101. Leydig cells are present, but their receptors can no longer respond effectively to LH. GnRH and FSH secretion remain normal. What is the most appropriate downstream prediction?
ⓐ. FSH secretion ceases immediately despite normal pituitary function
ⓑ. Spermatogenesis remains fully supported because normal FSH alone replaces androgen action
ⓒ. Sertoli-cell support alone maintains normal androgen-dependent spermatogenesis despite Leydig unresponsiveness
ⓓ. Androgen production falls and androgen support of spermatogenesis is weakened
Correct Answer: Androgen production falls and androgen support of spermatogenesis is weakened
Explanation: LH influences spermatogenesis indirectly through its action on Leydig cells. Functional LH signalling in these cells promotes androgen synthesis and secretion, and the resulting androgens help support spermatogenesis. If Leydig cells cannot respond effectively to LH, normal hormone concentration upstream cannot produce the usual target-cell response. Androgen production falls even though GnRH and FSH secretion remain available. The defect does not convert Sertoli cells into the main androgen-producing cells, nor does it directly change diploid spermatogonia into haploid cells. This case demonstrates the difference between hormone presence and target responsiveness: an intact upstream signal is ineffective when its specific target cell cannot respond normally.
102. Match each component of the spermatogenic hormonal pathway with its most direct relation. A Column II entry is used once.
| Column I | Column II |
|---|
| P. GnRH | 1. Acts on Sertoli cells |
| Q. LH | 2. Stimulates anterior-pituitary gonadotropin release |
| R. FSH | 3. Acts on Leydig cells |
| S. Androgens | 4. Support spermatogenesis |
ⓐ. P-2, Q-3, R-1, S-4
ⓑ. P-3, Q-2, R-4, S-1
ⓒ. P-2, Q-1, R-3, S-4
ⓓ. P-4, Q-3, R-1, S-2
Correct Answer: P-2, Q-3, R-1, S-4
Explanation: GnRH is released from the hypothalamus and stimulates the anterior pituitary to release the gonadotropins, giving P-2. LH then acts on Leydig cells in the interstitial tissue, so Q-3 follows. FSH acts on Sertoli cells within seminiferous tubules and promotes secretion of factors that assist spermiogenesis, fixing R-1. Androgens produced under LH influence contribute to the hormonal support of spermatogenesis, giving S-4. The mapping spans successive levels of regulation rather than four interchangeable hormones. It moves from a hypothalamic signal to pituitary hormones, then to testicular target cells and downstream reproductive support, preserving the source-target-effect logic of the pathway.
103. In a section of testis, cell type P lies between seminiferous tubules and responds to one pituitary gonadotropin. Cell type Q lies within the tubules, supports developing germ cells and responds to another gonadotropin. P and Q are respectively:
ⓐ. Leydig cells and Sertoli cells
ⓑ. Sertoli cells and Leydig cells
ⓒ. Spermatogonia and Leydig cells
ⓓ. Secondary spermatocytes and Sertoli cells
Correct Answer: Leydig cells and Sertoli cells
Explanation: The spatial description separates the two principal somatic cell types involved in hormonal regulation of spermatogenesis. Leydig cells occupy the interstitial spaces between seminiferous tubules and respond to LH by increasing androgen synthesis and secretion. Sertoli cells are located within the seminiferous tubules, support developing germ cells and respond to FSH by producing factors that assist spermiogenesis. Both position and hormone responsiveness point to the same identification. Location alone is insufficient if testicular cells are treated as one group; the additional functional clues establish the source-target relations. This arrangement links microscopic anatomy with endocrine regulation and explains why LH and FSH act through different testicular cell populations.
104. Evaluate the following hormonal relations.
I. LH acts primarily on Leydig cells.
II. FSH acts on Sertoli cells.
III. Androgens produced under LH influence support spermatogenesis.
IV. FSH stimulates Leydig cells to become the principal source of GnRH.
ⓐ. I and IV only
ⓑ. II and IV only
ⓒ. I, II and III only
ⓓ. I, III and IV only
Correct Answer: I, II and III only
Explanation: LH and FSH are both pituitary gonadotropins, but their major testicular targets differ. LH acts on Leydig cells and promotes androgen synthesis and secretion. Those androgens contribute to the hormonal environment supporting spermatogenesis. FSH acts on Sertoli cells and stimulates them to secrete factors that assist spermiogenesis. GnRH belongs farther upstream in the pathway and is produced by the hypothalamus rather than by Leydig cells under FSH stimulation. The first three statements preserve the correct hormone-target-effect relationships. The fourth incorrectly shifts both the target of FSH and the source of GnRH. Keeping the endocrine hierarchy intact is essential when predicting the effect of selective hormonal disturbances. An endocrine defect must be traced through its target cell before predicting the downstream effect on germ-cell development.
