2. Elimination of waste products
Nitrogenous wastes
Toxins
Drugs
Functions of the Urinary System
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3. Regulate aspects of homeostasis
Water balance
Electrolytes
Acid-base balance in the blood
Blood pressure
Red blood cell production
Activation of vitamin D
Functions of the Urinary System
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4. Organs of Urinary System
Kidneys
Urinary
bladder
Ureters
Urethra
4
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5. Kidney
Location
It is bean shaped
Each kidney lies in paravertebral grooves on
posterior abdominal wall retroperitoneally.
The kidneys extend from the level of the
T12 to L3
They receive some protection from ribs
5
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7. External Anatomy
The adult kidney weighs about 150 g
Size: 12 cm long, 6 cm wide, 3 cm thick
Color: reddish-brown
Shape: bean-shaped
The lateral surface of each kidney is convex, while
the medial is concave
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8. External Anatomy
Medial surface has a
vertical cleft called the
renal hilus that leads
into the space within
the kidney called the
renal sinus
On top of each kidney
is an adrenal gland
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9. External Anatomy
Ureters, renal blood
vessels, lymphatics,
and nerves enter the
kidney at the hilus
These structures
occupy the renal
sinus
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10. Supportive tissue
Kidneys are supported by three layers of supportive tissue
The renal capsule
The outer membrane that encloses, supports and protects the
kidney
adheres directly to the kidney surface and isolates it from
surrounding region
The adipose capsule
attaches the kidney to the posterior body wall and cushions it
against trauma
The renal fascia
dense fibrous connective tissue which surrounds the kidney
and anchors these organs to the surrounding structures
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13. Internal Anatomy: Cortex
The outer layer of the kidney
Light in color and has a granular appearance
Contains most of the nephron; main site for
filtration, reabsorption and secretion
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14. Internal Anatomy: renal medulla
Deep to the cortex; inner core of the kidney
Darker tissue which exhibits cone shaped
tissue masses called medullary or renal
pyramids
Contains the pyramids, columns, papillae, and
parts of the nephron
Used for salt, water and urea absorption
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15. Internal Anatomy: renal medulla
Renal pyramid
Triangular units in the medulla that house the
loops of Henle and collecting ducts of the nephron
Each renal pyramid has a base which is convex,
and an apex which tapers toward its papilla
Renal Papilla
The tip of the renal pyramid that releases urine
into a calyx
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17. Internal Anatomy: renal medulla
The apex, or papilla, points internally
The pyramids appear striped because they are
formed almost entirely of roughly parallel bundles of
urine collecting tubules
Inward extensions of cortical tissue called renal
columns separate the pyramids
Each medullary pyramid is surrounded by a capsule
of cortical tissue to form a lobe
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18. Internal Anatomy: renal pelvis
Within the renal sinus is the renal pelvis
This flat, funnel shaped tube is continuous
with the ureter leaving the hilus
Branching extensions of the renal pelvis form
2-3 major calyces, each of which sub-divides
to form several minor calyces
Calyx
A collecting sac surrounding the renal papilla
transports urine from the papilla to the renal pelvis
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19. Cont.…
Renal pelvis collects urine from all of the
calyces
Urine flows through the renal pelvis into the
ureter, which transports it to the bladder
The walls of the calyces, pelvis, and ureter
contain smooth muscle which contract to
move urine
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21. Blood Supply
Kidneys possess an extensive blood supply
Under normal resting conditions, the renal arteries
deliver approximately one-fourth of the total systemic
cardiac output (1200 ml) to the kidneys each minute
The renal arteries issue at right angles from the
abdominal aorta
Each renal artery divides into segmental arteries that
enter the hilus
The segmental arteries branches into lobar and then
interlobar arteries, which pass through the renal columns
toward the cortex
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22. Interlobar arteries then form arcuate arteries
Arcuate arteries branch into the cortex and lead to
interlobular arteries which distribute the blood
evenly throughout the cortex to the afferent
arterioles which serve the nephrons
Blood flow leaving the nephrons returns by veins of
the corresponding names
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26. The structural and functional units
kidneys
of the
Responsible for
Main structures
Glomerulus
Renal tubule
forming urine
of the nephrons
Nephrons
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27. A specialized
capillary bed
Attached to
arterioles on both
sides (maintains
high pressure)
Large afferent
arteriole
Narrow efferent
arteriole Figure 15.3c
Glomerulus
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28. Capillaries are
covered with
podocytes from
the renal tubule
The glomerulus
sits within a
glomerular capsule
(the first part of the
renal tubule) Figure 15.3c
Glomerulus
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32. Arise from efferent arteriole of the
glomerulus
Normal, low pressure capillaries
Attached to a venule
Cling close to the renal tubule
Reabsorb (reclaim) some substances
from collecting tubes
Peritubular Capillaries
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34. Nonselective passive process
Water and solutes smaller than proteins
are forced through capillary walls
Blood cells cannot pass out to the
capillaries
Filtrate is collected in the glomerular
capsule and leaves via the renal tubule
Filtration
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35. The peritubular
materials
Some water
Glucose
Amino acids
Ions
capillaries reabsorb several
Some reabsorption is passive, most is active
