Unit 20 - Urinary System
UNIT OBJECTIVES
1. Define the terms urology, retroperitoneal, hilum, renal cortex, renal medulla,
renal pyramid, and urinalysis.
2. Identify the primary functions of the urinary system.
3. Locate and identify at least one function for each of the following structures:
kidney, nephron, collecting ducts, renal sinus, renal calyx, renal pelvis, ureters,
urinary bladder, detrusor muscle, urethra, tubular network, glomerular capsule,
renal corpuscle, proximal convoluted tubule, Henle’s loop, descending limb of
Henle, ascending limb of Henle, distal convoluted tubule, vascular network,
renal artery, segmental artery, interlobar artery, arcuate artery, cortical artery,
afferent arteriole, glomerulus, efferent arteriole, peritubular capillaries, vasa
recta, cortical vein, arcuate vein, interlobar vein, segmental vein, and renal vein.
carrier molecules, glucose, sodium ions, water, chloride ions, urea, aldosterone,
and ADH.
13. Discuss and explain tubular secretion by relating it to the control of blood pH, be
sure to include: distal convoluted tubule, peritubular capillaries, carbon dioxide,
water, carbonic anhydrase, carbonic acid, bicarbonate ions, hydrogen ions, sodium ions, chloride ions, ammonia, and ammonium ions.
14. Discuss and explain the countercurrent multiplier mechanism, be sure to include: descending limb of Henle, ascending limb of Henle, vasa recta, collecting
duct, renal cortex, renal medulla, sodium ions, chloride ions, water, ADH, and
the glomerular filtrate.
15. Identify the effects of the following on urinary output and urine concentration: the
blood’s sodium concentration, aldosterone, the blood’s water level, ADH, blood
pressure, and diuretics.
4. Identify three factors that assist the movement of urine through a ureter.
16. Name the main urinary pigment and identify its origin.
5. Define the term micturition and describe how this process is controlled by the
micturition reflex and the urethra’s sphincters.
17. Differentiate between the following and identify a cause for each: bilirubinuria,
glycosuria, albuminuria, hematuria, pyuria, ketosis, kidney stones, and anuria.
6. List the three main activities necessary for urine formation and define each.
7. Explain glomerular filtration using the following terms: glomerular hydrostatic
pressure, capsular hydrostatic pressure, glomerular osmotic pressure, capsular
osmotic pressure, effective filtration pressure.
8. Define the term glomerular filtration rate and explain how the autonomic nervous system and the juxtaglomerular apparatus control it.
9. Compare the chemical composition of plasma with that of urine and the glomerular filtrate.
10. Identify the purposes of tubular reabsorption, tubular secretion and the countercurrent multiplier mechanism.
11. Define the following terms: active reabsorption, passive reabsorption, obligatory
reabsorption, and facultative reabsorption.
12. Discuss and explain tubular reabsorption, be sure to include: proximal convoluted tubule, distal convoluted tubule, collecting duct, peritubular capillaries,
18. State how the following systems are involved in excretion: integumentary system, digestive system, and respiratory system.
NOTES
I. Introduction to the System
A. Urology is the study of the urinary system. This system maintains the
blood’s volume and composition by removing the unwanted materials (i.e.,
ammonia, urea, etc.) produced by metabolism. It does this by producing a
fluid called urine.
B. The urinary system also regulates the blood’s pH, produces erythropoietin to
regulate erythropoiesis, and produces renin to control blood pressure.
II. Organs of the Urinary System
A. The kidneys are a pair of organs that are embedded in the posterior aspect
of the abdominal wall. This retroperitoneal position covers the kidneys
with parietal peritoneum. The parietal peritoneum protects the kidneys and
holds them in place.
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1. A kidney’s external depression is called its hilum. This is the site of nerve
and vessel penetration. Behind the hilum is a cavity called the renal sinus.
2. Internally, a kidney is organized into two regions: an outer renal cortex
and an inner renal medulla.
a. These layers both contain parts of a nephron. This functional unit is
responsible for urine formation.
b. A kidney’s nephrons are clustered into about 12 wedge-like structures
called renal pyramids. Each of the pyramid’s nephrons convey their
urine into collecting ducts. These tubes conduct the urine through the
renal medulla to the kidney’s hilum.
c. The kidney’s renal sinus is lined by a large sac called the renal pelvis. This sac’s margin possesses several small extensions called the
renal calyces. Each renal calyx collects urine from the collecting ducts
of one or two renal pyramids. The renal pelvis empties its urine into the
system’s ureters.
