Chapter 21: Reproductive System

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Chapter 21 Reproductive System
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Male Reproductive System

• Genital Tract
• In males the testes, held outside the body in the
  scrotum (optimum temp of about 350C), produce
  sperm.
• Sperm mature in coiled tubes atop each testis,
  called the epididymis (plural, epididymides).
• At ejaculation, sperm leave the testes through
  the vas deferens (plural, vasa deferentia), and
  pass through the ejaculatory ducts to the
  urethra.

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• Along the way, secretions (seminal fluid) are
  added from three glands two seminal vesicles,
  the donut-shaped prostate gland at the base of
  the urinary bladder, and paired bulbourethral
  glands.
• These glands add fructose (SV) for energy so
  sperm can swim, and prostaglandins (SV) that
  cause uterine contractions the secretions are
  slightly basic (prostate)
• Sperm with secretions from these glands is called
  semen.

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The male reproductive system
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Orgasm in Males

• The penis, the organ of sexual, intercourse,
  becomes erect from sexual arousal that stimulates
  cGMP in smooth muscle cells to allow erectile
  tissue to fill with blood arterioles dilate and
  veins are compressed.
• Orgasm involves ejaculation and muscular tension
  followed by muscular contractions and relaxation.
  
• Over 400 million sperm may be in each ejaculate.

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Penis anatomy
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Male Gonads, the Testes

• The testes, which produce sperm and male sex
  hormones, contain Seminiferous tubules
  (Spermatogenesis) surrounded by Interstitial
  cells (Testosterone)
• Testes originate in the abdominal cavity but
  descend into the scrotum where it is cool enough
  for sperm development.

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Testes
Interstitial cells that lie between the
seminiferous tubules within testes produce
testosterone.
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Seminiferous Tubules

• Seminiferous tubules inside the testes produce
  haploid sperm through spermatogenesis.
• Sustentacular cells (Sertoli cells) support,
  nourish, and regulate the cells during
  spermatogenesis.
• Sperm have a head, middle piece, and tail.

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• The head of the sperm is covered by a cap called
  the acrosome which stores enzymes needed to
  penetrate the egg.
• Sperm do not live more than 48 hours in the
  female genital tract.

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Hormonal Regulation in Males

• In both males and females, gonadotropin-releasing
  hormone, or GnRH, secreted by the hypothalamus
  stimulates the anterior pituitary to release two
  Gonadotropin Hormones from the Anterior Pituitary
  Gland. - Follicle-Stimulating Hormone (FSH) -
  Spermatogenesis and Luteinizing hormone (LH) -
  Testosterone.
• FSH stimulates the seminiferous tubules to
  produce sperm and the hormone Inhibin.

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• LH stimulates interstitial cells to produce
  testosterone.
• Testosterone brings about and maintains the male
  secondary sex characteristics.
• Testosterone exerts feedback control over the
  hypothalamus and anterior pituitary resulting in
  a constant amount of hormones and sperm
  production over time.

Lutenizing Hormone Testosterone
Follicle Stimulating Hormone (FSH)
Spermatogenesis