Histology NBME Full Questions and Answers
Latest 2026 | 200 Questions | Verified Answers |
Grade A
Introduction
This Histology NBME practice test is designed for medical students,
-medical
pre students, and health
professions trainees preparing for the NBME histology examination for the 2026 testing cycle. The 200
questions are based on verified exam materials from
ultiple
m sources and cover all critical domains required
for the NBME histology exam, including cellular ultrastructure, epithelial tissues, connective tissues, muscle
tissue, nervous tissue, cardiovascular system, respiratory system, gastrointestinal
, endocrine
tract system,
reproductive system, urinary system, integumentary system, and special senses. The exam format includes
multiple-choice questions with single best answers and complex multiple
-choice questions with combination
answers (e.g., "A and Cearcorrect") as seen on actual NBME examinations. Each question includes a
detailed rationale explaining the correct answer and relevant histological concepts,
-function
structure
relationships, or clinical correlations to reinforce learning and ensure
readiness.
exam
SECTION 1: CELLULAR ULTRASTRUCTURE & ORGANELLES (Questions 1 -25)
Question 1
A researcher is studying nuclear pore complexes using electron microscopy. Which statement accurately
describes the structure and function of nuclear pores?
A) They are approximately 10 nm in diameter and allow passive diffusion of all molecules
B) They are approximately 50 nm in diameter and their number correlates with cellular transcriptional
activity
C) They are approximately 100 nm in diameter and are only present in dividing cells
D) They are approximately 200 nm in diameter and function exclusively in mRNA export
Answer: B
Rationale:Nuclear pores are approximately 50 nm in diameter and serve as gateways for transport
between the nucleus and cytoplasm. The number of nuclear pores correlates with the transcriptional
activity of the cell
—cells with high metabolic activity (like hepatocy
tes) have more nuclear pores than
,inactive cells. The nuclear pore complex contains the nuclear lamina connection and regulates both
passive diffusion of small molecules and active transport of larger molecules like proteins and RNA.
Question 2
Which of the following components is NOT typically found within the plasma membrane structure?
A) Transmembrane proteins
B) Peripheral proteins
C) Cholesterol molecules
D) Microfibers
Answer: D
Rationale:The plasma membrane consists of a phospholipid bilayer containing transmembrane proteins
(integral proteins spanning the membrane), peripheral proteins (attached to membrane surfaces), and
cholesterol (regulating membrane fluidity). Microfibers (microfila
ments/actin filaments) are cytoskeletal
components located beneath the plasma membrane in the cytoplasm, not within the membrane structure
itself.
Question 3
The glycocalyx is best described as:
A) A protein layer beneath the plasma membrane
B) Carbohydrate chains linked to membrane proteins and lipids
C) A lipid bilayer surrounding the nucleus
D) A fibrous network of collagen fibers
Answer: B
Rationale: The glycocalyx consists of carbohydrate chains (glycoproteins and glycolipids) linked to
membrane components on the extracellular surface of the plasma membrane. It functions in cell
recognition, adhesion, and protection. The negative charges on these
rbohydrate
ca chains also contribute
to the cell's surface charge.
Question 4
,Regarding microtubule structure, which statement is correct?
A) They have a flexible wall composed of 9 protofilaments
B) They have a rigid wall composed of 13 protofilaments arranged in a hollow tube
C) They are solid rods composed of actin filaments
D) They consist of 22 protofilaments arranged in a triple helix
Answer: B
α and (
Rationale: Microtubules are rigid, hollow tubes composed of 13 protofilaments of tubulin dimers
β tubulin) arranged in a circular pattern. This rigid structure provides structural support, maintains cell
shape, and serves as tracks for intracellular transport. The "9+2" arrangement refers to the axoneme
structure in cilia and flagella, not the individ
ual microtubule composition.
Question 5
Which of the following processes involves the ingestion of liquid droplets by the cell?
A) Phagocytosis
B) Pinocytosis
C) Exocytosis
D) Receptor-mediated endocytosis
Answer: B
Rationale: Pinocytosis ("cell drinking") involves the ingestion of extracellular fluid and dissolved solutes
through small vesicles. Phagocytosis ("cell eating") involves ingestion of large particles. Exocytosis is the
release of materials from the cell. Receptor
-mediated endocytosis is specific for particular ligands bound
to receptors.
Question 6
The axoneme of a cilium exhibits which characteristic microtubule arrangement?
A) 9+0 arrangement
B) 9+2 arrangement
C) 9+3 arrangement
, D) 12+2 arrangement
Answer: B
Rationale:The axoneme of motile cilia and flagella has a "9+2" arrangement
—nine peripheral doublet
microtubules surrounding two central singlet microtubules. This structure is essential for ciliary
movement. The "9+0" arrangement is found in primary cilia-motil
(non e), and centrioles/basal bodies
have a "9+3" triplet arrangement.
Question 7
Which organelle is responsible for protein synthesis and is abundant in cells with high secretory activity?
A) Lysosomes
B) Rough endoplasmic reticulum
C) Smooth endoplasmic reticulum
D) Peroxisomes
Answer: B
Rationale:The rough endoplasmic reticulum (RER) is studded with ribosomes and is the site of protein
synthesis, particularly for secretory and membrane proteins. Cells with high secretory activity (plasma
cells, pancreatic acinar cells) have abundant RER. Smoothlacks
ER ribosomes and functions in lipid
synthesis and detoxification.
Question 8
Which of the following statements about centrioles is correct?