105. FSH secretion becomes markedly reduced while LH-Leydig signalling and androgen production remain functional. Which effect is most directly associated with the loss of FSH action?
ⓐ. Leydig cells can no longer receive LH
ⓑ. Sertoli-cell secretion of factors assisting spermiogenesis is reduced
ⓒ. GnRH is no longer produced by the hypothalamus
ⓓ. Androgen concentration necessarily falls even though LH-Leydig signalling remains intact
Correct Answer: Sertoli-cell secretion of factors assisting spermiogenesis is reduced
Explanation: FSH acts directly on Sertoli cells within the seminiferous tubules. In response, Sertoli cells secrete factors that assist spermiogenesis. A marked fall in FSH reduces this specific Sertoli-cell contribution. The stated conditions preserve LH-Leydig signalling and androgen production, so the expected effect should not be expanded into a primary failure of the Leydig pathway. GnRH also lies upstream in the hypothalamus and is not produced as a Sertoli-cell product. The case separates two parallel pituitary influences on the testis: LH acts through Leydig cells and androgens, while FSH acts through Sertoli cells. Selective reduction of one pathway leaves the other conceptually distinguishable. Structural integrity of a mature sperm does not replace hormonal regulation of its production, and hormonal support cannot replace a damaged sperm structure. The observation should be read in sequence, keeping completed upstream events intact and locating the first downstream transition that the manipulation prevents.
106. Match each major region of a human sperm with its position in the basic longitudinal organisation. A Column II entry is used once.
| Column I | Column II |
|---|
| P. Head | 1. Long posterior motile region |
| Q. Neck | 2. Anterior region containing the nucleus |
| R. Middle piece | 3. Short connecting region behind the head |
| S. Tail | 4. Region behind the neck containing numerous mitochondria |
ⓐ. P-2, Q-4, R-3, S-1
ⓑ. P-3, Q-2, R-4, S-1
ⓒ. P-2, Q-3, R-1, S-4
ⓓ. P-2, Q-3, R-4, S-1
Correct Answer: P-2, Q-3, R-4, S-1
Explanation: The sperm is organised longitudinally into head, neck, middle piece and tail. The head occupies the anterior end and contains the haploid nucleus, giving P-2. Immediately behind it lies the short neck, so Q-3 follows. The middle piece lies posterior to the neck and contains numerous mitochondria, fixing R-4. The tail forms the elongated posterior region associated with motility, giving S-1. These parts occur within a sperm enclosed by a plasma membrane and perform different but coordinated roles. Reading the structure from anterior to posterior makes the mapping coherent and prepares the structure-function links involving the acrosome in the head and mitochondria in the middle piece. Stage-specific terminology matters because changing the name of a cell or structure usually implies that a defined biological transition has occurred.
107. A sperm is described from its anterior end toward its posterior end. Region P contains an elongated haploid nucleus, Q is a short connector, R contains numerous mitochondria, and S forms the long motile portion. Which sequence identifies P to S?
ⓐ. Middle piece → neck → head → tail
ⓑ. Head → middle piece → neck → tail
ⓒ. Head → neck → middle piece → tail
ⓓ. Neck → head → tail → middle piece
Correct Answer: Head → neck → middle piece → tail
Explanation: The elongated haploid nucleus identifies P as the head. Q lies immediately behind the head and is described as a short connecting region, which identifies the neck. Numerous mitochondria are concentrated in the middle piece, so R corresponds to that region. S is the long motile portion and is the tail. The sequence from anterior to posterior is head, neck, middle piece and tail. Each label is supported by both position and internal feature, making the interpretation independent of an unseen diagram. The arrangement also links structure with later functional reasoning: the head participates directly in gamete interaction, while the mitochondria-rich middle piece supports movement of the tail. The supplied information is sufficient to locate the affected step, so unrelated upstream and downstream changes should not be assumed.
