Transcript AP-Chapter-17 - McLaren

ESSENTIALS OF A&P
FOR EMERGENCY CARE
CHAPTER
17
The Urinary System:
Filtration and Fluid
Balance
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
Copyright ©2011 by Pearson Education, Inc.
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Multimedia Asset Directory
Slide 13
Slide 24
Slide 40
Slide 50
Slide 51
Slide 54
Slide 111
Slide 112
Slide 113
Urinary System Animation
Renal Blood Flow Animation
Hypovolemic Shock Animation
Blood Loss and Blood Pressure Regulation Animation
Renin-Angiotension System Animation
Urinalysis Video
Renal Failure Video
Kidney Stones Video
Ultrasound Video
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Introduction
• The urinary system acts as a purification
plant, cleaning the blood of waste
materials.
• The liver does some purification, but the
urinary system controls electrolyte and
fluid balances for your body.
• The kidneys filter blood, reabsorb and
secrete ions, and produce urine.
• Without this important function you would
die in a few days.
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Learning Objectives
• Present an overview of the organs and
functions of the urinary system.
• Describe the internal and external
anatomy and physiology of the kidneys.
• Discuss the importance of renal blood
flow.
• Describe the process of urine formation.
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Learning Objectives
• Trace the pathways of reabsorption or
secretion of electrolytes and other
chemicals.
• List and discuss the importance of
hormones for proper kidney function.
• Describe the anatomy and physiology of
the bladder and urine removal from the
body.
• Discuss several common disorders of the
urinary system.
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Pronunciation Guide
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afferent arterioles (AFF er ent ahr TEE ree ohlz)
aldosterone (al DOSS ter own)
antidiuretic hormone (ADH) (AN tih dye yoo RET
ick)
atrial natriuretic peptide (AY tree al NAY tree your
ET ick PEP tide)
calyx, calyces (KAY licks, KAY leh seez)
cortical nephron (CORE tih cull NEFF rahn)
efferent arterioles (EFF er ent ahr TEE ree ohlz)
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Pronunciation Guide
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external urethral sphincter (yoo REE thral SFINK
ter)
glomerular capsule (gloh MAIR you ler)
glomerulus (gloh MAIR yoo lus)
juxtaglomedullary nephron (JUX tuh glow med
DULL lair ee NEFF rahn)
juxtaglomerular cells (JUX tuh glow MARE you lair)
renal hilium (REE nal HIGH lum)
renal medulla (REE nal meh DULL lah)
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Pronunciation Guide
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renin-angiotensin-aldosterone (RIN en-an gee oh
TEN sen-al DOSS ter own)
ureter (yoo REE ter)
urethra (you REE thrah)
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System Overview
• The urinary system consists of two
kidneys; bean-shaped organs located in
the superior dorsal abdominal cavity that
filter blood and make urine, and accessory
structures.
• A ureter is a tube that carries urine from
each kidney to the single urinary bladder,
located in the inferior ventral pelvic cavity.
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System Overview
• The urinary bladder is basically an
expandable sac that holds urine.
• The urethra is the tube that transports
urine from the bladder to the outside of the
body.
• The job of the urinary system is to make
urine, thereby controlling the body’s fluid
and electrolyte balance, and eliminating
waste products.
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System Overview
• To make urine, three processes are
necessary:
– Filtration – filtering the blood. What passes
through the filter is called a filtrate.
– Reabsorption – substances stay in the body
after being removed from urine
– Secretion – substances move from the blood
stream and leave the body in the urine
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Figure 17-1 Anatomy of the urinary system.
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External Anatomy of the Kidney
• The kidney is covered by a fibrous layer of
connective tissue called the renal capsule.
• The indentation that gives the kidney it’s
bean-shape is called the renal hilum.
• At the hilum, renal arteries bring blood to
the kidneys to be filtered and renal veins
take the filtered blood away from the
kidney. The ureter is also attached at the
hilum to transport urine from the kidney to
the bladder.
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Internal Anatomy of the Kidney
• The kidney can be divided into three
layers:
– Renal cortex – outer layer – grainy in
appearance and has little obvious structure to
the naked eye; this is where blood filtration
occurs
– Renal medulla – middle layer – contains a
number of triangle-shaped, striped areas
called renal pyramids
 Composed of collecting tubules for the urine that is
formed in the kidney
 Adjacent pyramids are separated by narrow renal
columns – extensions of cortical tissue
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Internal Anatomy of the Kidney
• The kidney can be divided into three
layers:
– Renal pelvis – inner layer – a funnel, divided
into two or three large collecting cups called
major calyces.
