301. A woman is \(49\,\text{years}\) old and still has menstrual cycles, while another reaches permanent cessation of cycles near \(51\,\text{years}\). Which interpretation is most appropriate?
ⓐ. Both observations are impossible because menopause occurs exactly at \(50\,\text{years}\)
ⓑ. The first observation proves pregnancy, while the second proves ovarian development has restarted
ⓒ. Both fit an approximate menopause age near \(50\,\text{years}\), not an exact compulsory birthday
ⓓ. Menopause should precede menarche whenever the age differs from \(50\,\text{years}\)
Correct Answer: Both fit an approximate menopause age near \(50\,\text{years}\), not an exact compulsory birthday
Explanation: The value near \(50\,\text{years}\) is an approximate reproductive-age reference for menopause, not a rule requiring every individual to stop cycling on an exact birthday. Continued cycles at \(49\,\text{years}\) and permanent cessation near \(51\,\text{years}\) are both compatible with an approximate boundary around that age. Menopause is defined by cessation of the female reproductive cycles, whereas menarche marks their beginning much earlier at puberty. The approximate biological value must be interpreted as a range-based reproductive landmark rather than as an absolute numerical cutoff. Age guidance should be combined with the reproductive event being described instead of converted into an absolute age cutoff.
302. A graph uses cycle day on the x-axis across about \(28/29\,\text{days}\). Curve P rises during follicular growth, curve Q shows a sharp mid-cycle maximum, and curve R remains relatively low before ovulation but rises strongly in the luteal phase. Which identification is most consistent with the trends?
ⓐ. P-estrogen, Q-LH, R-progesterone
ⓑ. P-progesterone, Q-estrogen, R-FSH
ⓒ. P-LH, Q-progesterone, R-estrogen
ⓓ. P-progesterone, Q-FSH, R-LH
Correct Answer: P-estrogen, Q-LH, R-progesterone
Explanation: The x-axis represents progression through a typical menstrual cycle, so the timing of each curve is decisive. Growing follicles are associated with increasing estrogen secretion during the follicular phase, matching curve P. The pronounced sharp maximum near mid-cycle is characteristic of the LH surge, which triggers ovulation, identifying Q. Progesterone is especially associated with the corpus luteum after ovulation and rises during the luteal phase, matching R. The graph combines three hormone relationships across one timeline rather than testing a single peak. Reading the trends in sequence also links the ovarian phases: follicular development and estrogen rise precede the LH surge, while luteal progesterone follows ovulation. A menstrual-cycle inference is strongest when hormone source, ovarian structure and uterine response are linked in the correct temporal order. Curve interpretation links a visual trend to the underlying reproductive event, so the timing of the change matters as much as its magnitude.
303. In a second menstrual-cycle graph, the mid-cycle LH surge and ovulation occur normally, but the usual luteal progesterone rise is almost absent and endometrial thickness begins to decline earlier than expected. Which defect best explains the paired trends?
ⓐ. Excessive follicular estrogen secretion before ovulation
ⓑ. Increased FSH action on developing follicles
ⓒ. Persistent activity of a highly functional corpus luteum
ⓓ. Inadequate corpus-luteum function after ovulation
Correct Answer: Inadequate corpus-luteum function after ovulation
Explanation: The graph places the defect after a normal LH surge and normal ovulation, so the pre-ovulatory follicular events have already occurred. The missing luteal progesterone rise points to poor endocrine activity of the corpus luteum, the post-ovulatory structure that normally secretes substantial progesterone. Progesterone helps maintain the endometrium during the luteal phase. If corpus-luteum function is inadequate, progesterone support falls and the endometrium can begin regressing earlier than it would under normal luteal maintenance. The paired hormonal and uterine trends arise from one post-ovulatory defect. A highly active corpus luteum would produce the opposite pattern by sustaining progesterone and maintaining the endometrial lining. Cycle-day values are approximate landmarks; the biological phase and hormonal relation are more informative than a rigid calendar interpretation. The graph supplies a pattern, while biological knowledge supplies the meaning of that pattern; neither should be used without the other.
304. In a mammary gland, cells lining structure P secrete milk into cavity Q. Q then drains through mammary tubules and progressively larger ducts. If secretion continues but Q cannot retain milk normally, which function is affected first?