108. Assertion: The acrosome is a cap-like structure in the sperm head that contributes to fertilisation.
Reason: The acrosome is located in the middle piece and contains numerous mitochondria.
ⓐ. Both Assertion and Reason are true, and Reason correctly explains Assertion
ⓑ. Both Assertion and Reason are true, but Reason does not explain Assertion
ⓒ. Assertion is true, but Reason is false; therefore Reason cannot explain Assertion
ⓓ. Assertion is false, but Reason is true; therefore Reason cannot explain Assertion
Correct Answer: Assertion is true, but Reason is false; therefore Reason cannot explain Assertion
Explanation: The assertion is true. The acrosome forms a cap-like structure associated with the sperm head and contains enzymes that assist the sperm during fertilisation. The reason is false since the mitochondria-rich region is the middle piece, not the acrosome. Numerous mitochondria in the middle piece provide energy related to tail movement and sperm motility. The acrosome and middle piece represent different structure-function relationships within the same cell. One contributes enzymes useful during sperm-oocyte interaction, while the other supports movement by supplying energy. Distinguishing these regions prevents a common error in which every specialised sperm component is assigned to the same location or function. Fertilisation requires viable gametes to meet at the appropriate oviductal site and then complete a defined sequence of sperm-oocyte interactions.
109. A sperm has a normal haploid nucleus, an intact mitochondria-rich middle piece and vigorous tail movement, but its acrosome lacks the enzymes normally associated with it. Which reproductive function is most directly threatened?
ⓐ. Production of androgens by Leydig cells
ⓑ. Successful sperm-oocyte interaction during fertilisation
ⓒ. Formation of secondary spermatocytes from primary spermatocytes during meiosis I
ⓓ. Release of GnRH from the hypothalamus
Correct Answer: Successful sperm-oocyte interaction during fertilisation
Explanation: The acrosome is a cap-like structure in the sperm head containing enzymes that assist fertilisation. The stated conditions preserve the haploid nucleus, middle-piece mitochondria and tail movement, so the sperm can still possess genetic material and motility. The selective loss concerns the acrosomal enzymatic contribution used when the sperm interacts with the oocyte during fertilisation. This defect occurs far downstream of meiotic sperm production and is unrelated to Leydig-cell androgen secretion or hypothalamic GnRH release. The case demonstrates that normal movement alone is not sufficient for all sperm functions. A sperm must also possess specialised head structures capable of contributing to the interaction required for entry into the oocyte.
110. Four sperm samples are examined after equal exposure to the same conditions.
| Sample | Middle-piece mitochondria | Tail structure | Observed motility |
|---|
| P | Normal | Intact | High |
| Q | Severely impaired | Intact | Very low |
| R | Normal | Absent | Very low |
| S | Normal | Intact | High |
Which inference is most strongly supported by comparing P with Q?
ⓐ. Acrosomal enzymes are produced by middle-piece mitochondria
ⓑ. Tail structure alone guarantees normal movement without energy supply
ⓒ. Mitochondrial impairment increases sperm motility even when the tail remains intact
ⓓ. Middle-piece mitochondria are important for energy supporting tail movement
Correct Answer: Middle-piece mitochondria are important for energy supporting tail movement
Explanation: Samples P and Q are especially informative since both have an intact tail, while their mitochondrial condition differs. P has normal middle-piece mitochondria and high motility, whereas Q has severely impaired mitochondria and very low motility. With tail structure held similar, the change in mitochondrial function is associated with the large reduction in movement. This supports the established role of numerous middle-piece mitochondria in providing energy for tail movement. Samples R and S add context but are not needed for the decisive comparison requested. The evidence does not establish that mitochondria form the acrosome or that tail structure alone is sufficient. It supports a structure-function link in which energy supply from the middle piece contributes to effective sperm motility. The most reliable reasoning links the named biological event to its immediate prerequisite and consequence rather than to distant processes.
111. A sperm retains a structurally intact tail, but energy production by the numerous mitochondria in its middle piece falls sharply. Which functional chain is most consistent with this change?
