Human Reproduction

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Human Reproduction
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Anatomy of the human male

• Main functions
• The production of sperm, the male gametes
• Spermatogenesis begins at puberty and continues
  until death
• Delivery of functional sperm to the female
  reproductive system

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Anatomy of the human male
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Anatomy of the human male

• Production of Semen (a fluid comprised of)
• Sperm, which are expelled through the ducts
  during ejaculation (1 of semen volume)
• Glandular secretions that carry, nourish, and
  protect the sperm (mostly sugars buffers)
• Testes (plural)
• Glands that produce sperm located outside
  abdominal cavity within the scrotum
• Scrotum (saclike pouch 1-3C below normal
  body temperature - sperm can only form at this
  lower temperature)

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How sperm leave the testes

• Seminiferous tubules carries/stores sperm in
  testes
• Epididymis a series of coiled ducts for
  maturation temporary storage of sperm
• Vas deferens tube which carries sperm past
  connecting lubricating and support glands

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How sperm leave the testes

• Lubricating and support glands
• (a.) Seminal vesicles secrete sugar-rich fluid
  that protects nourishes sperm
• (b.) Prostate gland produces an alkaline fluid
  that neutralizes both urine in the male urethra
  and the acidic environment of the vagina
• (c.) Bulbourethral glands secrete fluids that
  lubricates the male urethra and allows easier
  coitus (intercourse)

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How sperm leave the testes

• Urethra tube in the penis that transports semen
  out of the males body also transports urine
  from the urinary bladder
• Penis copulatory organ transient tumescence
• Ejaculation the release of semen through
  rhythmic contractions of smooth muscle in the Vas
  deferens

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Anatomy of the human male
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Anatomy of the human female

• Main functions
• To produce the female gametes (ova)
• To receive sperm
• To provide a suitable environment in which a
  fertilized ovum might develop during pregnancy

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Anatomy of the human female
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Anatomy of the human female

• Ovaries
• Contain follicles that nurture ova
• Produces sex hormones
• Functional from puberty to menopause

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Anatomy of the human female

• Oviducts (Fallopian Tubes)
• Convey (move) ova towards the uterus
• Muscular contractions cilia draw ovum (egg)
  into oviduct
• Location for fertilization to occur

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Anatomy of the human female

• Uterus (womb)
• Nourishes development of fertilized zygote
• Opens into the vagina at cervix
• Vagina
• Receives the penis during coitus
• Forms the birth canal
• Multiple layers of expandable smooth muscle
• Potential, not defined, space

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Anatomy of the human female
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Anatomy of the human female
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Puberty

• Puberty when secondary sexual characteristics
  develop and the potential for sexual reproduction
  is reached (sperm production or ovulation)
• Changes are controlled by hormones that initiate
  development of secondary sex characteristics
• Primary sex characteristics are internal and
  external reproductive organs (genitalia)

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Puberty in males (?)

• Secondary sex characteristics
• Primary hormone testosterone (testes)
• 2 Characteristics increased hair (body, pubic,
  facial), muscle development, deeper voice
• Spontaneous ejaculation

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Puberty in females (?)

• Secondary sex characteristics
• Primary hormone estrogen (ovaries)
• 2 Characteristics breast development, broadened
  pelvis, distribution of body fat increased hair
  (body pubic)
• Menarche (onset of menstruation)

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Reproductive hormones

• Testosterone (? testes)
• Sperm production secondary sexual
  characteristics
• Estrogen (? ovaries)
• Ova production, preparing uterus for fertilized
  zygote secondary sexual characteristics

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Hormonal control of the testes
Stimuli from otherareas in the brain

• Androgens, (testosterone most important),
  stimulate sperm production
• They also maintain homeostasis by a negative
  feedback mechanism that inhibits the secretion of
  FSH (follicle-stimulating hormone) and LH
  (luteinizing hormone)

