Human Reproduction

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Human Reproduction

• Structure and function of human reproductive
  structures

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Sexual reproduction terms

• Gametes--specialized reproductive cells
• Ova (eggs)--female gamete
• Sperm--male gametes
• Zygote--formed from fusion of gametes nuclei
  (fertilization)--fertilization and birth brainpop
  animation
• Result offspring have genetic information from
  2 parents
• Brainpop intro to reproduction

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Female Reproductive anatomy

• Ovaries(2)--produce eggs (ova pl., ovum sing.)
• produce sex hormones
• At birth, female has all the eggs she will ever
  have (approximately 2 million)
• At puberty (sexual maturity), 400 eggs will
  mature
• Each month, one ovary releases an egg into
  oviduct (fallopian tubes)--long tube that leads
  to the uterus
• Fertilization normally takes place in oviduct

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Female anatomy

• Uterus--muscular pear-shaped organ into which
  the egg travels (even in not fertilized)
• If egg is fertilized, implants in wall of
  uterus--gtpregnancy
• If not fertilized, egg disintegrates within 24
  hours after ovulation
• Cervix--narrow portion at the bottom of
  uterus--provides opening to uterus from vagina
• Vagina--muscular tube connects uterus to outside
  of body
• Birth canal through which infants pass when born

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Male reproductive anatomy

• Testes(2)--found in the scrotum (pouch of skin)
  outside of body--keeps testes away from heat of
  body
• Produce sperm in males at puberty (13 years old)
  in seminiferous tubules
• Produce sex hormones
• Sperm require 74 days to develop millions
  mature each day. Many needed because few will
  survive / reach egg
• Sperm contains
• Head--contains genetic material (DNA)
• Midsection--has mitochondria for energy
  production
• Tail--motility (movement) for travelling to egg

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Male reproductive anatomy

• Epididymis--long, coiled duct that stores sperm
  until ejaculation, which moves sperm out of the
  body
• Vas deferens(2)--tubes that rapidly transport
  sperm from epididymis out of body

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Male reproductive anatomy

• Penis--male organ of sexual intercourse and urine
  excretion
• Urethra--tube through which sperm (and urine)
  move out of the body
• Semen--thick, white fluid that carries sperm
• contains secretions
• seminal vesicles (2)--fructose for sperm
  nourishment
• prostate gland--basic solution to neutralize
  acidic environment of vagina
• Cowpers (bulbourethral) gland--provides
  lubricant also helps to clean urethra
• During ejaculation, 5 mL of semen released with
  300 million sperm cells

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Sexual intercourse

• Penis becomes rigid with arousal due to increased
  blood flow
• Vagina becomes lubricated with arousal
• Ejaculation caused by involuntary muscle
  contractions
• Sperm-containing semen released into vagina
• Sperm travel toward oviduct, although only
  thousands survive the 1 hour trip
• Fertilization--sperm release enzymes that change
  the outer layer of egg so sperm can enter
• Once one sperm enters, cell membrane of egg
  changes so no more sperm can enter--How do you
  get twins? (animation)
• Zygote (fertilized egg) travels to uterus for
  implantation and is nourished by blood flow from
  mother during pregnancy

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QUIZ--Hormones and Menstrual Cycle

• 1. Specifically, what body system deals
  with/controls hormones.
• 2. Name 3 organs in the human body that
  produce/control hormones
• 3. Name one of the sex hormones mentioned in the
  reading (other than estrogen, progesterone, and
  testosterone)

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Hormones and their control

• Endocrine system regulates hormones (chemical
  messengers)
• Sexual development and secondary sex
  characteristics
• Males--deeper voice, facial hair, etc.
• Females--widening hips, breast development
• Effect is slow and long-lasting
• Nervous system--response is quick and short
• Feedback control of hormones
• One hormone often stimulates organ, while another
  inhibits it
• Negative feedback--product of process stops
  process
• Positive feedback--product of process accelerated
  process
• Insulin and glucagon from pancreas control blood
  sugar

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Sites of hormonal control

• Anterior pituitary (endocrine gland in
  brain)produces
• 1. Luteinizing hormone (LH)
• 2. Follicle stimulating hormone (FSH)
• Hypothalamus (in brain)
• Regulates release of FSH and LH by acting on the
  pituitary
• Controls blood pressure, body temp., emotions
• Makes ADH and oxytocin

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Hormones in males

• FSH stimulates maturation of the testes and sperm
• LH stimulates release of testosterone (male sex
  hormone) from the testes
• Testosterone stimulates
• Sperm production, erection, and ejaculation
• Secondary sex characteristics

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Hormones in females

• Menstrual cycle-- monthly cycle that releases
  egg (ovum)
• Ovulation--release of an egg (ovum)
• Estrogen and progesterone--major female sex
  hormones
• 1. Produced by the ovaries
• 2. Stimulate sexual maturity
• 3. Regulate menstrual cycle (in part)

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Menstrual cycle

• Approximately 28 days
• Ovulation (release of egg at about day 14)
• Sperm survive 72 hours egg survives 24
  hours--gtFertilization can occur within about a
  four-day window
• If egg is not fertilized
• 1. Hormone levels drop
• 2. Decreased blood flow to lining of uterus
• 3. Part of the lining of uterus disintegrates
  and passes to outside of body (menstruation)
• loss of 50 mL to 150 mL of blood
• Lasts 3 to 7 days

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Specific menstrual hormones

• FSH--causes maturation of egg inside a sac
  (follicle) on the surface of ovary
• Estrogen--secreted by the developing follicle
• 1. Stimulates secretion of LH (stimulates
  ovulation and the production of estrogen)
• 2. Stimulates thickening of inner lining of
  uterus
• Progesterone--maintains thickness of lining of
  uterus and promotes pregnancy (implantation of
  fertilized egg)
• Corpus luteum formed after ovulation--releases
  estrogen and progesterone which together inhibit
  LH and maintain thick uterine lining

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Menopause

• Profound hormonal changes in women
• Signals end reproductive phase of life
• Occurs 45 - 50 years old