OpenStax Microbiology Chapter 25 Circulatory & Lymphatic
System Test Bank Actual Exam 2026/2027 – Complete 50
Questions with Detailed Rationales | 100% Verified | Pass
Guaranteed – A+ Graded
SECTION A: Anatomy & Defenses of the Circulatory and Lymphatic
Systems (Q1–Q8)
Q1: Which statement correctly describes the microbiota of the human circulatory
system?
A. Blood hosts a stable community of obligate anaerobes derived from the gut.
B. Blood contains transient Gram-positive cocci shed from the oral cavity as normal
flora.
C. The blood and lymph are normally sterile in healthy individuals, with no resident
normal microbiota. [CORRECT]
D. Blood carries the same microbial community as the intestinal lumen.
Correct Answer: C
Rationale: The cardiovascular and lymphatic systems are closed, sterile systems, so any
organism detected in blood or lymph indicates infection or contamination. Microbiota
reside on skin and mucosal surfaces, not within circulating blood.
Q2: A patient with an infected foot wound presents with red streaks extending up the
lower leg toward swollen, tender inguinal lymph nodes. This presentation is most
consistent with:
A. Necrotizing fasciitis
B. Lymphangitis — inflammation of the lymphatic vessels tracking from the infection
site toward the draining nodes [CORRECT]
C. Deep venous thrombosis
D. Erysipelas limited to the dermis of the foot
Correct Answer: B
Rationale: Visible red streaks radiating from a wound toward regional lymph nodes are
the classic sign of lymphangitis, indicating pathogens or inflammation tracking through
lymphatic vessels. DVT causes unilateral swelling without streaking, and necrotizing
fasciitis presents with rapidly advancing tissue destruction rather than linear streaks.
,Q3: A 64-year-old ICU patient has a temperature of 39.2°C, heart rate 122 bpm, blood
pressure 82/40 mm Hg unresponsive to 30 mL/kg of IV fluids, confusion, and a serum
lactate of 4.5 mmol/L. Blood cultures are pending. This patient is best classified as
having:
A. Simple bacteremia without systemic effects
B. Toxemia from exotoxin circulation
C. Transient viremia
D. Septic shock — sepsis with persistent hypotension and hypoperfusion despite
adequate fluid resuscitation [CORRECT]
Correct Answer: D
Rationale: The combination of systemic inflammatory signs, hypoperfusion (elevated
lactate, confusion), and refractory hypotension despite fluid defines septic shock, a
life-threatening complication of bloodstream infection. Bacteremia, toxemia, and
viremia do not by themselves imply the hypoperfusion and fluid-refractory hypotension
described.
Q4: During a bacterial infection, lymph nodes draining the infected region become
enlarged and tender primarily because:
A. Erythrocytes accumulate within the node sinuses
B. Lymph flow through the node is permanently blocked
C. Lymphocytes within the node proliferate in response to antigens filtered from the
lymph [CORRECT]
D. The node begins producing erythrocytes to replace lost blood
Correct Answer: C
Rationale: Lymph nodes filter antigens from lymph, triggering clonal proliferation of B
and T lymphocytes in germinal centers, which enlarges the node. Erythrocyte
accumulation and lymph flow blockage are not physiologic, and lymph nodes do not
perform hematopoiesis.
Q5: A patient who underwent splenectomy after trauma asks about her long-term
infection risks. The nurse practitioner explains that she is at greatest risk for severe,
potentially fatal infections caused by:
A. Encapsulated bacteria such as Streptococcus pneumoniae and Haemophilus
influenzae [CORRECT]
B. Dermatophyte fungi of the skin
C. Bacteriophages
D. Chlamydia trachomatis of the genitourinary tract
Correct Answer: A
, Rationale: The spleen filters blood and clears opsonized encapsulated organisms;
asplenic patients face heightened risk of overwhelming post-splenectomy infection
from pneumococcus, Hib, and similar organisms. Fungi of the skin, phages, and
chlamydia do not rely on splenic clearance.
Q6: Which term refers specifically to the presence of bacterial toxins circulating in the
bloodstream without the bacteria themselves multiplying there?
A. Bacteremia
B. Toxemia [CORRECT]
C. Septicemia
D. Viremia
Correct Answer: B
Rationale: Toxemia denotes circulating toxins; bacteremia is bacteria present in blood,
septicemia involves actively multiplying blood-borne bacteria, and viremia is the
presence of viruses in blood.
Q7: A hospitalized patient develops a Staphylococcus aureus bloodstream infection
three days after insertion of a central venous catheter. The factor that best explains why
this device increased the risk of septicemia is:
A. The catheter destroyed the patient's humoral immunity
B. The catheter created a toxin reservoir within the vessel lumen
C. The catheter activated classical complement by binding IgM
D. The catheter bypassed the intact skin barrier, providing microorganisms a direct
portal of entry into normally sterile blood [CORRECT]
Correct Answer: D
Rationale: Indwelling catheters breach the primary physical defense (skin) and
introduce organisms or biofilms directly into the sterile bloodstream. Complement
activation, toxin reservoirs, and humoral immunity are not the relevant mechanism.
Q8: Lymphangitis is best defined as:
A. Infection and swelling of the spleen
B. Inflammation of the tonsillar tissue
C. Infection of the bone marrow
D. Inflammation of the lymphatic vessels, often visible as red streaks from an infection
site toward regional lymph nodes [CORRECT]
Correct Answer: D
Rationale: Lymphangitis is the clinical manifestation of inflammatory spread along
lymphatic channels. Spleen infection, tonsillitis, and osteomyelitis describe entirely
different structures.
