Quiz: Epithelial Tissues Histology — 22 questions

1. How does an exocrine gland differ from an endocrine gland in the route used to release its products?

A. It releases products through apical cell fragments, whereas an endocrine gland releases products by whole-cell degeneration

B. It releases products into blood, whereas an endocrine gland releases products onto an epithelial surface or through a duct

C. It releases products onto an epithelial surface or through a duct, whereas an endocrine gland releases products into blood

D. It stores products in spherical units, whereas an endocrine gland stores products in tubular secretory portions

Answer: (C)

Explanation

Exocrine glands deliver secretions to an epithelial surface or through an excretory duct, while endocrine glands release their products directly into the blood. The option involving apical fragments describes apocrine secretion, not the basic distinction between exocrine and endocrine glands.

2. Which structural feature identifies a tubular gland?

A. Its secretory portion is organized as a tube, which may be straight, branched, or convoluted

B. Its secretory portion is arranged as follicles that store products outside the cells

C. Its secretory portion consists of isolated cells releasing products directly into blood

D. Its secretory portion consists of spherical units with narrow lumina arranged in clusters

Answer: (A)

Explanation

A tubular gland has a tube-shaped secretory portion that may be simple straight, branched straight, or simple convoluted. Spherical secretory units arranged in grape-like clusters characterize acinar glands rather than tubular glands.

3. What is the defining structural arrangement of an acinar gland?

A. Spherical functional units with narrow lumina assembled into grape-like clusters

B. Diffuse secretory cells scattered individually through connective tissue

C. Tube-shaped secretory portions arranged as straight or convoluted channels

D. Follicular units surrounding luminal material for endocrine storage

Answer: (A)

Explanation

Acinar glands are composed of spherical functional units with narrow lumina, and the acini are grouped in grape-like clusters. Tube-shaped portions describe tubular glands, while follicles and diffuse cells are endocrine arrangements.

4. Which combination best characterizes a serous cell?

A. It stores hormones in follicles and releases them through an excretory duct

B. It produces viscous mucin and contains a flattened basal nucleus with large PAS-positive vacuoles

C. It releases whole cells after degeneration and contains few organelles for protein synthesis

D. It produces a protein-rich enzymatic secretion and contains abundant rough endoplasmic reticulum with small apical vesicles

Answer: (D)

Explanation

Serous cells synthesize fluid, protein-rich secretions with enzymatic functions, often as proenzymes, and therefore have abundant rough endoplasmic reticulum and small apical secretory vesicles. Large PAS-positive vacuoles and a flattened basal nucleus are characteristic of mucous cells.

5. Which cellular features are most characteristic of a mucous cell?

A. Small apical secretory vesicles, abundant rough endoplasmic reticulum, and a rounded central nucleus

B. Apical cytoplasmic fragments, dense mitochondria, and a multilayered basal nucleus

C. Large PAS-positive secretory vacuoles, abundant supranuclear Golgi apparatus, and a flattened basal nucleus

D. Narrow lumina, spherical secretory units, and a grape-like arrangement of acini

Answer: (C)

Explanation

Mucous cells produce viscous mucin-rich secretions and characteristically contain large PAS-positive vacuoles, a prominent supranuclear Golgi apparatus, and a flattened basal nucleus. Small apical vesicles with abundant rough endoplasmic reticulum are associated with serous cells.

6. What cellular event distinguishes holocrine secretion from merocrine secretion?

A. Holocrine secretion releases an apical cytoplasmic fragment, whereas merocrine secretion uses whole-cell degeneration

B. Holocrine secretion releases the entire glandular cell after degeneration, whereas merocrine secretion uses exocytosis without cellular loss

C. Holocrine secretion stores products in follicles, whereas merocrine secretion stores products in narrow acinar lumina

D. Holocrine secretion transports products into blood, whereas merocrine secretion transports products through an excretory duct

Answer: (B)

Explanation

Holocrine secretion releases the whole secreting cell after it degenerates and desquamates, while merocrine secretion releases products by exocytosis and preserves the cell. Release of an apical cytoplasmic fragment is the defining mechanism of apocrine secretion.

