

69. Figure 16-15
Control of urination
Urine leaves
bladder via
urethra, thin
muscular tube lined
with several
different types of
epithelium along its
length

70. Figure 16-15
Control of urination
Parts of brain can
inhibit urination by
controlling internal
urethral sphincter,
valve at junction of
bladder and urethra,
and external
urethral sphincter,
valve that is part of
muscles of pelvic
floor

71. Figure 16-15
Control of urination
Sympathetic
stimulation of
these sphincters
prevents urine
from leaving body
Although you have
little control over
contractions of
bladder wall, you
have very good
voluntary control
over sphincters