 Each major calyx is divided into several minor
calyces, forming cup-shaped areas around the tips
of the pyramids.
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Internal Anatomy of Kidney
• The blood is filtered by millions of tiny
filters in the cortex, and the filtrate flows
through tiny tubules in the medulla and
collects in the renal pelvis.
• The renal pelvis, the enlarged proximal
portion of the ureter, empties into the
ureter where urine is carried to the
bladder.
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Figure 17-2 The internal and external anatomy of the kidney.
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Internal Anatomy of Kidney
• Blood vessels
– Good blood supply to the kidney is essential
to allow it to function properly – network of
blood vessels throughout kidney tissue.
– A single renal artery enters each kidney at the
hilum, branching into five segmental arteries.
– The segmental arteries branch into lobar
arteries in the renal sinus.
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Internal Anatomy of Kidney
• Blood vessels
– The lobar arteries branch into interlobar
arteries which pass through the renal
columns.
– Arcuate arteries originate from the interlobar
arteries and arch around the pyramids in the
renal medulla.
– Arcuate arteries give rise to cortical radiate
arteries which give rise to afferent arterioles.
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Internal Anatomy of Kidney
• Blood vessels
– Each afferent arteriole leads to a ball of
capillaries called a glomerulus.
– Efferent arterioles leave from the glomerulus.
 Travel to a specialized series of capillaries called
the peritubular capillaries and vasa recta (straight
collecting tubes) that are part of the renal nephron,
the functional unit of the kidney.
 The peritubular capillaries wrap around the
collecting tubules of the nephron, allowing efficient
movement of ions between blood and the fluid in
the nephron.
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Internal Anatomy of Kidney
• Blood vessels
– From each set of peritubular capillaries, blood
flows out the interlobular veins.
– From there, the blood flows out a series of
veins that are the direct reverse of the arteries
with the exception that there are no
segmental veins.
– The blood finally leaves the kidney via the
renal vein.
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Figure 17-3 Renal blood vessels and the pathway of blood through the renal system.
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The Nephron
• The functional unit of the kidney is the
nephron, consisting of millions of
microscopic funnels and tubules.
• The nephron can be divided into two
distinct parts:
– The renal corpuscle – a filter
– The renal tubule – where reabsorption and
secretion take place
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Renal Corpuscle
• Blood enters the renal corpuscle via the
glomerulus, a ball of capillaries.
• Surrounding the glomerulus is a doublelayered membrane called the glomerular
capsule, or Bowman’s capsule.
• The layers of the glomerular capsule are
similar to the layers of a serous
membrane.
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Renal Corpuscle
• The inner layer of the glomerular capsule,
the visceral layer, surrounds the
glomerular capillaries and is made of
specialized squamous epithelial cells
called podocytes. This makes for a very
efficient filter.
• The outer layer, the parietal layer, of the
glomerular capsule is simple squamous
epithelium and completes the filter.
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Renal Corpuscle
• Blood flows into the glomerulus and
everything BUT blood cells and a few
large molecules, mainly protein, are
pushed from the capillaries across the
filter and into the glomerular capsule.
• The material filtered from the blood into
the glomerular capsule is called
glomerular filtrate.
• If blood or protein leaks into urine it can
indicate a kidney filtration problem.
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Figure 17-4 The nephron.
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Renal Tubule
• The rest of the nephron is a series of
tubes known as renal tubules.
• Glomerular filtrate travels from the
glomerular capsule into the first part of the
renal tubule, the proximal tubule.
– The wall of the proximal tubule is made of
cuboidal epithelium with microvilli.
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Renal Tubule
• From the proximal tubule, glomerular
filtrate flows into the nephron loop (or the
Loop of Henle).
– The nephron loop consists of the descending
loop (similar in structure to the proximal
tubule) and the ascending loop (simple
cuboidal epithelium).
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Renal Tubule
• Glomerular filtrate travels from the
nephron loop to the distal tubule.
– The wall of the distal tubule is like that of the
ascending branch of the nephron loop.
– From the distal tubule, glomerular filtrate flows
into one of several collecting ducts, made of
cuboidal epithelium.
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Renal Tubule
• The collecting ducts lead to minor calyces,
then to major calyces, the renal pelvis, and
the ureter.
• At this point, the glomerular filtrate is urine.
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Figure 17-5 A functional renal unit.
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Renal Tubule
• Blood vessels are in close proximity to the
nephrons because substances move
between the tubules and the bloodstream.
– Blood approaches the nephron via the
afferent arteriole.
– Blood flows from the afferent arteriole into the
glomerulus.
– Blood flows from the glomerulus via the
efferent arteriole into the peritubular
capillaries and vasa recta.
