WGU D313 Anatomy and Physiology II with Lab Objective Assessment | OA V1
and V2 | Full Questions and Answers with Rationales | 2026/2027 Updated |
100% Correct.
Questions 1–20
1. A damaged sinoatrial node no longer initiates cardiac impulses normally.
Which structure would most likely assume pacemaker activity next?
A. Purkinje fibers
B. Atrioventricular node
C. Bundle branches
D. Papillary muscles
Correct Answer: B. Atrioventricular node
Rationale: The atrioventricular (AV) node has an intrinsic firing rate and can serve as a
secondary pacemaker if the sinoatrial node fails. Purkinje fibers can also generate impulses but
normally do so at a slower rate. Bundle branches conduct impulses rather than normally
initiating the heartbeat, and papillary muscles prevent AV valve prolapse during ventricular
contraction.
2. Constriction of the afferent arteriole supplying a renal corpuscle would most
directly cause which change?
A. Increased glomerular hydrostatic pressure
B. Increased glomerular filtration rate
C. Decreased glomerular filtration rate
D. Increased pressure in Bowman's capsule
Correct Answer: C. Decreased glomerular filtration rate
Rationale: Constriction of the afferent arteriole decreases blood entering the glomerulus. This
reduces glomerular hydrostatic pressure and therefore lowers the glomerular filtration rate
(GFR). Pressure in Bowman's capsule does not increase simply because afferent blood flow falls.
3. During quiet inspiration, which sequence occurs?
,A. Diaphragm relaxes → thoracic volume decreases → alveolar pressure falls
B. Diaphragm contracts → thoracic volume increases → alveolar pressure falls
C. Diaphragm contracts → thoracic volume decreases → alveolar pressure rises
D. Diaphragm relaxes → thoracic volume increases → alveolar pressure rises
Correct Answer: B. Diaphragm contracts → thoracic volume increases → alveolar
pressure falls
Rationale: Contraction of the diaphragm enlarges the thoracic cavity. According to the pressure-
volume relationship, increasing lung volume reduces alveolar pressure below atmospheric
pressure, allowing air to flow inward.
4. Fat and partially digested protein enter the duodenum. Which hormone is
most strongly associated with stimulating pancreatic enzyme release and
gallbladder contraction?
A. Gastrin
B. Secretin
C. Cholecystokinin
D. Aldosterone
Correct Answer: C. Cholecystokinin
Rationale: Cholecystokinin (CCK) is released from the small intestine in response especially to
fats and proteins. It stimulates pancreatic enzyme secretion and causes gallbladder contraction.
Secretin primarily promotes bicarbonate-rich pancreatic secretion in response to acidic chyme.
5. Which hormonal event most directly triggers ovulation?
A. Rapid decrease in estrogen
B. Surge in luteinizing hormone
C. Increase in prolactin
D. Decrease in follicle-stimulating hormone only
Correct Answer: B. Surge in luteinizing hormone
Rationale: Sustained high estrogen late in the follicular phase produces positive feedback that
causes the luteinizing hormone (LH) surge. The LH surge triggers rupture of the mature follicle
and release of the secondary oocyte.
,6. Which immune cell can differentiate into a plasma cell after appropriate
activation?
A. Neutrophil
B. B lymphocyte
C. Cytotoxic T lymphocyte
D. Natural killer cell
Correct Answer: B. B lymphocyte
Rationale: Activated B lymphocytes differentiate into plasma cells that secrete antibodies and
into memory B cells that support a faster response to future exposure. Cytotoxic T cells directly
kill infected or abnormal cells rather than producing antibodies.
7. Blood returning from the lungs enters which cardiac chamber first?
A. Right atrium
B. Right ventricle
C. Left atrium
D. Left ventricle
Correct Answer: C. Left atrium
Rationale: Oxygenated blood returns from the lungs through the pulmonary veins and enters the
left atrium. It then passes through the mitral valve into the left ventricle before entering systemic
circulation.
8. Which nephron segment normally reabsorbs the greatest percentage of filtered
water, sodium, glucose, and amino acids?
A. Proximal convoluted tubule
B. Descending limb of the nephron loop
C. Distal convoluted tubule
D. Collecting duct
Correct Answer: A. Proximal convoluted tubule
Rationale: The proximal convoluted tubule performs bulk reabsorption. Nearly all filtered
glucose and amino acids and a large proportion of sodium and water are normally reclaimed
there. Later nephron segments are important for fine regulation.
, 9. Pulmonary surfactant primarily prevents which problem?
A. Excessive mucus production
B. Alveolar collapse caused by surface tension
C. Increased oxygen binding to hemoglobin
D. Constriction of the trachea
Correct Answer: B. Alveolar collapse caused by surface tension
Rationale: Surfactant produced by type II alveolar cells reduces surface tension at the air-liquid
interface. This makes alveoli easier to inflate and decreases their tendency to collapse during
expiration.
10. Which digestive structure is primarily responsible for most nutrient
absorption?
A. Esophagus
B. Stomach
C. Small intestine
D. Large intestine
Correct Answer: C. Small intestine
Rationale: The small intestine provides a very large absorptive surface through folds, villi, and
microvilli. Most digested carbohydrates, amino acids, lipids, vitamins, minerals, and water are
absorbed there.
11. Which cells in the testes directly produce testosterone?
A. Sertoli cells
B. Leydig cells
C. Spermatogonia
D. Epididymal cells
Correct Answer: B. Leydig cells
Rationale: Interstitial or Leydig cells produce testosterone in response to LH. Sertoli cells
support developing sperm and respond primarily to FSH and testosterone.
and V2 | Full Questions and Answers with Rationales | 2026/2027 Updated |
100% Correct.
