Seeley’s
ESSENTIALS OF
Anatomy &
Physiology
Tenth Edition
Cinnamon Vanputte
Jennifer Regan
Andrew Russo
See separate PowerPoint slides for all figures and tables
pre-inserted into PowerPoint without notes.
© 2019 McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
2
Chapter 18
Urinary System
and Fluid Balance
Lecture Outline
© 2019 McGraw-Hill Education
3
Urinary System
1
The urinary system is the major excretory
system of the body.
Some organs in other systems also eliminate
wastes, but they are not able to compensate in
the case of kidney failure.
© 2019 McGraw-Hill Education
4
Urinary System
2
Figure 18.1
© 2019 McGraw-Hill Education
5
Urinary System Functions
1. Excretion
2. Regulation of blood volume and blood
pressure
3. Regulation of blood solute concentration
4. Regulation of extracellular fluid pH
5. Regulation of red blood cell synthesis
6. Regulation of Vitamin D synthesis
© 2019 McGraw-Hill Education
6
Components of the Urinary System
Two kidneys
Two ureters
One urinary bladder
One urethra
© 2019 McGraw-Hill Education
7
Urinary System
Figure 18.2a
© 2019 McGraw-Hill Education
8
Kidney Characteristics
Bilateral retroperitoneal organs
Shape and size:
• bean shaped
• weighs 5 ounces (bar of soap or size of fist)
Location:
• between 12th thoracic and 3rd lumbar vertebra
© 2019 McGraw-Hill Education
9
Kidney Structures
1
Renal capsule:
• connective tissue around each kidney
• protects and acts as a barrier
Hilum:
• indentation
• contains renal artery, veins, nerves, ureter
© 2019 McGraw-Hill Education
10
Kidney Structures
2
Renal sinus:
• contains renal pelvis, blood vessels, fat
Renal cortex:
• outer portion
Renal medulla:
• inner portion
© 2019 McGraw-Hill Education
11
Kidney Structures
Renal pyramid:
• junction between cortex and medulla
Calyx:
• tip of pyramids
Renal pelvis:
• where calyces join
• narrows to form ureter
© 2019 McGraw-Hill Education
3
12
Longitudinal Section of the Kidney
Figure 18.3
© 2019 McGraw-Hill Education
13
Nephron
The nephron is the functional unit of the kidney.
Each kidney has over one million nephrons.
There are two types of nephrons in the kidney:
•
juxtamedullary
•
cortical
Approximately 15% are juxtamedullary
The nephron includes the renal corpuscle, proximal
tubule, loop of Henle, distal tubule and collecting duct
© 2019 McGraw-Hill Education
14
Nephron Components
1
Renal corpuscle:
structure that contains a Bowman’s capsule and
glomerulus
Bowman’s capsule:
• enlarged end of nephron
• opens into proximal tubule
• contains podocytes (specialized cells
• around glomerular capillaries)
Glomerulus:
• contains capillaries wrapped around it
© 2019 McGraw-Hill Education
15
Nephron Components
2
Filtration membrane:
• in renal corpuscle
• includes glomerular capillaries, podocytes, basement
membrane
Filtrate:
• fluid that passes across filtration membrane
© 2019 McGraw-Hill Education
16
Nephron Components
3
Proximal tubule:
• where filtrate passes first
Loop of Henle:
• contains descending and ascending loops
• water and solutes pass through thin walls by
diffusion
© 2019 McGraw-Hill Education
17
Nephron Components
4
Distal tubule:
• structure between Loop of Henle and collecting duct
Collecting duct:
• empties into calyces
• carry fluid from cortex through medulla
© 2019 McGraw-Hill Education
18
Flow of Filtrate through Nephron
1. Renal corpuscle
2. Proximal tubule
3. Descending loop of Henle
4. Ascending loop of Henle
5. Distal tubule
6. Collecting duct