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Renal Tubule
• Blood vessels are in close proximity to the
nephrons because substances move
between the tubules and the bloodstream.
– These surrounding blood vessels allow for
reabsorption and secretion.
– Blood leaves the nephron via the cortical
radiate veins.
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Clinical Application: Trauma,
Ischemia, and Kidney Damage
• The kidney is well vascularized, with each
nephron surrounded by blood vessels.
• The flow of blood is controlled by the
afferent arteriole. When blood flow
decreases for a period of time, oxygen
delivery to the nephron decreases and
ischemia results.
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Clinical Application: Trauma,
Ischemia, and Kidney Damage
• Blood flow can be decreased by any
number of hormonal mechanisms causing
prolonged vasoconstriction, such as
severe blood loss.
• If the situation continues long enough, the
tissues will become ischemic and
eventually die, causing kidney failure that
can be temporary or permanent.
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From the Streets:
Renal Trauma
• The kidneys are well protected in the
retroperitoneal space.
• Trauma to the kidneys usually is the result
of penetrating trauma.
• Signs and symptoms
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Urine Formation
• The kidney controls fluid and electrolyte
balance by controlling urine volume and
composition.
• In order to form urine, the nephron must
perform three processes:
– Glomerular filtration
– Tubular reabsorption
– Tubular secretion
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Filtration
• During glomerular filtration, fluid and
molecules pass from the glomerular
capillaries into the glomerular capsule.
– Across a filter composed of the walls of the
capillaries and the podocytes of the
glomerular capsule
– The filtrate flows into the renal tubule where
the chemistry is controlled by reabsorption
and secretion
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Filtration
• During glomerular filtration, fluid and
molecules pass from the glomerular
capillaries into the glomerular capsule.
– Filtration moves fluid and chemicals into the
nephron from blood
– Glomerular filtrate is chemically similar to
blood
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From the Streets:
Kidney Stones
• Kidney stones, or renal calculi, are formed
by crystals in the kidney’s collection
system.
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Figure 17-10 Cross section through a kidney showing multi- ple stones, including one
“staghorn” stone in the renal pelvis.
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From the Streets:
Kidney Stones
•
•
•
•
•
Causes
Risk factors
Signs and symptoms
Diagnostic tests
Treatment
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From the Streets:
Hemodialysis
• Renal failure (RF) can be either acute
(ARF) or chronic (CRF).
• ARF is a sudden drop in urine output to
less than half a liter per day.
• Causes
• Signs and symptoms
• Treatment
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Reabsorption and Secretion
• Urine is chemically different from plasma
because reabsorption and secretion
control the concentration of chemicals and
volume of urine.
– Substances that are reabsorbed pass from
the renal tubule into the peritubular capillaries
and return to the blood stream.
– Substances that are secreted pass through
the peritubular capillaries into the renal tubule
and eventually leave the body as urine.
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Reabsorption and Secretion
• Urine is chemically different from plasma
because reabsorption and secretion
control the concentration of chemicals and
volume of urine.
– Some substances, like glucose, are
completely reabsorbed while substances like
metabolic waste products (urea and
creatinine) are almost completely secreted as
urine.
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Figure 17-7 The processes involved in urine formation.
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Table 17-1 Kidney Fluid Chemistry.
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Control of Filtration
• Filtration is controlled by several factors.
– Filter size – determines what gets through the
filter
 Podocytes and capillary walls of the renal
corpuscle create a filter with fixed openings.
 Plasma, and many of the substances dissolved in
plasma, pass through the filter, but blood cells,
platelets, and large molecules, can’t get into a
healthy kidney.
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Control of Filtration
• Filtration is controlled by several factors.
– Pressure
 Higher pressure on one side of the filter allows
chemicals to be pushed though the filter more
quickly.
 Higher blood pressure in the glomerular capillaries
increases filtration, while lower pressure decreases
filtration.
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Figure 17-8 Filter selectivity.
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Figure 17-9 Comparison of damaged and healthy kidneys.
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Control of Filtration
• Changes in blood pressure change
filtration rate.
– Minor changes in systolic blood pressure do
not change glomerular pressure because it is
protected by a mechanism called
autoregulation.
 As systemic BP increases, the afferent arterioles
leading into the glomerulus constrict, decreasing
the amount of blood getting into the glomerulus.
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Control of Filtration
• Changes in blood pressure change
filtration rate.
– Autoregulation can be overridden.
 Since the kidney regulates fluid volume, the kidney
can work with the cardiovascular system to
regulate blood pressure.
 Glomerular filtration can decrease to conserve fluid
when blood pressure falls, or increase filtration if
blood pressure rises.