System Test Bank Actual Exam 2026/2027 – Complete 50
Questions with Detailed Rationales | 100% Verified | Pass
Guaranteed – A+ Graded
SECTION A: Anatomy & Defenses of the Circulatory and Lymphatic
Systems (Q1–Q8)
Q1: Which statement correctly describes the microbiota of the human circulatory
system?
A. Blood hosts a stable community of obligate anaerobes derived from the gut.
B. Blood contains transient Gram-positive cocci shed from the oral cavity as normal
flora.
C. The blood and lymph are normally sterile in healthy individuals, with no resident
normal microbiota. [CORRECT]
D. Blood carries the same microbial community as the intestinal lumen.
Correct Answer: C
Rationale: The cardiovascular and lymphatic systems are closed, sterile systems, so any
organism detected in blood or lymph indicates infection or contamination. Microbiota
reside on skin and mucosal surfaces, not within circulating blood.
Q2: A patient with an infected foot wound presents with red streaks extending up the
lower leg toward swollen, tender inguinal lymph nodes. This presentation is most
consistent with:
A. Necrotizing fasciitis
B. Lymphangitis — inflammation of the lymphatic vessels tracking from the infection
site toward the draining nodes [CORRECT]
C. Deep venous thrombosis
D. Erysipelas limited to the dermis of the foot
Correct Answer: B
Rationale: Visible red streaks radiating from a wound toward regional lymph nodes are
the classic sign of lymphangitis, indicating pathogens or inflammation tracking through
lymphatic vessels. DVT causes unilateral swelling without streaking, and necrotizing
fasciitis presents with rapidly advancing tissue destruction rather than linear streaks.
,Q3: A 64-year-old ICU patient has a temperature of 39.2°C, heart rate 122 bpm, blood
pressure 82/40 mm Hg unresponsive to 30 mL/kg of IV fluids, confusion, and a serum
lactate of 4.5 mmol/L. Blood cultures are pending. This patient is best classified as
having:
A. Simple bacteremia without systemic effects
B. Toxemia from exotoxin circulation
C. Transient viremia
D. Septic shock — sepsis with persistent hypotension and hypoperfusion despite
adequate fluid resuscitation [CORRECT]
Correct Answer: D
Rationale: The combination of systemic inflammatory signs, hypoperfusion (elevated
lactate, confusion), and refractory hypotension despite fluid defines septic shock, a
life-threatening complication of bloodstream infection. Bacteremia, toxemia, and
viremia do not by themselves imply the hypoperfusion and fluid-refractory hypotension
described.
Q4: During a bacterial infection, lymph nodes draining the infected region become
enlarged and tender primarily because:
A. Erythrocytes accumulate within the node sinuses
B. Lymph flow through the node is permanently blocked
C. Lymphocytes within the node proliferate in response to antigens filtered from the
lymph [CORRECT]
D. The node begins producing erythrocytes to replace lost blood
Correct Answer: C
Rationale: Lymph nodes filter antigens from lymph, triggering clonal proliferation of B
and T lymphocytes in germinal centers, which enlarges the node. Erythrocyte
accumulation and lymph flow blockage are not physiologic, and lymph nodes do not
perform hematopoiesis.
Q5: A patient who underwent splenectomy after trauma asks about her long-term
infection risks. The nurse practitioner explains that she is at greatest risk for severe,
potentially fatal infections caused by:
A. Encapsulated bacteria such as Streptococcus pneumoniae and Haemophilus
influenzae [CORRECT]
B. Dermatophyte fungi of the skin
C. Bacteriophages
D. Chlamydia trachomatis of the genitourinary tract
Correct Answer: A
, Rationale: The spleen filters blood and clears opsonized encapsulated organisms;
asplenic patients face heightened risk of overwhelming post-splenectomy infection
from pneumococcus, Hib, and similar organisms. Fungi of the skin, phages, and
chlamydia do not rely on splenic clearance.
Q6: Which term refers specifically to the presence of bacterial toxins circulating in the
bloodstream without the bacteria themselves multiplying there?
A. Bacteremia
B. Toxemia [CORRECT]
C. Septicemia
D. Viremia
Correct Answer: B
Rationale: Toxemia denotes circulating toxins; bacteremia is bacteria present in blood,
septicemia involves actively multiplying blood-borne bacteria, and viremia is the
presence of viruses in blood.
Q7: A hospitalized patient develops a Staphylococcus aureus bloodstream infection
three days after insertion of a central venous catheter. The factor that best explains why
this device increased the risk of septicemia is:
A. The catheter destroyed the patient's humoral immunity
B. The catheter created a toxin reservoir within the vessel lumen
C. The catheter activated classical complement by binding IgM
D. The catheter bypassed the intact skin barrier, providing microorganisms a direct
portal of entry into normally sterile blood [CORRECT]
Correct Answer: D
Rationale: Indwelling catheters breach the primary physical defense (skin) and
introduce organisms or biofilms directly into the sterile bloodstream. Complement
activation, toxin reservoirs, and humoral immunity are not the relevant mechanism.
Q8: Lymphangitis is best defined as:
A. Infection and swelling of the spleen
B. Inflammation of the tonsillar tissue
C. Infection of the bone marrow
D. Inflammation of the lymphatic vessels, often visible as red streaks from an infection
site toward regional lymph nodes [CORRECT]
Correct Answer: D
Rationale: Lymphangitis is the clinical manifestation of inflammatory spread along
lymphatic channels. Spleen infection, tonsillitis, and osteomyelitis describe entirely
different structures.