7. Papillary duct
© 2019 McGraw-Hill Education
19
Blood Flow through Kidney
1. Renal artery
2. Interlobar artery
3. Arcuate artery
4. Interlobular artery
5. Afferent arteriole
6. Glomerulus
7. Efferent arteriole
8. Peritubular capillaries
9. Vasa recta
10. Interlobular vein
11. Arcuate vein
12. Interlobar vein
© 2019 McGraw-Hill Education
20
Blood Flow Through the Kidney
Figure 18.6
© 2019 McGraw-Hill Education
21
Urine Formation
1
Urine formation involves three processes:
• Filtration – occurs in the renal corpuscle
• Reabsorption – it involves removing substances
from the filtrate and placing back into the blood
• Secretion – it involves taking substances from the
blood at a nephron area other than the renal
corpuscle and putting back into the nephron tubule
© 2019 McGraw-Hill Education
22
Urine Formation
2
Figure 18.7
© 2019 McGraw-Hill Education
23
Urine Formation-Filtration
1
Movement of water, ions, small molecules
through filtration membrane into Bowman’s
capsule
19% of plasma becomes filtrate
180 Liters of filtrate are produced by the
nephrons each day
1% of filtrate (1.8 liters) become urine rest is
reabsorbed
© 2019 McGraw-Hill Education
24
Urine Formation-Filtration
2
Only small molecules are able to pass through
filtration membrane
Formation of filtrate depends on filtration
pressure
Filtration pressure forces fluid across filtration
membrane
Filtration pressure is influenced by blood
pressure
© 2019 McGraw-Hill Education
25
Urine Production-Reabsorption
99% of filtrate is reabsorbed and reenters
circulation
Proximal tubule is primary site for reabsorption
of solutes and water
Descending Loop of Henle concentrates filtrate
Reabsorption of water and solutes from distal
tubule and collecting duct is controlled by
hormones
© 2019 McGraw-Hill Education
26
Urine Concentration
1
The descending limb of the loop of Henle is a
critical site for water reabsorption.
The filtrate leaving the proximal convoluted
tubule is further concentrated as it passes
through the descending limb of the loop of
Henle.
The mechanism for this water reabsorption is
osmosis.
© 2019 McGraw-Hill Education
27
Urine Concentration
2
The renal medulla contains very concentrated
interstitial fluid that has large amounts of Na+, Cl−,
and urea.
The wall of the thin segment of the descending limb
is highly permeable to water.
As the filtrate moves through the medulla
containing the highly concentrated interstitial fluid,
water is reabsorbed out of the nephron by osmosis.
The water enters the vasa recta.
© 2019 McGraw-Hill Education
28
Urine Concentration
3
The ascending limb of the loop of Henle dilutes
the filtrate by removing solutes
The thin segment of the ascending limb is not
permeable to water, but it is permeable to
solutes
Consequently, solutes diffuse out of the
nephron
© 2019 McGraw-Hill Education
29
Urine Production—Secretion
1
Tubular secretion removes some substances
from the blood.
These substances include by-products of
metabolism that become toxic in high
concentrations and drugs or other molecules
not normally produced by the body.
Tubular secretion occurs through either active or
passive mechanisms.
© 2019 McGraw-Hill Education
30
Urine Production—Secretion
2
Ammonia secretion is passive.
Secretion of H+, K+, creatinine, histamine, and
penicillin is by active transport.
These substances are actively transported into
the nephron.
The secretion of H+ plays an important role in
regulating the body fluid pH.
