Human Reproduction Biology Part 1

• Reproduction


  The process by which offspring are produced, may be sexual or asexual
• Sexual reproduction


  Involves the production of gametes or sex cells, where male and female gametes fuse to form a zygote
• Gametogenesis


  Diploid cells undergo cell division and differentiation to form mature haploid gametes
• Meiosis


  The process of cell division that produces the gametes
• Zygote


  The cell formed by the fusion of male and female gametes, which then grows to form a new individual
• Humans use only sexual reproduction, which produces individuals different from each other
• Functions of the male reproductive system

  • Manufacture male gametes (sperm)
  • Deliver sperm to sites of fertilization
• Sperm


  • Haploid nucleus containing genetic information
  • Acrosome with enzymes
  • Mitochondria in midpiece to provide energy
  • Tail to enable swimming
• Male reproductive organs


  • Testes
  • Epididymis
  • Vas deferens
  • Urethra
  • Penis
  • Seminal vesicles
  • Prostate gland
  • Cowper's gland
• Scrotum


  Sac of skin that keeps testes at slightly lower temperature than body
• Sperm production and maturation

  1. Produced in seminiferous tubules of testes

  2. Move to epididymis for maturation and storage

  3. Pass through vas deferens to urethra
• Seminal fluid


  Secreted by seminal vesicles, prostate and Cowper's gland, provides nutrients and alkaline medium for sperm
• Semen


  Mixture of sperm and seminal fluid
• Valve prevents urine and semen from mixing in urethra
• Erection


  Penis becomes erect when spaces in its structure fill with blood
• Female gamete (ovum)


  • Large size
  • Non-motile
  • Thousands produced each month
• Female reproductive organs


  • Ovaries
  • Oviducts
  • Uterus
  • Cervix
  • Vagina
• Menstrual cycle


  Cyclic changes in the female reproductive system, involving release of an ovum and preparation of the uterus for implantation
• Hormones


  Chemical messengers that regulate development of male and female sex characteristics during puberty
• Egg


  • Large
  • Not capable of locomotion (movement)
  • Thousands of mature egg cells in each every 827 only Que is cele med each month
• Sperm


  • Very Small
  • Capable of locomotion since it
  • Produced every day in huge numbers (around Imillion per ejeculation)
• Secondary sexual characteristics


  Develop during puberty under the control of reproductive hormones
• Primary sexual characteristics


  In girls are the ovaries, in boys are the testes
• Oestrogen


  The female reproductive hormone produced by the ovary, triggers the development of female secondary sexual characteristics
• Changes in females during puberty due to oestrogen


  • Growth spurt
  • Growth of hair under the arms and pubic hair
  • The breasts develop
  • The external genitals grow and the skin darkens
  • A female pattern of fat is deposited on the hips, buttocks, and thighs
  • The brain changes and matures
  • Mature eggs start to form every month in the ovaries
  • The Uterus grows and becomes active, and menstruation begins
• Testosterone


  The main male reproductive hormone produced by the testes, triggers the development of male secondary sexual characteristics
• Changes in males during puberty due to testosterone

  • Growth spurt
  • Pubic hair, underarm hair and facial hair
  • The larynx gets bigger and the voice breaks
  • The external genitilia and the skin darkens
  • The teles grow and become active
  • Producing sperm throughout life
  • The shoulders and chest broaden as muscle develops
  • The brain matures
• Menstruation


  The monthly flow of blood from the uterus, also called a period
• Menstrual Cycle


  A regular cycle of events, including the regular build up and shedding of the lining of the uterus and the release of an ovum from an ovary, occurring on average every 28 days from puberty to middle age
• Purpose of Menstrual Cycle

  To prepare the lining of the uterus to receive the fertilized ovum. If the ovum is not fertilized, the lining of the uterus is shed.
• Menstrual Cycle


  1. Menstruation (lining of uterus shed)

  2. Ovum development (FSH causes Graafian Follicle formation)

  3. Ovulation (LH causes ovum release)

  4. Corpus Luteum formation (produces progesterone)
• Oestrogen levels


  Rise from day 1 to peak just before day 14, causing uterine wall to thicken and egg to mature
• Progesterone levels


  Stay low from day 1-14 and start to rise once ovulation has occurred, causing further thickening of uterine lining. A fall in progesterone levels causes the uterine lining to break down (menstruation/period)