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Human Reproduction - Male Reproductive System

Grade 12CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The male reproductive system is located in the pelvis region and includes a pair of testes, accessory ducts, glands, and the external genitalia.

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The testes are situated outside the abdominal cavity within a pouch called the scrotum, which maintains a temperature 2−2.5∘C2-2.5^\circ C lower than the internal body temperature, essential for spermatogenesis.

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Each testis contains about 250250 testicular lobules, each housing 1−31-3 highly coiled seminiferous tubules where sperm are produced.

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Seminiferous tubules are lined by two types of cells: male germ cells (spermatogonia, 2n2n) and Sertoli cells (nurturing cells).

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Leydig cells (interstitial cells) are present in the regions outside the seminiferous tubules and synthesize/secrete testicular hormones called androgens (e.g., Testosterone).

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The male accessory ducts include the rete testis, vasa efferentia, epididymis, and vas deferens. The pathway of sperm is: Seminiferous tubules →\rightarrow Rete testis →\rightarrow Vasa efferentia →\rightarrow Epididymis →\rightarrow Vas deferens →\rightarrow Ejaculatory duct →\rightarrow Urethra.

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The male accessory glands (seminal vesicles, prostate, and bulbourethral glands) secrete seminal plasma, which is rich in fructose, Ca2+Ca^{2+}, and specific enzymes.

📐Formulae

Semen=Spermatozoa+Seminal Plasma\text{Semen} = \text{Spermatozoa} + \text{Seminal Plasma}

Tscrotum=Tbody−(2∘C to 2.5∘C)T_{scrotum} = T_{body} - (2^\circ C \text{ to } 2.5^\circ C)

Total Sperm per Ejaculate≈200 to 300×106\text{Total Sperm per Ejaculate} \approx 200 \text{ to } 300 \times 10^6

Fertility Criteria=(≥60% normal shape/size)∩(≥40% vigorous motility)\text{Fertility Criteria} = (\ge 60\% \text{ normal shape/size}) \cap (\ge 40\% \text{ vigorous motility})

💡Examples

Problem 1:

A male individual produces approximately 250250 million sperm per ejaculate. According to standard physiological requirements for normal fertility, how many of these sperm must exhibit vigorous motility?

Solution:

For normal fertility, at least 40%40\% of the total sperm count must show vigorous motility. Calculation: 40% of 250×106=40100×250,000,000=100,000,00040\% \text{ of } 250 \times 10^6 = \frac{40}{100} \times 250,000,000 = 100,000,000.

Explanation:

As per the NCERT/CBSE guidelines, for normal human fertility, at least 60%60\% of sperm must have normal shape and size, and at least 40%40\% of the total sperm in an ejaculate must show vigorous motility.

Problem 2:

Identify the chromosomal ploidy of the following cells: (i) Spermatogonia, (ii) Primary Spermatocytes, (iii) Secondary Spermatocytes, and (iv) Spermatids.

Solution:

(i) Spermatogonia: 2n2n (4646 chromosomes), (ii) Primary Spermatocytes: 2n2n (4646 chromosomes), (iii) Secondary Spermatocytes: nn (2323 chromosomes), (iv) Spermatids: nn (2323 chromosomes).

Explanation:

Spermatogonia undergo mitosis to form primary spermatocytes (both 2n2n). Primary spermatocytes then undergo Meiosis-I to form haploid (nn) secondary spermatocytes, which undergo Meiosis-II to form haploid (nn) spermatids.