3. The bladder’s apex points downward. This region contains the urinary
bladder’s sphincters. These circular pieces of muscle control the flow of
urine into the urethra.
a. The internal sphincter is a piece of smooth muscle that is involuntarily
controlled by the urinary bladder’s stretch receptors. These receptors
automatically dilate this sphincter, when the urinary bladder is full. This
response is called the micturition reflex.
b. The external sphincter is a piece of skeletal muscle that is voluntarily
controlled by the cerebrum. Usually, this control does not develop until
two years of age. The reason, it takes about two years to innervate the
external sphincter.
D. The urethra is a tube that connects the urinary bladder to the body’s outside. Because of its position, the urethra removes urine from the body. In
men, this tube also transports semen.
III. The Nephron: Tubular and Vascular Components
B. The ureters are a pair of tubes that convey urine to the urinary bladder.
These tubes are composed of mucous membranes and smooth muscle.
1. The ureter’s mucous membrane lines its lumen. This layer protects the
ureter from the highly acidic urine.
2. The ureter’s smooth muscle performs peristalsis. This rhythmic contraction propels urine to the urinary bladder. Urine is also propelled by gravity
and hydrostatic pressure.
C. The urinary bladder is a sac-like organ that lies near the base of the pelvic
cavity. When full, this sac resembles an inverted pear.
1. The urinary bladder temporarily stores urine. Therefore, it solves the
problem of constant urination.
2. The wall of the urinary bladder contains smooth muscle and stretch receptors.
a. The bladder’s smooth muscle is called the detrusor muscle. This
muscle’s contraction causes the bladder to empty. This process is
called urination or micturition.
b. The bladder’s stretch receptors trigger the micturition reflex. This is
accomplished by controlling the bladder’s detrusor muscle and its
sphincters.
A. A nephron’s tubular network is responsible for the collection and production
of urine. Therefore, it regulates the blood’s composition and volume.
1. The opening to the tubular network is called the glomerular capsule or
Bowman’s capsule. This cup-like structure is located within the kidney’s
renal cortex and it surrounds a capillary bed called the glomerulus.
a. The glomerular capsule and its glomerulus are collectively called a renal corpuscle.
b. The renal corpuscle functions in producing a glomerular filtrate by way
of filtration. This happens as plasma filters through the pores of the
corpuscle’s walls.
2. The glomerular capsule moves its glomerular filtrate into a highly coiled
tube called the proximal convoluted tubule. This tube functions in reabsorption and secretion. These processes help to convert the glomerular
filtrate into urine.
3. The proximal convoluted tubule conveys the filtrate to Henle’s loop. This
series of tubes (i.e., descending limb, loop, and ascending limb) enters
the renal medulla. Here, they continue to refine the filtrate by using the
countercurrent multiplier mechanism.
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4. The ascending limb of Henle returns the filtrate to the renal cortex. Here,
it merges with the distal convoluted tubule. The distal convoluted tubule uses reabsorption and secretion to modify the glomerular filtrate as
it moves to the collecting duct.
5. The collecting duct connects the distal convoluted tubule to a renal calyx. Besides conveying the glomerular filtrate, the collecting duct uses
reabsorption to finish the refining process. When it leaves this tube, the
glomerular filtrate has been transformed into urine.
B. A nephron’s vascular network is responsible for the delivery and removal
of blood. This network also assists the tubular network with the formation of
urine.
1. Blood is conveyed to the kidneys by the renal arteries. Once inside the
kidney, the renal arteries branch. These branches are called the segmental arteries. The segmental arteries deliver blood to the interlobar arteries.
2. The interlobar arteries follow the renal columns to deliver blood to the
arcuate arteries.
3. The arcuate arteries arc over the renal pyramids and branch into many
cortical arteries.
4. Each cortical artery travels into the renal cortex. Here, the blood vessel
delivers blood to a nephron by attaching to its afferent arteriole.