ⓐ. Formation of mammary lobes from uterine tissue
ⓑ. Conversion of milk into colostrum inside lactiferous ducts
ⓒ. Temporary accumulation of secreted milk within the alveolar lumen
ⓓ. Production of milk by the mammary ampulla instead of alveolar cells
Correct Answer: Temporary accumulation of secreted milk within the alveolar lumen
Explanation: Mammary alveoli contain the milk-secreting cells, and the milk they produce enters the cavity or lumen of each alveolus before moving into the duct system. The stated conditions preserve secretion by the alveolar cells but removes the ability of the lumen to retain the secretion normally. The earliest affected function is accumulation of milk within the alveolar cavity before drainage. Mammary tubules, ducts, ampulla and lactiferous ducts form the downstream pathway rather than replacing the alveoli as the primary secretory units. This structure-function distinction separates milk production from its initial collection and later transport. A normal duct system cannot restore the lost local storage step if the alveolar lumen itself cannot hold the secreted milk.
305. A semen sample contains \(250\,\text{million}\) sperm. Exactly \(60\%\) have normal shape and size, and exactly \(40\%\) show vigorous motility. No information is given about whether the same sperm belong to both groups. Which conclusion is justified?
ⓐ. Exactly \(60\%\) of all sperm satisfy both criteria
ⓑ. Each threshold is met, but the overlap between normal-shaped and vigorously motile sperm is unknown
ⓒ. Exactly \(40\%\) of all sperm satisfy both criteria
ⓓ. No vigorously motile sperm can have normal shape, so the two percentage groups must be completely separate
Correct Answer: Each threshold is met, but the overlap between normal-shaped and vigorously motile sperm is unknown
Explanation: The total count is \(250\,\text{million}\), while the two reported percentages describe different properties of that population. Exactly \(60\%\) have normal shape and size, so \(0.60\times250=150\,\text{million}\) sperm meet the morphology criterion. Exactly \(40\%\) are vigorously motile, so \(0.40\times250=100\,\text{million}\) meet the motility criterion. These two subset sizes do not reveal how many sperm belong to both subsets. Their overlap could vary while the two marginal percentages remain unchanged. The values therefore show that the stated morphology and vigorous-motility thresholds are met separately, but they do not justify an exact percentage for sperm satisfying both characteristics simultaneously. These percentages form a set-overlap relation rather than a simple percentage conversion: separate percentages for morphology and motility cannot be combined into one shared percentage unless the relationship between the two groups is supplied. No single shared-subset count follows from the two percentages alone.
306. For a quantitative estimate, take a fetal ovarian population of \(2{,}000{,}000\) oogonia and a pubertal residual pool of \(60{,}000\text{–}80{,}000\) primary follicles in the same ovary. Approximately what percentage of the original numerical value does the pubertal range represent?
ⓐ. \(3\%\text{–}4\%\)
ⓑ. \(6\%\text{–}8\%\)
ⓒ. \(30\%\text{–}40\%\)
ⓓ. \(60\%\text{–}80\%\)
Correct Answer: \(3\%\text{–}4\%\)
Explanation: The lower end of the pubertal range is compared with the stated fetal numerical value as \(60{,}000/2{,}000{,}000=0.03\), or \(3\%\). The upper end gives \(80{,}000/2{,}000{,}000=0.04\), or \(4\%\). The pubertal residual range represents approximately \(3\%\text{–}4\%\) of the starting numerical value used in the calculation. The result illustrates the scale of follicular attrition before puberty rather than providing an exact biological survival rate for every individual. The comparison uses an explicitly stated approximate fetal value and the normal pubertal range to quantify how dramatically the ovarian germ-cell or follicular population declines during development. The ratio is a comparison of two approximate population values, not a claim that exactly \(96\%\text{–}97\%\) of one fixed cohort was destroyed by a single event. Developmental loss occurs over time, and the calculation simply expresses the relative scale of the remaining pubertal pool under the stated numerical assumptions.
307. A cell is released from a mature Graafian follicle with a zona pellucida intact. It has completed meiosis I but not meiosis II. Which description is accurate at the moment of ovulation?
ⓐ. It is a mature diploid ovum with \(46\) chromosomes
ⓑ. A primary oocyte still arrested in prophase I and therefore not yet released by ovulation
ⓒ. A haploid secondary oocyte whose meiosis II can finish after fertilisation begins
ⓓ. It is a first polar body destined to form the zygote
Correct Answer: A haploid secondary oocyte whose meiosis II can finish after fertilisation begins
Explanation: The female gametic cell released during ovulation is the secondary oocyte, not a fully completed post-meiosis-II ovum. During follicular development, the primary oocyte completes meiosis I and produces the large haploid secondary oocyte together with the first polar body. The secondary oocyte then remains at the next meiotic stage until fertilisation is initiated by sperm entry, which triggers completion of meiosis II and formation of the second polar body. The presence of the zona pellucida is also consistent with the ovulated secondary oocyte. This timing distinction prevents ovulation from being incorrectly treated as the point at which the entire female meiotic programme has already finished.
