UROGENITAL SYSTEM PHYSIOLOGY.............

Urogenital system physiology

1. Urinary System
and Body Fluids
Podocytes
Omara Albert Martin, phdo(IPI-Maya),
DE Asbl(Aesthetic Dentistry)
@omara_albertm (social media)
[email protected]
[phone], [phone]
CC: Family Dental Clinic, Gulu
: Tara Dental Clinic, Iganga
: LY Community Clinic, Bboza
: Bava Dental Services, Maya

2. Functions of the Urinary System
•The kidneys
produce urine
•The ureters
transport urine to
the urinary bladder
•The urinary bladder
stores urine
•The urethra
transports urine to
the outside of the
body

3. Functions of the Urinary System
•The following functions are performed by
the kidneys:
1.Excretion (eliminates waste)
2.Regulate blood volume and pressure
3.Regulation of the concentration of solutes in
the blood (ion concentration)
4.Regulation of extracellular fluid pH
5.Regulation of red blood cell synthesis
6.Vitamin D production

4. Kidney Anatomy and Histology
•Location and
External Anatomy of
the Kidneys
–Lie behind the
peritoneum
(retroperitoneal)
on the posterior
abdominal wall on
each side of the
vertebral column

5. Kidney Anatomy and Histology
•Surrounded by a renal
capsule and fat and is
held in place by the
renal fascia
•The hilum, on the
medial side of each
kidney, is where blood
vessels and nerves
enter and exit the
kidney

6. Kidney Anatomy and Histology
•The hilum, on the
medial side of each
kidney, is where blood
vessels and nerves
enter and exit the
kidney

7. Renal medulla
Renal column
papilla of pyramid
Renal sinus
Renal pelvis
Major calyx
Renal cortex
Renal pyramid
Minor calyx
Ureter

8. Internal Anatomy and Histology of
the Kidneys
•Two layers: cortex and
medulla
–renal columns extend
into the medulla between
the renal pyramids
–tips of the renal pyramids
project to the minor
calyces
•Minor calyces open into the
major calyces, which open
into the renal pelvis
•Renal pelvis leads to the
ureter

10. Internal Anatomy and Histology of
the Kidneys
•Functional unit of the
kidney - nephron
•Parts of a nephron:
–renal corpuscle
–proximal convoluted
tubule
–loop of Henle
–distal convoluted
tubule

11. Internal Anatomy and Histology of
the Kidneys
Renal corpuscle
a. Bowman’s capsule
b. glomerulus.

12. Internal Anatomy and Histology of
the Kidneys
•Proximal convoluted
tubule
- made up of simple
cuboidal epithelial cells
with brushing border of
microvilli which
increases the functional
surface area for an
optimum reabsorption
and hormonal
secretion.

13. Internal Anatomy and Histology of
the Kidneys
Loop of Henle:
a. descending and thin
ascending limb - made
up of simple squamous
cells.
b. thick ascending
limb - made up of
simple cuboidal
to low columnar cells

14. Internal Anatomy and Histology of
the Kidneys
Distal convoluted tubule
(DCT) - made up of
simple cuboidal cells.
Last part of DCT and
collecting duct - made
up of simple cuboidal
cells consisted of 2 types
of cells:
a. principal cell – has
receptor for antidiuretic
hormone (ADH) and
aldosteron.
b. Intercalated cells –
function in regulating
blood pH.

15. Cortex
Medulla
Medulla

16. Renal corpuscle
(Bowmann’s capsule
and glomerulus)
Bowmann’s capsule is
double layered cap on the
glomerulus
a. Arteriole
b. Parietal layer
c. Proximal convoluted tubule
d. Visceral layer
Renal tubules
P
PD
D

17. Internal Anatomy and Histology of
the Kidneys
.
Fluid leaves the blood in the
glomerulus and enters
Bowman’s capsule
The nephron empties
through the distal
convoluted tubule into a
collecting duct
The collecting ducts empty
into papillary ducts,
which empty into minor
calyces

18. Internal Anatomy and Histology of
the Kidneys
•Cortical nephrons
–85% of total nephrons
–Located in the cortex
•Juxtamedullary nephrons
–Are located at the cortex-
medulla junction
–Have loops of Henle that
deeply invade the
medulla
–Have extensive thin
segments
–Are involved in the
production of
concentrated urine

