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The Urinary System
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
EIGHTH EDITION
ELAINE N. MARIEB
adapted by H. Goon
May 2010
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
A) Functions of the Urinary System
1. Elimination of waste products (kidneys filter
200 liters of blood daily)
 nitrogenous wastes (urea, uric acid)
 toxins
 drugs
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
hemodialysis
_____________________________________________________________________________________
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Peritoneal dialysis uses a natural filter inside your body—the lining of
your belly, called the peritoneal membrane—to remove wastes and extra
fluid from your body, and restore the normal balance of certain minerals
in the blood (electrolytes). The dialysis fluid fills the belly and “pulls out”
extra minerals and fluids from the bloodstream. These wastes then drain
out of the body along with the dialysis fluid into a collection bag.
Peritoneal dialysis is usually done at home.
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
2. Regulate aspects of homeostasis
 Water balance
 Electrolytes (ions: Na+, K+, Cl-, HCO3-)
 Acid-base (pH) balance in the blood
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B) Organs of the Urinary system Plus
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B) Organs of the Urinary system
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B) Organs of the Urinary system
 Kidneys
 Ureters
 Urinary bladder
 Urethra
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Kidney Location and External Anatomy
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Figure 25.2a
C) Kidneys
1. Location
 against the dorsal body wall
 at the level of T12 to L3
 The right kidney is slightly lower than the
left
 an adrenal gland is above each kidney
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2. Coverings of the Kidneys
a) Renal capsule
 fibrous covering on each kidney
b) Adipose capsule
 cushions and protects the kidney
 keeps the kidney in its correct location
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3. Regions of the Kidney
a) Renal cortex –
outer region
b) Renal medulla –
middle region
c) Renal pelvis –
inner collecting
tube
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d) ureters, renal
blood vessels,
lymphatics, and
nerves enter and
exit at the hilum
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4. Kidney Structures
a) medullary/renal pyramids – triangular
regions of tissue in the medulla
b) renal columns – extensions of cortex-like
material inward in between pyramids
c) calyces – cup-shaped branches that funnel
urine towards the renal pelvis
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5. Blood Flow in the Kidneys
~ one-fourth (1200 ml) of systemic cardiac
output flows through the kidneys each minute
Figure 15.2c
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Regions of the Kidney
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6. Nephrons
a) The structural and functional units of the
kidneys [1 million per kidney]
b) Responsible for forming urine
c) Main structures of the nephron
 renal corpuscle (glomerulus +
glomerular capsule)
 renal tubule
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
d) glomerulus
 a specialized capillary bed
 continuous with arterioles
at both ends (maintains
high pressure)
 afferent arteriole
(large)
 efferent arteriole
(narrower)
Figure 15.3c
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 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
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e) renal tubule
i. glomerular capsule (Bowman’s capsule) is
a cup-shaped tubule that surrounds the
glomerulus
ii. Proximal convoluted tubule
iii. Loop of Henle
iv. Distal convoluted tubule
Figure 15.3b
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
7. Blood Supply to Kidneys/Nephrons
•
•
•
•
aorta
renal artery (enters at hilus of kidney)
segmental artery
lobar artery
Figure 15.2c
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• interlobar artery = in between renal
pyramids
• arcuate artery = lateral branching of
interlobar vessels at the boundary between
the cortex and medulla
• interlobular artery = final branching of
arcuate into afferent arterioles which enter
the glomerulus
Figure 15.2c
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Blood flow to and from the kidney:
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8. Types of Nephrons
a) Cortical nephrons
 Located entirely in the cortex of the kidney
 85% of the nephrons
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b) Juxtamedullary nephrons
 found at the boundary of the cortex
and medulla
 involved in the production of
concentrated urine
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
9. Peritubular Capillaries
 network of capillaries surrounding the renal
tubule; formed by the branching of the
efferent arteriole
 normal, low pressure capillaries
 attach to a venule
 reabsorb (reclaim) some substances from
renal tubule
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?????
