Answers to Illustration Questions 54517–2: Most of us would probably survive a range of
88 to 105F (31to 41C).
17–3: If you follow the arrows from all of the end
products of digestion, you will see that they
converge at pyruvic acid and acetyl CoA.
17–4: No. Only amino acids in the diet (or from
transamination) can be used to synthesize pro-
teins. Notice that no other arrows go to proteins.
17–5: The one on the right has more surface area in
proportion to weight. Or put another way: a
small interior with a large surface—which
would be true for an infant.CHAPTER 1818–1: You can see that the left renal artery is short (so
is the right one) and is a direct branch of the
abdominal aorta, where BP is relatively high
because it is close to the left ventricle.
18–2: Renal corpuscles and convoluted tubules are
found in the renal cortex. The renal cortex and
medulla have blood vessels (the renal pelvis is a
space).
18–3: The podocyte’s many “feet” contribute to the
filter for blood. The lining of the proximal con-
voluted tubule has microvilli, which increase
the surface area for reabsorption. (Let’s go a
step further: What is meant by a threshold level
for reabsorption?)
18–4: Tubular secretion takes place from the blood in
the peritubular capillaries to the filtrate in the
renal tubule. Hydrogen ions, creatinine, and
ammonia are secreted, as are the metabolic
products of medications.
18–5: Aldosterone affects both: It increases the reab-
sorption of sodium ions and the excretion of
potassium ions.
18–6: Carbon dioxide is used to make carbonic acid,
which then yields a hydrogen ion to be excreted
and a bicarbonate ion to be retained.
18–7: The internal urethral sphincter is involuntary;
the external urethral sphincter is voluntary. (A
step further: What kind of muscle tissue is the
detrusor muscle, and is it voluntary or involun-
tary?)CHAPTER 1919–1: Cerebrospinal fluid and aqueous humor are the
tissue fluid of the CNS and eye, respectively.19–2: On a hot day urine volume might decrease and
sweat volume might increase. Loss of water
vapor in exhaled air might also increase.
19–3: Tissue fluid is most like blood plasma, and you
knew this because you knew that tissue fluid is
made directly from plasma by filtration, a
process that would not greatly affect elec-
trolytes.
19–4: A kidney tubule cell obtains a hydrogen ion
from the reaction of carbon dioxide and water
to form carbonic acid, which ionizes.CHAPTER 2020–1: The 23 chromosomes are found in the head of
the sperm.
20–2: The secondary oocyte completes meiosis when
(if) the ovum is fertilized.
20–3: The ductus deferens carries sperm from the
epididymis to the urethra.
20–4: Seminiferous tubule (site of formation) to the
rete testis to the epididymis to the ductus
deferens. (Let’s go a step further: What is the
function of the interstitial cells and the susten-
tacular cells of the testis?)
20–5: The uterus is above the urinary bladder, and
during pregnancy will not displace the bladder
(though it will compress the bladder).
20–6: The myometrium is thicker in this view; it is
made of smooth muscle. (A step further: Which
uterine layer regularly changes in thickness?)
20–7: The labia cover the urethral and vaginal open-
ings to prevent drying of their mucous mem-
branes.
20–8: Prolactin stimulates milk production and oxy-
tocin stimulates release of milk. (A step further:
Which hormones contribute to the growth of
the mammary glands?)
20–9: LH triggers ovulation, then transforms the
ruptured follicle into the corpus luteum. (A step
further: Which hormones are secreted by the
corpus luteum?)CHAPTER 2121–1: The father, because the sperm cell will have
either an X or a Y chromosome. (The egg cell
will always have an X chromosome.)
21–2: The inner cell mass will become the embryo; it
is made of embryonic stem cells.29Scanlon(p3) App-G 8/17/06 11:08 AM Page 545