ⓐ. Reduced energy supply → weaker tail movement → reduced sperm motility
ⓑ. Reduced energy supply → increased acrosomal enzymes → greater sperm entry
ⓒ. Reduced energy supply → increased chromosome number → diploid sperm
ⓓ. Reduced energy supply → increased androgen secretion → enhanced motility
Correct Answer: Reduced energy supply → weaker tail movement → reduced sperm motility
Explanation: The middle piece contains numerous mitochondria that provide energy needed for movement of the sperm tail. If mitochondrial energy production falls sharply while the tail remains structurally present, the most direct functional consequence is reduced ability to drive vigorous tail movement. Reduced tail movement then lowers sperm motility, an important property for successful transport toward the site of fertilisation. The change does not alter the haploid chromosome number of the sperm or cause the sperm itself to secrete androgens. Acrosomal enzymes belong to the head region and represent a separate fertilisation-related specialisation. The causal chain links one altered cellular component to its immediate mechanical effect and then to the resulting whole-cell behaviour.
112. Consider the stated criteria associated with a normal fertile ejaculate.
I. The total sperm count is about \(200\text{–}300\,\text{million}\).
II. At least \(60\%\) of sperm should have normal shape and size.
III. At least \(40\%\) should show vigorous motility.
IV. Vigorous motility must be present in at least \(80\%\) of sperm.
ⓐ. I and IV only
ⓑ. II and IV only
ⓒ. I, II and III only
ⓓ. I, III and IV only
Correct Answer: I, II and III only
Explanation: The stated reference values combine three different properties of an ejaculate. The total sperm count is about \(200\text{–}300\,\text{million}\). Morphological quality is represented by the requirement that at least \(60\%\) of sperm have normal shape and size, while motility quality is represented by at least \(40\%\) showing vigorous movement. The fourth statement raises the motility threshold to \(80\%\), which is not the value in the stated criteria. All three dimensions must remain conceptually separate: total number, morphology and vigorous motility are not interchangeable measurements. The valid set is the one that preserves the count range along with the \(60\%\) morphology threshold and \(40\%\) vigorous-motility threshold. A selective condition changes only the processes that depend on it directly; preserved processes in the stated information remain evidence against a broader failure.
113. An ejaculate contains \(250\,\text{million}\) sperm. What are the minimum numbers corresponding separately to the stated thresholds of normal shape and size and vigorous motility?
ⓐ. \(100\,\text{million}\) normal-shaped and \(150\,\text{million}\) vigorously motile
ⓑ. \(125\,\text{million}\) normal-shaped and \(100\,\text{million}\) vigorously motile
ⓒ. \(150\,\text{million}\) normal-shaped and \(150\,\text{million}\) vigorously motile
ⓓ. \(150\,\text{million}\) normal-shaped and \(100\,\text{million}\) vigorously motile
Correct Answer: \(150\,\text{million}\) normal-shaped and \(100\,\text{million}\) vigorously motile
Explanation: The morphology threshold is \(60\%\) of the total sperm count. For \(250\,\text{million}\) sperm, \(0.60\times250\,\text{million}=150\,\text{million}\). The vigorous-motility threshold is \(40\%\), giving \(0.40\times250\,\text{million}=100\,\text{million}\). These values are separate minimum counts derived from the same total population. They should not be added together, since the information does not state that the morphology and motility groups are mutually exclusive. A sperm could belong to both categories. The biological meaning is that the ejaculate must be assessed on more than total sperm number alone: a sufficient proportion must also satisfy the stated morphological and motility criteria. These two minimum counts cannot be combined into a single count of sperm satisfying both properties unless their overlap is known. The calculation keeps separate criteria for one ejaculate distinct: total number, morphology and vigorous motility describe different features that must be interpreted without inventing an unstated intersection.
114. An ejaculate contains \(220\,\text{million}\) sperm. Of these, \(58\%\) have normal shape and size and \(45\%\) show vigorous motility. Relative to the stated criteria, which assessment is appropriate?
