The document provides an overview of the urinary system, including its anatomy and functions. Some key points: - The kidneys filter blood to remove waste and regulate fluid balance. Each kidney contains around 1 million nephrons, the functional units that filter blood into urine. - The nephron is made up of blood vessels and tubules that work together to filter blood, reabsorb useful molecules, and secrete waste molecules into urine. - Urine is formed in four steps - glomerular filtration, tubular reabsorption, tubular secretion, and concentration by the collecting duct. Nearly all the filtrate is reabsorbed except for waste products. - Hormones

1. The Urinary System
Prepared by: vivek sir
vivek
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2. TABLE OF CONTENT
1) General Introduction
2) Anatomy of Urinary System
3) Urine Formation
4) Urine Storage and Elimination
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3. Composition of the Urinary System
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4. Functions of the Kidneys
1) filter blood plasma, separate
wastes, return useful materials
to the blood, and eliminate the
wastes.
Toxic nitrogenous wastes
- ammonia, urea, uric acid, creatine, and
creatinine
- cause diarrhea, vomiting, and cardiac arrhythmia,
convulsions, coma, and death.
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5. Functions of the Kidneys
1) filter blood plasma,
separate wastes, return
useful materials to the
blood, and eliminate the
wastes.
2) regulate blood volume
and osmolarity.
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6. 3) produce hormones
1. renin
2. erythropoietin
3. calcitrol
Functions of the Kidneys
4) regulate acid-base balance
of the body fluids.
5) detoxify superoxides, free
radicals, and drugs.
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7. ANATOMY OF THE KIDNEYS
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8. - The kidneys lie along the posterior abdominal wall
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9. - The medial surface of the kidney is concave with
a hilum carrying renal nerves and blood vessels.
The renal parenchyma is divided into an outer
cortex and inner medulla.
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10. Extensions of the cortex
(renal columns) project
toward the sinus, dividing
the medulla into 6-10
renal pyramids. Each
pyramid is conical with a
blunt point called the
papilla facing the sinus.
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11. The papilla is nestled into
a cup called a minor calyx,
which collects its urine.
Two or three minor calyces
merge to form a major
calyx. The major calyces
merge to form the renal
pelvis.
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12. - The kidney contains 1.2 million nephrons, which
are the functional units of the kidney.
- A nephron consists of :
i. blood vessels
afferent arteriole
glomerulus
efferent arteriole
ii. renal tubules
proximal convoluted tubule
loop of Henle
distal convoluted tubule
The Nephron
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13. afferent arteriole
glomerulus
efferent arteriole
proximal
convoluted
tubule
distal
convoluted
tubule
Loop of Henle
blood
blood
The Nephron
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14. - Most components of
the nephron are within
the cortex.
The Nephron
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15. Nephrons are connected to renal artery/vein and
ureter.
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16. The glomerulus is enclosed in a two-layered glomerular
(Bowman's) capsule.
Proximal
tubule
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17. URINE FORMATION
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18. The kidney produces urine through 4 steps.
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19. Glomerular
Filtrate
Tubular fluid
Urine
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20. 1) Glomerular Filtration
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21. The Filtration Membrane
From the plasma to the
capsular space, fluid passes
through three barriers.
fenestrated
epithelium
basement
membrane
foot processes
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22. The Filtration Membrane
Almost any molecule smaller
than 3 nm can pass freely
through the filtration membrane
into the capsular space.
These include:
Water, electrolytes, glucose, amino acids,
lipids, vitamins, and nitrogenous wastes
Kidney infections and trauma commonly damage
the filtration membrane and allow plasma
proteins or blood cells to pass through.
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23. Blood cells
in urine
Plasma proteins
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24. Filtration Pressure
Glomerular filtration follows the same principles
that govern filtration in other capillaries.
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25. Glomerular Filtration Rate (GFR)
- is the amount of filtrate formed per
minute by the two kidneys combined.
- For the average adult male, GFR is
about 125 ml/min.
- This amounts to a rate of 180 L/day.
- An average of 99% of the filtrate is
reabsorbed, so that only 1-2 L of urine
per day is excreted.
