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Spermatogenic Support Mechanisms
MCQ questions and answers.
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MCQ Questions
1. Which arrangement most directly allows Sertoli cells to create a protected microenvironment for developing spermatocytes while still permitting their progression toward the adluminal compartment?
A.
Tight junctions between adjacent Sertoli cells forming the blood-testis barrier
B.
Gap junctions between Leydig cells surrounding seminiferous tubules
C.
Desmosomes between spermatids and the basement membrane
D.
Fenestrated capillaries opening directly into the seminiferous lumen
Correct Answer:
Tight junctions between adjacent Sertoli cells forming the blood-testis barrier
Explanation:
Sertoli-cell tight junctions divide the seminiferous epithelium into basal and adluminal compartments, protecting meiotic and postmeiotic germ cells from many blood-borne substances and immune reactions while supporting their development.
2. A selective disruption of Sertoli-cell tight junctions would most immediately compromise which spermatogenic support mechanism?
A.
Maintenance of a distinct adluminal environment for meiotic germ cells
B.
Secretion of testosterone by interstitial Leydig cells
C.
Formation of sperm flagella by epididymal epithelial cells
D.
Storage of mature spermatozoa in the seminal vesicles
Correct Answer:
Maintenance of a distinct adluminal environment for meiotic germ cells
Explanation:
Sertoli-cell tight junctions establish the blood-testis barrier and maintain the specialized adluminal environment required by meiotic and later germ cells. Their disruption directly affects this support function.
3. Which Sertoli-cell product binds testosterone and helps maintain a high androgen concentration within the seminiferous tubules?
A.
Inhibin
B.
Androgen-binding protein
C.
Luteinizing hormone
D.
Follicle-stimulating hormone
Correct Answer:
Androgen-binding protein
Explanation:
Sertoli cells secrete androgen-binding protein, which binds testosterone and retains it near developing germ cells. The high local androgen concentration is important for effective spermatogenic support.
4. If androgen-binding protein secretion by Sertoli cells were markedly reduced while circulating testosterone remained normal, which change would be most likely within the testis?
A.
Reduced retention of testosterone near the seminiferous epithelium
B.
Complete cessation of testosterone synthesis by Leydig cells
C.
Increased formation of the blood-testis barrier by germ cells
D.
Direct conversion of spermatids into primary spermatocytes
Correct Answer:
Reduced retention of testosterone near the seminiferous epithelium
Explanation:
Androgen-binding protein concentrates and retains testosterone in the seminiferous-tubule environment. Reduced secretion would impair local androgen availability even if blood testosterone remained normal.
5. Which pairing correctly identifies a Sertoli-cell function and its direct relevance to spermatogenesis?
A.
Phagocytosis of residual bodies; removal of cytoplasmic remnants from developing spermatids
B.
Secretion of bile salts; digestion of sperm-cell membranes
C.
Production of hemoglobin; oxygen transport through the seminiferous lumen
D.
Synthesis of digestive enzymes; extracellular digestion of spermatogonia
Correct Answer:
Phagocytosis of residual bodies; removal of cytoplasmic remnants from developing spermatids
Explanation:
During spermiogenesis, excess cytoplasm is shed as residual bodies. Sertoli cells phagocytose and process these remnants, providing structural and metabolic support to developing sperm cells.
6. Which endocrine interaction most directly supports Sertoli-cell-mediated spermatogenesis?
A.
FSH acts on Sertoli cells, while LH stimulates Leydig cells to produce testosterone
B.
FSH acts on Leydig cells, while LH stimulates Sertoli cells to secrete inhibin
C.
Both FSH and LH act only on spermatids within the seminiferous lumen
D.
Inhibin stimulates Leydig cells, while testosterone directly activates spermatogonia without Sertoli cells
Correct Answer:
FSH acts on Sertoli cells, while LH stimulates Leydig cells to produce testosterone
Explanation:
FSH directly supports Sertoli-cell functions, including nourishment and androgen-binding protein secretion. LH stimulates Leydig cells to produce testosterone, which acts with Sertoli-cell support to sustain spermatogenesis.
7. A selective failure of inhibin secretion by Sertoli cells would most directly disturb which regulatory aspect of spermatogenic support?
A.
Negative feedback control of pituitary FSH secretion
B.
Binding of testosterone within the seminiferous tubules
C.
Formation of tight junctions by Leydig cells
D.
Conversion of spermatocytes into Sertoli cells
Correct Answer:
Negative feedback control of pituitary FSH secretion
Explanation:
Sertoli-cell inhibin provides negative feedback mainly on pituitary FSH secretion. Loss of inhibin therefore disrupts hormonal regulation of Sertoli-cell activity and spermatogenic support.
8. Why is the blood-testis barrier particularly important for meiotic and postmeiotic germ cells rather than for spermatogonia located near the basement membrane?
A.
Meiotic and postmeiotic cells express differentiation-associated antigens that may be recognized as non-self by the immune system
B.
Spermatogonia cannot survive in contact with oxygen, whereas spermatozoa require direct blood exposure
C.
Leydig cells are found only inside the adluminal compartment and must be isolated from spermatogonia
D.
The barrier prevents all nutrients from reaching spermatogonia but allows antibodies to reach spermatids
Correct Answer:
Meiotic and postmeiotic cells express differentiation-associated antigens that may be recognized as non-self by the immune system
Explanation:
Later germ cells develop after immune tolerance is established and may display antigens not present earlier in life. The Sertoli-cell barrier helps isolate these cells from immune surveillance while Sertoli cells provide local support.
9. Which sequence best represents the cooperation required for androgen-dependent spermatogenic support?
A.
LH stimulation of Leydig cells, testosterone production, androgen binding by Sertoli cells, and action on developing germ cells
B.
FSH stimulation of Leydig cells, inhibin production, testosterone destruction, and spermatid apoptosis
C.
Sertoli-cell secretion of LH, Leydig-cell secretion of FSH, and antibody-mediated germ-cell maturation
D.
Direct testosterone release by spermatids followed by its conversion into FSH within Sertoli cells
Correct Answer:
LH stimulation of Leydig cells, testosterone production, androgen binding by Sertoli cells, and action on developing germ cells
Explanation:
LH stimulates Leydig cells to synthesize testosterone. Sertoli cells bind and retain this androgen through androgen-binding protein, creating the local hormonal environment needed for germ-cell development.
10. Which observation would most strongly indicate that Sertoli cells are failing to provide metabolic support even though the blood-testis barrier remains structurally intact?
A.
Developing germ cells undergo degeneration despite preserved Sertoli-cell junctions
B.
Leydig cells increase testosterone synthesis in response to LH
C.
Spermatogonia remain adjacent to the basement membrane
D.
Interstitial capillaries continue to surround the seminiferous tubules
Explanation:
Sertoli cells nourish and metabolically support germ cells in addition to forming the blood-testis barrier. Germ-cell degeneration with intact junctions suggests failure of their nutritional or trophic support rather than barrier formation.
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