 The sympathetic nervous system can control urine
production through the adrenal medulla.
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Clinical Application:
Diabetic Nephropathy
• Diabetes Mellitus (DM) is characterized by
high glucose levels from inadequate, or
lack of, insulin. The high glucose levels
wreak havoc on the osmotic balance of
blood. The kidneys work hard to remove
excess glucose, and urine output is high.
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Clinical Application:
Diabetic Nephropathy
• Over time the kidney is damaged, (diabetic
nephropathy), beginning with a thickening
of the filter surface of the glomerular
capsule, eventually leading to breakdown
of kidney tissue, destroying the filtering
ability. Substances that would normally not
pass through, like protein and blood, begin
to appear in urine.
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Clinical Application:
Diabetic Nephropathy
• Kidney function deteriorates. Diabetics can
prevent the onset of kidney damage by
controlling their blood sugar levels,
preventing high blood pressure, and
reducing blood cholesterol levels. This is
the leading cause of kidney disease in
America.
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Control of Tubular Reabsorption
and Secretion
• Tubular reabsorption and secretion control
the chemistry and volume of urine.
– Substances that are reabsorbed move from
the tubule back to the blood stream via the
peritubular capillaries and stay in the body.
– Substances that are secreted stay in the
tubule and eventually leave the body via the
urine.
• Anything that affects reabsorption and
secretion affects urine chemistry.
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Control of Tubular Reabsorption
and Secretion
• The first thing that affects tubular
reabsorption and secretion is tubule
permeability.
– Each section of the tubule can reabsorb and
secrete different substances.
– Molecules move across membranes through
several different methods including diffusion and
active transport.
– Differences in tubular permeability result in
dramatic differences in what molecules are
reabsorbed or secreted in each part of the tubule.
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Table 17-2 Individual Tubule Functions.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Clinical Application:
Kidney Stones
• Kidney stones result when substances in
the urine crystallize in the renal tubule,
often because the concentration of the
molecule is higher than normal. The cause
of stones is frequently a mystery.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Clinical Application:
Kidney Stones
• Stones can be made of calcium, uric acid,
or caused by kidney infections. Some
people are more susceptible than others.
Some stones pass unnoticed, while others
that are larger or irregularly shaped may
lodge in the tubule, obstructing flow and
irritating nearby tissues.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Clinical Application:
Kidney Stones
• Symptoms include blood in the urine and
severe flank pain. Stones may move on
their own or may be treated with increased
fluid intake, lithotripsy (shock waves to
break the stone), or surgery if these don’t
work. Patients are asked to filter their urine
to look for the passage of these stones,
some as small as sand.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Control of Tubular Reabsorption
and Secretion
• Special type of circulation around the
nephron loop, called countercurrent
circulation
– Ions move across cell membranes from
higher to lower areas of concentration.
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Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Control of Tubular Reabsorption
and Secretion
• Special type of circulation around the
nephron loop, called countercurrent
circulation
– Water and ions tend to move in opposite
directions, making it impossible to move both
without the special environment around the
nephron loop.
 Concentration gradient, with low ion concentration
at the beginning of the descending loop and high
concentration at the tip of the loop
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Control of Tubular Reabsorption
and Secretion
• Special type of circulation around the
nephron loop, called countercurrent
circulation
– Water and ions tend to move in opposite
directions, making it impossible to move both
without the special environment around the
nephron loop.
 Differences in permeability between the
descending loop (water) and ascending loop (ions)
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Control of Tubular Reabsorption
and Secretion
• Countercurrent circulation (cont’d)
– Filtrate flows into the descending loop,
reabsorbing water and increasing the
concentration of ions. As the filtrate enters the
ascending loop, fluid is concentrated because
of water loss, the membrane is permeable to
only ions, and ions move across the
membrane.
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Figure 17-12 Sites of tubular reabsorption and secretion.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Applied Science:
Electrolyte and Acid Balance
• The kidney maintains electrolyte balance
by selectively excreting or reabsorbing
electrolytes within the tubular system.
• The relationship between hydrogen ions
(H+) and bicarbonate ions (HCO3)
determines the blood pH (level of acidity or
alkalinity). This is called the acid/base
relationship.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Applied Science:
Electrolyte and Acid Balance
• If too much acid is present, H+ will be
excreted to a greater level in the urine and
more bicarbonate ions will be reabsorbed.
• The respiratory system also plays a role
by blowing off more carbon dioxide, which
is an acid.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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From the Streets:
Disturbances in Acid-Base Balance
• Maintenance of normal acid-base balance
is one of the body’s most important
homeostatic functions.