6. The afferent arteriole delivers its blood to the nephron’s glomerulus.
7. The glomerulus generates a glomerular filtrate from its blood. After this
filtration occurs, the blood exits the glomerulus through an efferent arteriole.
8. The efferent arteriole delivers blood to the nephron’s peritubular capillaries and vasa recta. These capillary beds assist the nephron’s tubular
network in refining the glomerular filtrate.
a. The peritubular capillaries surround the nephron’s proximal and distal convoluted tubules. These capillaries help to refine the urinary filtrate into urine by assisting in reabsorption and secretion.
b. The vasa recta surround Henle’s loop. These capillaries assist with
the countercurrent multiplier mechanism.
9. The peritubular capillaries and vasa recta deliver blood to the kidneys
cortical veins. These veins merge to form the arcuate veins.
10. The arcuate veins arc over the renal pyramids to deliver blood to the
interlobar veins.
11. The interlobar veins travel down the renal columns to deliver blood to the
kidney’s renal vein.
12. The renal vein removes the blood from the kidney by delivering it to the
inferior vena cava.
IV. Nephrons perform three activities to produce urine. These activities are: glomerular filtration, tubular reabsorption, and tubular secretion. Let’s examine
these activities in more detail.
A. Glomerular filtration is a process that produces a glomerular filtrate from
the body’s blood. This happens as the filtrate passes through the wall of the
renal corpuscle.
1. Glomerular filtration separates the blood’s larger particles from its smaller
particles. Because of this action, the glomerular filtrate does not contain
blood cells or many of the plasma’s proteins. Instead, it contains water,
glucose, sodium, and urea, among others.
2. Like capillary filtration, glomerular filtration is controlled by pressure gradients. These gradients involve: glomerular hydrostatic pressure, capsular
hydrostatic pressure, glomerular osmotic pressure, and capsular osmotic
pressure.
a. Glomerular hydrostatic pressure (GHP) is the fluid (blood) pressure
within the glomerulus. This pushing pressure (about 60mm of mercury)
forces fluid into the glomerular capsule.
b. Capsular hydrostatic pressure (CHP) is the fluid (filtrate) pressure
within the glomerular capsule. This pushing pressure (about 15mm of
mercury) forces fluid into the glomerulus.
c. Glomerular osmotic pressure (GOP) is determined by the concentration of proteins in the glomerulus. These proteins pull fluid into the
glomerulus. Since the glomerular blood contains many proteins, its
osmotic pressure is about 27mm of mercury.
d. Capsular osmotic pressure (COP) pulls fluid into the glomerular filtrate. However, this force is essentially zero because the filtrate contains little or no protein.
3. Using these figures, we can calculate the nephron’s effective filtration
pressure (EFP).
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EFP = (GHP + COP)–(CHP + GOP)
or
EFP = (60 + 0)–(15 + 27)
or
EFP = 18
4. An effective filtration pressure of 18mm of mercury causes about 10% of
the plasma that enters the glomerulus to enter the capsule. This amount
is equivalent to 48 gallons of filtrate generated by the kidneys per day.
This amount is called the glomerular filtration rate (GFR).
5. The kidney’s GFR is directly proportional to the GHP. Therefore, an increase in the GHP causes an increase in the GFR and vice versa. If the
GHP falls below 42mm of mercury, glomerular filtration stops. This problem is called anuria or renal failure.
6. Since the GHP is so important, its regulation is independent of the cardiovascular system’s pressure. This enables the GFR to remain constant
with drastic changes in the systemic blood pressure. The regulation of the
nephron’s GHP is controlled by: an autoregulation mechanism, hormonal
secretion, or by the autonomic nervous system.
a. The autoregulation mechanism of the GHP is controlled by the nephron’s juxtaglomerular apparatus. The apparatus is located within the
walls of the afferent and efferent arterioles and it is designed to control
their diameter. Therefore, the mechanism is autoregulatory because
the vessels control their own diameter.
1. Under normal circumstances, the afferent arteriole is larger in diameter than the efferent arteriole. This design causes pressure to build
within the glomerulus because more blood enters the capillary bed
than leaves it. As a result, the glomerulus can maintain a higher
pressure than the average capillary. However, this can be adjusted
by the juxtaglomerular apparatus.
