Biology 12

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Biology 12

• Unit 2 Reproduction and Development
• Male System

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The Male Reproductive System

• The Testes are the primary male reproductive
  organs or gonads. They produce sex hormones and
  sperm.
• The Scrotum is the sac that contains the
  testes.

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• The testes are held outside the body cavity so
  the testes are kept at a temperature below body
  temperature. Sperm cannot be produced at body
  temperature. Clip

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• The Vas deferens is the tube that carries mature
  sperm towards the urethra.
• The Urethra is the structure that carries urine
  and semen.
• The Ejaculatory duct and a sphincter work
  together to prevent urine and semen from being in
  the urethra at the same time.

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• Semen is the fluid that contains the sperm and
  other fluids that assist in sperm motility.
• The Parasympathetic nerve that leads to the penis
  causes the sinuses of the erectile tissue to
  swell with blood during sexual arousal. The
  arteries leading to the penis becoming dilated
  while the swollen tissue constricts the blood
  flow leaving the penis.

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• Impotency occurs when the male is unable to
  sustain an erection. There are many factors that
  can cause impotency. (Stress, hormonal, damage to
  the parasympathetic nerve, etc.)

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Testes and Spermatogenesis

• The Sertoli cell provides nourishment for the
  developing sperm cells. The sperm has a
  much-reduced cytoplasm to increase its motility.
  Clip

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• The head of the sperm has an enzyme filled entry
  capsule called an Acrosome. Its function is to
  digest the outer layer of the egg so the sperm
  can enter during fertilization.

head
midpiece
acrosome
tail
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Seminal Fluid

• The Seminal vesicles add fructose (for sperm
  nutrition) and prostaglandins to the semen
  (seminal fluid). The prostaglandins triggers a
  response in the female reproductive tract that
  aids in sperm motility.
• The Prostate gland secretes a buffer that
  protects the sperm in the acidic environment of
  the vagina.

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• Protection of the sperm from any acidic urine
  found in the urethra is provided by the
  mucus-rich fluid from the Cowper's
  (bulbourethral) gland. The secretions may also
  help in sperm motility. Clip

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Hormonal Control

• Androsterone and Testosterone are produced in the
  Interstitial cells of the testes. These hormones
  stimulate spermatogenesis, initiate the male sex
  drive, direct the development of the primary sex
  characteristics, and influence the development of
  the Secondary sex characteristics during Puberty.

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• Anabolic Steroids are male sex hormones that have
  important medical uses, but are also abused by
  many athletes looking for shortcuts in their
  training.
• Male FSH stimulates the production of sperm.
• Male LH promotes production of testosterone.

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• A Negative-feedback mechanism controls the male
  reproductive system. Recall from the endocrine
  chapter that the pituitary produces and stores
  Gonadotropic hormones, which regulate the testes.

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• The pituitary is under control of the
  hypothalamus (a region of the brain - not an
  endocrine gland). At puberty the hypothalamus
  begins releasing Gonadotropin-releasing hormone
  (GnRH). GnRH stimulates the pituitary to
  release FSH and LH. Clip

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Male Structures
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Vasectomy

• A small incision is made in the scrotum
• The vas deferens is tied off in two places and a
  section of the vas is removed
• The scrotum is closed, and the procedure is
  repeated on the other side
• This procedure is done in a doctors office under
  local anaesthetic

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Hormonal Control in Males
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Hormonal Control in Males
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Spermatogenesis