Biol 12
Excretion Review
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Chapter Overview.
The lungs excrete
and the liver excretes
pigments. The skin excretes
, which contains
, and the kidneys excrete ammonia, urea, uric acid, and creatinine, all
wastes.
The path of urine is through the kidneys,
, urinary
bladder, and finally,
.
Macroscopically, the kidneys are divided into the cortex,
, and pelvis.
Microscopically, they contain the
.
Each nephron has it’s own blood supply; the
arteriole approaches
the glomerular capsule and divides to become the glomerulus. The spaces between the
podocytes of the glomerular capsule allow
molecules to enter the
capsule from the glomerulus, a capillary tuft. The
arteriole, leaves the
capsule and immediately branches into the
capillaries.
Each region of the nephron is anatomically suited to its task in urine formation. The
spaces between the podocytes of the glomerular capsule allow
molecules to enter the capsule from the glomerulus, a papillary knot. The cuboidal
epithelial cells of the proximal convoluted tubule have many mitochondria and microvilli
to carry out
transport (following passive transport) from the tubule to blood.
IN contrast, the cuboidal epithelial cells of the distal convoluted tubule have numerous
mitochondria but lack microvilli. They carry out active transport from the blood to the
tubule.
Urine is composed primarily of
waste products and salts in
water.
The steps in urine formation are
filtration; tubular
and tubular
, as explained in Figure 16.6. Water is reabsorbed from all
parts of the tubule, and the loop of the nephron establishes an
gradient that draws water from the descending loop of the nephron and also the collecting
duct.
The kidneys contribute to homeostasis not only by ridding the body of nitrogenous
wastes but also by helping control the pH and saltwater balance of the blood. The latter
also determines blood
, which is controlled by several hormones,
including ADH,
, and ANH.
Various types of problem, including repeated urinary infections, can lead to kidney
failure, which necessitates receiving a kidney from a donor or undergoing
by utilizing a kidney machine or CAPD.
Study Questions
16.1 Four Excretory Organs
Concepts:
- Excretion rids the body of unwanted substances, particularly the waste product so
metabolism.
- Several organs assist in the process of excretion, but only the kidneys produce
urine.
Biol 12
Excretion Review
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1. List the four organs of excretion and their products of excretion.
a.
b.
c.
d.
Where in the body is urea produced?
What molecules are used to
form urea?
2. Creatine phosphate in muscles results in the end product
. The
breakdown of nucleotides produces
, which in the joints produces
the ailment called
.
16. 2 – Urinary System
Concept: The urinary system consists of organs that produce, store, and rid the body
of urine.
3. What is the function of the kidney?
. The
are muscular tubes that convey urine from the kidneys
toward the bladder. The
is a hollow, muscular organ that can
hold urine. The
extends from the urinary bladder to an
external opening. In males, the urethra transports both urine and
.
4. The three regions of the kidney include the renal
, an outer
granulated layer, the renal
, which consists of cone-shaped renal
pyramids, and the renal
.
16.3: Anatomy of a Nephron
Concepts:
- The work of an organ is dependent on its microscopic anatomy; nephrons within a
kidney produce urine.
- Structure suits the function, and this can be illustrated by studying the microscopic
anatomy of a nephron.
5. Blood that supplies the nephron comes from the afferent arteriole and goes to the
, to the efferent arteriole, to the
capillaries, to the venule, and to the renal vein.
6. The cuplike structure called the
, or Bowman’s capsule, has
an inner layer made up of cells termed
that form pores for
passage of small molecules from the glomerulus into the glomerular capsule. This
process is called
.
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Excretion Review
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7. The proximal
tubule has cuboidal epithelial cells that have
that increase the surface area for
In the
loop of
, the tube narrows and makes an U-turn. The cells of the
convoluted tubule have many mitochondria but lack microvilli.
Molecules move from the blood into the tubule, a process called
. Distal
convoluted tubules enter one
.
16.4: Urine Formation
Concept:
- Like many physiological processes, urine formation is a multi-step process.
8. IN
filtration, blood pressure in the glomerulus forces
water and small molecules from the glomerulus into the
capsule. This is a filtration process.
9. The glomerular filtrate contains small dissolved molecules in approximately the
same concentration as
. Tubular reabsorption occurs as molecules
are reabsorbed from the
to the blood in the peritubular capillary.
When sodium ions are actively reabsorbed,
ions follow passively
from the tubule into the blood.
10. Nutrients such as glucose and amino acids are selectively returned to the blood at the
proximal convoluted tubule because those molecules are recognized by
molecules. After all of a substance’s carriers are in use, any excess of the substance
in the filtrate will appear in the
. Tubular
occurs when
substances are removed from blood and added to tubular fluids in the
convoluted tubule. Such substances include hydrogen and ammonium ions.