2. The juxtaglomerular apparatus monitors the flow of blood into the
glomerulus and its pressure. If the systemic pressure is low, the arterioles respond by dilating the afferent arteriole and constricting the
efferent arteriole. This elevates the GHP which maintains the GFR. If
the systemic pressure is high, the opposite occurs to maintain the
GFR.
b. If the autoregulation mechanism cannot compensate for changes in
the systemic pressure, the apparatus secretes hormones to help
solve the problem.
1. Renin is secreted by the apparatus to invoke the renin-angiotensin
pathway. This culminates in the production of angiotensin II by the
lungs. Remember, angiotensin II has two functions. One, it stimulates
the secretion of aldosterone (hopefully to increase blood volume by
retaining sodium ions). Two, it is a potent vasoconstrictor (hopefully
to decrease the size of the system). Hopefully, these actions raise
blood pressure to prevent renal failure.
2. Erythropoietin is released by the apparatus to increase blood volume. Remember, erythropoietin stimulates red blood cell production.
The higher number of circulating red blood cells thicken the blood.
This concentration attracts water to it.
c. The arterioles’ vasomotor responses are also controlled by the autonomic nervous system. The ANS uses a sympathetic nerve to control
constriction in the nephron’s afferent arteriole. This nerve fiber uses
epinephrine to stimulate vasoconstriction. Therefore, the greater the
stimulation by the ANS, the slower the GFR.
7. Because the glomerular filtrate consists of both good and bad materials, it
must be refined before it can be eliminated as urine. Therefore, the tubular network performs reabsorption and filtration before urine is removed
from the body.
B. Tubular reabsorption removes materials from the glomerular filtrate and
places them within the nephron’s vascular network. Although this process
predominately occurs in the proximal convoluted tubule, reabsorption happens throughout the tubular network. Because reabsorption removes most
of the glomerular filtrate’s contents, only 1 to 2 liters of urine are produced
each day.
1. The tubular network can reabsorb a variety of materials: water, glucose,
amino acids, sodium, chloride, urea, etc. These materials may be reabsorbed actively or passively.
a. Active reabsorption is a process requiring energy. The body uses this
process to remove valuable solutes from the glomerular filtrate (i.e.,
glucose and sodium).
b. Passive reabsorption is a process that does not require energy. This
reabsorption is driven by concentration gradients (i.e., water) or ionic
attraction (i.e., chloride ions).
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2. Reabsorption may also be obligatory or facultative.
a. Obligatory reabsorption happens because the body does not have a
choice (i.e., some tubules must reabsorb water because of the concentration gradient).
b. In facultative reabsorption, the body selects the materials to reabsorb. The body uses hormones to indicate its choices and the tubules
carry out the directives (i.e., the distal convoluted tubule facultatively
reabsorbs sodium, when stimulated by aldosterone).
3. The proximal convoluted tubule is responsible for most of the nephron’s tubular reabsorption. This reabsorption occurs from the from the
tubule into the peritubular capillary.
a. The proximal convoluted tubule actively reabsorbs glucose. This active transport mechanism is obligatory (running continually) and is limited by the number of glucose permeases present. Glucose is rarely
found in the urine, because the number of sugar permeases is usually
sufficient to remove all the glucose that is found in the filtrate. However, glucose will be found in the urine, if the filtrate’s level of glucose
exceeds the tubule’s number of sugar permeases. This is called glycosuria and it usually happens as a manifestation of diabetes mellitus.
b. Like glucose, sodium is actively reabsorbed by the proximal convoluted tubule. Like glucose, this mechanism is obligatory and restricted
by the number of sodium permeases present.
c. The sodium ions are not exchanged for another cation. Therefore, an
electrolytic imbalance occurs between the filtrate and the surrounding
tissue. The tissue becomes more positive as the sodium ions accumulate. Therefore, the filtrate’s chloride ions passively follow because of
their attraction to sodium.
d. The accumulation of solutes outside the proximal convoluted tubule
establishes a concentration gradient. Therefore, water passively
moves from the filtrate into the tissues because the tissues are more
concentrated than the filtrate. This movement is obligatory and it reabsorbs 80% of the water from the filtrate.