Hypothalamus
Releasinghormone
Anteriorpituitary
Negative feedback
FSH
LH
Androgenproduction
Testis
Spermproduction
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Oogenesis Production of ova

• Oogenesis occurs within the ovaries
• Lifetime supply of primary oocytes is present at
  birth that are frozen in Prophase I
• One (maybe more) primary oocyte matures each
  menstrual cycle to form a secondary oocyte
  polar body
• If the secondary oocyte is fertilized, it
  completes meiosis and becomes a haploid ovum
  another polar body

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Oogenesis Production of ova
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Ovum maturation in ovary
releasesprogesterone
maintainsuteruslining
produces estrogen
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Reproductive Cycle of the Adult Human Female

• A cyclical pattern of hormone secretion and
  reproductive events.
• Humans and many other primates have menstrual
  cycles.
• If implantation of a fertilized zygote does not
  occur, the endometrium (lining of uterus) is shed
  through the cervix and vagina in the process
  called menstruation.

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The Menstrual Cycle

• The series of changes in the female reproductive
  system that includes producing an ovum and
  preparing the uterus for receiving it.
• Once an ovum has been released during ovulation,
  the part of the follicle that remains in the
  ovary develops into a structure called the corpus
  luteum.
• The menstrual cycle begins during puberty and
  continues for 30 to 40 years, until menopause.
• At menopause, the female stops releasing ova and
  the secretion of female hormones decreases.

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The Menstrual Cycle

• Divided into three phases the flow phase, the
  follicular phase, and the luteal phase.
• The timing of each phase of the menstrual cycle
  correlates with hormone output from the pituitary
  gland, changes in the ovaries, and changes in the
  uterus.

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Menstrual cycle
LH
FSH

• Controlled by a complex interaction of 4
  hormones
• follicle stimulating hormone (FSH)
• luteinizing hormone (LH)
• estrogen
• progesterone

ovulation egg release
egg development
corpus luteum
estrogen
progesterone
lining of uterus
0
7
14
21
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Days
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Menstrual cycle Flow phase

• Day 1 of the menstrual cycle (1st phase) is the
  day menstrual flow begins.
• The shedding of blood, fluid, mucus, and
  epithelial cells that make up the endometrium
  (the internal lining of the uterus) begins.
• Contractions of the uterine muscles help expel
  the uterine lining and can cause discomfort in
  some females.
• The level of FSH in the blood begins to rise, and
  a follicle in one of the ovaries begins to mature
  as meiosis of the prophase I cell proceeds.

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Menstrual cycle Follicular phase

• Follicular (2nd) phase lasts from about day 6 to
  day 14.
• As the follicle containing a primary oocyte
  continues to develop, it secretes estrogen, which
  stimulates the repair of the endometrial lining
  of the uterus.
• Day 14 ovulation occurs
• Ovulation follicle enlarges and ruptures ovary
  wall ovum is released to oviduct.
• Mittelschmerz ovulation pain

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Menstrual cycle Luteal phase

• Luteal (3rd) phase begins after ovulation ( day
  15).
• Progesterone increases the blood supply of the
  endometrium.
• These changes correspond to the arrival of a
  fertilized ovum (zygote).
• If the ovum is not fertilized, the rising levels
  of progesterone and estrogen from the corpus
  luteum cause the hypothalamus to inhibit the
  release of FSH and LH.

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Menstrual cycle Luteal phase

• Without fertilization, the corpus luteum
  degenerates and stops secreting progesterone or
  estrogen.
• As hormone levels drop, the thick lining of the
  uterus begins to shed.
• If fertilization occurs the endometrium begins
  secreting a fluid rich in nutrients for the
  embryo.