A) They are composed of 9 doublet microtubules
B) They are composed of 9 triplet microtubules
C) They are composed of 13 singlet microtubules
D) They lack microtubules entirely
Answer: B
Latest 2026 | 200 Questions | Verified Answers |
Grade A
Introduction
This Histology NBME practice test is designed for medical students,
-medical
pre students, and health
professions trainees preparing for the NBME histology examination for the 2026 testing cycle. The 200
questions are based on verified exam materials from
ultiple
m sources and cover all critical domains required
for the NBME histology exam, including cellular ultrastructure, epithelial tissues, connective tissues, muscle
tissue, nervous tissue, cardiovascular system, respiratory system, gastrointestinal
, endocrine
tract system,
reproductive system, urinary system, integumentary system, and special senses. The exam format includes
multiple-choice questions with single best answers and complex multiple
-choice questions with combination
answers (e.g., "A and Cearcorrect") as seen on actual NBME examinations. Each question includes a
detailed rationale explaining the correct answer and relevant histological concepts,
-function
structure
relationships, or clinical correlations to reinforce learning and ensure
readiness.
exam
SECTION 1: CELLULAR ULTRASTRUCTURE & ORGANELLES (Questions 1 -25)
Question 1
A researcher is studying nuclear pore complexes using electron microscopy. Which statement accurately
describes the structure and function of nuclear pores?
A) They are approximately 10 nm in diameter and allow passive diffusion of all molecules
B) They are approximately 50 nm in diameter and their number correlates with cellular transcriptional
activity
C) They are approximately 100 nm in diameter and are only present in dividing cells
D) They are approximately 200 nm in diameter and function exclusively in mRNA export
Answer: B
Rationale:Nuclear pores are approximately 50 nm in diameter and serve as gateways for transport
between the nucleus and cytoplasm. The number of nuclear pores correlates with the transcriptional
activity of the cell
—cells with high metabolic activity (like hepatocy
tes) have more nuclear pores than
,inactive cells. The nuclear pore complex contains the nuclear lamina connection and regulates both
passive diffusion of small molecules and active transport of larger molecules like proteins and RNA.
Question 2
Which of the following components is NOT typically found within the plasma membrane structure?
A) Transmembrane proteins
B) Peripheral proteins
C) Cholesterol molecules
D) Microfibers
Answer: D
Rationale:The plasma membrane consists of a phospholipid bilayer containing transmembrane proteins
(integral proteins spanning the membrane), peripheral proteins (attached to membrane surfaces), and
cholesterol (regulating membrane fluidity). Microfibers (microfila
ments/actin filaments) are cytoskeletal
components located beneath the plasma membrane in the cytoplasm, not within the membrane structure
itself.
Question 3
The glycocalyx is best described as:
A) A protein layer beneath the plasma membrane
B) Carbohydrate chains linked to membrane proteins and lipids
C) A lipid bilayer surrounding the nucleus
D) A fibrous network of collagen fibers
Answer: B
Rationale: The glycocalyx consists of carbohydrate chains (glycoproteins and glycolipids) linked to
membrane components on the extracellular surface of the plasma membrane. It functions in cell
recognition, adhesion, and protection. The negative charges on these
rbohydrate
ca chains also contribute
to the cell's surface charge.
Question 4
,Regarding microtubule structure, which statement is correct?
A) They have a flexible wall composed of 9 protofilaments
B) They have a rigid wall composed of 13 protofilaments arranged in a hollow tube
C) They are solid rods composed of actin filaments
D) They consist of 22 protofilaments arranged in a triple helix
Answer: B
α and (
Rationale: Microtubules are rigid, hollow tubes composed of 13 protofilaments of tubulin dimers
β tubulin) arranged in a circular pattern. This rigid structure provides structural support, maintains cell
shape, and serves as tracks for intracellular transport. The "9+2" arrangement refers to the axoneme
structure in cilia and flagella, not the individ
ual microtubule composition.
Question 5
Which of the following processes involves the ingestion of liquid droplets by the cell?
A) Phagocytosis
B) Pinocytosis
C) Exocytosis
D) Receptor-mediated endocytosis
Answer: B
Rationale: Pinocytosis ("cell drinking") involves the ingestion of extracellular fluid and dissolved solutes
through small vesicles. Phagocytosis ("cell eating") involves ingestion of large particles. Exocytosis is the
release of materials from the cell. Receptor
-mediated endocytosis is specific for particular ligands bound
to receptors.
Question 6
The axoneme of a cilium exhibits which characteristic microtubule arrangement?
A) 9+0 arrangement
B) 9+2 arrangement
C) 9+3 arrangement
, D) 12+2 arrangement
Answer: B
Rationale:The axoneme of motile cilia and flagella has a "9+2" arrangement
—nine peripheral doublet
microtubules surrounding two central singlet microtubules. This structure is essential for ciliary
movement. The "9+0" arrangement is found in primary cilia-motil
(non e), and centrioles/basal bodies
have a "9+3" triplet arrangement.
Question 7
Which organelle is responsible for protein synthesis and is abundant in cells with high secretory activity?
A) Lysosomes
B) Rough endoplasmic reticulum
C) Smooth endoplasmic reticulum
D) Peroxisomes
Answer: B
Rationale:The rough endoplasmic reticulum (RER) is studded with ribosomes and is the site of protein
synthesis, particularly for secretory and membrane proteins. Cells with high secretory activity (plasma
cells, pancreatic acinar cells) have abundant RER. Smoothlacks
ER ribosomes and functions in lipid
synthesis and detoxification.
Question 8
Which of the following statements about centrioles is correct?
A) They are composed of 9 doublet microtubules
B) They are composed of 9 triplet microtubules
C) They are composed of 13 singlet microtubules
D) They lack microtubules entirely
Answer: B