19. Internal Anatomy and Histology of
the Kidneys
Bowman’s capsule
a. outer parietal layer
b. inner visceral layer
consisting of podocytes
Filtration membrane:
a. Endothelium of
glomerular capillaries
(with fenestrae)
b. Basement membrane
c. Podocytes (with
filtration slits)

20. Capillary Beds of the Nephron
•Every nephron has
two capillary beds
–Glomerulus
–Peritubular capillaries
•Each glomerulus is:
–Fed by an afferent
arteriole
–Drained by an efferent
arteriole

21. Capillary Beds of the Nephron
•Blood pressure in the
glomerulus is high
because:
–Arterioles are high-
resistance vessels
–Afferent arterioles
have larger
diameters than
efferent arterioles
•Fluids and solutes are
forced out of the blood
throughout the entire
length of the glomerulus

22. Arteries and Veins of the Kidneys
•Renal artery enters the
kidney and branches
many times, forming
afferent arterioles
•Efferent arterioles
from the glomeruli
supply the peritubular
capillaries and vasa
recta

23. Arteries and Veins of the Kidneys
•Peritubular capillaries
and vasa recta join
small veins that
converge to form the
renal vein, which exits
the kidney

25. Arteries and Veins of the Kidneys
•Juxtaglomerular
apparatus
–granular cells of the
afferent arteriole
–macula densa (part
of the distal
convoluted tubule)
–http://www.wisc-
online.com/objects/a
p2204/ap2204.swf

26. Urine Production
•Kidneys filter the body’s
entire plasma volume
60 times each day
•Glomerular filtrate:
–contains all plasma
components except
protein
–loses water,
nutrients, and
essential ions to
become urine

27. Urine Production
•Urine contains
metabolic wastes and
unneeded substances
•Urine is produced by
the processes of
1. Filtration
2. Tubular reabsorption
3. Tubular secretion

28. Urine production
•Glomerular filtration
–Water and solutes smaller than proteins are forced through the
capillary walls and pores of the glomerular capsule into the renal
tubule
•Tubular reabsorption
–Water, glucose, amino acids and needed ions are transported
out of the filtrate into the tubule cells and then enter the capillary
blood
•Tubular secretion
- H+, K+, creatinine and drugs are removed from the peritubular
blood and secreted by the tubule cells into the filtrate

30. Tab.
23.1

31. Urine Formation
Fig. 23.7

32. Abnormal urinary constituents
Substance Name of condition Possible causes
Glucose Glycosuria Nonpathological: excessive intake of sugary
foods
Pathological: diabetes mellitus
Proteins Proteinuria
Albuminuria
Nonpathological: physical excertion,
pregnancy
Pathological: glomerulonephritis, hypertension
Pus (WBC
and bacteria)
Pyuria Urinary tract infection
RBC Hematuria Bleeding in the urinary tract (due to trauma,
kidney stones, infection)
HemoglobinHemoglobinuria Various: transfusion reaction, hemolytic
anemia
Bile pigmentBilirubinuria Liver disease (hepatitis)

33. Urine Production
•Filtration
–The glomerular filtration rate is the amount of filtrate
produce per minute
–The filtrate is plasma minus blood cells, platelets,
and blood proteins
•Most (99%) of the filtrate is reabsorbed

34. Urine Production
Filtration pressure is
responsible for filtrate
formation.
–Glomerular
capillary pressure
minus capsule
pressure minus
blood colloid
osmotic pressure
–Changes are
primarily caused
by changes in
glomerular
capillary pressure

35. Urine Production
•Regulation of Glomerular Filtration Rate
–Autoregulation dampens systemic blood pressure
changes by altering afferent arteriole diameter
•Under normal conditions, renal autoregulation
maintains a nearly constant glomerular filtration
rate
•Autoregulation entails two types of control
–Myogenic: responds to changes in pressure in
the renal blood vessels
–Flow-dependent tubuloglomerular feedback:
senses changes in the juxtaglomerular
apparatus
–Sympathetic stimulation decreases renal blood
flow and afferent arteriole diameter