Questions 1–20
1. A damaged sinoatrial node no longer initiates cardiac impulses normally.
Which structure would most likely assume pacemaker activity next?
A. Purkinje fibers
B. Atrioventricular node
C. Bundle branches
D. Papillary muscles
Correct Answer: B. Atrioventricular node
Rationale: The atrioventricular (AV) node has an intrinsic firing rate and can serve as a
secondary pacemaker if the sinoatrial node fails. Purkinje fibers can also generate impulses but
normally do so at a slower rate. Bundle branches conduct impulses rather than normally
initiating the heartbeat, and papillary muscles prevent AV valve prolapse during ventricular
contraction.
2. Constriction of the afferent arteriole supplying a renal corpuscle would most
directly cause which change?
A. Increased glomerular hydrostatic pressure
B. Increased glomerular filtration rate
C. Decreased glomerular filtration rate
D. Increased pressure in Bowman's capsule
Correct Answer: C. Decreased glomerular filtration rate
Rationale: Constriction of the afferent arteriole decreases blood entering the glomerulus. This
reduces glomerular hydrostatic pressure and therefore lowers the glomerular filtration rate
(GFR). Pressure in Bowman's capsule does not increase simply because afferent blood flow falls.
3. During quiet inspiration, which sequence occurs?
,A. Diaphragm relaxes → thoracic volume decreases → alveolar pressure falls
B. Diaphragm contracts → thoracic volume increases → alveolar pressure falls
C. Diaphragm contracts → thoracic volume decreases → alveolar pressure rises
D. Diaphragm relaxes → thoracic volume increases → alveolar pressure rises
Correct Answer: B. Diaphragm contracts → thoracic volume increases → alveolar
pressure falls
Rationale: Contraction of the diaphragm enlarges the thoracic cavity. According to the pressure-
volume relationship, increasing lung volume reduces alveolar pressure below atmospheric
pressure, allowing air to flow inward.
4. Fat and partially digested protein enter the duodenum. Which hormone is
most strongly associated with stimulating pancreatic enzyme release and
gallbladder contraction?
A. Gastrin
B. Secretin
C. Cholecystokinin
D. Aldosterone
Correct Answer: C. Cholecystokinin
Rationale: Cholecystokinin (CCK) is released from the small intestine in response especially to
fats and proteins. It stimulates pancreatic enzyme secretion and causes gallbladder contraction.
Secretin primarily promotes bicarbonate-rich pancreatic secretion in response to acidic chyme.
5. Which hormonal event most directly triggers ovulation?
A. Rapid decrease in estrogen
B. Surge in luteinizing hormone
C. Increase in prolactin
D. Decrease in follicle-stimulating hormone only
Correct Answer: B. Surge in luteinizing hormone
Rationale: Sustained high estrogen late in the follicular phase produces positive feedback that
causes the luteinizing hormone (LH) surge. The LH surge triggers rupture of the mature follicle
and release of the secondary oocyte.
,6. Which immune cell can differentiate into a plasma cell after appropriate
activation?
A. Neutrophil
B. B lymphocyte
C. Cytotoxic T lymphocyte
D. Natural killer cell
Correct Answer: B. B lymphocyte
Rationale: Activated B lymphocytes differentiate into plasma cells that secrete antibodies and
into memory B cells that support a faster response to future exposure. Cytotoxic T cells directly
kill infected or abnormal cells rather than producing antibodies.
7. Blood returning from the lungs enters which cardiac chamber first?
A. Right atrium
B. Right ventricle
C. Left atrium
D. Left ventricle
Correct Answer: C. Left atrium
Rationale: Oxygenated blood returns from the lungs through the pulmonary veins and enters the
left atrium. It then passes through the mitral valve into the left ventricle before entering systemic
circulation.
8. Which nephron segment normally reabsorbs the greatest percentage of filtered
water, sodium, glucose, and amino acids?
A. Proximal convoluted tubule
B. Descending limb of the nephron loop
C. Distal convoluted tubule
D. Collecting duct
Correct Answer: A. Proximal convoluted tubule
Rationale: The proximal convoluted tubule performs bulk reabsorption. Nearly all filtered
glucose and amino acids and a large proportion of sodium and water are normally reclaimed
there. Later nephron segments are important for fine regulation.
, 9. Pulmonary surfactant primarily prevents which problem?
A. Excessive mucus production
B. Alveolar collapse caused by surface tension
C. Increased oxygen binding to hemoglobin
D. Constriction of the trachea
Correct Answer: B. Alveolar collapse caused by surface tension
Rationale: Surfactant produced by type II alveolar cells reduces surface tension at the air-liquid
interface. This makes alveoli easier to inflate and decreases their tendency to collapse during
expiration.
10. Which digestive structure is primarily responsible for most nutrient
absorption?
A. Esophagus
B. Stomach
C. Small intestine
D. Large intestine
Correct Answer: C. Small intestine
Rationale: The small intestine provides a very large absorptive surface through folds, villi, and
microvilli. Most digested carbohydrates, amino acids, lipids, vitamins, minerals, and water are
absorbed there.
11. Which cells in the testes directly produce testosterone?
A. Sertoli cells
B. Leydig cells
C. Spermatogonia
D. Epididymal cells
Correct Answer: B. Leydig cells
Rationale: Interstitial or Leydig cells produce testosterone in response to LH. Sertoli cells
support developing sperm and respond primarily to FSH and testosterone.
