Human Reproduction

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Human Reproduction Development

• Textbook Chapter 36
• Review Book Topic 4

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Reproduction

• Necessary process to ensure the continuation of a
  species
• Involves the union of an egg cell and a sperm
  cell, development of a fetus, and the birth of an
  infant
• Involves organs, glands and hormones of both male
  and female reproductive systems

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Sex Cell Development

• Males
• Occurs in testes
• Spermatocytes
• mature into
• sperm cells
• Occurs daily from puberty to death

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• Females
• Occurs in the ovary
• Born with all of the immature eggs a female will
  use monthly from puberty to menopause
• All eggs are stored in 1st meiotic division in
  the ovary until it receives hormone signals to
  develop

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Male Reproductive System

• Reproductive organ Testes
• Located outside
• of the body cavity
• in a pouch called
• the scrotum
• Sperm develop-
• ment requires a
• temperature lower than 37ºC

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• Reproductive cells Sperm
• Produced in testes at the seminiferous tubules
• 100-200 million are produced
• each day
• Travel to epididymis
• On top of each testes
• Sperm mature and are stored
• there

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• When released from the body, sperm travel through
  the vans deferens into urethra
• Urethra - tube which carries semen and
• urine out of the body through the penis

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• Sperm require a nourishing fluid to survive long
  enough to fertilize the egg
• Semen fluid containing sperm,
• nourishment, and other fluids from male
• reproductive glands

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• Seminal vesicles (ejaculatory ducts)
• secrete fluids plus sugar into the semen
• (provides energy, proteins, and enzymes
• for sperm)
• Prostate gland and bulbourethral glands
• secretes an alkaline solution to the semen
• to neutralize acidic conditions the sperm
• could encounter (ex. urethra, female
• system, etc.)

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TRY LABELING THIS!!
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• Answers  
• 1.  TESTIS 2.  EPIDIDYMIS 3.  VAS DEFERENS
  4.  URETHRA 5.  BULBOURETHRAL GLAND
• 6.  SEMINAL VESICLE / EJACULATORY DUCT7. 
  BLADDER 8.  PROSTATE 9.  PENIS 10. URETHRA

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Male Hormones

• Testosterone hormone necessary for the
  production of sperm
• Made in the testes
• Influences male secondary sex characteristics
• Facial body hair
• Broad shoulders
• Increased muscle development
• Deeper voice
• Receding hairline baldness (older)

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• Puberty period of growth when sexual maturity
  is reached
• Three hormones are released from the hypothalamus
  that influence puberty
• Gonadotropin-releasing hormone (GnRH)
• Follicle-stimulating hormone (FSH)
• Promotes sperm production
• Luteinizing hormone (LH)
• Promotes production and
• secretion of testosterone

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Female Reproductive System

• Specialized to produce eggs cells, receive sperm
  and to provide the perfect environment for
  fertilization and development of a fetus
• Reproductive organ ovaries
• Two
• About the size of an almond

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• Reproductive cell egg (ovum)
• Oocytes immature eggs
• Every 28 days, oocyte development is stimulated
  and becomes an egg
• Surrounded by follicle cells
• Protection
• Nourishment

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• Ovulation mature egg ruptures out of ovary wall

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• After egg is released from ovary
• Absorbed by fimbriae (finger-like hair structure)
• Travels to oviduct (fallopian tube) which
  connects to the uterus
• Uterus (womb) is where the baby develops before
  birth
• Roughly the size of your fist
• Cervix is the narrow opening into the vagina from
  the uterus

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Female Hormones

• Reproductive hormones estrogen progesterone
• Released by ovaries
• Anterior pituitary
• gland releases LH
• FSH

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• During puberty, increases in estrogen cause
  breasts to develop, hips to widen, and fat tissue
  to increase
• Also will experience first menstrual cycle
• Occurs each month to help prepare the
• female body for pregnancy

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• Reproductive System BrainPop

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Menstrual Cycle

• Length varies from 23 to 35 days
• Typically last 28 days
• Three phases
• Flow phase
• Follicular phase
• Luteal phase

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• Flow phase
• Day 1 menstrual flow begins
• Shedding of blood, tissue fluid, mucus and
  epithelial cells from endometrium (uterine tissue
  lining)
• Bleeding occurs because outer layers of
  endometrium tear away, rupturing blood vessels
• Day 5 repair of endometrial lining
• Becomes thicker as cycle continues

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• Follicular phase
• Estrogen level is low
• Anterior pituitary releases FSH LH to stimulate
  the egg to mature in the ovary
• 1 week
• Egg maturation releases estrogen causing FSH LH
  levels to drop (negative feedback)

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• Day 12 high levels
• of estrogen cause
• the release of a
• surge of LH
• Causes follicle to
• rupture, releasing
• egg
• Ovulation occurs

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• Luteal phase
• After ovulation, follicle changes
• into the corpus luteum
• Produces high amounts of progesterone
• Breaks down at end of cycle, production
• of estrogen and progesterone stops
• Signals release of endometrium lining
• New flow phase begins

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• If egg is fertilized, development will occur and
  menstrual cycle does not begin
• Progesterone levels will remain high
• Increased flow of blood to endometrium
• Corpus luteum does not break down
• Endometrium accumulates lipids
• and secretes fluid rich in nutrients
• for developing embryo

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• Menstrual Cycle BrainPop

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Fertilization

• Fertilization process where sperm and egg
  combine, forming a diploid cell
• Occurs in upper portion of the oviduct near the
  ovary
• Sperm is deposited in the vagina through
  ejaculation (release of semen from the penis)
• Sperm can survive for 48 hours inside the female
• Unfertilized egg can only survive for 24 hours

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• Out of the 300 million sperm deposited, only a
  couple hundred will reach the egg
• A single sperm cannot
• penetrate the plasma
• membrane of the egg
• One sperm will fertilize
• the egg but many are
• needed for the process
• to occur

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• Tip of each sperm contains lysosomes which
  contain enzymes used to digest the eggs membrane
• When weak enough, one sperm penetrates,
  fertilizing the egg
• Immediately the egg forms a barrier to prevent
  any other sperm from penetrating the fertilized
  egg

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Embryo Development

• Fertilized egg is known as a zygote
• Travels through oviduct by smooth muscle
  contractions and by cilia lining the oviduct
• 30 hrs after fertilization, zygote undergoes
  first mitosis and cell division
• After 3 days, zygote leaves
• oviduct and enters uterus
• Now referred to as a morula (solid ball of cells)

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• Day 5, morula has developed into a blastocyst
  (hallow ball of cells)
• Attaches to uterine lining on day 6 and is fully
  implanted by day 10
• Blastocyst stage is where identical twins can
  result if cells are split into two

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Embryonic Development Structures

• Amnion thin sac which forms around the embryo
  and is filled with amniotic fluid to cushion and
  insulate the egg.
• Chorion, the allantois, and yolk form the
  placenta two weeks after fertilization
• Chorion and allantois help form the placenta
• Yolk serves as the first red blood cell formation
  for the embryo

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• Placenta organ that provides food and oxygen as
  well as removes wastes from the baby (grows into
  the wall of the uterus)
• Umbilical chord contains blood vessels which
  serves as the connection between mother and child
  (no blood ever mixes, just very close so
  diffusion occurs)

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6 Weeks
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12 Weeks
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14 Weeks
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16 Weeks
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16/20/24 Weeks
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28/32 Weeks
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30 Weeks
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• Fetal Development BrainPop