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26. GFR must be precisely
controlled.
a. If GFR is too high
- increase in urine output
- threat of dehydration and electrolyte
depletion.
b. If GFR is too low
- insufficient excretion of wastes.
c. The only way to adjust GFR from
moment to moment is to change
glomerular blood pressure.
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27. Renal Autoregulation
- the ability of the kidneys to maintain a
relatively stable GFR in spite of the
changes (75 - 175 mmHg) in arterial
blood pressure.
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28. The nephron has two ways to
prevent drastic changes in GFR
when blood pressure rises:
1) Constriction of the afferent
arteriole to reduce blood flow into
the glomerulus
2) Dilation of the efferent arteriole
to allow the blood to flow out
more easily.
Change in an opposite direction if blood pressure falls
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29. Mechanisms of Renal Autoregulation
1) myogenic response
2) tubuloglomerular feedback
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30. 1) myogenic response
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31. 2) tubuloglomerular feedback
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32. 1) Glomerular Filtration
2) Tubular Reabsorption
3) Tubular Secretion
4) Concentrating Urine by Collecting Duct
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33. About 99% of
Water and other
useful small
molecules in the
filtrate are
normally
reabsorbed back
into plasma by
renal tubules.
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34. Reabsorption in Proximal
Convoluted Tubules
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35. - The proximal convoluted
tubule (PCT) is formed by
one layer of epithelial cells
with long apical microvilli.
- PCT reabsorbs about
65% of the glomerular
filtrate and return it to the
blood.
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36. 1) transcellular route
2) paracellular route
Routes of Proximal
Tubular Reabsorption
PCT
peritubular capillary
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37. Mechanisms of Proximal Tubular
Reabsorption
1) Solvent drag
2) Active transport of sodium.
3) Secondary active transport of glucose, amino
acids, and other nutrients.
4) Secondary water reabsorption via osmosis
5) Secondary ion reabsorption via electrostatic
attraction
6) Endocytosis of large solutes
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38. Osmosis
Water moves from a compartment of low osmolarity
to the compartment of high osmolarity.
low osmolarity
( high H2O conc.)
high osmolarity
( low H2O conc.)
H2O
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39. 1) Solvent drag
- driven by high
colloid osmotic
pressure (COP) in the
peritubular capillaries
- Water is reabsorbed
by osmosis and
carries all other
solutes along.
- Both routes are
involved.
Proteins stay
H2O
Proteins
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40. 2) Active transport of sodium
Sodium pumps (Na-K ATPase) in basolateral
membranes transport sodium out of the cells against its
concentration gradient using ATP.
capillary PCT cell Tubular
lumen
Na+
K+
Na+
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41. There are also pumps for other ions
capillary PCT cell Tubular
lumen
Ca++
Ca++
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42. - Various cotransporters can carry both Na+ and
other solutes. For example, the sodium-
dependent glucose transporter (SDGT) can
carry both Na+ and glucose.
3) Secondary active transport of glucose, amino
acids, and other nutrients
Na+
Glucose
capillary PCT cell
Na+
K+
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43. Amino acids and many other nutrients are
reabsorbed by their specific cotransporters
with sodium.
Na+
capillary PCT cell
Na+
K+
amino acids
3) Secondary active transport of glucose, amino
acids, and other nutrients
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44. Sodium reabsorption makes both
intracellular and extracellular fluid hypertonic
to the tubular fluid. Water follows sodium into
the peritubular capillaries.
4) Secondary water reabsorption via osmosis
H2O
Na+
Na+
capillary PCT cell Tubular
lumen
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45. Negative ions tend to follow the positive
sodium ions by electrostatic attraction.
5) Secondary ion reabsorption via
electrostatic attraction
Na Na+
Cl-
capillary PCT cell Tubular
lumen
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46. The glomerulus filters a small amount of protein
from the blood. The PCT reclaims it by endocytosis,
hydrolzes it to amino acids, and releases these to the
ECF by facilitated diffusion.
6) Endocytosis of large solutes
protein
capillary PCT cell Tubular
lumen
amino acids
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47. The Transport Maximum
- There is a limit to the amount of solute that the renal
tubule can reabsorb because there are limited numbers of
transport proteins in the plasma membranes.