308. A male reproductive figure shows structure P as an elongated, highly coiled structure attached along the posterior surface of the testis. P receives sperm after the vasa efferentia and continues into the vas deferens. P is the:
ⓐ. testis
ⓑ. epididymis
ⓒ. seminal vesicle
ⓓ. ejaculatory duct
Correct Answer: epididymis
Explanation: The spatial and pathway clues both identify P as the epididymis. It lies along the posterior surface of the testis and receives sperm arriving through the vasa efferentia. From the epididymis, the transport pathway continues into the vas deferens. The rete testis is situated earlier within the testicular drainage sequence, while the seminal vesicle is an accessory gland whose duct joins the later vas-deferens pathway. The ejaculatory duct also occurs farther downstream. The figure integrates location with duct continuity: a posterior testicular structure positioned between the vasa efferentia and vas deferens is the epididymis, fixing its place in the directional sperm-transport route. The same identity is supported independently by position and by transport order, so either clue points to the epididymis and together they remove ambiguity with neighbouring ducts. This dual evidence is stronger than relying on shape alone in a reproductive-system figure.
309. A testicular section shows highly coiled seminiferous tubules containing germ cells and Sertoli cells. Region P between adjacent tubules contains blood vessels, immunologically competent cells and cell type Q. Selective destruction of Q would most directly produce which outcome?
ⓐ. Loss of Sertoli-cell nutrition with normal androgen secretion
ⓑ. Failure of spermatogonial mitosis caused by loss of the tubular lumen
ⓒ. Reduced androgen secretion despite intact Sertoli cells in the tubules
ⓓ. Conversion of interstitial blood vessels into androgen-secreting cells
Correct Answer: Reduced androgen secretion despite intact Sertoli cells in the tubules
Explanation: The decisive spatial clue is that Q lies in the interstitial region outside the seminiferous tubules. This region contains blood vessels, immunologically competent cells and interstitial or Leydig cells. Leydig cells are the androgen-secreting cells of the testis. Sertoli cells occupy the seminiferous tubules and provide nutritional and functional support to developing germ cells. Selective destruction of Q removes Leydig-cell endocrine activity without directly eliminating Sertoli cells. The two compartments perform related but distinct roles: seminiferous tubules contain the developing germ-cell system and its Sertoli support, while the interstitial compartment supplies androgens. The expected immediate endocrine consequence is reduced androgen production despite preservation of the tubular Sertoli population.
310. A semen sample is separated into fraction P containing sperm cells and cell-free fraction Q. Q contains accessory-gland secretions rich in fructose, calcium and certain enzymes. Recombining P and Q restores the original sample. Which interpretation is accurate?
ⓐ. Q is seminal plasma, while semen consists of sperm together with Q
ⓑ. Q is semen, while P alone is seminal plasma
ⓒ. Q is sperm cytoplasm released during spermiation
ⓓ. Q is exclusively bulbourethral secretion and contains no other glandular contribution
Correct Answer: Q is seminal plasma, while semen consists of sperm together with Q
Explanation: Semen contains two broad components: sperm cells and seminal plasma. The cell-free fraction Q contains the fluid secretions contributed by the male accessory glands and is described as rich in fructose, calcium and certain enzymes. That composition identifies Q as seminal plasma. Fraction P contains the spermatozoa. Recombining the cellular sperm fraction with the seminal-plasma fraction reconstructs semen. The terms cannot be exchanged: seminal plasma refers to the fluid component, whereas semen includes both sperm and that fluid. Bulbourethral secretion contributes to lubrication, but seminal plasma is not limited to that one gland. The separation experiment distinguishes the cellular and fluid components of the ejaculate through both composition and reconstitution.
311. Spermatogenesis, epididymal passage and vas-deferens transport are normal. The seminal-vesicle duct also joins the vas deferens normally, but the ejaculatory duct formed beyond their junction is completely obstructed. Which effect follows most directly?