© 2019 McGraw-Hill Education
31
Urine Concentration and Volume
Regulation
Three major hormonal mechanisms are involved
in regulating urine concentration and volume:
1. renin-angiotensin-aldosterone
2. the antidiuretic hormone (ADH)
3. the atrial natriuretic hormone
© 2019 McGraw-Hill Education
32
Renin-Angiotensin-Aldosterone
Mechanism
1
1. Renin acts on angiotensinogen to produce
angiotensin I
2. Angiotensin-converting enzyme converts
angiotensin I to angiotensin II
3. Angiotensin II causes vasoconstriction
© 2019 McGraw-Hill Education
33
Renin-Angiotensin-Aldosterone
Mechanism
2
4. Angiotensin II acts on adrenal cortex to
release aldosterone
5. Aldosterone increases rate of active transport
of Na+ in distal tubules and collecting duct
6. Volume of water in urine decreases
© 2019 McGraw-Hill Education
34
Aldosterone Actions
Figure 18.14
© 2019 McGraw-Hill Education
35
Antidiuretic Hormone Mechanism
1. ADH is secreted by the posterior pituitary
gland
2. ADH acts of kidneys, causing them absorb
more water (decrease urine volume)
3. Result is to maintain a normal blood volume
and blood pressure
© 2019 McGraw-Hill Education
ADH and the Regulation of
Extracellular Fluid
36
Figure 18.15
© 2019 McGraw-Hill Education
37
Atrial Natriuretic Hormone
1
1. ANH is secreted from cardiac muscle in the
right atrium of the heart when blood
pressure increases
2. ANH acts on kidneys to decrease Na+
reabsorption
3. Sodium ions remain in nephron to become
urine
4. Increased loss of sodium and water reduced
blood volume and blood pressure
© 2019 McGraw-Hill Education
38
Atrial Natriuretic Hormone
2
Figure 18.16
© 2019 McGraw-Hill Education
39
Ureters and Urinary Bladder
1
Ureters:
• small tubes that carry urine from renal pelvis of
kidney to bladder
Urinary bladder:
• in pelvic cavity
• stores urine
• can hold a few ml to a maximum of 1000 milliliters
© 2019 McGraw-Hill Education
40
Urethra
Urethra:
• tube that exits bladder
• carries urine from urinary bladder to outside of body
© 2019 McGraw-Hill Education
41
Ureters and Urinary Bladder
2
Figure 18.18
© 2019 McGraw-Hill Education
42
Urine Movement
Micturition reflex:
• activated by stretch of urinary bladder wall
• action potentials are conducted from bladder to
spinal cord through pelvic nerves
• parasympathetic action potentials cause bladder to
contract
• stretching of bladder stimulates sensory neurons to
inform brain person needs to urinate
© 2019 McGraw-Hill Education
43
Body Fluid Compartments
The intracellular fluid compartment includes the
fluid inside all the cells of the body.
Approximately two-thirds of all the water in the
body is in the intracellular fluid compartment.
The extracellular fluid compartment includes all the
fluid outside the cells.
The extracellular fluid compartment includes,
interstitial fluid, plasma, lymph, and other special
fluids, such as joint fluid, and cerebrospinal fluid.
© 2019 McGraw-Hill Education
44
Composition of Fluids
Intracellular fluid contains a relatively high
concentration of ions, such as K+, magnesium
(Mg2+), phosphate (PO43−), and sulfate (SO42−),
compared to the extracellular fluid.
It has a lower concentration of Na+, Ca2+, Cl−,
and HCO3− than does the extracellular fluid.
© 2019 McGraw-Hill Education
45
Exchange Between Fluid
Compartments
The cell membranes that separate the body fluid
compartments are selectively permeable.
Water continually passes through them, but ions
dissolved in the water do not readily pass through
the cell membrane.
Water movement is regulated mainly by hydrostatic
pressure differences and osmotic differences
between the compartments.
Osmosis controls the movement of water between
the intracellular and extracellular spaces.
© 2019 McGraw-Hill Education
46
Regulation of Extracellular Fluid
Composition
Thirst Regulation
Ion Concentration Regulation
© 2019 McGraw-Hill Education
47
Thirst Regulation
Water intake is controlled by the thirst center
located in the hypothalamus
When the concentration of ions in the blood
increases, it stimulates the thirst center to cause
thirst
When water is consumed, the concentrations of
blood ions decreases, due to a dilution effect; this
causes the sensation of thirst to decrease
© 2019 McGraw-Hill Education
48
Thirst Regulation of Extracellular Fluid
Concentration
Figure 18.20
© 2019 McGraw-Hill Education
49
Ion Concentration Regulation
1
Regulating the concentrations of positively
charged ions, such as Na+, K+, and Ca2+, in the
body fluids is particularly important.