• The body compensates by three main
mechanisms:
– Buffer system
– Respiratory system
– Renal system
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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From the Streets:
Acid-Base Abnormalities
•
•
•
•
Respiratory acidosis
Respiratory alkalosis
Metabolic acidosis
Metabolic alkalosis
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Control of Tubular Reabsorption
and Secretion
• The third factor that affects reabsorption
and secretion are several hormones that
regulate blood pressure.
– Antidiuretic Hormone
– Aldosterone
– Atrial Natriuretic Peptide
– Renin-Angiotensin-Aldosterone
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Control of Tubular Reabsorption
and Secretion
• Hormonal control
– Antidiuretic hormone (ADH) is made by
the hypothalamus and secreted from the
posterior pituitary when BP decreases
or ionic concentration increases.
 ADH increases permeability of distal
tubules and the collecting duct.
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Control of Tubular Reabsorption
and Secretion
• Hormonal control
– Antidiuretic hormone (ADH) is made by
the hypothalamus and secreted from the
posterior pituitary when BP decreases
or ionic concentration increases.
 More water is reabsorbed, increasing blood
volume, increasing blood pressure, and
diluting the ionic concentration.
 Less urine is produced.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Control of Tubular Reabsorption
and Secretion
• Hormonal control
– Antidiuretic hormone (ADH) is made by
the hypothalamus and secreted from the
posterior pituitary when BP decreases
or ionic concentration increases.
 Alcohol or caffeine inhibit ADH production,
increasing urine production.
Essentials of A&P for Emergency Care
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Control of Tubular Reabsorption
and Secretion
• Hormonal control
– Aldosterone is an adrenocorticosteroid
secreted by the adrenal cortex.
 It is secreted when plasma sodium decreases or
plasma potassium increases.
 It increases the reabsorption of sodium ions and
secretion of potassium ions – increasing serum
sodium levels and decreasing serum potassium
levels – by the distal tubule and ascending limb of
the nephron loop.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Control of Tubular Reabsorption
and Secretion
• Hormonal control
– Aldosterone is an adrenocorticosteroid
secreted by the adrenal cortex.
 As sodium is reabsorbed, water is also reabsorbed,
decreasing urine volume.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Control of Tubular Reabsorption
and Secretion
• Hormonal control
– Atrial natriuretic peptide (ANP) is secreted by
the atria of the heart when blood volume
increases.
 ANP decreases sodium reabsorption and thus
increases urination.
– The renin-angiotensin-aldosterone system is
a series of chemical reactions that regulate
blood pressure.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Control of Tubular Reabsorption
and Secretion
• Hormonal control (cont’d)
– Decrease in blood flow to the kidney:
 Causes a special group of cells near the
glomerulus, the juxtaglomerular apparatus, to
secrete renin into the blood stream.
 The liver secretes a chemical called
angiotensinogen.
 Renin converts angiotensinogen into angiotensin I.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Control of Tubular Reabsorption
and Secretion
• Hormonal control (cont’d)
– Decrease in blood flow to the kidney:
 Another enzyme made by the lungs, angiotensin
converting enzyme (ACE), converts angiotensin I to
angiotensin II, increasing thirst, increasing ADH
secretion, increasing aldosterone secretion, and
causing vasoconstriction. These increase blood
pressure by increasing fluid volume.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Clinical Application:
Polycystic Kidney Disease
• Polycystic kidney disease (PKD) is a
genetic disorder. Large cysts form in the
kidneys. One form of PKD is so serious
that patients die in infancy. The more
common form is an adult onset disorder
characterized by decreasing kidney
function as normal nephrons are
destroyed by cysts.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Clinical Application:
Polycystic Kidney Disease
• As more cysts develop the kidneys get
very large – one weighed 22 pounds.
There is no cure except transplantation of
the kidney. It occurs in about half a million
people in the United States.
Essentials of A&P for Emergency Care
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The Urinary Bladder
and Urination Reflex
• Glomerular filtrate flows out the collecting
duct, into the minor calyces, and then into
the major calyces, forming the renal pelvis.
• Once the glomerular filtrate leaves the
collecting ducts, its concentration can’t be
changed and it is urine.
• Urine collects in the renal pelvis and flows
down the ureters to the urinary bladder,
where it is stored.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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From the Streets:
Urinary Tract Infection (UTI)
• Urinary Tract Infections (UTI) affect the
urethra, bladder, ureter, kidney, and even
the prostate gland.
• Risk factors
• Signs and symptoms
• Treatment
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Urinary Bladder
• The urinary bladder is a small hollow
organ posterior to the pubic symphysis
and behind the peritoneum.
– It is lined with transitional epithelium, the only
epithelium stretchy enough to expand as the
bladder fills.