ⓐ. Sperm cannot leave the seminiferous tubules for the rete testis
ⓑ. Seminal-vesicle secretion cannot be produced by its gland
ⓒ. Obstruction of the ejaculatory duct prevents sperm from leaving the epididymis for the vas deferens
ⓓ. Sperm and seminal-vesicle fluid cannot pass through the blocked ejaculatory duct into the urethra
Correct Answer: Sperm and seminal-vesicle fluid cannot pass through the blocked ejaculatory duct into the urethra
Explanation: The obstruction lies after the vas deferens has received the seminal-vesicle duct and formed the ejaculatory duct. All earlier events named in the stated information remain normal, so sperm can be produced, leave the testis, pass through the epididymis and travel along the vas deferens. Seminal-vesicle secretion can also be produced and reach its duct. The blocked segment prevents the combined contents from proceeding through the ejaculatory duct into the urethra. This is a transport defect rather than a failure of sperm formation or glandular synthesis. Locating a blockage relative to the duct junction is essential: processes upstream may continue normally even though their products cannot reach the downstream common passage needed for ejaculation. Correct anatomical reasoning starts from the affected segment and follows only the processes that normally depend directly on that segment.
312. Two selective uterine defects are compared. In individual P, the endometrium is severely damaged but the myometrium is functional. In individual Q, the endometrium is functional but the myometrium cannot contract strongly. Which comparison is most appropriate?
ⓐ. P primarily loses labour force, whereas Q primarily loses implantation
ⓑ. P has impaired endometrial cycling and implantation; Q has impaired contractions during delivery
ⓒ. P and Q both lose only the external perimetrium
ⓓ. P has normal implantation despite endometrial damage, whereas Q cannot form an endometrium despite intact lining
Correct Answer: P has impaired endometrial cycling and implantation; Q has impaired contractions during delivery
Explanation: The endometrium and myometrium belong to the same uterus but perform different reproductive functions. The endometrium is the inner glandular lining that undergoes cyclical changes and provides the tissue in which a blastocyst implants. Severe damage to this layer in P affects menstrual-cycle changes and implantation while leaving the muscular layer intact. The myometrium is the thick smooth-muscle layer responsible for the strong uterine contractions required during parturition. A selectively noncontractile myometrium in Q can leave the endometrial functions relatively preserved while weakening the force needed for delivery. The comparison demonstrates that uterine reproductive functions are partitioned among layers rather than performed uniformly by the entire uterine wall. The ovary, oviduct, uterus and vagina form a coordinated pathway, but each structure contributes a distinct reproductive function. The preserved functions in the stated information rule out a system-wide failure, so the predicted effect should begin at the first process that directly depends on the altered component.
313. A uterine arrangement is described as follows: P is the inner glandular lining, Q is the thick muscular layer, R is the cervical canal, and S is the vagina. During normal childbirth, which relation correctly combines force generation with the passage used for delivery?
ⓐ. P generates the force, while Q and R form the birth canal
ⓑ. Q generates the force, while R and S together form the birth canal
ⓒ. R generates the force, while P and S together form the birth canal
ⓓ. S generates the force, while P and Q form the birth canal
Correct Answer: Q generates the force, while R and S together form the birth canal
Explanation: Q is the myometrium, the thick smooth-muscle layer of the uterus. During parturition, strong contractions of this layer provide the mechanical force needed to expel the foetus. R is the cervical canal and S is the vagina. Together these two passages constitute the birth canal. P, the endometrium, has major roles in cyclical uterine changes and implantation but does not generate the powerful expulsive contractions of labour. The arrangement separates two requirements for delivery: a muscular force-producing structure and an anatomically continuous passage through which delivery occurs. Normal childbirth depends on coordination of these functions, even though they are performed by different uterine and reproductive-tract structures.
314. Alveolar secretion, mammary tubules, mammary ducts and the mammary ampulla remain functional, but the lactiferous duct is completely blocked. Which change is expected first in the normal milk pathway?
ⓐ. Alveolar cells stop being the milk-secreting cells
ⓑ. Milk from every mammary lobe stops entering its mammary tubules after the lactiferous duct is blocked
ⓒ. Milk cannot leave the alveolar lumen for mammary tubules
ⓓ. Milk reaches the ampulla but cannot exit through the blocked lactiferous duct
Correct Answer: Milk reaches the ampulla but cannot exit through the blocked lactiferous duct
Explanation: Milk is secreted by alveolar cells into the alveolar lumen and then moves through a defined sequence: mammary tubules, mammary ducts, mammary ampulla and finally the lactiferous duct. The stated conditions leave every component upstream of the lactiferous duct functional. Milk can be secreted, leave the alveoli and travel through the tubules and ducts to the ampulla. The complete obstruction occurs only at the final named segment, so normal external drainage fails after the ampulla. This differs from a blockage near the alveoli, where milk would be prevented from reaching the larger duct system. Tracing the pathway from secretion site to outlet fixes the first location at which movement becomes impossible. Colostrum is the early antibody-containing milk that contributes to neonatal resistance during the first days after birth. The changed condition is local, which means the reasoning should follow its direct dependency rather than assume that every reproductive stage fails simultaneously.