ⓐ. Only the total-count criterion is below the stated range
ⓑ. The morphology criterion is below threshold, while count and vigorous motility satisfy their stated values
ⓒ. The vigorous-motility criterion is below threshold, while count and morphology satisfy their stated values
ⓓ. All three stated criteria are satisfied
Correct Answer: The morphology criterion is below threshold, while count and vigorous motility satisfy their stated values
Explanation: Each sperm-quality measure must be compared with its own stated criterion. The total sperm count is \(220\,\text{million}\), which lies within the range of about \(200\text{–}300\,\text{million}\) per ejaculate. Vigorous motility is \(45\%\); since the stated minimum is \(40\%\), this condition is satisfied. Morphology is different: \(58\%\) of sperm have normal shape and size, which is below the stated minimum of \(60\%\). No averaging of the three values is appropriate because count, morphology and vigorous motility measure different properties of the sperm population. The biological assessment is therefore that total count and vigorous motility meet their respective stated values, whereas the morphology percentage does not. This comparison also shows why a sample can satisfy two semen-related criteria while failing a third; one favourable measurement cannot compensate numerically for a separate threshold that has not been reached.
115. Four semen samples have the following measurements.
| Sample | Total sperm count | Normal shape and size | Vigorous motility |
|---|
| P | \(240\,\text{million}\) | \(64\%\) | \(44\%\) |
| Q | \(190\,\text{million}\) | \(68\%\) | \(46\%\) |
| R | \(260\,\text{million}\) | \(57\%\) | \(48\%\) |
| S | \(280\,\text{million}\) | \(66\%\) | \(38\%\) |
Using the stated count range and percentage thresholds, which sample satisfies all three criteria?
ⓐ. P
ⓑ. Q
ⓒ. R
ⓓ. S
Correct Answer: P
Explanation: The comparison requires all three columns to be checked for every candidate. The stated sperm-count range is about \(200\text{–}300\,\text{million}\), at least \(60\%\) should have normal shape and size, and at least \(40\%\) should show vigorous motility. Sample P has \(240\,\text{million}\) sperm, \(64\%\) normal morphology and \(44\%\) vigorous motility, so it satisfies every threshold. Q has acceptable percentages but its total count of \(190\,\text{million}\) is below the stated range. R has an acceptable count and motility but only \(57\%\) normal morphology. S has an acceptable count and morphology but only \(38\%\) vigorous motility. The table demonstrates that a sample must meet the independent numerical conditions simultaneously. Biological interpretation is strongest when it distinguishes what the observation proves from events that remain possible but untested.
116. Determine the correct combination of the following relations after sperm leave the testis.
I. Secretions from the epididymis and vas deferens contribute to conditions supporting sperm maturation and motility.
II. Secretions from the seminal vesicles and prostate also contribute to the post-testicular fluid environment.
III. Accessory-duct and gland functions are maintained by androgens.
IV. These post-testicular secretions convert haploid sperm into diploid cells.
ⓐ. I and IV only
ⓑ. II and IV only
ⓒ. I, II and III only
ⓓ. I, III and IV only
Correct Answer: I, II and III only
Explanation: Sperm leaving the testis encounter secretions contributed by several structures of the male reproductive tract. The epididymis and vas deferens, together with secretions from the seminal vesicles and prostate, contribute to conditions that aid sperm maturation and motility. The functions of the accessory ducts and glands are also maintained by androgens. None of these secretions changes the chromosome number of sperm. Sperm remain haploid with \(23\) chromosomes until participation in fertilisation, where the male and female gametic contributions together restore the diploid condition in the zygote. The first three statements describe linked post-testicular support relations, while the fourth incorrectly assigns a ploidy-changing role to reproductive-tract secretions.
117. Sperm production in the testes is normal, but secretory contributions from the epididymis and vas deferens are experimentally reduced while the ducts remain open. Which conclusion is most consistent with the stated role of these secretions?
ⓐ. Primary spermatocytes can no longer complete meiosis I inside the testis
ⓑ. Post-testicular support for sperm maturation and motility is reduced
ⓒ. The sperm chromosome number rises from \(23\) to \(46\)
ⓓ. GnRH secretion shifts from the hypothalamus to the epididymis
Correct Answer: Post-testicular support for sperm maturation and motility is reduced
Explanation: The treatment leaves testicular sperm production normal and keeps the ducts physically open, so the experimental change concerns secretory support after sperm have left the testis. Secretions associated with the epididymis and vas deferens contribute to sperm maturation and motility. Reducing those secretions is expected to weaken that post-testicular support even though transport through the ducts can still occur. The evidence does not justify a conclusion that meiosis inside seminiferous tubules has stopped, since the stated conditions preserve sperm production. It also provides no mechanism for changing haploid chromosome number or relocating GnRH production. The strongest inference stays close to the altered variable: reduced reproductive-tract secretion affects the maturation and motility environment encountered by sperm after testicular release. A structural change should be followed forward along the normal male pathway rather than used to infer unrelated changes in every reproductive organ.