4. The distal convoluted tubule is responsible for most of the nephron’s
facultative reabsorption. This reabsorption is under the control of aldosterone and it provides additional support, should the proximal convoluted tubule fail to supply the body’s needs.
a. Aldosterone stimulates the distal convoluted tubule to actively reabsorb sodium ions by exchanging them for potassium ions. This exchange is not equal because sodium is more permeable to the duct
than potassium. Therefore, more sodium is reabsorbed from the tubule
than potassium is secreted into it. The result, a little water is passively
reabsorbed as it follows the sodium back into the peritubular capillary.
b. Note, the body monitors the level of potassium ions in the blood to control this mechanism. Remember, hyperkalemia causes an irregular
heartbeat. This mechanism will help to solve that problem. It also helps
to compensate for sodium ions lost through sweating.
5. The collecting duct uses an active mechanism to facultatively reabsorb
water from the filtrate. This mechanism occurs when a person is dehydrated and it is initiated by the secretion of ADH. Antidiuretic hormone
uses energy to open pores within the walls of the collecting duct. This
allows water to move out of the collecting duct into the more concentrated
renal medulla by osmosis. This concentration gradient is established by
the countercurrent multiplier mechanism. In summary, ADH causes an
increase in the concentration of urine as it decreases the urine’s volume.
C. Tubular secretion or tubular excretion removes materials from the nephron’s vascular network and places them within the glomerular filtrate. This
process predominately occurs along the proximal convoluted tubule and the
collecting duct.
1. The nephron’s peritubular capillaries can secrete: drugs, ammonia, sodium ions, hydrogen ions, potassium ions, creatinine, etc. Like reabsorption, tubular secretion can be active, passive, obligatory, or facultative.
2. Tubular secretion plays an integral role in regulating the blood’s pH. The
proximal convoluted tubule accomplishes this task by secreting hydrogen ions or bicarbonate ions to solve acidotic and alkalotic problems.
Cells of the proximal convoluted tubule have this ability because they
contain carbonic anhydrase.
a. During acidosis (respiratory or metabolic), the cells in this area increase their metabolic rate. This creates carbon dioxide which carbonic
anhydrase combines with water to form carbonic acid. As the acid
ionizes, it produces hydrogen and bicarbonate ions.
1. The hydrogen ions created within the cells are exchanged for sodium ions within the filtrate. Once inside the tubule’s cells, these sodium ions are exchanged for hydrogen ions within the blood. Once
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inside the tubule’s cells, the hydrogen ions are exchanged for more
sodium ions from the filtrate. The result, sodium ions are reabsorbed
by the blood while its hydrogen ions are secreted.
2. The bicarbonate ions created within the cells are exchanged for
chloride ions within the blood. Once inside the cells, these chloride
ions are exchanged for bicarbonate ions from the filtrate. Once inside the tubule’s cells, these bicarbonate ions are exchanged for
more chloride ions from the blood. The result, bicarbonate ions are
reabsorbed by the blood while its chloride ions are secreted.
3. The proximal convoluted tubule may also respond to acidosis by
creating ammonium ions (NH4). This occurs when the acidosis has
been happening for a while and the filtrate is becoming too acidic.
The proximal convoluted tubule has this ability because it can deaminate amino acids. Remember, deamination creates ammonia.
Ammonia is a strong base that will accept the hydrogen ions entering from the blood or those being created from carbonic acid. The
creation of ammonium ions neutralizes the acid because the hydrogen ions are no longer free. The result, the ammonium ions can be
safely traded for more sodium ions from the filtrate without changing
its pH.
4. In summary, the proximal convoluted tubule responds to acidosis by
secreting hydrochloric acid and ammonium chloride while reabsorbing sodium bicarbonate. This makes the kidney very efficient in controlling the blood’s acidosis. It removes acid from the blood while
adding additional buffer.
b. During alkalosis (respiratory or metabolic), the cells in this area solve
this problem by adding acids to the blood while removing buffers from
it.
1. Like acidosis, the proximal convoluted tubule responds to alkalosis
by increasing its metabolism to create carbonic acid from carbon
dioxide and water. However, it reverses its exchange of ions.
2. The tubule reabsorbs the hydrogen ions by exchanging them for
sodium ions from the blood. The tubule secretes bicarbonate ions
by trading them for chloride ions from the filtrate. The result, the tubule compensates for the alkalosis by adding hydrochloric acid to
the blood while removing sodium bicarbonate.