– The ability to stretch is enhanced by a series
of pleats called rugae.
Essentials of A&P for Emergency Care
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Urinary Bladder
• The urinary bladder is a small hollow
organ posterior to the pubic symphysis
and behind the peritoneum.
– The bladder has a muscular wall consisting of
several layers of circular and longitudinal
smooth muscle and is covered by connective
tissue and parietal peritoneum.
Essentials of A&P for Emergency Care
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Figure 17-13 The urinary bladder.
Essentials of A&P for Emergency Care
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Urination Reflex
• As urine accumulates, the bladder fills and
stretches.
– This stretch triggers the urinary reflex and the
need to void to empty the bladder.
– Urination had been thought to be a spinal
reflex, but new research indicates it is
controlled by the brain.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Urination Reflex
• As urine accumulates, the bladder fills and
stretches.
– When the bladder is full, signals are sent from
the bladder to the spinal cord to the pons. The
pons sends parasympathetic signals down the
spinal cord, causing contraction of the
muscular walls of the bladder, and the bladder
empties.
Essentials of A&P for Emergency Care
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Urination
• Urine leaves the bladder via the urethra, a
thin muscular tube lined with several
different types of epithelium along its
length.
– Part of your brain can inhibit urination by
controlling the internal urethral sphincter, a
valve at the junction of the bladder and the
urethra, and the external urethral sphincter, a
valve that is part of the muscles of the pelvic
floor.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Urination
• Urine leaves the bladder via the urethra, a
thin muscular tube lined with several
different types of epithelium along its
length.
– Sympathetic stimulation of these sphincters
prevents urine from leaving the body.
– Although you have little control over bladder
contraction, you have good control over the
sphincters starting from age 2, or slightly later
in boys.
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Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Figure 17-15 Control of urination.
Essentials of A&P for Emergency Care
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Clinical Application:
Urinary Tract Infections (UTIs)
• Urinary tract infection is caused by the
movement of fecal bacteria into the urinary
tract.
• Symptoms may include frequent, painful
urination, bloody or cloudy urine with an
unusual odor, and low abdominal/pelvic
pain caused by bladder spasm.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Clinical Application:
Urinary Tract Infections (UTIs)
• Treatment should begin promptly to avoid
kidney damage from infection traveling
from the bladder to the kidney.
• UTIs are more common in women
because their urethra is shorter. Drinking
plenty of water can help prevent infections.
Once diagnosed, they are treated with
antibiotics and increased fluid intake.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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From the Streets:
Acute Renal Failure
• Acute renal failure (ARF) is a deterioration
in renal function over hours or days.
• Recovery depends upon restoration of
renal blood flow and clearance of tubular
toxins.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Common Disorders of the
Urinary System
• Overuse or abuse of drugs can severely
affect renal function because the kidney
excretes most medications after the liver
breaks them down. Analgesic nephropathy is
caused by long term use of pain relievers,
particularly non-steroidal anti-inflammatory
drugs (NSAIDS) like ibuprofen or naproxen,
particularly if combined with caffeine,
codeine, or acetaminophen. OTCs can cause
chronic kidney damage leading to kidney
failure.
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Chronic Renal Failure
• Chronic renal failure (CRF) is an ongoing,
progressive disease of the kidney.
• The progression may be controlled by
treating the underlying cause of the
damage, or controlling BP and cholesterol.
• CRF can lead to end-stage renal disease
(ESRD), the final stage of renal failure.
• Treatment for ESRD is dialysis or
transplantation.
Essentials of A&P for Emergency Care
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Diabetes Insipidus
• Diabetes insipidus (DI) is an endocrine
disorder characterized by too little ADH or
insensitivity of the kidney to ADH.
• The result is copious amounts of urine
being produced, dehydration, and rising
sodium levels as the body tries,
unsuccessfully, to conserve water. If not
treated it can be fatal.
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Diabetes Insipidus
• The opposite of this disorder is water
intoxication, in which patients have
uncontrollable thirst and drink so much
water they create dangerously low sodium
levels because of the volume of water
diluting it. This can lead to brain damage
or death.
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Glomerulonephritis
• Glomerulonephritis is inflammation of the
glomerulus.
• Glomerulosclerosis is scarring of the
glomerulus.
• Both cause damage to the delicate filter
apparatus.
• When the filter is damaged, blood cells
and blood proteins enter the filtrate and
eventually appear in urine.
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Glomerulonephritis
• Removal of waste products is decreased
and electrolyte balance is usually
abnormal due to the change in urine
chemistry.
• There are many causes, including
bacterial infection, diabetic nephropathy,
systemic lupus erythematosus (SLE), and
genetic disorders including Alport
syndrome and Goodpasture’s syndrome.
