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Male Reproductive System

AIPMT Biology Aspirants, read out the next AIPMT Biology Study material/ Notes of Male Reproductive System, Accessory Ducts and Sex glands, important for AIPMT Biology.Free online notes for AIPMT

Reproductive Duct System in males or Accessory sex ducts in males consists of Rete Testis, Vas efferentia, Epididymis, Vas (Ductus) deferens, Ejaculatory ducts, and Urethra. Duct system transports and stores sperm, helps in their maturation, and conveys them to the exterior.

AIPMT Biology - Testis with Reprodutive System of Ducts

Testis with Reprodutive System of Ducts

ACCESSORY SEX DUCTS

Epididymis

  • Comma-shaped organ along the posterior border of each testis. Each epididymis consists mostly of the tightly coiled ductus epididymis.
  • Vas efferentia (Efferent ducts) from the testis join the ductus epididymis at the larger, superior portion of the epididymis called the Head of Epididymis. Narrow mid-portion of the epididymis is called as Body of Epididymis, and smaller, inferior portion is the Tail of Epididymis.
  • Tail of epididymis continues as Vas (Ductus) deferens that ascends to the abdomen and loops over the urinary bladder.
  • Epididymis is the site of sperm maturation, in which sperm acquire motility and ability to fertilize an ovum. It also stores sperm which can remain viable here for several months.

Ducts of Testis

  • Sertoli cells produce fluid for sperm transport that pushes sperm and fluid along the lumen of seminiferous tubules and then into a series of very short ducts. These short ducts lead to a network of ducts in the testis called the Rete testis.
  • Through rete testis, sperms from seminiferous tubules move into the vasa efferentia (efferent ducts). Vasa efferentia leave the testis and open into Epididymis. Epididymis leads to vas deferens.

Vas (Ductus) deferens

  • In tail of epipidymis, ductus epididymis becomes less constricted and also their diameter increases, which is then continues as Vas (Ductus) deferens.
  • It then ascends along the posterior border of epididymis and enters into the pelvic cavity. In pelvic cavity, it loops over the ureter and passes down the posterior surface of the urinary bladder.
  • Dilated terminal portion of the vas deferens is called as
  • Ampulla combines with a duct from seminal vesicle and opens into urethra as the ejaculatory ducts.

Ejaculatory Ducts

  • One pair i.e. (2 in no.) Each ejaculatory duct is formed by the union of the duct from seminal vesicle and the vas deferens (Ampulla of vas deferens).
  • Ejaculatory ducts form just superior to the base of the prostate gland and pass through it, and then terminate in the prostatic urethra, where they eject sperm and seminal vesicle secretions just
    before the release of semen from the urethra to the exterior.
  • These ducts store and transport the sperms from the testis to the outside through urethra.

Urethra

  • Urethra is the shared terminal duct of the reproductive and urinary systems in males.
  • It serves as a passageway for both semen and urine.
  • Urethra originates from the urinary bladder and extends through the penis to its external opening called urethral meatus.
  • It is about 20 cm long and is subdivided into three parts: Prostatic urethra , Intermediate/ Membranous urethra and Spongy urethra.
  • Initial portion is known as Prostatic urethra as it passes through the prostate gland and is about 2–3 cm long. Middle part is known as the Membranous urethra (1 cm long), as it passes through deep muscles. Last part passes through corpus spongiosum of the penis, so it is known as Spongy urethra (15–20 cm long).

ACCESSORY SEX GLANDS

  • Include Seminal vesicles, Prostate gland, and Bulbourethral glands.
  • These glands secrete most of the liquid portion of semen.

Seminal Vesicles

  • Seminal vesicles or seminal glands are pouch-like structures and lie posterior to the base of the urinary bladder and anterior to the rectum.
  • These glands occur in pair (2 in no.)
  • Glands secrete alkaline, viscous fluid called as  seminal fluid (seminal plasma) that contains fructose, calcium, prostaglandins and clotting factors. Fructose is used for ATP production by sperm. Prostaglandins contribute to sperm motility and viability and help in contractions within the female reproductive tract. Clotting factors coagulate semen after ejaculation.
  • Alkaline nature of the seminal fluid helps to neutralize the acidic environment of the male urethra and female reproductive tract that otherwise would inactivate and kill sperm.
  • Seminal fluid makes about 60% of the volume of semen and comes out through ejaculatory duct.

Prostate Gland

  • Prostate gland is single, doughnut-shaped gland.
  • It is located inferior to the urinary bladder and surrounds the prostatic urethra.
  • It secretes milky, slightly acidic fluid (pH approx. 6.5).
  • Prostatic fluid consists of citric acid, proteolytic enzymes, acid phosphatase and seminalplasmin.
  • Seminalplasmin in prostatic fluid acts as an antibiotic that can destroy bacteria.
  • Prostatic ducts secrete prostatic fluid into the prostatic urethra.
  • Prostatic fluid makes up about 25% of the volume of semen and help in motility and viability of sperms.

Bulbourethral Glands

  • These are paired glands. Also known as Cowper’s glands.
  • They are of about the size of peas and are located inferior to the prostate on either side of the membranous urethra.
  • Ducts of these glands open into the spongy urethra.
  • Secretions of bulbourethral glands help in the lubrication of the penis.
  • These glands secrete an alkaline fluid which helps to protect the passing sperm from acids present in urine in the urethra.
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