7. Why is the pancreas classified as an amphicrine gland?

A. It performs an exocrine function by releasing mucus and an endocrine function by degenerating entire glandular cells

B. It performs an exocrine function by releasing bile and an endocrine function by storing thyroid hormones in follicles

C. It performs an exocrine function by secreting pancreatic juice and an endocrine function by releasing insulin and glucagon

D. It performs an exocrine function through sebaceous cells and an endocrine function through apical cytoplasmic fragments

Answer: (C)

Explanation

The pancreas is amphicrine because it secretes pancreatic juice as an exocrine product and releases insulin and glucagon as endocrine hormones. Bile secretion and blood-directed glycogen-related products describe the liver, another amphicrine gland.

8. What is the principal functional role of a microvillus?

A. It provides a long branched projection for immobile surface specialization

B. It forms deep basal membrane folds that power electrolyte transport with mitochondria

C. It propels fluid or particles across the epithelial surface through coordinated movement

D. It increases the apical exchange surface and transport capacity for absorption

Answer: (D)

Explanation

Microvilli are short finger-like apical projections specialized for absorption, increasing exchange surface and transport capacity. Propelling fluid or particles is the role of motile cilia, whereas deep mitochondrial membrane folds are basolateral specializations.

9. Which description best distinguishes a stereocilium from a cilium?

A. A stereocilium is a short absorptive projection measuring about $1\,\mu\text{m}$ in length

B. A stereocilium is an immobile, thin, branched apical expansion containing an actin filament cytoskeleton

C. A stereocilium is a motile projection containing a ciliary axoneme with dynein arms and radial spokes

D. A stereocilium is a basal membrane fold packed with mitochondria for active electrolyte transport

Answer: (B)

Explanation

Stereocilia are immobile, thin, branched apical expansions related to microvilli and supported by actin filaments. Motility and dynein-containing axonemes characterize cilia, not stereocilia.

10. Which feature is characteristic of a cilium?

A. It is a short absorptive projection about $0.1\,\mu\text{m}$ in diameter and $1\,\mu\text{m}$ long

B. It is an immobile branched projection that can reach approximately $80\,\mu\text{m}$ and contains actin filaments

C. It is a deep basolateral invagination containing mitochondria for water and electrolyte transport

D. It is a motile apical projection that moves fluid or particles and is typically $6\text{–}10\,\mu\text{m}$ long

Answer: (D)

Explanation

Cilia are motile apical projections that move fluid or particles and measure approximately $6\text{–}10\,\mu\text{m}$ in length. Long, branched, immobile projections are stereocilia, while short absorptive projections are microvilli.

11. Which epithelial arrangement is best suited for rapid trans-epithelial exchange in vascular endothelium?

A. A single layer of tall columnar cells

B. Several layers of cuboidal cells

C. A single layer of flattened cells

D. Several layers of flattened cells

Answer: (C)

Explanation

Simple squamous epithelium consists of one thin layer of flattened cells, making it suitable for exchange and forming vascular endothelium. Stratified squamous epithelium has multiple layers and is better associated with protection than with rapid exchange.

12. A tissue appears multilayered because its nuclei lie at different heights, but every cell contacts the basal lamina; which epithelium is present?

A. Simple cuboidal epithelium

B. Transitional epithelium

C. Pseudostratified epithelium

D. Stratified squamous epithelium

Answer: (C)

Explanation

Pseudostratified epithelium appears multilayered because its nuclei occupy different levels, yet every cell rests on the basal lamina. In truly stratified epithelium, some cell layers do not contact the basal lamina.

13. Which epithelial type allows the urinary tract to expand during filling through specialized superficial umbrella cells?

A. Simple squamous epithelium

B. Pseudostratified epithelium

C. Stratified columnar epithelium

D. Transitional epithelium

Answer: (D)

Explanation

Transitional epithelium is stratified and contains superficial umbrella cells that accommodate stretching in the urinary tract. Pseudostratified epithelium can appear multilayered but does not have this urinary stretching arrangement.

14. Which junction class primarily permits direct intercellular communication through channels between neighboring cells?

A. Sealing tight junctions

B. Communicating gap junctions

C. Anchoring junctions

D. Basal hemidesmosomes

Answer: (B)

Explanation

Gap junctions are communicating junctions that allow neighboring cells to exchange signals and small molecules through intercellular channels. Tight junctions instead regulate sealing, while anchoring junctions strengthen mechanical attachment.