315. Nine primary spermatocytes each complete meiosis I and meiosis II normally, and all resulting spermatids complete spermiogenesis. Spermiation is then completely blocked. Which set of observations is expected?
ⓐ. \(36\) spermatozoa formed; \(0\) released into the lumen; \(23\) chromosomes each
ⓑ. \(18\) spermatozoa formed; \(18\) released into the lumen; \(46\) chromosomes each
ⓒ. \(36\) secondary spermatocytes formed; \(36\) released into the lumen; \(23\) chromosomes each
ⓓ. \(9\) spermatozoa formed; \(0\) released into the lumen; \(46\) chromosomes each
Correct Answer: \(36\) spermatozoa formed; \(0\) released into the lumen; \(23\) chromosomes each
Explanation: Each primary spermatocyte produces two secondary spermatocytes after meiosis I, and those two cells produce four haploid spermatids after meiosis II. For \(9\) primary spermatocytes, the total is \(9\times4=36\) spermatids. Spermiogenesis transforms these spermatids into \(36\) spermatozoa without changing their haploid chromosome number, so each contains \(23\) chromosomes. The final blocked event is spermiation, which normally releases formed spermatozoa from their Sertoli-cell association into the seminiferous-tubule lumen. Since spermiation alone is prevented, spermatozoa can still be formed but none of these newly formed cells are released into the lumen through the normal process. The calculation separates cell formation, differentiation, release and ploidy. Meiosis changes chromosome state, whereas spermiogenesis changes cell form; keeping these processes separate prevents stage errors. Upstream events that have already occurred remain established; the defect should be traced forward only through processes that require the impaired structure or signal.
316. Four hormonal interventions are followed by measurements of Leydig-cell androgen output and FSH-dependent Sertoli activity.
| Record | Intervention | Androgen output | FSH-dependent Sertoli activity |
|---|
| P | Selective FSH loss | Reduced | Preserved |
| Q | GnRH suppression | Preserved | Preserved |
| R | Selective LH loss with FSH maintained | Reduced | Relatively preserved |
| S | Leydig cells unresponsive to LH | Preserved | Reduced |
Which record is internally consistent with the hormonal pathway?
ⓐ. P
ⓑ. Q
ⓒ. R
ⓓ. S
Correct Answer: R
Explanation: LH and FSH act through different testicular targets. LH acts on Leydig cells and stimulates androgen synthesis and secretion. FSH acts on Sertoli cells and stimulates secretion of factors that assist spermiogenesis. In record R, LH is selectively lost while FSH remains available. A reduction in Leydig-cell androgen output is expected, while the FSH-dependent Sertoli pathway can remain relatively preserved. GnRH suppression would tend to reduce both pituitary gonadotropins rather than preserve both downstream branches. Selective FSH loss primarily affects the Sertoli pathway rather than directly removing LH-driven androgen secretion. A Leydig cell unable to respond to LH would also show reduced, not preserved, androgen output. The consistent row respects both hormone-target branches simultaneously. Spermiation releases formed spermatozoa from Sertoli-cell association, while spermiogenesis is the preceding transformation of spermatids into spermatozoa.
317. Two sperm populations are compared. Population P has defective middle-piece mitochondria but a normal acrosome. Population Q has normal middle-piece mitochondria and tail structure but lacks functional acrosomal enzymes. Which differential effect is most likely?