Action potentials, muscle contraction, and
normal cell membrane permeability depend on
the maintenance of a narrow range of these
concentrations.
© 2019 McGraw-Hill Education
50
Ion Concentration Regulation
2
Negatively charged ions, such as Cl−, are
secondarily regulated by the mechanisms that
control the positively charged ions.
The negatively charged ions are attracted to the
positively charged ions; when the positively
charged ions are transported, the negatively
charged ions move with them.
© 2019 McGraw-Hill Education
51
Sodium Ions
Sodium ions (Na+) are the dominant ions in the
extracellular fluid.
About 90 to 95% of the osmotic pressure of the
extracellular fluid results from sodium ions and
from the negative ions associated with them.
Stimuli that control aldosterone secretion influence
the reabsorption of Na+ from nephrons of the
kidneys and the total amount of Na+ in the body
fluids.
Sodium ions are also excreted in sweat.
© 2019 McGraw-Hill Education
52
Potassium Ions
Electrically excitable tissues, such as muscles
and nerves, are highly sensitive to slight changes
in the extracellular K+ concentration.
The extracellular concentration of K+ must be
maintained within a narrow range for these
tissues to function normally.
Aldosterone plays a major role in regulating the
concentration of K+ in the extracellular fluid.
© 2019 McGraw-Hill Education
53
Calcium Ions
The extracellular concentration of Ca2+ is maintained
within a narrow range.
Increases and decreases in the extracellular
concentration of Ca2+ have dramatic effects on the
electrical properties of excitable tissues
Parathyroid hormone (PTH), secreted by the
parathyroid glands, increases extracellular Ca2+
concentrations.
Calcitonin reduces the blood Ca2+ concentration
when it is too high.
© 2019 McGraw-Hill Education
54
Phosphate and Sulfate Ions
Some ions, such as phosphate ions (PO43−) and
sulfate ions (SO42−), are reabsorbed by active
transport in the kidneys.
The rate of reabsorption is slow, so that if the
concentration of these ions in the filtrate exceeds
the nephron’s ability to reabsorb them, the excess
is excreted into the urine.
As long as the concentration of these ions is low,
nearly all of them are reabsorbed by active
transport.
© 2019 McGraw-Hill Education
55
Regulation of Acid-Base Balance
1
Buffers
• chemicals resist change in pH of a solution
• buffers in body contain salts of weak acids or bases
that combine with H+
• three classes of buffers: proteins, phosphate buffer,
bicarbonate buffer
© 2019 McGraw-Hill Education
56
Regulation of Acid-Base Balance
2
Respiratory system involvement in acid-base:
• responds rapidly to changes in pH
• increased respiratory rate raises blood pH (more
alkalotic) due to increased rate of carbon dioxide
elimination from the body
• reduced respiratory rate reduces pH (more acidic)
due to decreased rate of carbon dioxide elimination
from the body
© 2019 McGraw-Hill Education
57
Regulation of Acid-Base Balance
3
Kidney Involvement in acid-base:
• nephrons secrete H+ into urine and directly regulate
pH of body fluids
• more H+ secretion if the pH is decreasing and less H+
secretion if pH is increasing
© 2019 McGraw-Hill Education
58
Acidosis and Alkalosis
Acidosis occurs when the pH of blood falls below
7.35
There are two types of acidosis based upon the
cause: respiratory and metabolic
Alkalosis occurs when the pH of blood increases
above 7.45
There are two types of alkalosis based upon the
cause: respiratory and metabolic
© 2019 McGraw-Hill Education