15. How do epithelial junctions help preserve specialized membrane domains?

A. They replace the basal lamina beneath epithelial cells

B. They prevent membrane proteins from diffusing between domains

C. They convert connective tissue into an epithelial layer

D. They increase diffusion of proteins across the entire membrane

Answer: (B)

Explanation

Epithelial junctions maintain membrane specialization by restricting movement of membrane proteins between distinct domains. Unrestricted diffusion would blur these territories rather than preserve their specialized functions.

16. Which structure lies consistently at the interface between epithelium and connective tissue?

A. The serous cavity

B. The basal lamina

C. The apical membrane

D. The epithelial lumen

Answer: (B)

Explanation

The basal lamina is a constant interface structure separating epithelial tissue from underlying connective tissue and contains components such as type IV collagen and laminin. The apical surface instead faces a lumen or the exterior.

17. In the kidney, which substances can pass through the basal-lamina molecular sieve while large proteins are retained?

A. Large proteins, lipids, and intact cells

B. Collagen fibers, enzymes, and membrane fragments

C. Water, ions, and small organic molecules

D. Red blood cells, platelets, and antibodies

Answer: (C)

Explanation

The glomerular basal lamina permits water, ions, and small organic molecules according to its pore arrangement, while excluding large proteins. The molecular sieve therefore separates smaller filtrate components from larger protein molecules.

18. Which sequence correctly describes the main stages of paraffin histology preparation?

A. Fixation, aqueous staining, dehydration, xylene clearing, and paraffin infiltration

B. Dehydration, fixation, xylene clearing, paraffin infiltration, and unoriented block formation

C. Fixation, dehydration, xylene clearing, paraffin infiltration, and oriented block formation

D. Fixation, paraffin infiltration, dehydration, xylene clearing, and oriented block formation

Answer: (C)

Explanation

Paraffin preparation proceeds from fixation through dehydration, xylene clearing, paraffin infiltration, and formation of an oriented inclusion block. Rehydration is associated with preparing sections for aqueous staining rather than with the initial embedding sequence.

19. A laboratory preparing tissue for light microscopy should generally use which section thickness?

A. 0.2–0.7 mm

B. 50–70 nm

C. 2–10 µm

D. 20–70 µm

Answer: (C)

Explanation

Microtomy produces sections about 2–10 µm thick for light microscopy. The nanometer range of 50–70 nm is characteristic of ultramicrotomy for electron microscopy.

20. Which combination best characterizes epithelial tissue?

A. Loosely arranged cells in a vascular matrix, lacking a defined basal lamina

B. Contractile cells surrounding vessels, arranged in branching bundles

C. Migratory cells suspended in fluid, specialized for antibody production

D. Polarized cohesive cells on a basal lamina, lacking blood vessels within the tissue

Answer: (D)

Explanation

Epithelia consist of cohesive, polarized cells arranged on a basal lamina and are avascular within the epithelial tissue. Their connective-tissue support can contain blood vessels, which distinguishes epithelial avascularity from the vascularity of supporting tissue.

21. What distinguishes synthesis from excretion in glandular epithelium?

A. Synthesis removes cellular waste, whereas excretion assembles proteins and mucins

B. Synthesis makes the secretory product, whereas excretion determines where it is released

C. Synthesis determines the target tissue, whereas excretion supplies the needed organelles

D. Synthesis releases the product into blood, whereas excretion builds it with organelles

Answer: (B)

Explanation

Glandular cells use specialized organelles to synthesize products, while excretion describes their release through a duct, onto an epithelial surface, or into blood. Release location therefore does not define the synthesis process.

22. Why must epithelial tissues undergo continuous renewal?

A. Their cells divide only after injury and are removed mainly through vascular transport

B. Their cells survive for a few hours to a few days and are removed by desquamation or apoptosis

C. Their cells persist for several years and are replaced when connective tissue loses its vessels

D. Their cells remain permanently in place but periodically enlarge through increased protein synthesis

Answer: (B)

Explanation

Epithelial cells have short life spans, often ranging from a few hours to a few days, so they must be continually replaced after desquamation or apoptosis. Renewal is therefore a normal maintenance process rather than a response restricted to tissue injury.