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Female reproductive cycle
Feedback
eggmatures is released(ovulation)
builds up uterus lining
estrogen
progesterone
FSH LH
fertilized egg(zygote)
maintainsuterus lining
HCG
pituitarygland
pregnancy
progesterone
GnRH
corpus luteum breaks down progesterone
drops menstruation
maintainsuterus lining
hypothalamus
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Female hormones

• FSH LH
• released from pituitary gland
• stimulates ova development hormone release
• peak release release of ova (ovulation)

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Female hormones

• Estrogen
• released from ovary cells around developing ova
• stimulates growth of lining of uterus
• decreasing levels initiate menstruation

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Female hormones

• Progesterone
• released from corpus luteum in ovaries
• stimulates blood supply to lining of uterus
• decreased levels sustains menstruation

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Hormonal coordination of the menstrual and
ovarian cycles

• FSH (follicle stimulating hormone) produced by
  pituitary gland stimulates development of
  follicle
• LH (luteinizing hormone) stimulates the
  development of the corpus luteum stimulates
  ovulation

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Hormonal coordination of the menstrual and
ovarian cycles

• Estrogen secreted by ovaries, stimulates
  development of uterine lining before implantation
• Progesterone secreted by corpus luteum,
  maintains uterine lining during pregnancy

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Fertilization

• Fertilization is the union of a sperm and an ovum
  to form a diploid zygote.
• Fertilization results in a zygote and triggers
  embryonic development.
• Occurs normally inside of fallopian tube
  (oviduct).
• Fertilization is NOT pregnancy!
• (PATHWAY) Tens of millions of sperm enter the
  vagina ? cervix ? uterus ? oviducts
  (fertilization)
• sperm ovum? zygote
• 23(n) 23(n) ? 46(2n)

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Fertilization

• Only one of the many millions of sperm entering
  the vagina will penetrate this human ovum to
  initiate fertilization

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Fertilization

• The shape of a human sperm cell is adapted to its
  function
• Sperm cell is enzymes, DNA mitochondria!

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Multiple Fertilizations

• If two (or more) ova are released in the same
  cycle and fertilized ? fraternal siblings
  (different DNA)
• If one ova is fertilized and mitotically divides
  into two (or more) separate zygotes ? identical
  siblings (same DNA)

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Fertilization
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Implantation

• Implantation The fertilized zygote implants into
  thickened uterine lining and the embryo starts to
  secrete the hormone human chorionic gonadotropin
  (HCG) (the hormone used for pregnancy tests)
• HCG keeps the corpus luteum functional and
  continuing to secrete progesterone.
• By the third or fourth month, the placenta takes
  over for the corpus luteum, secreting enough
  estrogen and progesterone to maintain the
  pregnancy.
• Implantation Pregnancy!

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Embryonic Development

• Development series of orderly, precise steps
  that transform a zygote into a multicellular
  embryo
• Embryo early development stages of a
  multicellular organism
• Includes
• 1. cell division (mitotic)
• 2. cell growth
• 3. cell differentiation altering of
  unspecialized mitotic embryonic cells into
  specialized cells, tissues, organs

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Early Embryonic Development

• Cleavage is the first major phase of embryonic
  development
• It is the rapid succession of cell divisions
  (Mitotic)
• It creates a multicellular embryo from the zygote
• NO growth
• Embryonic growth cannot occur until implantation
  occurs

ZYGOTE
Blastocoel
Cross sectionof blastula
BLASTULA(hollow ball)
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Early Embryonic Development

• Stages
• Morula solid ball of cells
• Blastula single layer of cells surrounding a
  fluid-filled cavity called the blastocoel
• NO growth still dividing original single cell
  mass

ZYGOTE
Blastocoel
Cross sectionof blastula
BLASTULA(hollow ball)
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Embryonic Development

• Gastrulation is the second major phase of
  embryonic development
• The cells at one end of the blastula move inward

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Embryonic Development

• Organs start to form after gastrulation
• Embryonic tissue layers begin to differentiate
  into specific tissues and organ systems

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Embryonic Membranes

• Amnion fluid filled sac for protection
• Chorion will form the embryos part of the
  placenta
• Yolk sac produces first blood cells germ
  cells