36. Tubular Reabsorption
•A transepithelial
process whereby
most tubule
contents are
returned to the
blood

37. Tubular Reabsorption
•Transported substances
move through three
membranes
–Luminal and
basolateral
membranes of
tubule cells
–Endothelium of
peritubular
capillaries
•Only Ca
2+
, Mg
2+
, K
+
, and
some Na
+
are reabsorbed
via paracellular pathways

38. Tubular Reabsorption
•Filtrate is reabsorbed
by:
–diffusion
–facilitated diffusion
–active transport
–symport
–antiport from the
nephron and
collecting ducts into
the peritubular
capillaries and vasa
recta

39. Tubular Reabsorption
•Proximal convoluted
tubule reabsorbs 65% of
filtrate water and NaCl
(solutes)
•Descending limb of the
loop of Henle reabsorbs
15% of filtrate water
•Ascending limb of the
loop of Henle reabsorbs
25% of filtrate NaCl
•Distal convoluted
tubules and collecting
ducts reabsorb up to
19% of filtrate water and
9%-10% of filtrate water
respectively

40. Tubular Reabsorption
•Waste products and
toxic substances are
concentrated in the
urine

41. Fig. 23.9
Reabsorption in the Proximal Convoluted Tubule

42. Fig. 23.10
Reabsorption in the Thick Segment of the Ascending
Limb of the Loop of Henle

43. Tubular Secretion
•Substances are secreted in the proximal or distal
convoluted tubules and the collecting ducts
•Hydrogen ions, K+, and some substances not
produced in the body are secreted by antiport
mechanisms

44. Fig. 23.11
Summary of Urine
Concentrating Mechanism

45. Maintaining the Medullary
Concentration Gradient
Necessary for the production
of concentrated urine
Addition of solutes increases
the medullary interstitial
fluid concentration.
a. ascending limb of the
loop of Henle adds
NaCl, but not water
b. Urea cycles between
the collecting ducts
and the thin segments
of the loop of Henle

46. Maintaining the Medullary
Concentration Gradient
•The vasa recta uses a
countercurrent
mechanism that
removes reabsorbed
water and solutes
without disturbing the
medullary concentration
gradient
•http://www.cellphys.ubc.
ca/undergrad_files/urine.
swf

47. Fig.
23.13
Blood Flow Through the Vasa Recta

48. Hormonal Regulation of Urine
Concentration and Volume
•Antidiuretic Hormone (ADH)
–Secreted by the posterior pituitary
–Inhibits diuresis
•This equalizes the osmolality of the filtrate and
the interstitial fluid
–Increases water permeability in the distal
convoluted tubules and collecting ducts by
stimulating the insertion of aquaporin-2 molecules
into apical membranes
–In the presence of ADH, 99% of the water in filtrate
is reabsorbed

49. Hormonal Regulation of Urine
Concentration and Volume
•ADH regulates blood osmolality by altering
water reabsorption
–An increase in blood osmolality or a significant
decrease in blood pressure stimulates increased
ADH secretion
•Increases water reabsorption and as a result
–Blood osmolality decreases
–Blood volume and blood pressure increase
–Urine concentration increases
–Urine volume decreases

50. Hormonal Regulation of Urine
Concentration and Volume
–A decrease in blood osmolality or a significant
increase in blood pressure stimulates decreased
ADH secretion
•Decreases water reabsorption and as a result
–Blood osmolality increases
–Blood volume and blood pressure decrease
–Urine concentration decreases
–Urine volume increases

51. Fig.
23.14
Effect of ADH on Water
Movement

53. Hormonal Regulation of Urine
Concentration and Volume
•Renin—Angiotensin—Aldosterone
–Renin, produced by the kidneys, causes the
conversion of angiotensinogen to angiotensin I
–Angiotensin-converting enzyme converts
angiotensin I into angiotensin II, which stimulates
aldosterone secretion from the adrenal cortex
–Aldosterone affects Na
+
and Cl
-
transport in the
nephron and collecting ducts by stimulating an
increase in transport proteins