ⓐ. P retains normal motility despite mitochondrial damage, whereas Q alone shows reduced motility
ⓑ. P shows impaired motility, whereas Q may reach the oocyte but has impaired assistance during sperm entry
ⓒ. P reaches the oocyte with normal motility, whereas Q cannot be transported through the female tract
ⓓ. P primarily loses acrosomal function, whereas Q primarily loses middle-piece energy production
Correct Answer: P shows impaired motility, whereas Q may reach the oocyte but has impaired assistance during sperm entry
Explanation: The two defects affect different sperm functions. Numerous mitochondria in the middle piece supply energy for tail movement, so population P is expected to have reduced motility even though its acrosome is structurally normal. Population Q preserves the mitochondrial middle piece and tail, so movement through the female reproductive tract can remain possible. Its defective acrosome affects a later functional requirement: acrosomal secretions assist the fertilising sperm in passing through the oocyte coverings during entry. The comparison separates transport competence from entry competence. A sperm may be disadvantaged before reaching the oocyte through poor motility, or it may reach the oocyte yet remain impaired at the fertilisation interface because its acrosomal function is defective. The zona-pellucida interaction both permits the successful sperm-oocyte encounter and is followed by changes that prevent polyspermy.
318. LH and FSH rise normally during the follicular phase, developing follicles mature appropriately and estrogen secretion increases. The uterine endometrium nevertheless fails to regenerate after menstruation. Which site is most directly implicated by this pattern?
ⓐ. a defect in Leydig-cell androgen synthesis
ⓑ. a defect in spermiogenesis within the testicular seminiferous tubules
ⓒ. a defect in the mid-cycle LH surge mechanism
ⓓ. a defect in uterine endometrial regeneration and proliferation
Correct Answer: a defect in uterine endometrial regeneration and proliferation
Explanation: The observations indicate that the ovarian side of the follicular phase is functioning: gonadotropin activity rises, follicles develop and estrogen secretion increases. The abnormality appears in the parallel uterine event, where the endometrium should regenerate by proliferation after menstrual shedding. Since the upstream ovarian and pituitary features are supplied as normal, the most direct location of the defect is the endometrial proliferative response itself rather than follicular development. This case illustrates that ovarian and uterine changes are coordinated but remain biologically distinguishable. A normal ovarian hormone pattern does not guarantee a normal uterine outcome when the responding tissue is selectively defective. The evidence specifically isolates the missing follicular-phase uterine component. Menarche and menopause mark reproductive boundaries, while the recurring ovarian and uterine cycle occupies the intervening reproductive years. The most defensible prediction respects the boundary of the manipulation and avoids assigning secondary failures that the stated conditions do not require.
319. Ovulation occurs, the corpus luteum forms normally and circulating progesterone reaches the expected luteal level. The endometrium, however, is experimentally unable to respond to progesterone. Which outcome is most consistent?
ⓐ. The LH surge cannot have occurred
ⓑ. Progesterone concentration must immediately fall to zero
ⓒ. Normal circulating progesterone guarantees normal endometrial maintenance even when the tissue cannot respond to it
ⓓ. Luteal hormone production may remain normal while maintenance of an implantation-ready endometrium is impaired
Correct Answer: Luteal hormone production may remain normal while maintenance of an implantation-ready endometrium is impaired
Explanation: The supplied information distinguishes hormone production from target-tissue response. Ovulation and corpus-luteum formation have occurred normally, and progesterone has reached its expected luteal concentration. The missing link is the ability of the endometrium to respond to that hormone. Progesterone normally helps maintain the endometrium in a condition favourable for implantation. If the target tissue cannot respond, an adequate circulating hormone concentration cannot produce the normal uterine effect. The case does not require failure of the preceding LH surge or immediate disappearance of progesterone, since both upstream events are explicitly preserved. This demonstrates a general endocrine principle within the reproductive system: normal hormone secretion and normal target response are separate requirements for the complete physiological outcome. Pregnancy interrupts the ordinary menstrual pattern, so absence of bleeding must be interpreted with the supplied conditions.
320. Assertion: A normal mid-cycle LH surge followed by successful ovulation does not guarantee fertilisation.
Reason: Fertilisation additionally requires viable sperm and the secondary oocyte to be present in the ampullary region with suitable temporal overlap.
ⓐ. 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: Both Assertion and Reason are true, and Reason correctly explains Assertion
Explanation: The assertion is true. The LH surge induces rupture of the mature Graafian follicle and ovulation, but ovulation only makes the female gamete available. Fertilisation requires an additional set of conditions involving the male gamete. Viable sperm must travel through the female reproductive tract, reach the ampullary region and overlap in time with the viable secondary oocyte. The reason accurately states these extra requirements and directly explains why normal ovulation cannot guarantee fertilisation. An ovarian event and a gamete-fusion event are connected in sequence but are not equivalent. This distinction is important when interpreting reproductive success: completion of an upstream prerequisite increases the possibility of the next event without making that downstream event inevitable.
