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Human Reproduction

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Human Reproduction & Development – PowerPoint PPT presentation

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Title: Human Reproduction


1
Human Reproduction Development
2
Overview of Reproduction
  • Sexual reproduction involves the union of 2
    _______ to form a zygote.
  • gametes
  • Sexual reproduction produces offspring that are
    like, yet unlike the parents because
  • genetic diversity resulting from both parents
    contributing ½ of the childs genes, mutations,
    crossing over, independent assortment.
  • What process produces egg and sperm?
  • Meiosis
  • How many chromosomes are in each egg and sperm?
  • 23
  • What is an advantage of sexual reproduction over
    asexual reproduction?
  • Genetic diversity / survival of the fittest

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4
Definitions
  • Gonad
  • structure that produces gametes (ovaries and
    testes)
  • Endocrine system
  • System of glands that secrete hormones into the
    blood stream
  • Gland
  • Component of endocrine system makes hormones,
    which are chemical messengers that affect other
    parts of the body.
  • Fertilization
  • Fusion of egg and sperm
  • Copulation
  • Sexual intercourse internal fertilization

5
Male Reproductive System and Anatomy Physiology
  • Male gonad
  • Testis (plural testes)
  • Scrotum
  • Sac or pouch of skin that holds the testes
    outside of body cavity (sperm develop at temps.
    2-3 degrees lower than body temp.). Testes
    descend into scrotum during 9th month of embryo
    development.
  • Testes produce ___ and ___ (male gametes).
    Within the testes are 500 tightly coiled tubes
    called ___ ___. These produce sperm starting
    when the male reaches puberty. The sperm
    produced are stored in the ___. The testosterone
    produced causes development of the secondary sex
    charactistics, such as ____, and also causes
    production of the sperm.
  • Testosterone, sperm, seminiferous tubules,
    epididymis
  • Body hair growth, increased height, wider chest,
    deeper voice

6
Human Sperm
  • Size
  • Much smaller than egg, which must contain
    nutrients, motile.
  • Parts
  • Head contains DNA and enzymes to digest membrane
    around egg. Flagellum propels sperm to egg.
  • Energy
  • ATP made in mitochondria (aerobic respiration) in
    neck of sperm. Fructose is sugar that is burned.

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8
Sperm Delivery
  • Epididymis
  • Sperm stored for 2-3 days.
  • Vas deferens
  • Ciliated tube that carries sperm from epididymis
    to urethra (past next 3 structures).
  • Seminal Vesicles
  • Secretes alkaline (basic) sugar (fructose)
    solution.
  • Cowpers Gland
  • Secretes mucous which lubricates tubes.
  • Prostate Gland
  • secretes alkaline solution to counter acidic
    condition in vagina and urethra.
  • Urethra
  • secretions all put into urethra and mix w/ sperm.
    All of these together make up semen. Some of
    the semen is secreted before ejaculation to
    lubricate urethra. It does contain sperm!

9
Sperm Delivery contd
  • Erection
  • When aroused blood flow to penis increases, blood
    fills spongy tissue in penis, creates a
    hydrostatic skeleton.
  • Penis
  • Urethra carries semen out through penis in a
    process called ejaculation contractions of
    smooth muscle lining ducts. (about 3-5 ml of
    semen is produced each time).
  • The semen that is ejaculated contains about 130
    million sperm. Why are so many sperm produced?
  • Sperm must swim upstream all the way to fallopian
    tube.
  • Many sperm use up their sugar supply before
    reaching egg.
  • Acidity of vagina disables many sperm.

10
What is the main factor that det-ermines which
sperm makes it to the egg?
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12
Female Reproductive System Anatomy and Physiology
  • Female gonad
  • Ovary
  • Difference from male gonad?
  • All eggs are made before birth, released
    regularly after puberty. Male gametes are made
    at puberty and released sporadically for the rest
    of males life.

13
Female Reproductive System Anatomy and Physiology
Contd
  • One of the ovaries release an egg during the
    uterine cycle. Four stages of this cycle are
  • 1. Follicular
  • Development of follicle, in which egg matures
    10-14 days from end of menstruation to ovulation.
  • 2. Ovulation
  • Egg released from ovary when follicle ruptures.
  • 3. Luteal
  • Development of corpus luteum 10-14 days from
    ovulation to menstruation. Egg is moving from
    fallopian tube to uterus.
  • 4. Menstruation
  • Shedding of uterine lining and blood that was
    prepared for fetus 5 days.