Most reabsorption occurs in the proximal
convoluted tubule
Reabsorption
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37. Reverse
Some materials move from the
peritubular capillaries into the renal
tubules
Hydrogen and potassium ions
Creatinine
Materials left in the renal tubule
toward the ureter
move
Secretion – Reabsorption in
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39. Medical Diagnosis
Colored somewhat yellow due to the
pigment urochrome (from the
destruction of hemoglobin)
Sterile
Slightly aromatic
Normal pH of around 6
Specific gravity of 1.001 to
and solutes
1.035
Characteristics of Urine Used for
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40. Slender tubes attaching the kidney to
the bladder
Continuous with the renal pelvis
Enter the posterior aspect of the
Runs behind the peritoneum
Peristalsis aids gravity in urine
bladder
transport
Ureters
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42. Trigone – three openings
Two
One
from the ureters
to the urethrea
Urinary Bladder
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43. Three layers of smooth muscle
(detrusor muscle)
Mucosa made of transitional epithelium
Walls are thick and folded in
bladder
an empty
Bladder can expand significantly without
increasing internal pressure
Urinary Bladder Wall
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44. Thin-walled tube that carries urine from
the bladder to the outside of the body
peristalsis
Release of urine is controlled by two
sphincters
Internal urethral sphincter (involuntary)
External urethral sphincter (voluntary)
by
Urethra
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45. Length
Females – 3–4 cm (1 inch)
Males – 20 cm (8 inches)
Location
Females – along wall of the vagina
Males – through the prostate and penis
Urethra Gender Differences
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46. Function
Females – only carries urine
Males – carries
for sperm cells
urine and is a passageway
Urethra Gender Differences
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47. Both sphincter muscles must open to
allow voiding
The internal urethral sphincter is relaxed
after stretching of the bladder
Activation is from an impulse sent to the
spinal cord and then back via the pelvic
splanchnic nerves
The external urethral sphincter must be
voluntarily relaxed
Micturition (Voiding)
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48. Normal
body
Young
Young
amount of water in the human
adult females
adult males –
– 50%
60%
Babies – 75%
Old age – 45%
Water is necessary for many
functions and levels must be
body
maintained
Maintaining Water Balance
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50. Changes in electrolyte balance causes
water to move from one compartment to
another
Alters blood volume and blood
Can impair the activity of cells
pressure
The Link Between Water and Salt
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51. Water intake must equal water output
Sources for water intake
Ingested foods and fluids
Water produced from metabolic processes
Sources for water output
Vaporization out of the lungs
Lost in perspiration
Leaves the body in the feces
Urine production
Maintaining Water Balance
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52. Dilute urine is produced if water intake
is excessive
Less urine (concentrated) is produced
large amounts of water are lost
Proper concentrations of various
electrolytes must be present
if
Maintaining Water Balance
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53. Reabsorption
Regulation is primarily by hormones
Antidiuretic hormone (ADH) prevents
excessive water loss in urine
Aldosterone regulates sodium ion content
extracellular fluid
Triggered by the rennin-angiotensin
mechanism
Cells in the kidneys and hypothalamus
are active monitors
of
Regulation of Water and Electrolyte
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55. Blood
Blood pH must remain between 7.35
and 7.45 to maintain homeostasis
Alkalosis – pH above 7.45
Acidosis – pH below 7.35
Most ions originate as byproducts
cellular metabolism
of
Maintaining Acid-Base Balance in
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56. Blood
Most acid-base balance is maintained
by the kidneys
Other acid-base
Blood buffers
Respiration
controlling systems
Maintaining Acid-Base Balance in
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57. Molecules react to prevent dramatic
changes in hydrogen ion (H+)
concentrations
H+
Bind to when pH drops
H+
Release when pH rises
Three major chemical buffer
Bicarbonate buffer system
Phosphate buffer system
Protein buffer system
systems
Blood Buffers
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58. Mixture of carbonic acid (H2CO3) and
sodium bicarbonate (NaHCO3)
Bicarbonate ions (HCO3 ) react with
–
strong acids to change them to weak
acids
Carbonic acid dissociates in the presence
of a strong base to form a weak base and
water
The Bicarbonate Buffer System
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59. Acid-Base Balance
Carbon dioxide in the blood is converted to
bicarbonate ion and transported in the
plasma
Increases in hydrogen ion concentration
produces more carbonic acid
Excess hydrogen ion can be blown off with
the release of carbon dioxide from the lungs
Respiratory rate can rise and fall depending
on changing blood pH
Respiratory System Controls of
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60. Balance
Excrete bicarbonate ions if needed
Conserve or generate new bicarbonate
ions if needed
Urine pH varies from 4.5 to 8.0
Renal Mechanisms of Acid-Base
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61. Urinary System
Functional kidneys
the third month
are developed by
Urinary system of a newborn
Bladder is small
Urine cannot be concentrated
Developmental Aspects of the
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62. Urinary System
Control of the voluntary
sphincter does not start
urethral
until age 18
months
Urinary infections are the only common
problems before old age
Developmental Aspects of the
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63. There is a progressive decline in urinary
function
The bladder shrinks with aging
Urinary retention is common in males
Aging and the Urinary System
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