D. The countercurrent multiplier mechanism (CMM) is responsible for elevating the ion concentration within the renal medulla. Its purpose is to enable the nephron to produce a concentrated urine under any circumstance.
It does this by making the collecting duct’s reabsorption of water more efficient. The actions of the loop of Henle and the vasa recta make the CMM
possible.
1. The countercurrent multiplier mechanism got its name because the fluids
with the loop of Henle and the vasa recta flow opposite to one another.
Their action also results in multiplying the concentration of ions within the
renal medulla (examine the countercurrent multiplier mechanism diagram).
2. The descending limb of Henle is relatively impermeable to sodium and
chloride ions yet permeable to water. This causes the filtrate’s concentration to increase as it moves through the descending limb because water
leaves the limb to enter the medulla’s more concentrated tissues. This
water has little impact on the concentration of the medullary tissues because the ascending part of the vasa recta absorbs and carries this water
away.
3. The ascending limb of the vasa recta wants to absorb this water so that
its concentration matches that of the surrounding tissues. As blood moves
through the ascending limb of this blood vessel, the tissues become more
dilute. Therefore, the limb loses sodium and chloride ions to the tissue
and absorbs water to lower its concentration.
4. The ascending limb of Henle actively transports chloride ions into the
surrounding tissues. Sodium ions passively follow because the chloride
ions are negative. The movement of sodium and chloride ions causes the
filtrate’s concentration to decrease as it travels through the ascending
limb because this limb is impermeable to water. These ions remain
trapped within the medulla because:
a. They will not be absorbed by the descending limb of Henle.
b. If they are absorbed by the descending limb of the vasa recta, they will
be dragged back down into the renal medulla. Upon moving through
the ascending limb of the vasa recta, the sodium and chloride ions diffuse back out into the medulla before the blood enters the renal cortex.
5. In brief, the CMM causes the kidney’s cortical tissues to be dilute and its
medullary tissues to be concentrated. This concentration gradient is always maintained and it enables the body to concentrate its urine under
any circumstance.
a. The collecting duct carries the dilute filtrate through the more concentrated medulla. If the body has plenty of water, the filtrate remains dilute
and it passes into the urinary bladder. As a result, the body releases a
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large volume, dilute urine. If the body is dehydrated, the body releases
ADH.
b. ADH opens pores within the walls of the collecting duct (an active
movement). This action causes rapid reabsorption water from the collecting duct because of the concentration gradient maintained within
the renal medulla. Therefore, the urinary filtrate becomes more concentrated and its concentration is proportional to the amount of ADH
released. The result, the body voids a low volume, more concentrated
urine.
c. Reabsorption of water from the collecting duct does not effect the concentration of the renal medulla. This water will eventually move into the
ascending limb of the vasa recta by osmosis. Here, it remains as the
blood tries to match the concentration of the dilute cortical tissues.
V. Under normal conditions, urinary output is about 1 to 2 liters per day. However, this value can be influenced by a variety of factors.
A. The blood’s concentration influences the secretion of aldosterone and
ADH. These hormones reduce urinary output as they perform their job.
1. Aldosterone is secreted to replenish low sodium levels. This decreases
urinary output because water is passively reabsorbed from the filtrate as
sodium is actively reabsorbed.
2. ADH is secreted to rehydrate the body. This decreases urinary output
because water is reabsorbed from the urinary filtrate. Urinary output will
increase if ADH is chronically low. This ailment is called diabetes insipidus.
B. Diuretics are drugs that inhibit the facultative reabsorption of water. Therefore, they increase urinary output. Diuretics accomplish this task by blocking
the action or secretion of ADH or aldosterone. The frequent urination stimulated by diuretics will also lower the blood’s volume. Therefore, doctors administer diuretics to treat patients with hypertension.
1. Hypertension can be caused for several reasons. However, many middleaged men experience hypertension because they lose control over their
renin-angiotensin pathway and hypersecrete renin.
2. Remember, this pathway should only be initiated when blood pressure is
chronically low. If a person with normal blood pressure accidentally hypersecretes renin, they will experience high blood pressure. Doctors treat
this problem by administering an ACE inhibitor. This drug blocks the
conversion of angiotensin I into angiotensin II. Thus, it returns the blood
pressure to normal.