54. Fig. 23.15
Effect of Aldosterone on
Ion Movement

55. Hormonal Regulation of Urine
Concentration and Volume
Atrial Natriuretic
Hormone
•Produced by the heart
when blood pressure
increases
•Inhibits Na+ reabsorption
in the kidneys, resulting in
increased urine volume
and decreased blood
volume and blood pressure
•Inhibits ADH secretion and
dilates arteries and veins

56. Fig. 23.16
ANH and the Regulation of Na
+
and Water

57. Anatomy and Histology of the Ureters
and Urinary Bladder
•The walls of the ureter and urinary bladder consist of
1. Mucosa
•Epithelium
–Transitional epithelium permits changes in size
•Lamina propria – loose connective tissue
2. Muscular coat
–Contraction of the smooth muscle moves urine
–Inner longitudinally and outer circular
–The muscle of bladder is called detrusor muscle
3. Fibrous adventitia

58. Ureter Urinary bladder

59. Anatomy and Histology of the Urethra
–The urethra is lined with transitional and
stratified squamous epithelium
•Males have an internal urethral sphincter of
smooth muscle that prevents retrograde
ejaculation of semen
•An external urethral sphincter of skeletal
muscle allows voluntary control of urination

60. Fig.
23.17

61. Urine Movement
•Urine Flow Through the Nephron and
Ureters
–A pressure gradient causes urine to flow
from Bowman’s capsule to the ureters
–Peristalsis moves urine through the ureters

62. Urine Movement
•Micturition Reflex
–Stretch of the urinary bladder stimulates a
reflex that causes the urinary bladder to
contract and inhibits the external urethral
sphincter
–Higher brain centers can stimulate or inhibit
the micturition reflex
–Voluntary relaxation of the external urethral
sphincter permits urination and contraction
prevents it

63. Fig.
23.18
Micturition
Reflex

65. Effects of Aging on the Kidneys
•There is a gradual decrease in the size
of the kidney
–Associated with a decrease in renal blood
flow
–The number of functional nephrons
decreases
•Renin secretion and vitamin D synthesis
decreases
•Nephron secretion and absorbtion
declines

66. Body Fluids
•Today body water volume (60%) body weight
•Intracellular fluid is inside cells (40%)
•Extracellular fluid is outside cells (20%)and includes
interstitial fluid (80%) and plasma (20%)

67. Intracellular Fluid
•Substances used or produced inside the
cell
•Substances exchanged with the
extracellular fluid
•Plasma membrane regulates the
movement of materials
•The difference between intracellular and
extracellular fluid concentrations
determines water movement

68. Fig.
23.19
Regulation of Intracellular Fluid

69. Regulation of Body Fluid Concentration
and Volume
•Water Input
–Ingested (90%) or produced in metabolism
(10%)
–Habit and social setting influence thirst
•Increase in extracellular osmolality
•Decrease in blood pressure stimulates the
sense of thirst
–Wetting of the oral mucosa or stretch of the
gastrointestinal tract inhibits thirst

70. Regulation of Body Fluid Concentration
and Volume
•Water Output
–Lost through evaporation from the
respiratory system and the skin (insensible
perspiration and sweat) (35%)
–Loss into the gastrointestinal tract normally
is small (4%)
–The kidneys are the primary regulator of
water excretion (61%)

71. Tab.
23.3

72. Fig.
23.20
Effect of Blood Osmolality and Pressure
on Water Intake

73. Regulation of Body Fluid Concentration
and Volume
•Regulation of Extracellular Fluid
Osmolality
–An increase in extracellular fluid osmolality
stimulates thirst and ADH secretion
•Increased fluid intake
•Increased water reabsorption in the kidneys
–A decrease in extracellular osmolality
inhibits thirst and decreases ADH secretion
•Decreased fluid intake
•Decreased water reabsorption in the kidneys

74. Fig.
23.21
Summary of Blood Osmolality Regulation

75. Regulation of Body Fluid Concentration
and Volume
•Regulation of Extracellular Fluid Volume
–Decreased extracellular fluid volume results in
•Increased aldosterone secretion
•Decreased ANH secretion
•Increased ADH secretion
•Increased sympathetic stimulation of the afferent
arterioles
•Increased thirst
•Decreased glomerular filtration rate
•Increased reabsorption of Na+ and water