Chorion
Amnion
Allantois
Yolk sac
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Embryonic Membranes

• Allantois will form the umbilical cord
  (ropelike structure that attaches embryo to
  uterus)
• Umbilical cord brings nutrients in/wastes out of
  fetus
• Ties into hepatic artery vein in fetus -
  bellybutton

Chorion
Amnion
Allantois
Yolk sac
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The Placenta

• Placenta A growing fetus exchanges nutrients,
  oxygen, and wastes with the mother through the
  placenta
• Made of maternal and fetal tissues
• Substances pass both ways, but blood does not mix

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Placenta

• Nutrients, wastes, gasses diffuse across
  capillaries

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Fetal Development

• Gestation is pregnancy
• It begins at implantation and continues until
  parturition (birth)
• Pregnancy in humans usually lasts about 280 days,
  calculated from the first day of the mothers
  last menstrual period.
• Embryonic development of essential organs occurs
  in early pregnancy.
• The embryo may encounter risks from faults in its
  genes from mothers exposure to environmental
  factors.

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Human fetal development is divided into equal
trimesters

• First trimester (0 to 3 months)
• The most rapid changes occur during the first
  trimester (most developmentally important)10
  weeks
• eeks10 weeks
• 10 weeks

4 weeks
10 weeks
7 weeks
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Human fetal development is divided into equal
trimesters

• Second trimester (4 to 6 months)
• Increase in size of fetus
• General refinement of human features

12 weeks
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Human fetal development is divided into equal
trimesters

• The fetus spends much of the 2nd 3rd trimesters
  just growing
• and doing flip-turns kicks inside amniotic sac

Week 20
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Human fetal development is divided into equal
trimesters

• 24 weeks (6 months 2nd trimester)

• Fetus is covered with fine, downy hair called
  lanugo
• Its skin is protected by a waxy material called
  vernix

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Human fetal development is divided into equal
trimesters

• Third trimester (7 to 9 months)
• 30 weeks
• (7.5 months)

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Human fetal development is divided into equal
trimesters

• 32 weeks (8 months)

The fetus sleeps 90-95 of the day sometimes
experiences REM sleep, an indication of dreaming
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Human fetal development is divided into equal
trimesters

• Third trimester
• Growth and preparation for birth
• Provides time for maternal body to prepare for
  birth

Nooo!!! I dont want to go to Murdochs class!
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Three stages of labor

• Dilation of the cervix is the first stage
• Cervix starts at less than 1 cm dilation (open)
  and reaches full dilation at 10 cm
• Longest stage of labor (6-12 hours or longer
  maybe MUCH longer!)

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Three stages of labor

• Expulsion is the second stage
• Period from full dilation of the cervix to
  delivery of the infant
• Uterine contractions occur every 2-3 minutes
  (positive feedback)

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Three stages of labor

• Expulsion is the second stage
• Mother feels urge to push down with her abdominal
  muscles
• Infant is forced down and out of uterus and
  vagina within a period of about 20 minutes

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Three stages of labor

• The delivery of the placenta is the final stage
  of labor
• Usually occurs within 15 minutes after the birth
  of the baby
• Some placentas are saved and frozen as they are
  a source of stem cells

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Labor Birth Positive Feedback
positive feedback
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The end of the journey!
And you think 9 months of Biology is hard!
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Lactation the mam in mammal

• Lactation milk production
• Lactation is another positive feedback system
• Suckling stimulates the hypothalamus ?pituitary
  gland to release oxytocin
• Oxytocin stimulates mammary glands to secrete
  milk
• Continued suckling continues milk production

Yes, males have mammary glands too!
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Growth and Aging

• Once a baby is born, growth and learning
  continue.
• Human growth varies with age and is somewhat
  gender dependent.
• Females develop earlier

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An adult ages

• As an adult ages, his or her body undergoes many
  distinct changes
• -Slower metabolism
• -White hair
• -Thinner bones
• -Vision hearing diminish