VI. Urine consists of 95% water and 5% solute. The urinary solute is composed of
a variety of substances (i.e., urea, creatinine, etc.). By studying the composition of urine (urinalysis), doctors can diagnose several ailments. Let’s examine this topic more closely.
A. The amber color of urine is attributed to urochrome. This pigment is produced by the liver from hemoglobin as the liver catabolizes old red blood
cells. As urochrome is produced, it is placed in the bloodstream, where it is
removed by the kidneys. Urine becomes darker as urochrome’s concentration increases. Doctors use this coloration to determine the hydration of a
patient.
B. Bilirubin is seldom found in urine because its blood level is low. Like urochrome, this material is produced by the liver from red blood cell (hemoglobin) catabolism. When bilirubin is found in urine, it is called bilirubinuria.
This condition is a sign of liver dysfunction.
C. Sugar is seldom found in urine because the convoluted tubules have more
than enough carriers to remove it. When sugar is found in the urine, it is
called glycosuria. Glycosuria can be a temporary as the result of a poor
diet. It can also be long-term, a sign of diabetes mellitus.
D. Albumin is seldom found in urine because it is not permeable to the glomerular capsule. When albumin is found in urine, it is called albuminuria. This
ailment can be caused by hypertension or be part of a disease process.
Some ailments will perforate the glomerular capsule. If this occurs, the capsule will not be able to filter out the proteins from the urinary filtrate.
E. Erythrocytes are seldom found in the urine. However, their presence is
called hematuria. Like, albuminuria, hematuria can be caused by a perforated glomerular capsule or by hypertension.
F. Leukocytes are seldom found in urine. However, their presence is called
pyuria. Pyuria is usually the result of a tubular infection.
G. Keto acids and ketones are seldom found in urine because their blood levels are low. When ketones are found in the urine, it is called ketosis or acetonuria. This ailment is caused by excessive beta oxidation. Excessive beta
oxidation is associated with diabetes mellitus, starvation, a low carbohydrate
diet, etc.
H. Renal calculi or kidney stones are seldom found in urine. Kidney stones
are caused by high blood salt concentrations or by prolonged dehydration.
These conditions cause the stones to form within the renal pelvis and they
block the flow of urine. This causes a considerable amount of pain because
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the stones are insoluble in urine. Doctors use ultrasound techniques and
diuretics to disintegrate the stones.
20. Urine formation requires three activities: reabsorption, filtration, and secretion.
Answers in Appendix A
VII. Because the removal of metabolic wastes is a big burden, other body systems
assist the kidneys with this task.
A. The integumentary system primarily removes heat, water, salts, and urea.
This occurs as the body sweats.
B. The digestive system primarily removes water and salts. This occurs as
the body defecates.
C. The respiratory system primarily removes carbon dioxide. This occurs as
the body respires.
URINARY SYSTEM SELF QUIZ
True or False
1. ANS can control GFR.
2. The ascending limb of Henle actively transports sodium ions; chloride ions passively follow.
3. Aldosterone stimulates the distal convoluted tubule to actively reabsorb sodium
ions.
4. The nephron is the functional unit of the kidney.
5. GHP will increase, if the afferent arteriole is constricted and the efferent arteriole
is dilated.
6. Most of the body’s water is conserved through active reabsorption.
7. The kidneys secrete hydrogen ions in the form of ammonium ions. These ions
are exchanged for sodium ions.
8. Renal tubules can buffer blood because they can produce hydrogen and bicarbonate ions from carbon dioxide and water.
9. The urethra transports urine from the kidney to the urinary bladder.
10. Urinary output is directly proportional to the blood’s aldosterone level.
11. The glomerular filtrate contains glucose and urea, but not proteins.
12. A decrease in the GOP causes an increase in GFR.
13. The countercurrent multiplier mechanism enables the kidney to produce a concentrated urine.
14. A renal corpuscle functions in secretion.
15. Pyuria is the presence of protein in the urine.
16. ADH causes the facultative reabsorbtion of water by the collecting duct.
17. The juxtaglomerular apparatus monitors the systemic blood pressure to control
the nephron’s GFR.