11. Excretion of hypertonic urine is dependent upon what two sites in the nephron?
In the ascending limb of the loop of the nephron (loop of Henle), the thick portion
actively transports out
into the tissue of the outer renal
medulla. The concentration of salt is greater in the direction of the
. The
ascending limb is
to water.
leaks from the
collecting duct and contributes to the high solute concentration. Water leaves the
limb of the loop of the nephron. Due to the osmotic gradient, water
diffuses out of the
duct into the renal medulla so that urine
becomes hypotonic.
16.5: Regulatory Functions of the Kidneys
Concept:
- the kidneys rid the body of nitrogenous wastes and help regulate the pH and the
salt/water balance of blood.
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Excretion Review
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12. Write True or False for each of the statements below.
a. the juxtaglomerular apparatus is between the afferent arteriole
and distal convoluted tubule.
b. Increased blood pressure causes the afferent arteriole cells to secrete renin.
c. Renin converts angiotensinogen into angiotensin II.
d. Angiotensin-converting enzyme changes angiotensin I into angiotensin II
e. Angiotensin I stimulates the adrenal cortex to release aldosterone.
f. Aldosterone decreases Na+ reabsorption into the blood, which leads to greater
blood volume.
13. The antidiuretic hormone is released by the
. When ADH
is present, more
is reabsorbed, and a decreased amount of
results. The atrial natriuretic hormone is released by the
of the heart
when stretched due to increased blood volume. ANH inhibits secretion of
and aldosterone and causes the excretion of
, which causes the
blood volume and blood pressure to decrease.
14.
are agents that increase the flow of urine. Alcohol causes diuresis
because it inhibits the secretion of
. If blood is acidic, the
nephrons of the kidney will excrete
in combination with NH3, while Na+
and bicarbonate ions are reabsorbed since NaHCO3 is a base. If blood is basic, fewer
H+ are excreted.
16.6: Problems with Kidney Function
Concept: The kidneys are vital body organs, and malfunction causes illness and even
death.
15. Infection of the urethra is called
. Infection of the bladder is called
. Infection of the kidneys is called
.
Accumulation of urea in the blood is called
. Which is
worse: accumulation of urea in the blood or retention of water and salts?
. Presence of albumin in the urine is detected by a
.
16.
is defined as the diffusion of dissolved molecules through
a semipermeable membrane. During
, the patient’s blood is
passed through a semipermeable membranous tube, which is in contact with a
balanced salt solution. In CAPD, a fresh amount of dialysate is introduced directly
into the
from a bag attached to a permanently implanted
plastic tube.
Objective Questions: Completion and Short Answer Questions:
1. The removal of metabolic wastes from the body is called
. The
primary excretory organ of the body is the
, but other excretory
organs include the
,
, and the
Biol 12
Excretion Review
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2. The gross structure of the kidney, when cut lengthwise, shows three regions. The
outermost portion is granular and is called the
. It dips down
between a radially striated inner layer called the
, which consists of
cone-shaped tissue masses termed
. The
is a central space continuous with the ureter. Microscopically, the kidney is composed of
over one million
.
3. Label the following parts of the nephron in the diagram shown below.
4. The structure of each part of the nephron suits its function. The inner layer of the
glomerular capsule is composed of squamous epithelial cells called
that have long processes forming pores for filtration. The cells of the proximal
convoluted tubule have numerous
that increase the surface area
for tubular reabsorption. The descending limb of the loop of the nephron allows water to
leave, but the
limb is imperious to water. The cells of the distal
convoluted tubule have numerous
that provide energy for
active transport in tubular secretion.
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Excretion Review
5. The process that is used to divide the blood into the filterable and non-filterable
components is called
. The process that transports molecules from
the nephron tubules into the surrounding capillaries is called tubular
.
In tubular
, molecules are removed from the blood and added
to the tubular fluids.
6. Complete the following table to illustrate what takes place in different parts of the
nephron. For the heading molecules, use the following terms: protein, blood cells, water,
glucose, salt, urea, amino acids, H+, and ammonia.
Nephron Structure
Major Event (process)
Molecules (present, to be
removed, to be added)
Glomerulus
Glomerular Capsule
Proximal convoluted
tubule
Loop of the Nephron
Distal convoluted tubule
Collecting Duct
7. The
apparatus helps to maintain blood volume by
releasing renin from the
arteriole cells whenever there is decreased
blood volume or blood pressure. Renin, an enzyme, converts
into angiotensin I, which in turn is converted to angiotensin II by the
enzyme in the lungs. Angiotensin II constricts blood vessels, thereby increasing blood
pressure, and stimulates the adrenal cortex to release
. This
hormone promotes the reabsorption of
ions into the blood at the
distal convoluted tubule, followed by increased
reabsorption, which
leads to increased blood volume and blood pressure.