The kidneys remove 180 liters of
filtrate from the blood per day.
How much urine do you actually
eliminate per day?
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D) Urine Formation Processes
glomerular filtration
- tubular reabsorption
+ tubular secretion
urine
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
1. Filtration
 The fenestrated glomerular endothelium
allows water and solutes (filtrate) to easily
pass from the blood in the glomerulus into
the glomerular capsule
 Nonselective passive process
 Water and solutes are forced through
capillary walls b/c glomerular blood pressure
is high, which causes a high net filtration
pressure
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Glomerular Filtration Rate (GFR)
Figure 24.10
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 Plasma proteins are not filtered due to
large size
 GFR (glomerular filtration rate)= total
amount of filtrate formed per minute by
the kidneys [180L/day]
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2. Tubular Reabsorption
a) occurs as the peritubular capillaries
reabsorb several materials [NOTE: back into
bloodstream]
 some water
 glucose
 amino acids
 ions
b) most reabsorption is via active transport,
and occurs in the proximal convoluted
tubule (PCT)
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c) materials NOT reabsorbed:

nitrogenous waste products
 urea
 uric acid
 creatinine
 excess water
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3. Tubular Secretion – reabsorption in
“reverse”
Some materials move from the peritubular
capillaries back into the filtrate (urine)
forming in the renal tubules:
 hydrogen and potassium ions
 creatinine
 drugs
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Formation of Urine
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E) Hormonal control of urine formation
1. ADH (anti-diuretic hormone)
 from pituitary gland
 causes reabsorption of water (so urine
contains less water) in DCT & collecting duct
2. aldosterone
 from adrenal gland
 causes Na+ reabsorption in DCT & collecting
duct (e.g. water retention triggered by low
blood volume or low blood pressure)
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e.g. Alcohol and urine production
• ADH acts on the kidney to reabsorb water
back into bloodstream (makes urine more
concentrated)
• Alcohol inhibits the pituitary secretion of
anti-diuretic hormone (ADH), which then
causes ADH levels to drop.
 Therefore, the kidneys don't reabsorb
as much water and the kidneys
produce a higher volume of URINE
(more diluted).
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F) Characteristics of Urine for Medical Diagnosis
 somewhat yellow color due to the
pigment urochrome (from the destruction
of hemoglobin) and solutes
 sterile
 slightly aromatic
 normal pH ~ 6
 specific gravity of 1.001 to 1.035
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
G) Ureters
 a pair of slender tubes that transport urine
from the kidney to the bladder
 Continuous with the renal pelvis
 Enter the posterior aspect of the bladder
 peristalsis aids gravity in urine transport
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H) Urinary bladder
 muscular, hollow organ
 stores up to 600 mL of urine (~ 2 cups)
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I) Urethra
 short tube that transports urine out of the
bladder
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J) Micturition (urinary reflex)
 stretch receptors are stimulated when the
bladder fills with 150 mL, then 300 mL of
urine; capacity of 600 mL
 The muscles controlling micturition are
controlled by the autonomic and somatic
nervous systems.
 During the storage phase the internal
urethral sphincter remains tense and the
detrusor muscle (in walls of the bladder) is
relaxed.
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 During micturition, parasympathetic
stimulation causes the detrusor muscle to
contract and the internal urethral sphincter
to relax.
 The external urethral sphincter (skeletal
muscle) is under somatic control and is
consciously relaxed during micturition.
e.g. potty training!
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Review: Micturition = urination reflex
(Fill in the blanks!)
 at 300 mL, stretch receptors in the bladder
wall are triggered
 parasympathetic impulses trigger:
 contraction of the detrusor muscle layer
 relaxation of the internal urethral
sphincter muscle
 relaxation of the external urethral
sphincter (skeletal muscle)
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
?? Regulation of Glomerular Filtration
 Three mechanisms control the GFR
 Renal autoregulation (intrinsic system)
 Neural controls
 The renin-angiotensin system (hormonal
mechanism)
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