76. Regulation of Body Fluid Concentration
and Volume
•Regulation of Extracellular Fluid Volume
–Increased extracellular fluid volume results in
•Decreased aldosterone secretion
•Increased ANH secretion
•Decreased ADH secretion
•Decreased sympathetic stimulation of the afferent arterioles
•Decreased thirst
•Increased glomerular filtration rate
•Decreased reabsorption of Na+ and water

77. Fig.
23.22
Summary of
Blood Volume
Regulation

78. Regulation of Specific Electrolytes in the
Extracellular Fluid
•Regulation of Sodium Ions
–The kidneys are the major route by which
Na+ is excreted
–Excretion is regulated by aldosterone and
ANH
–Lost in sweat
–With association anions are responsible for
90%-95% of extracellular osmotic pressure

79. Tab.
23.4

80. Regulation of Specific Electrolytes in the
Extracellular Fluid
•Regulation of Chloride Ions
–Dominant negatively charged ions in
extracellular fluid
–Regulated by the mechanisms regulating
cations
•Regulation of Potassium Ions
–Reabsorbed from the proximal convoluted
tubule
–Secreted into the distal convoluted tubule
–Aldosterone increases the amount of K+
secreted

81. Fig. 23.23
Summary of Blood K
+
Regulation

82. Tab.
23.5

83. Regulation of Specific Electrolytes in the
Extracellular Fluid
•Regulation of Calcium Ions
–Parathyroid hormone increases
extracellular Ca2+ levels
•Increases osteoclast activity
•Increases reabsorption from the kidneys
•Stimulates active vitamin D production
–Vitamin D stimulates Ca2+ uptake in the
intestines
–Calcitonin decreases extracellular Ca2+
levels by inhibiting osteoclasts

84. Fig.
23.24
Summary
of Blood
Ca
2+

Regulation

85. Tab.
23.6

86. Regulation of Acid-Base Balance
•Acids release H+ into solution, and
bases remove them
•Buffers respond almost instantaneously
to changes in pH, whereas the
respiratory system takes minutes and the
kidneys may take hour to days
•The kidneys have the greatest ability to
regulate pH precisely

87. Fig.
23.25
Summary of
Acid-Base
Balance
Regulation

88. Regulation of Acid-Base Balance
•Buffer Systems
–A buffer resists changes in pH
•When H+ are added to a solution, the buffer
removes them
•When H+ are removed from a solution, the
buffer replaces them
–Carbonic acid/bicarbonate, proteins,
phosphate compounds, and ammonia are
important buffers

89. Respiratory Regulation of Acid-Base Balance
•Achieved through the carbonic
acid/bicarbonate buffer system
–As carbon dioxide levels increase, pH
decreases
–As carbon dioxide levels decrease, pH
increases
–Carbon dioxide levels and pH affect the
respiratory centers

90. Respiratory Regulation of Acid-Base Balance
•The pH affects the respiratory centers
•Hypoventilation increases blood carbon
dioxide levels, and hyperventilation
decreases blood carbon dioxide levels
–Decreased pH increases the rate and depth
of respiration, which lowers carbon dioxide
levels and increases blood pH
–Increased pH decreases the rate and depth
of respiration, which increases carbon
dioxide levels and decreases blood pH

91. Fig.
23.26
Respiratory
Regulation
of Body
Acid-Base
Balance

92. Renal Regulation of Acid-Base Balance
•For each H
+
added to the blood, a HCO
3
-
is
removed; for each H
+
removed from the blood, a
HCO
3
-
is added
•For each H
+
secreted into the filtrate, a HCO
3
-
is
removed from the filtrate and a HCO
3
-
is added to
the blood
•Hydrogen phosphate (HPO
4
2-
) and ammonia (NH
3)
are the major non-bicarbonate bases in the filtrate
–When H
+
combines with HPO
4
2-
and NH
3, the filtrate is
buffered, allowing additional H
+
to be secreted
–For each H
+
that combines with HPO
4
2-
and NH
3, a new
HCO
3
-
is added to the blood
•The metabolism of glutamine produces new HCO
3
-

93. Fig.
23.27
Reabsorption of HCO
3
-

94. Fig.
23.28
Hydrogen Ion Secretion

95. Page
759