118. Androgen action becomes markedly deficient even though the anatomical accessory ducts and accessory glands are still present. Which effect is most consistent with the stated androgen relationship?
ⓐ. Spermatogenesis remains fully normal solely because the accessory ducts and glands are anatomically present
ⓑ. Accessory-gland function remains fully normal despite marked androgen deficiency
ⓒ. Patency of the reproductive ducts alone preserves every androgen-dependent function
ⓓ. Normal maintenance and function of androgen-dependent accessory ducts and glands are impaired
Correct Answer: Normal maintenance and function of androgen-dependent accessory ducts and glands are impaired
Explanation: Androgens do more than participate in support of spermatogenesis. They also maintain the functions of the male accessory ducts and glands. If androgen action becomes markedly deficient, the structures may still be anatomically present, but their normal functional maintenance is compromised. The effect should not be interpreted as conversion of ducts into germ-cell-producing tissue or as a change in the identity of seminal plasma. GnRH remains a hypothalamic hormone and does not become a secretion of the vas deferens. This distinction separates structural presence from endocrine support: an organ or duct can remain physically identifiable while its normal reproductive function is altered when the hormonal signal that maintains that function is insufficient.
119. A defect reduces LH stimulation of Leydig cells. FSH-Sertoli signalling remains intact, but androgen concentration falls substantially. Which combined consequence best follows from the androgen decrease?
ⓐ. Support of spermatogenesis and maintenance of accessory-duct and gland functions can both be compromised
ⓑ. Only accessory-duct and gland functions are affected; spermatogenesis is completely androgen-independent
ⓒ. Only spermatogenesis is affected; accessory ducts and glands are independent of androgen action
ⓓ. Normal FSH-Sertoli signalling fully compensates for reduced androgen in both processes
Correct Answer: Support of spermatogenesis and maintenance of accessory-duct and gland functions can both be compromised
Explanation: Reduced LH stimulation lowers the normal endocrine activation of Leydig cells, so androgen synthesis and secretion decline. Androgens have more than one relevant relation in the male reproductive system. They contribute to the hormonal support of spermatogenesis and also maintain the functions of the accessory ducts and glands. A substantial androgen decrease can affect both of these downstream areas even though FSH-Sertoli signalling remains intact. FSH cannot simply replace every androgen-dependent function. The chromosome number of sperm is determined by meiotic events rather than by androgen concentration, and Sertoli cells do not transform into Leydig cells to compensate. This integrated pathway links one upstream hormonal defect to two distinct androgen-dependent reproductive consequences. Selective changes in Sertoli, Leydig or germ-cell function can be distinguished by asking whether support, androgen secretion or cell division is altered first.
120. Arrange the early events of human oogenesis in their correct developmental order.
ⓐ. Oogonium formation → primary follicle formation → meiosis I completion → prophase I arrest
ⓑ. Oogonium formation → entry into meiosis I → prophase I arrest → primary follicle formation
ⓒ. Primary follicle formation → oogonium formation → prophase I arrest → meiosis I completion
ⓓ. Entry into meiosis I → oogonium formation → primary follicle formation → prophase I arrest
Correct Answer: Oogonium formation → entry into meiosis I → prophase I arrest → primary follicle formation
Explanation: Human oogenesis begins during embryonic development. Oogonia are formed in the fetal ovaries and enter meiosis I. They do not immediately complete this division; instead, they become arrested in prophase I and are then called primary oocytes. Each primary oocyte becomes surrounded by a layer of granulosa cells, producing a primary follicle. The important developmental dependency is that meiotic entry and prophase I arrest precede the establishment of the primary-follicle arrangement. Completion of meiosis I occurs much later, after follicular development has progressed considerably. Reading the sequence from fetal germ-cell formation through meiotic arrest prevents the later event of meiosis I completion from being incorrectly placed before the prolonged primary-oocyte stage.