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16
  • Maturation of the ovum (egg) is controlled by
    ____.
  • Hormones
  • 1. Releasing factors from brain
  • Stimulate pituitary gland (near brain) to make
    Follicle Stimulting Hormone.
  • 2. FSH causes a follicle to form, in which
  • an ovum matures.
  • 3. FHS also stimulates the follicle to increase
    production of estrogens. The pituitary gland
    senses this and produces Luteinizing Hormone
    (LH).
  • 4. LH causes the follicle to mature. Ovulation
    occurs when
  • A mature egg is released into a fallopian tube.

17
Egg Delivery
  • The ovum is released into the oviduct or
    fallopian tube. It is drawn in by the action of
    cilia because
  • The ovary doesnt touch the fallopian tube.

18
Egg Delivery Contd
  • The uterus is a hollow, muscular organ with thick
    walls that are line with mucous membranes, glands
    and blood vessels.
  • Meanwhile the lining of the uterus builds up. LH
    causes the ruptured follicle to become the corpus
    luteum. This now secretes progesterones, another
    kind of female hormone.
  • These hormones (progesterone estrogen) prepare
    the lining of the uterus to receive and nourish a
    fertilized egg, whether or not the egg is
    actually fertilized.

19
Egg Delivery Contd
  • Ovum is fertilized
  • Fertilized egg moves through fallopian tube and
    embeds in soft tissue of uterus.
  • Ovum is not fertilized
  • Corpus luteum breaks down (so progesterone levels
    drop). Lining of uterus detaches and is shed
    along with blood and unfertilized egg in
    menstruation.

20
Life Within the Uterus
  • Where does fertilization usually occur?
  • Fallopian tube
  • Ectopic Pregnancy
  • Occurs when the zygote embeds somewhere other
    than the uterus such as the ovary or fallopian
    tube. Extremely painful and possibly fatal for
    mom and baby.

21
Life Within the Uterus Contd
  • What keeps more than one sperm from fertilizing
    the egg?
  • The 1st sperm that enters causes a chemical
    change to occur in the cell membrane of the egg,
    that prevents other sperm from entering.
  • Diploid (2n 46) condition is restored. Mitotic
    divisions begin.

22
Life Within the Uterus Contd
  • What is the difference between an embryo and a
    fetus?
  • Embryo
  • 1st 6-8 weeks, up to 2 cm long
  • Fetus
  • After 8 weeks, all basic tissues are present
    rapid growth

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24
Life Within the Uterus Contd
  • What is the chorion and what does it do for the
    embryo?
  • Chorion (a membrane) grows around the embryo
    after it implants in the uterine wall. It has
    many folds and projections called villi.
  • Placenta area where chorionic villi meet moms
    blood supply.
  • Blood vessels from baby lead to placenta through
    umbilical cord. Materials diffuse between mom
    and baby.

25
Life Within the Uterus Contd
  • There is no direct blood connection between mom
    and fetus. Some disease, drugs, medicines,
    bacteria, viruses can cross the placenta, some
    cannot.
  • The placenta acts like an endocrine gland too.
    Explain why?
  • It secretes the hormone HCG (Human Chorionic
    Gonadotropin) which keeps the corpus luteum
    making progesterone. Progesterone maintains the
    lining of the uterus.

26
Life Within the Uterus Contd
  • Why was your umbilical cord cut?
  • So the baby doesnt bleed through the cut blood
    vessels in the cord.
  • What comprises the afterbirth?
  • The placenta and amnion (sac of fluid around the
    baby for protection/moisture)

27
Life Within the Uterus Contd
  • Does the baby get O2 from breathing the fluid
    into its lungs?
  • No, food/waste/gas exchange occurs through the
    umbilical cord/placenta.
  • Why do they make babies cry when the are first
    born?
  • The babys lungs are filled with fluid. Making
    them cough/cry makes them expel fluid so that
    they can breathe air.

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