Bio 30 reproductive system

• Reproduction in humans and other mammals

  The process by which sperm and egg cells are produced, brought together, join in fertilization and develop into a new individual
• Fecundity


  The ability of an organism to produce abundant or healthy offspring
• Male gonads


  • Testes
• Female gonads


  • Ovaries
• Ovum


  1 egg
• Ova


  Plural of ovum
• Fertilization


  The fusion of male and female sex cells
• Internal fertilization


  Uniting sperm and egg in the female body
• Zygote


  A cell resulting from the union of a male and female sex cell
• Embryo


  The early stages of development
• Fetus


  The later stages of an unborn offspring's development
• Male Reproductive System


  • Epididymis
  • Vas deferens
  • Ejaculatory duct
  • Cowper's gland
  • Urethra
  • Seminal vesicle
  • Prostate gland
  • Testes
  • Penis
• Testes


  • The male gonads which contain seminiferous tubules and interstitial cells
  • Produce sperm cells in the seminiferous tubules
  • Produce testosterone in the interstitial cells
  • Supported outside the body by a sac called the scrotum
  • A slightly lower body temperature is required for proper sperm production
• Epididymis


  • An area for sperm storage and maturation
  • Sperm gain motility in this area
• Vas Deferens


  A tube that allows sperm to pass from the epididymis to the urethra
• Seminal vesicle


  Secretes a sugary fluid (semen) which contains fructose (nourishes sperm) and prostaglandins which stimulate uterine contractions helping to carry sperm to the female's uterine tubes
• Prostate gland


  • Structure which contributes to the seminal fluid (semen)
  • Secretes an alkaline buffer that protects sperm cells against the acidic environment of the vagina
• Cowper's gland


  Adds mucous to the urethra prior to ejaculation to assist sperm movement and protect them from the acids in the urethra
• Urethra


  • A tube from the bladder, through the penis, to the body exterior
  • Seminal fluid and urine exit through the urethra
• Penis


  • A copulatory organ
  • Normally it is flaccid, but becomes erect to dispel sperm cells
• Glands that collectively produce sperm

  • Testes (sperm)
  • Seminal vesicles (sugar)
  • Prostate gland (alkaline buffer to protect)
  • Cowper's gland (alkaline mucus to clean)
• Seminiferous tubules


  Tubes that produce sperm from cells called spermatogonia
• Sertoli cells


  • Nourish and protect the sperm
  • Have FSH receptors that activate the production of sperm
• Interstitial cells


  Surround the seminiferous tubules and they produce testosterone, the male sex hormone
• Path of Sperm


  Testes -> seminiferous tubules -> Epididymis -> Vas deferens -> Urethra
• Erection


  • Erectile tissue in the penis becomes rigid due to vasodilation and blood flow into spaces, with veins compressed to stop blood outflow
  • Controlled by a reflex arc involving the spinal cord
• Semen


  An average of 4 ml containing about 400 – 500 million sperm are ejected
• Vasectomy


  Cutting the vas deferens to prevent sperm cells from being ejaculated
• Volume of ejaculation = 2.75 ml
• pH of semen = 7.2 – 7.6
• Sperm count per ml = 50 – 150 million
• Only a few sperm reach the egg
• Average sperm count has decreased from 113 million/ml to 66 million/ml in past 40 years
• Infertility = <20 million/ml
• Factors leading to infertility are environmental toxins, estrogens in meat, radiation, pesticides, marijuana, alcohol
• Hormones and their functions in the male reproductive system

  • Testosterone (Interstitial cells): Stimulates spermatogenesis, promotes and regulates development of secondary sex characteristics, associated with sex drive levels
  • Follicle-stimulating hormone (FSH) (Pituitary gland): Stimulates the production of sperm cells in the seminiferous tubules
  • Luteinizing hormone (LH) (Pituitary gland): Promotes the production of Testosterone by the interstitial cells
  • Gonadotropin-releasing hormone (GnRH) (Hypothalamus): Stimulates secretion of FSH and LH
• Hormonal control of the male reproductive system at puberty

  1. Hypothalamus produces GnRH, which stimulates the anterior pituitary to release FSH and LH

  2. FSH stimulates sertoli cells within the seminiferous tubules to start producing sperm

  3. LH stimulates the interstitial cells within the testis to start producing testosterone

  4. Testosterone contributes to sperm production and also causes secondary sex characteristics to begin to develop
• Hormone levels are regulated through negative feedback
• Sertoli cells produce inhibin which inhibits FSH when there is not enough testosterone in the blood
• Blood testosterone levels at different stages in a man's life

  • 1 to 7.9 years: 40 ng/dL
  • 8 to 10.9 years: 42 ng/dL
  • 11 to 11.9 years: 260 ng/dL
  • 12 to 13.9 years: 420 ng/dL
  • 14 to 17.9 years: 1000 ng/dL
  • 18 to 29 years: 1100 ng/dL