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Hemolytic Uremic Syndrome
• Hemolytic uremic syndrome is a disorder
caused by an infection with the bacteria E.
coli, typically from eating undercooked
meat.
• The bacteria infects the digestive tract and
releases toxins which destroy RBCs.
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Hemolytic Uremic Syndrome
• The damaged RBCs lodge in blood
vessels in the kidney, blocking them and
preventing blood flow to the nephron.
• Without treatment, permanent kidney
damage may result.
• A blood transfusion of the wrong type of
blood can have much the same effect.
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Essentials of A&P for Emergency Care
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Snapshots from the Journey
• The urinary system consists of paired
kidneys and paired ureters, which carry
urine to the single urinary bladder. The
urethra transports urine from the bladder
to outside the body. The function of the
urinary system is control of fluid and
electrolyte balance and elimination of
nitrogen-containing waste.
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Snapshots from the Journey
• The kidney is bean shaped and covered in
a capsule. It has an indentation known as
the renal hilum and an interior cavity
known as the renal sinus. The kidney can
be divided into three layers: the renal
cortex, renal medulla, and renal pelvis.
The renal pelvis is a funnel that is divided
into large pipes, the major calyces.
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Snapshots from the Journey
• Each major calyces is divided into several
minor calyces. The renal pelvis empties
into the ureter.
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Snapshots from the Journey
• The kidney is very well vascularized.
Blood is supplied to each kidney by a renal
artery. The blood vessels split into smaller
and smaller branches until there are
millions of tiny arterioles, the afferent
arterioles. The afferent arterioles supply
millions of nephrons, the functional unit of
the kidney, with blood. Blood leaves the
kidney by a series of veins and ultimately
returns to circulation via the renal vein.
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Snapshots from the Journey
• The nephron is the functional unit of the
kidney. There are millions of nephrons in
each kidney. The nephron is divided into
two parts. The renal corpuscle, consisting
of the glomerulus (capillaries) and the
glomerular capsule, filters blood and
produces glomerular filtrate.
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Snapshots from the Journey
• The renal tubule, consisting of the
proximal tubule, nephron loop, distal
tubule, and collecting ducts, control the
concentration and volume of urine by
reabsorbing and secreting water,
electrolytes, and other molecules. The
walls of the nephron are made of
epithelium. The type of epithelium
changes depending on the specific
function of each part of the nephron.
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Snapshots from the Journey
• Urine is formed by a combination of three
processes: glomerular filtration, tubular
reabsorption, and tubular secretion. The
selectivity of the glomerular filter is
determined by the size of the openings in
the filter and the difference between the
blood pressure of the glomerulus and the
pressure in the glomerular capsule.
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Snapshots from the Journey
• The size of the filter does not change
unless the glomerulus is damaged.
Protein, for example, cannot pass through
the filter. However, the filtration rate will
change if the pressure in the glomerulus
changes. Most of the time, autoregulation,
control of the diameter of the afferent
arteriole, keeps glomerular pressure and
the glomerular filtration rate constant.
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Snapshots from the Journey
• But sympathetic stimulation can regulate
(in this case decrease) glomerular filtration
and urine output due to constriction of
afferent arterioles.
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Snapshots from the Journey
• Tubular reabsorption and secretion is
controlled by differences in tubular
permeability. The proximal tubule is the
most versatile, reabsorbing dozens of
different molecules. The nephron loop is
part of an elaborate countercurrent
mechanism, with the descending loop
permeable to water and ascending loop
permeable to ions.
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Snapshots from the Journey
• The distal tubule and collecting ducts
reabsorb water. The permeability of the
renal tubule can be regulated by a number
of hormones that control blood pressure.
These hormones, aldosterone, ADH, atrial
natriuretic peptide, and others, regulate
blood pressure by regulating urine volume
and ion secretion. Changes in urine
volume change total body fluid volume and
thereby change blood pressure.
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Snapshots from the Journey
• The urinary bladder is a collecting and
storage structure for urine and is located in
the pelvic cavity. It has a muscular wall.
Contractions of the muscle result in
voiding (urination), emptying the bladder.
Urination is a reflex controlled by
parasympathetic neurons in the pons.
Signals from a full bladder reach the pons.
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Snapshots from the Journey
• The neurons in the pons then send signals
for the bladder to contract. Sympathetic
neurons control two valves, the internal
and external urethral sphincters, which
allow significant conscious control of the
urination reflex.
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Case Study
Jane has recently developed very annoying
symptoms. She has to go to the restroom
several times a day. Sometimes it seems
she spends every waking moment in there.