- If all the transporters are occupied as solute molecules
pass through, some solute will remain in the tubular fluid
and appear in the urine.
Na+
Glucose
Example of diabetes
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48. Glucose in urine
high glucose in blood
high glucose in filtrate
Exceeds Tm for glucose
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49. Reabsorption in the
Nephron Loop
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50. - The primary purpose
is to establish a high
extracellular osmotic
concentration.
- The thick ascending
limb reabsorbs solutes
but is impermeable to
water. Thus, the tubular
fluid becomes very
diluted while
extracellular fluid
becomes very
concentrated with
solutes.
mOsm/L
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51. The high osmolarity enables the collecting duct
to concentrate the urine later.
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52. Reabsorption in Distal
Convoluted Tubules
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53. - Fluid arriving in the
DCT still contains about
20% of the water and
10% of the salts of the
glomerular filtrate.
- A distinguishing feature
of these parts of the renal
tubule is that they are
subject to hormonal
control.
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54. Aldosterone
a. secreted from adrenal
gland in response to a 
Na+ or a  K+ in blood
b. to increase Na+ absorption
and K+ secretion in the DCT
and cortical portion of the
collecting duct.
c. helps to maintain blood
volume and pressure.
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55. Atrial Natriuretic Factor
- secreted by the atrial
myocardium in response to
high blood pressure.
- It inhibits sodium and
water reabsorption,
increases the output of both
in the urine, and thus
reduces blood volume and
pressure.
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56. 1) Glomerular Filtration
2) Tubular Reabsorption
3) Tubular Secretion
4) Concentrating Urine by Collecting Duct
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57. Tubular Secretion
- Renal tubule extracts chemicals from the blood and
secretes them into the tubular fluid.
- serves the purposes of waste removal and acid-base
balance.
H+
H+
capillary PCT cell Tubular
lumen
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58. 1) Glomerular Filtration
2) Tubular Reabsorption
3) Tubular Secretion
4) Concentrating Urine by Collecting Duct
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59. 1. The collecting duct
(CD) begins in the
cortex, where it
receives tubular fluid
from numerous
nephrons.
2. CD reabsorbs water.
Cortex
collecting
duct
urine
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60. 1. Driving force
The high
osmolarity of extracellular
fluid generated by NaCl
and urea, provides the
driving force for water
reabsorption.
2. Regulation
The medullary
portion of the CD is not
permeable to NaCl but
permeable to water,
depending on ADH.
Cortex
mOsm/L
medulla
urine
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61. a. In a state of full hydration,
antidiuretic hormone (ADH) is
not secreted and the CD
permeability to water is low,
leaving the water to be
excreted.
Cortex
mOsm/L
medulla
Control of Urine Concentration depends on the
body's state of hydration.
urine
b. In a state of dehydration,
ADH is secreted; the CD
permeability to water
increases. With the increased
reabsorption of water by
osmosis, the urine becomes
more concentrated.
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62. Cortex
medulla
urine
No more reabsorption after tubular fluid leaving CD
urine
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63. Composition and Properties of Urine
Fresh urine is clear, containing no blood
cells and little proteins. If cloudy, it could
indicate the presence of bacteria, semen,
blood, or menstrual fluid.
Urine Properties
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64. Substance Blood Plasma
(total amount)
Urine
(amount per day)
Urea 4.8 g 25 g
Uric acid 0.15 g 0.8 g
Creatinine 0.03 g 1.6 g
Potassium 0.5 g 2.0 g
Chloride 10.7 g 6.3 g
Sodium 9.7 g 4.6 g
Protein 200 g 0.1 g
HCO3
- 4.6 g 0 g
Glucose 3 g 0 g
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65. Urine Volume
An average adult produces 1-2 L of urine per
day.
a. Excessive urine output is called
polyuria.
b. Scanty urine output is oliguria. An
output of less than 400 mL/day is
insufficient to excrete toxic wastes.
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66. Diabetes
- is chronic polyuria resulting from various
metabolic disorders, including Diabetes
mellitus and Diabetes insipidus
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67. Diabetes mellitus
- caused by either
1) deficiency of insulin
(Type I) or
2) deficiency of insulin
receptors (Type II).