8. Another hormone that regulates blood volume is
, which comes
from the posterior lobe of the pituitary gland. If an individual does not drink much water
on a particular day, ADH is released and more water is reabsorbed from the renal tubules
into the surrounding peritubular capillaries, which means a(n)
(increased/decreased) urine volume. ADH secretion is inhibited by
Excretion Review
Biol 12
True (T) or False (F) Questions
If you believe the statement to be false, rewrite the statement as a true one.
9. There is a greater osmotic concentration in the outer renal medulla region than in the
inner renal medulla region.
Answer
. Restatement:
10. The ascending limb of the loop of the nephron is impermeable to water.
Answer
. Restatement:
11. Hangovers after drinking alcohol may be due to dehydration as a result of alcohol
stimulating ADH secretion.
Answer
. Restatement:
12. The hormone ADH is released from the adrenal cortex, whereas aldosterone is
released from the posterior pituitary.
Answer
. Restatement:
13. The kidneys help to regulate salt balance, blood volume, and the pH of the blood.
Answer
. Restatement:
14. During continuous ambulatory peritoneal dialysis, a dialysate is placed into the
abdominal cavity.
Answer
. Restatement:
For questions 15-19, match the following excretory products to each of the sources
below.
a. urea
c. uric acid
e. urochrome
b. creatinine d. bile pigments
15.
16.
17.
hemoglobin
heme
CO2 + ammonia
18.
19.
nucleotides
Creatine phosphate
7
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Excretion Review
Biol 12
For questions 20-24, match the following excretory organs to each of the excretory
products below.
a. skin
c. lungs
b. liver
d. kidneys
20.
21.
22.
bile pigments
urochrome
water, salts, some urea
23.
24.
CO2 + water
water, urea, salts
For questions 25-29, match the following enzymes or hormones to each of their
functions below.
a. renin
b. aldosterone
c. angiotensin converting enzyme
25.
26.
27.
28.
29.
d. antidiuretic hormone
e. atrial natriuretic hormone
inhibits secretion of renin and aldosterone
promotes water reabsorption, decreases urine
converts angiotensin I into angiotensin II
converts angiotensinogen to angiotensin I
promotes Na+ reabsorption in the distal tubule
For questions 30-35, match the following conditions to each of the statements below.
a. uremia
b. urinalysis
c. pyelonephritis
d. urethritis
e. cystitis
f. dialysis
30. infection of the urinary bladder
31. infection of the urethra
32. determination of urine content
33. infection of the kidneys
34. accumulation of urea in the blood
35. diffusion of dissolved molecules through a semipermeable membrane
Multiple Choice Questions.
36. Which of the following describes the flow of urine through the urinary system
correctly?
a. urethra, urinary bladder, ureter, kidney
b. kidney, ureter, urinary bladder, urethra
c. kidney, urethra, urinary bladder, ureter
d. urinary bladder, ureter, kidney, urethra
e. kidney, urinary bladder, ureter, urethra
Biol 12
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Excretion Review
37. Which of the following statements is NOT correct about water reabsorption in the
kidney?
a. Salt is actively transported out of the ascending limb
b. Water leaves the ascending limb
c. Water leaves the descending limb
d. Water may leave the collecting duct
e. Urea contributes to the high solute concentration in inner medulla
38. Which process accounts for H+ and ammonium ions to be removed from the blood
and added to the distal convoluted tubule?
a. glomerular filtration
b. tubular reabsorption
c. tubular secretion
d. osmosis
e. diffusion
39. The composition of the glomerular filtrate is about the same as that found in the
a. proximal convoluted tubule
b. distal convoluted tubule
c. ascending limb of loop of nephron
d. collecting duct
e. plasma
40. Which sequence correctly describes the flow through various parts of the nephron?
a. glomerulus, glomerular capsule, proximal convoluted tubule, nephron loop.
b. Glomerular capsule, nephron loop, proximal convoluted tubule, distal
convoluted tubule
c. Proximal convoluted tubule, distal convoluted tubule, nephron loop,
collecting duct
d. Nephron loop, collecting duct, distal convoluted tubule, proximal convoluted
tubule
e. Distal convoluted tubule, collecting duct, nephron loop, glomerulus,
glomerular capsule.
41. The juxtaglomerular apparatus is found between the
a. glomerular capsule and afferent arteriole
b. efferent arteriole and distal convoluted tubule
c. afferent arteriole and distal convoluted tubule
d. afferent arteriole and proximal convoluted tubule
e. proximal convoluted tubule and collecting duct
42. If blood becomes acidic,
are excreted and
a. H+ and Na+ ; NH3 and HCO3b. H+ and HCO3-; NH3 and Na+
c. H+ and NH3 ; Na+ and HCO3d. H+ and glucose; Na+ and HCO3-
are reabsorbed.
Biol 12
Excretion Review
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