Male Reproductive System Quiz

Male Reproductive System

• The male reproductive system is comprised of gonads, ducts, and accessory sex glands.
• Gonads produce gametes (sperm) and hormones.
• Ducts transport, receive, and store gametes.
• Accessory sex glands produce materials to support gametes.
• Male reproductive organs secrete androgen hormones, produce sperm, and facilitate fertilization.
• Urology is the study of the urinary system including diseases and disorders of the male reproductive system.
• Andrology is the study of only male reproductive diseases.

Anatomy of Male Reproductive System

• Gonads:
  • Testes are the male gonads, the site for gamete and hormone production.
• System of ducts:
  • Epididymis, ductus deferens, ejaculatory duct, and urethra are involved in storing and transporting gametes.
• Supporting structures:
  • The scrotum and penis deliver and/or assist in joining gametes.
• Accessory sex glands:
  • Seminal vesicles, prostate gland, and bulbourethral glands produce secretions to support gametes.

Scrotum

• The scrotum consists of skin and subcutaneous tissue.
• Its function is regulating the temperature of the testes, which is required for sperm production.
• The dartos muscle contracts in cold temperatures, causing the skin of the scrotum to become firm and wrinkled, decreasing its size.
• Cremaster muscles are skeletal muscle fibers that control the position of the scrotum and testes.
• They contract to move the testes closer to the body when it's cold for warmth.

Testes

• Paired oval-shaped male gonads found in the scrotum.
• Equivalent to ovaries in females. Develop in the embryo's abdominal cavity.
• Descend into the scrotum in the last two months before or shortly after birth
• Consist of about 200-300 lobules.
• Each lobule contains 1-4 convoluted loops called seminiferous tubules.
• Between the tubules are Leydig cells that secrete testosterone after puberty.
• Sertoli cells in seminiferous tubules support, protect, nourish sperm cells, and produce inhibin.
• Seminiferous tubules converge to form a single straight tubule which moves into the rete testes (tubular network).
• Leave the scrotum as the deferent duct (vas deferens) in the spermatic cord.
• The tunica albuginea, a fibrous connective tissue, surrounds each testis.

Testes Function

• Seminiferous tubules produce sperm (spermatozoa) via spermatogenesis starting at puberty and continuing till old age, driven by testosterone.
• Successful spermatogenesis happens at temperatures 3°C below normal body temperature.
• Androgens promote the development of masculine characteristics.

Testes (Clinical Application)

• Cryptorchidism is a condition where the testes do not descend into the scrotum. 80% descend spontaneously during the first year of life.
• Untreated bilateral cryptorchidism can cause sterility due to high temperatures in the pelvic cavity.

Spermatogenesis

• A process where seminiferous tubules in the testes produce spermatozoa (sperm).
• Takes about 65-75 days.
• In early embryonic development, primordial germ cells enter the testes and differentiate into spermatogonia.
• Spermatogonia are immature cells until puberty.
• At puberty, they undergo mitosis to become primary spermatocytes.
• Meiosis I divides primary spermatocytes into secondary spermatocytes.
• Meiosis II divides secondary spermatocytes into spermatids.
• Spermiogenesis matures spermatids into spermatozoa.

Sperm

• Seminiferous tubules produce about 300 million sperm per day.
• Sperm production begins at puberty and continues throughout the male's life.
• Sperm mature in the epididymis. The epididymis has a tightly coiled ductus epididymis.
• Sperm help to propel into the vas deferens during ejaculation.
• Sperm are stored in the epididymis for several months.
• Mature sperm consist of a head, midpiece, and tail.
• The head contains DNA.
• The acrosome is on the tip of the head, with enzymes to penetrate secondary oocytes for fertilization.
• The midpiece contains mitochondria that provide energy (ATP). The tail is involved in locomotion.
• Sperm survive approximately 48 hours in the female reproductive tract.

System of Ducts

• Consists of the epididymis, ductus deferens, ejaculatory duct, and urethra.
• The epididymis is a long, tightly-coiled tube where sperm mature and are stored.
• The ductus deferens, or vas deferens, carries sperm from the epididymis to the ejaculatory duct.
• The ejaculatory duct passes through the prostate gland to empty into the urethra.
• The urethra is a shared pathway for both urine and sperm.
• Sphincter muscles prevent urine from entering the urethra during ejaculation. It also transports sperm from the urinary bladder to the urethra external orifice
• Spermatic cord is the proximal portion of the ductus deferens.

