Structure of Male Reproductive System — Revision Notes

⚡ 30-Second Revision

Testes — Primary sex organs, produce sperm and testosterone. Located in scrotum.
Scrotum — Pouch for testes, maintains $2-2.5^circ\text{C}$ lower temp for spermatogenesis.
Seminiferous Tubules — Site of sperm production. Contain Spermatogonia & Sertoli cells.
Sertoli Cells — Nourish sperm, form blood-testis barrier, secrete inhibin, ABP.
Leydig Cells — Interstitial cells, produce androgens (testosterone).
Epididymis — Sperm maturation (motility, fertilizing capacity) and storage.
Vas Deferens — Transports sperm from epididymis to ejaculatory duct.
Accessory Glands — Seminal vesicles, Prostate, Bulbourethral glands.
Seminal Vesicles — Secrete fructose, prostaglandins, clotting factors (60-70% semen volume).
Prostate Gland — Secretes citrate, PSA, seminalplasmin (20-30% semen volume).
Bulbourethral Glands — Secrete mucus, alkaline fluid (lubrication, neutralize acidity).
Semen — Sperm + Seminal Plasma.
Urethra — Common passageway for urine and semen.
Penis — Male copulatory organ, contains corpora cavernosa & corpus spongiosum (erectile tissue).
Sperm Pathway — Seminiferous tubules $\rightarrow$ Rete testis $\rightarrow$ Vasa efferentia $\rightarrow$ Epididymis $\rightarrow$ Vas deferens $\rightarrow$ Ejaculatory duct $\rightarrow$ Urethra.

2-Minute Revision

The male reproductive system is designed for sperm production, maturation, and delivery, alongside hormone synthesis. The testes, housed in the temperature-regulating scrotum, are the primary organs.

Within the testes, seminiferous tubules produce sperm, supported by nourishing Sertoli cells. In the interstitial spaces, Leydig cells synthesize testosterone. Sperm then travel through a series of ducts: from the seminiferous tubules to the rete testis, then vasa efferentia, entering the epididymis for maturation and storage.

From the epididymis, the vas deferens transports sperm, joining with the seminal vesicle duct to form the ejaculatory duct, which opens into the urethra.

Crucial for sperm viability are the accessory glands: seminal vesicles (fructose, prostaglandins), prostate gland (citrate, PSA), and bulbourethral glands (mucus, alkaline fluid). Their secretions form seminal plasma, which combines with sperm to create semen.

The penis, with its erectile tissues, facilitates semen delivery. Remember the pathway: Seminiferous tubules $\rightarrow$ Rete testis $\rightarrow$ Vasa efferentia $\rightarrow$ Epididymis $\rightarrow$ Vas deferens $\rightarrow$ Ejaculatory duct $\rightarrow$ Urethra.

5-Minute Revision

Let's consolidate our understanding of the male reproductive system, focusing on high-yield concepts for NEET. The system is divided into primary sex organs, accessory ducts, accessory glands, and external genitalia.

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Primary Sex Organs: Testes

* Located in the scrotum to maintain a temperature $2-2.5^circ\text{C}$ lower than body temperature, essential for spermatogenesis. The cremaster and dartos muscles regulate this temperature.

* Each testis contains seminiferous tubules, the sites of sperm production. Here, spermatogonia develop into sperm, supported by Sertoli cells (which nourish, form the blood-testis barrier, and secrete inhibin/ABP).

* In the interstitial spaces between tubules, Leydig cells produce testosterone, the primary male androgen.

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Accessory Ducts: Transport Pathway

* Sperm from seminiferous tubules $\rightarrow$ Rete testis (network) $\rightarrow$ Vasa efferentia (10-20 small ducts) $\rightarrow$ Epididymis (coiled tube on testis, site of sperm maturation and storage, where sperm gain motility and fertilizing capacity) $\rightarrow$ Vas deferens (long muscular tube, transports sperm during ejaculation) $\rightarrow$ Joins seminal vesicle duct to form Ejaculatory duct $\rightarrow$ Opens into Urethra (common pathway for urine and semen).