She hasn’t slept through the night for more
than a week. She goes to the doctor, who
orders a series of tests to differentiate
between several disorders that cause
frequent urination: diabetes mellitus,
overactive bladder, and urinary tract
infection.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Jane’s Test Results
•
•
•
•
•
Urine bacteria – no
Blood in the urine – no
Leukocytes in urine – no
Glucose – normal
Proteins – no
• What is your diagnosis and why?
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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From the Streets
You are called to the scene of a 38-year-old
male complaining of “severe waves of pain”
that radiates from his right side to his groin.
He states, “it feels like pieces of glass are
moving through my side”. He is restless and
claims his urine is reddish in color. You note
facial grimacing, tachycardia, low grade
fever, and pink, warm and moist skin. He
drinks a 2-liter of caffeinated soda a day.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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From the Streets Questions
• What is his most likely diagnosis?
• Why is his urine reddish in color?
• Why does he complain of “waves of pain”
and “it feels like pieces of glass are
moving through my side”?
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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From the Streets Questions
• Identify a key risk factor for his condition.
• What is his prognosis?
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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From the Streets Questions
• What is his most likely diagnosis? Kidney
stone (renal calculus)
• Why is his urine reddish in color? He has
blood in his urine (hematuria)
• Why does he complain of “waves of pain”
and “it feels like pieces of glass are
moving through my side”? As peristalsis
moves the stone down the ureter toward
the urinary bladder it feels as he
describes.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
Copyright ©2011 by Pearson Education, Inc.
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From the Streets Questions
• Identify a key risk factor for his condition.
Caffeine consumption
• What is his prognosis? Once the stone
passes he will be more comfortable. He
will want to be transported for hydration
and pain management. Upon discharge a
urine strainer will be given so that he can
save the stone and take it with him when
he follows up with his physician.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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End of Chapter
Review Questions
1. The function of this part of the renal
tubule is filtration of blood:
a. Renal calyx
b. Renal corpuscle
c. Renal cortex
d. Renal columns
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Review Questions
2. The collecting ducts are found in this part
of the kidney.
a. Renal Cortex
b. Renal Medulla
c. Renal Pelvis
d. Renal Pyramids
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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Review Questions
3. This tube leads from the urinary bladder
to the outside.
a. Collecting ducts
b. Distal tubule
c. Ureter
d. None of these
Essentials of A&P for Emergency Care
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Review Questions
4. The ion responsible for causing acidic
blood is:
a. Na+
b. H+
c. K+
d. HCO3-
Essentials of A&P for Emergency Care
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Review Questions
5. The renal hormone secreted by the
hypothalamus when blood pressure
decreases to promote the reabsorption of
water is:
a. Aldosterone
b. Atrial natriuretic peptide
c. Antidiuretic hormone
d. Epinephrine
Essentials of A&P for Emergency Care
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Review Questions
6. Why do the cells in the proximal tubule
have microvilli?
a. To increase surface area
b. To move particles along the mucociliary
escalator
c. To differentiate it from the distal tubule
d. To increase filtration rate
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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End of Chapter
Review Questions
7. Which of the following is a possible
cause of blood in the urine?
a. Decreased filtration
b. UTI
c. Decreased tubular reabsorption
d. Decreased blood pressure
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End of Chapter
Review Questions
8. If a patient experiences severe
dehydration, what would you expect to
happen to urine volume?
a. It would increase
b. It would decrease
c. It would stay the same as usual
d. Not enough information
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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End of Chapter
Review Questions
1. Most substances are reabsorbed or
secreted in this part of the renal tubule:
__________.
2. This part of the renal tubule has an
elaborate counter-current mechanism for
reabsorption of sodium and water:
__________.
3. This hormone is released by the heart
when fluid volume increases:
__________.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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End of Chapter
Review Questions
4. Urination reflex is mediated by this part
of the CNS __________.
5. As blood pressure decreases, this
hormone is released by the adrenal
cortex. __________
6. The _______ is the funnel-shaped end of
the ureter.
Essentials of A&P for Emergency Care
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End of Chapter
Review Questions
1. List and explain the activity of three
regulators of kidney function.
2. Explain the three processes necessary
for urine formation. In which part of the
nephron are these functions performed?
3. Describe the structure of the wall of the
urinary bladder.
4. Explain the control of urination reflex.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
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End of Chapter
Review Questions
5. Trace the flow of blood into, through, and
out of the kidney.
6. Explain the symptoms of one kidney
disorder. Relate the symptoms to kidney
function.
Essentials of A&P for Emergency Care
Bruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe
Copyright ©2011 by Pearson Education, Inc.
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