Ejaculatory Duct

• Formed from the union of the duct from the ductus deferens and seminal vesicle.
• Each ejaculatory duct passes through the prostate gland and empties into the urethra.
• The function of the ejaculatory duct is to empty spermatozoa into the prostatic urethra.

Urethra

• Extends from the urinary bladder to the external urethral orifice.
• Acts as a shared pathway for urine and semen.
• Sphincter muscles prevent urine from entering the urethra during ejaculation.

System of Ducts (Clinical Application)

• Vasectomy is a sterilization method in which the ductus deferens is cut and tied.
• As a result, no sperm enters the ejaculate.

Accessory Sex Glands

• Consists of seminal vesicles, prostate gland, and bulbourethral glands.
• They secrete fluids to nourish and protect sperm.

Seminal Vesicles

• Secrete an alkaline, viscous fluid that contains fructose (energy), prostaglandins (motility and viability), and proteins (to coagulate semen).
• The fluid helps neutralize acids in the male urethra and female reproductive tract.
• About 60% of semen volume is from seminal vesicles.
• Contract and expel fluid during ejaculation.

Prostate Gland

• Secretes a thin, milky fluid that makes up 30% of semen.
• The fluid enhances sperm motility and contains clotting enzymes that thicken semen.

Bulbourethral Glands

• Secretes an alkaline substance to protect sperm by neutralizing acids from urine.
• Secretes mucus to lubricate the penis.
• This prevents sperm damage during ejaculation.

Semen (Seminal Fluid)

• Mixture of sperm and seminal fluid.
• Makes up 60% of the semen volume.
• Typical volume: 2.5-5 mL with 50-150 million sperm/mL
• Slightly alkaline pH (7.2-7.7) due to seminal vesicle secretions.
• Coagulates after ejaculation due to clotting proteins.
• Contains an antibiotic to destroy certain bacteria.
• If less than 20 million sperm/mL, the man is infertile.

Penis

• Located anterior to the scrotum.
• Has a root, body, and glans.
• Composed of erectile tissue (corpus cavernosa and corpus spongiosum).
• Transfers sperm into the vagina.
• Prepuce or foreskin covers the glans.

Penis (Clinical Connection)

• Circumcision surgically removes the foreskin for religious or hygienic reasons.
• Circumcision can lower the risk of UTIs, protect against penile cancer, and reduce transmission of sexually transmitted diseases.

Ejaculation

• Ejaculation is a sympathetic reflex coordinated by the lumbar portion of the spinal cord that pushes semen out of the urethra at the exterior.
• Erection is blood sinus expansion under the influence of sexual excitation.
• Semen is propelled by smooth muscle contractions in the ductus deferens, seminal vesicles, and prostate gland.
• Before ejaculation occurs, peristaltic contractions cause semen to enter the urethra. This is called emission, a discharge of a small amount of semen.
• Muscle sphincters at the base of the bladder close to prevent urine from entering during ejaculation.
• Sperm comprises 10% of the ejaculate; the rest is seminal and prostatic fluids.
• Sperm travel through the seminiferous tubules → rete testis → efferent ducts → ductus epididymis → vas (ductus) deferens → ejaculatory duct → urethra.

Ejaculation (Clinical Application)

• Premature ejaculation results from anxiety or other psychologic factors and an oversensitive glans.
• Erectile dysfunction (ED) is the consistent inability of an adult male to ejaculate or attain/maintain an erection long enough for intercourse, often due to insufficient release of nitric oxide.

Hormonal Control

• At puberty, gonadotropin-releasing hormone stimulates the anterior pituitary to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
• FSH initiates spermatogenesis. LH assists spermatogenesis and stimulates testosterone production.
• Inhibin decreases FSH release.
• Testosterone promotes the development of masculine characteristics, controls growth/development/functioning of sex organs, stimulates bone growth/protein anabolism and sperm maturation.
• Testosterone production is regulated by negative feedback mechanisms.
• Sertoli cells produce inhibin, which inhibits FSH release.

Puberty in Males

• Occurs between 10 to 14 years old.
• Puberty is associated with increases in muscle and bone growth and weight, enlargement of the larynx and deepening of the voice, growth of hair and enlargement of the scrotum, penis, and prostate gland, maturation of seminiferous tubules and sperm production, and thickening and oiliness of skin.