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Keratinized Stratified Epithelium
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MCQ Questions
1. In keratinized stratified squamous epithelium, which layer contains the mitotically active cells that replenish the more superficial layers?
A.
Stratum corneum
B.
Stratum granulosum
C.
Stratum basale
D.
Stratum lucidum
Correct Answer:
Stratum basale
Explanation:
The stratum basale is the deepest epithelial layer and contains proliferating cells attached to the basement membrane. Their descendants migrate toward the surface and undergo keratinization.
2. What is the principal functional significance of the thick, nonliving surface layer in keratinized stratified epithelium?
A.
It permits rapid diffusion of gases
B.
It resists abrasion and reduces water loss
C.
It secretes digestive enzymes onto the surface
D.
It provides a contractile force for surface movement
Correct Answer:
It resists abrasion and reduces water loss
Explanation:
The surface layer consists of flattened, dead, keratin-filled cells. This tough barrier protects underlying tissues from mechanical stress and limits evaporation.
3. A biopsy shows several layers of cells, with cuboidal to columnar cells at the basement membrane and flattened, anucleate cells packed with keratin at the free surface. How should the epithelium be classified?
Explanation:
The multiple layers establish that the epithelium is stratified, while the flattened keratin-filled superficial cells identify it as squamous and keratinized.
4. During maturation in keratinized stratified epithelium, which sequence best represents the movement and transformation of cells?
A.
Superficial cells divide, migrate basally, and lose keratin
B.
Basal cells divide, migrate apically, flatten, and accumulate keratin
C.
Basal cells migrate laterally, become ciliated, and secrete mucus
D.
Intermediate cells divide repeatedly, remain nucleated, and form glandular ducts
Explanation:
Cells originate in the basal layer, move toward the epithelial surface, become progressively flatter, accumulate keratin, lose their nuclei, and eventually form the protective superficial layer.
5. Which structural feature most directly explains why keratinized stratified epithelium can tolerate repeated surface abrasion without exposing living cells immediately?
A.
A single layer of metabolically active cells
B.
A multilayered organization with a replaceable keratinized surface
C.
A basement membrane composed of contractile fibers
D.
A surface layer formed by mucus-secreting cells
Correct Answer:
A multilayered organization with a replaceable keratinized surface
Explanation:
Multiple layers provide cellular reserves beneath the surface, while the outer keratinized layer is gradually shed and replaced by cells arising from the basal layer.
6. Which location is most characteristically lined by keratinized stratified squamous epithelium because it experiences substantial abrasion and exposure to the external environment?
A.
Alveolar air sacs
B.
Epidermis of the skin
C.
Lining of blood vessels
D.
Parietal layer of a serous membrane
Correct Answer:
Epidermis of the skin
Explanation:
The epidermis is formed by keratinized stratified squamous epithelium, whose multiple layers and keratinized surface protect the body against abrasion, pathogens, and water loss.
7. Why are the superficial cells of keratinized stratified epithelium generally unable to perform normal cellular metabolism?
A.
They are isolated from the basement membrane by several layers and lose their nuclei and organelles during keratinization
B.
They contain excessive mitochondria that inhibit glycolysis
C.
They remain permanently connected to blood capillaries
D.
They are replaced before completing differentiation
Correct Answer:
They are isolated from the basement membrane by several layers and lose their nuclei and organelles during keratinization
Explanation:
The epithelium is avascular, so nutrients must diffuse from deeper tissues. As cells migrate outward, they lose nuclei and organelles and become dead, keratin-filled protective cells.
8. Which combination correctly matches a feature of keratinized stratified epithelium with its functional consequence?
A.
Multiple layers — increased resistance to mechanical injury
B.
Avascularity — direct oxygen uptake from the external surface
C.
Anucleate surface cells — rapid mitotic division at the surface
D.
Keratin-filled cells — enhanced diffusion of water across the epithelium
Correct Answer:
Multiple layers — increased resistance to mechanical injury
Explanation:
The presence of several cellular layers allows superficial cells to be lost without immediately damaging the underlying living tissue, thereby increasing resistance to abrasion.
9. A defect selectively removes the keratinized surface while leaving the basal layer intact. Which change would most likely occur first?
A.
Immediate conversion of the epithelium into simple squamous epithelium
B.
Exposure of living, more hydrated epithelial layers and increased susceptibility to water loss
C.
Formation of blood vessels within the epithelial layers
D.
Loss of all cell division in the basal layer
Correct Answer:
Exposure of living, more hydrated epithelial layers and increased susceptibility to water loss
Explanation:
Removal of the keratinized surface exposes underlying living cells that do not provide the same barrier to abrasion and water loss as the fully keratinized layer.
10. Which observation would most reliably distinguish keratinized stratified squamous epithelium from its non-keratinized counterpart in a histological section?
A.
Presence of a superficial layer of flattened cells lacking nuclei and filled with keratin
B.
Presence of a single layer of flattened cells resting on a basement membrane
C.
Presence of numerous mucus-secreting cells between epithelial layers
D.
Presence of cilia on every superficial cell
Correct Answer:
Presence of a superficial layer of flattened cells lacking nuclei and filled with keratin
Explanation:
Keratinized stratified squamous epithelium has a distinct anucleate, keratin-rich surface layer. This layer is absent in non-keratinized stratified squamous epithelium.
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