- Diabetes mellitus features
high glucose in the blood
(hyperglycemia)
glucose
cell
cell
blood
insulin
receptors
insulin
pancreatic  cell
glycogen
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68. - When glucose in
tubular fluid exceeds
the transport maximum
(180 mg/100 ml), it
appears in urine
(glycosuria).
- Glucose in tubular
fluid hinders water
reabsorption by
osmosis, causing
polyuria.
high
urine
volume
high glucose
high glucose
in filtrate
Retain H2O by
osmosis
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69. Diabetes insipidus
- is caused by
inadequeate ADH
secretion.
- Due to the shortage
of ADH, water
reabsorption in CD is
compromised, leading
to polyuria.
 urine
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70. Diuresis
refers to excretion of large amount of urine.
Natriuresis
refers to enhanced urinary excretion of sodium
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71. Diuretics
- are chemicals that increase
urine volume. They are used for
treating hypertension and
congestive heart failure
because they reduce overall
fluid volume.
- work by either increasing
glomerular filtration or reducing
tubular reabsorption. Caffeine
falls into the former category;
alcohol into the latter (alcohol
suppresses the release of
ADH).
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72. Many diuretics produce
osmotic diuresis by
inhibiting sodium
reabsorption
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73. Renal Function Tests
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74. Renal Clearance
a. the volume of blood plasma
from which a particular waste is
removed in 1 minute.
b. can be measured indirectly by
measuring the waste
concentration in blood and
urine, and the urine volume.
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75. 2. Glomerular Filtration Rate
a. Measuring GFR requires a
substance that is not secreted or
reabsorbed at all. Inulin, a polymer
of fructose, is suitable.
b. Inulin filtered by the glomeruli
remains in the renal tubule and
appears in the urine; none is
reabsorbed, and the tubule does not
secrete it. For this solute, GFR is
equal to the renal clearance.
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76. Hemodialysis
artificially clearing wastes from the blood
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77. 1) Dialysis
machine
- efficient
- inconvenient
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78. 2) Continuous
ambulatory
peritoneal
dialysis (CAPD)
Dialysis
fluid
- The peritoneal
membrane is a natural
dialysis membrane
- convenient
- less efficient
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79. Urine Storage and Elimination
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80. The Ureters
The ureters are muscular tubes leading from the
renal pelvis to the lower bladder.
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81. The Urinary Bladder
- is a muscular sac on the floor of the pelvic cavity.
- is highly distensible and expands superiorly.
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82. The openings of the two ureters and the urethra mark a
triangular area called the trigone on the bladder floor.
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83. The Urethra
- conveys urine from the urinary bladder to the
outside of the body.
Females male
3-4 cm ~18 cm
greater risk of
urinary tract
infections
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84. The male urethra has three
regions:
1) prostatic urethra
2) membranous urethra
3) penile urethra.
Difficulty in voiding urine
with enlarged prostate
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85. In both sexes:
- internal urethral sphincter- under involuntary control.
- external urethral sphincter - under voluntary control
internal urethral sphincter
external urethral sphincter
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86. Spinal
cord
Voiding Urine in infants
micturition reflex
When the bladder contains about 200 ml of urine, stretch receptors in the wall send
impulses to the spinal cord. Parasympathetic signals return to stimulate contraction
of the bladder and relaxation of the internal urethral sphincter.
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87. 2. Once voluntary control has developed, emptying of the bladder
is controlled predominantly by a micturition center in the pons. This
center receives signals from stretch receptors and integrates this
information with cortical input concerning the appropriateness of
urinating at the moment. It sends back impulses to stimulate
relaxation of the external sphincter.
Once voluntary control has developed, emptying of the
bladder is controlled predominantly by a micturition center
in the pons. This center receives signals from stretch
receptors and integrates this information with cortical input
concerning the appropriateness of urinating at the
moment. It sends back impulses to stimulate relaxation of
the external sphincter.
Voiding Urine in adults
Voluntary
control
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88. SUMMARY
1) General Introduction
2) Anatomy of Urinary System
3) Urine Formation
4) Urine Storage and Elimination
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