18. Ketosis is the presence of glucose in the urine.
19. The cortical vein delivers blood directly to the interlobar vein.
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Unit 20 - Urinary System
URINARY PARTS TO KNOW
Kidney
hilum
renal cortex
renal medulla
renal pyramids
renal column
major calyx
minor calyx
renal pelvis
renal sinus
renal artery
renal vein
segmental artery
interlobar artery
interlobar vein
arcuate artery
arcuate vein
cortical artery
cortical vein
peritubular capillaries
vasa recta
Ureter
Urinary Bladder
Urethra
Nephron
renal corpuscle
glomular capsule
glomerulus
proximal convoluted tubule
descending limb of Henle
loop of Henle
ascending limb of Henle
distal convoluted tubule
collecting duct
afferent arteriole
efferent arteriole
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Unit 20 - Urinary System
Urinary Crossword
1
2
3
4
5
6
7
8
9
11
20
12
13
17
18
21
22
10
14
15
19
23
26
24
27
30
29
32
34
37
38
35
39
40
42
36
41
43
44
49
50
45
46
47
51
48
52
53
56
25
28
31
33
16
54
55
57
58
62
66
63
68
71
61
69
65
70
72
74
75
77
79
60
64
67
73
59
76
78
80
ACROSS
1 stimulates facultative reabsorption of water 2 wrds.
9 Arts and Entertainment channel abbv.
11 renal corpuscle does this
13 collects urine from the collecting ducts 2 wrds.
17 elemental symbol for cobalt abbv.
18 movie monster
19 Occupational Therapy abbv.
20 Caribbean music
22 secretion of chloride ions will help correct this
24 diabetes insipidus causes urine volume to be this
26 secretion and reabsorption refine the filtrate into this
27 holy woman
28 alone
29 pinna
30 this ion can be traded for hydrogen ion abbv.
31 lack of iodine can cause this
32 rodent
33 functional unit of the kidney
35 electronics company
37 __ Ladd, actor
38 to color a house again
40 to salivate
42 network that contains the urinary filtrate
43 world's fair
44 hypersecretion of this chemical can cause hypertension abbv.
46 fluid pressure within the filtrate that is essentially zero abbv.
47 et cetera abbv.
49 to remove materials from the blood and place them in the filtrate
51 ocular
53 once held
55 hairlike projection from the surface of a cell
56 tax collection agency abbv.
57 by mouth
58 tubules can do this process to buffer secreted hydrogen ions
63 to become hostile
64 kitchen convenience
65 election month abbv.
66 mistakes
68 classical musical play
70 proximal convoluted tubule passively reabsorbs this
71 performing platform
73 people with diabetes mellitus may pass this in their urine
74 lyrical poem
75 each
77 actor/director Howard
79 study of urine
80 renal pelvis lines this chamber 2 wrds.
DOWN
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Unit 20 - Urinary System
1 this vessel deliver blood to the glomerulus 2 wrds.
2 this system can also remove urea
3 up to the time of
4 MSH stimulates this
5 enzyme used by tubular cells to cope with changes in pH 2 wrds.
6 location of the calcaneal bones
7 to take out of the filtrate and place in the blood
8 snake-like fish
10 this sphincter is voluntarily controlled
12 drug used to control the renin-angiotensin pathway 2 wrds.
14 meaningless sounds
15 this ion is used in trading for bicarbonate
16 a Hindu theistic philosophy
21 elemental symbol for argon abbv.
22 prefix for flight
23 a pair
25 location of kidney within the body
33 aldosterone stimulates facultative reabsorption of this ion abbv.
34 National Rifle Association abbv.
36 waterfowl
39 a major division of geological time
41 prescription
45 Drug Enforcement Agency abbv.
48 the loop of Henle does this abbv.
50 this describes the reabsorption of water by the proximal convoluted tubule
52 fluid found within the tubular network
53 this will be reabsorbed during alkalosis
54 micturition
59 Russian space station
60 type of immune cell abbv.
61 neither
62 this tube conveys urine to the urinary bladder
63 old soap: ____ the World Turns
67 regional term for kidney
69 physical education abbv.
72 hustle and bustle
75 respiratory system is concerned with this
76 this can adjust the glomerular filtration rate abbv.
78 elemental symbol for lithium abbv.
Answers in Appendix B
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