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Accessory Glands: Seminal Plasma Production

* Seminal Vesicles: Paired glands, contribute 60-70% of semen volume. Secretions are alkaline, rich in fructose (energy for sperm), prostaglandins (stimulate uterine contractions), and clotting factors.

* Prostate Gland: Single gland, contributes 20-30% of semen volume. Secretions are milky, slightly acidic, contain citrate (nutrient), PSA (liquefies semen), and seminalplasmin (antibiotic).

* Bulbourethral Glands (Cowper's Glands): Paired, pea-sized glands. Secrete clear, viscous, alkaline fluid for lubrication and neutralizing urethral acidity before ejaculation. * Semen = Sperm (approx.

5%) + Seminal Plasma (approx. 95%).

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External Genitalia: Penis

* Copulatory organ, contains three columns of erectile tissue: two corpora cavernosa and one corpus spongiosum (surrounds urethra). These fill with blood for erection.

Key Takeaways: Memorize the sperm pathway, the specific secretions and functions of each accessory gland, and the distinct roles of Sertoli and Leydig cells. Understand the importance of scrotal thermoregulation. These are the most frequently tested aspects.

Prelims Revision Notes

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Testes (Primary Sex Organs):

* Location: Scrotum, outside abdominal cavity. * Function: Spermatogenesis (sperm production) and androgen (testosterone) synthesis. * Temperature: $2-2.5^circ\text{C}$ lower than body temperature, maintained by scrotum (dartos and cremaster muscles).

* Covering: Tunica albuginea (dense fibrous capsule). * Lobules: ~250 per testis, each with 1-3 seminiferous tubules. * Seminiferous Tubules: Site of spermatogenesis. * Spermatogonia: Immature germ cells.

* Sertoli Cells (Sustentacular cells): Nourish developing sperm, form blood-testis barrier, secrete inhibin (regulates FSH) and ABP (androgen-binding protein). * Leydig Cells (Interstitial cells): Located outside seminiferous tubules, produce androgens (testosterone) under LH stimulation.

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Accessory Ducts (Sperm Transport):

* Rete Testis: Network collecting sperm from seminiferous tubules. * Vasa Efferentia (Efferent Ductules): 10-20 tubules from rete testis to epididymis. * Epididymis: Highly coiled tube on posterior testis.

Site of sperm maturation (gain motility and fertilizing capacity) and storage. * Vas Deferens (Ductus Deferens): Ascends from epididymis, loops over bladder. Transports sperm by peristalsis. Cut in vasectomy.

* Ejaculatory Duct: Formed by union of vas deferens and seminal vesicle duct. Opens into urethra. * Urethra: Common terminal duct for urine and semen in males. Divided into prostatic, membranous, and penile parts.

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Accessory Glands (Seminal Plasma Production):

* Seminal Vesicles (Paired): Posterior to bladder. Contribute 60-70% semen volume. Secretions: alkaline, fructose (energy), prostaglandins (uterine contractions), clotting factors. * Prostate Gland (Single): Inferior to bladder, surrounds urethra.

Contributes 20-30% semen volume. Secretions: milky, slightly acidic, citrate (nutrient), PSA (liquefies semen), seminalplasmin (antibiotic). * Bulbourethral Glands (Cowper's Glands, Paired): Inferior to prostate.

Secretions: clear, viscous, alkaline fluid for lubrication and neutralizing urethral acidity. * Semen: Sperm + Seminal Plasma.

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External Genitalia:

* Scrotum: Pouch housing testes, thermoregulation. * Penis: Male copulatory organ. Contains erectile tissues: two corpora cavernosa and one corpus spongiosum (surrounds urethra). Glans penis (tip) covered by prepuce (foreskin).

Vyyuha Quick Recall

To remember the pathway of sperm: Some Really Very Excellent Vacations End Unfortunately.

Seminiferous tubules
Rete testis
Vasa efferentia
Epididymis
Vas deferens
Ejaculatory duct
Urethra