Male Reproductive System

Male Reproductive System

  • Function of the male reproductive system:
    • Reproduce by producing and delivering sperm.
    • Sperm is produced inside the testis.
  • The reproductive system also includes other parts that aid in the maturation and delivery of sperm.

Testis

Capsule

  • Made of dense irregular connective tissue.
    • Provides physical protection.
    • Contains extensions known as septa.
    • These smaller septa help produce lobules of the testis.
  • Inside the lobules are tightly coiled tube-like structures known as seminiferous tubules.
    • Function: Site of sperm production.

Epididymis

  • A tightly coiled structure that stores and matures sperm.
    • Sperm prior to the epididymis is immature.
    • Maturation occurs as sperm travel through the lengthy epididymis, allowing adequate time for development.
  • Once matured, sperm cells are sent to the vas deferens.

Structure of Seminiferous Tubules

Epithelium

  • Composed of simple columnar epithelium.
    • Cells known as sustentacular (Sertoli) cells.
    • Function: Sustain and support the developing sperm cells as they mature.
  • Immature sperm cells move from the basal surface (where they are formed) towards the apical surface (where they mature).
    • Once matured, they enter the lumen of the tubules.

Interstitial Cells

  • Found in-between the seminiferous tubules.
    • Produce testosterone.
    • An average male produces approximately 100 million sperm cells per day.
    • Sufficient sperm are necessary to ensure successful fertilization given the harsh conditions sperm may encounter.

Anatomy of Sperm Cells

  • Contains an organelle known as acrosome.
    • The acrosome holds digestive enzymes essential for penetrating the jelly coat of the oocyte (egg).
    • The jelly coat acts as a protective barrier to prevent inadequate sperm from fertilizing the oocyte.
    • Many sperm are required to break through the jelly coat.
    • The sperm's nucleus joins with the oocyte's nucleus to form a fertilized egg.

Midpiece

  • Contains numerous mitochondria for ATP production.
    • The midpiece has rods that influence flagellum operation.

Flagellum

  • The tail of the sperm cell.
    • Responsible for propelling the sperm toward the oocyte.
    • Damaged or older sperm cells are broken down by macrophages.

Sperm Production Conditions

  • The testis must be maintained at approximately 30 degrees Celsius for effective sperm production.
    • Normal body temperature is 37 degrees Celsius.
    • Scrotum: Holds the testis and has muscles that adjust their position to regulate temperature.
    • If it's too hot, the muscles relax, lowering the scrotum away from the body.
    • If too cold, muscles contract, pulling the scrotum closer to the body.

Anatomy of the Testes

  • Testes descend outside of the abdominal cavity to maintain optimal temperature for sperm production.
  • Gubernaculum:
    • Adjusts the position of the testes during development by shortening.
    • The descent occurs as the testis moves through the inguinal canal into the scrotum around the time of birth.
    • The canal also allows the passage of the vas deferens, blood vessels, and nerves.

Muscles and Structures Associated with the Testes

Spermatic Cord

  • Comprises five structures, including:
    • Vas deferens: Transports sperm from the epididymis to the ejaculatory ducts.
    • Cremaster muscle: Part of the spermatic cord, helps regulate testis temperature.
    • Dartos muscle: Surrounds the testis, contracting or relaxing to adjust position based on temperature.
    • Testicular artery: Supplies blood to the testis.
    • Pampiniform plexus: A network of veins that drain blood from the testis.

Undescended Testis

  • Condition where the testis remains in the abdominal cavity, leading to reduced sperm production capability.
    • Treatment often involves surgical descent.

Inguinal Hernia

  • Occurs when a portion of the intestines bulges through the inguinal canal due to excessive abdominal pressure.
    • Factors causing this condition can include heavy lifting or straining.
    • Treatment typically involves surgery to reposition the intestines.

Testicular Torsion

  • A condition where the spermatic cord twists, potentially restricting blood flow to the testis.
    • Causes can include rapid temperature changes or spontaneous occurrence.
    • Treatment usually requires surgery to untwist the cord.

Varicocele

  • Characterized by varicose veins in the pampiniform plexus.
    • Results in blood pooling and higher temperatures affecting sperm production.
    • Commonly associated with male infertility, especially in men aged 20-30.

Testicular Cancer

  • Typically occurs in men aged 20-40.
    • Symptoms may include a lump that feels like a frozen pea.
    • Treatment often requires removal of the affected testis.

Epididymis

  • Functions as the storage and maturation site for sperm cells.
    • Stereocilia: Structures on the apical surface that nourish the sperm as they mature.
  • After maturation in the epididymis, sperm enter the vas deferens.

Vas Deferens

  • Organ responsible for transporting sperm to the ejaculatory duct.
    • Uses peristalsis to move sperm along.
    • May be interrupted through a procedure known as vasectomy, which cuts the vas deferens as a form of birth control.

Vasectomy Procedure

  • Common form of birth control in the United States.
    • After cutting, the ends of the vas deferens may be tied or cauterized.
    • Reversal is possible but less so if scar tissue forms or ends are cauterized.

Pathway of Sperm Cells

  • Begins in seminiferous tubules, moves to epididymis, then into vas deferens, followed by the ejaculatory duct.
  • Sperm mix with fluids from the seminal vesicles and prostate gland to form seminal fluid.

Glands in the Male Reproductive System

  • Seminal vesicles: Produce fluids essential for sperm mobility and survival.
  • Prostate gland: Encases the prostatic urethra, contributing to seminal fluid.
  • Bulbourethral gland: Produces lubricating secretions enhancing the efficacy of ejaculation.
  • Functions of Seminal Fluid:
    • Assists swimming of sperm.
    • Provides sugars (e.g., fructose) for ATP production.
    • Neutralizes acid in the urinary tract and female vagina to prevent sperm damage.

Prostate Gland

  • Surrounds prostatic urethra, houses ejaculatory ducts.
  • Grows throughout a male's life, sometimes constricting urethra and causing urination difficulties.
    • Generally occurs in older men, medication may be required to alleviate symptoms.

Prostate Cancer

  • Affects approximately 1 in 10 men, often diagnosed in their 40s-50s.
  • Detection involves palpation to identify hard lumps indicating potential cancer.
    • A biopsy may be performed for confirmation.

External Anatomy of the Penis

  • Glans penis: Head, covered by prepuce (foreskin).
  • Body of the penis: The majority of the structure is composed of erectile tissue.

Circumcision

  • The surgical removal of the prepuce, typically performed in newborns for various reasons, including hygiene.
  • Some evidence suggests circumcision may reduce risk of urinary tract infections.

Internal Anatomy of the Penis

  • Comprised of erectile tissue, allowing erection when engorged with blood.

Types of Erectile Tissue

  • Corpora cavernosa: Multiple structures allowing significant blood engorgement for erection.
  • Corpus spongiosum: Surrounds the spongy urethra, limiting blood engorgement to keep the urethra open.

Erection Mechanism

  • Arteries dilate to increase blood flow into erectile tissues.
  • Veins are compressed to maintain blood within erectile tissues during erection.

Viagra and Erection Problems

  • Initially designed as a blood pressure medication.
  • Enhances vascular dilation, promoting erection.
    • Risk of benign conditions if used by those without erectile dysfunction.

Broken Penis

  • Occurs when dense irregular connective tissue of the erectile tissue capsule ruptures, typically from trauma during sexual activity.