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Human Reproduction

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Title: Human Reproduction


1
Human Reproduction
2
Human Reproduction
3
Human Reproduction
  • Male Reproductive Anatomy
  • Spermatogenesis and Male Hormones
  • Male Reproductive Technologies and Birth Control
  • Female Reproductive Anatomy
  • Oogenesis and Female Hormones
  • Uterine and Ovarian Cycles
  • Development of the Fetus
  • Parturition and Lactation
  • Teratogens and Birth Defects
  • Reproductive Technologies

4
Human Reproduction
5
Reproduction
  • ensures the survival of a species
  • Sexual reproduction produces offspring with new
    and unique characteristics that may increase
    their chance of survival.

6
Reproduction
  • 2 types of gametes (sex cells)
  • Males 1 billion sperm each day from the ages
    13-90
  • Females born with 400, 000 eggs, 400 mature
    from ages 12 to 50

7
Reproduction
  • The average gestational period for a human is 266
    days.

8
Male Reproductive System
  • The male reproductive structures are responsible
    for
  • producing sperm
  • storing sperm
  • delivering sperm
  • to the female

9
Male Reproductive System
10
Male Reproductive System
  • Scrotum
  • holds the testes away from the body to keep them
    cool.
  • Sperm production only occurs at temperatures
    about 3 degrees below body temperature.

11
Male Reproductive System
  • Testis
  • descend about 2 months before birth
  • spermatogenesis
  • seminiferous tubule that produce sperm

12
Male Reproductive System
  • Epididymis holds sperm for about 2-4 days while
    they mature

13
Male Reproductive System
  • Vas Deferens
  • conducts sperm during ejaculation
  • vasectomy the vas deferens cut and tied off, to
    prevent conduction of sperm.

14
Male Reproductive System
  • Ejaculatory Duct propels semen and sperm through
    the urethra.
  • Urethra conduction of urine and semen out of the
    penis.
  • a sphincter muscle closes off the bladder,
    preventing urine from exiting the urethra.

15
Male Reproductive System
  • Penis
  • male organ for copulation. Beneath the skin,
    lies the urethra surrounded by spongy protective
    tissue that expands to form the glans penis.
  • Prepuce (foreskin) is a loose sheath of skin
    covering the glans penis of uncircumcised males.
    The foreskin produces an oily secretion known as
    smegma.

16
Seminal Fluid
  • Is produced by three different glands
  • Seminal Vesicles
  • fluid high in fructose that provides energy sperm
    need to swim
  • Prostaglandins which cause contractions of
    muscles in the female reproductive tract to help
    move sperm in

17
Seminal Fluid
  • Prostate Gland
  • milky white alkaline fluid that neutralizes the
    acidity of the vagina
  • Cowpers Gland
  • buffered fluid that cleanses and neutralizes the
    acidity in the urethra

18
Spermatogenesis
  • Spermatozoa are the smallest cells in the body.
    They have very little cytoplasm in the head, and
    a large tail (flagellum).

19
Spermatogenesis
  • Spermatogonia undifferentiated germ cells that
    have 46 chromosomes
  • Primary Spermatocytes larger cells that undergo
    meiosis I

20
  • Secondary spermatocytes cells that undergo
    meiosis II
  • Spermatids cells with 23 chromosomes, that are
    ready to mature in the epididymis
  • Spermatozoa mature sperm cells

21
  • Sertoli Cells- nourish sperm cells

22
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23
Terminology
  • Erection
  • parasympathetic nerve impulses dilate the
    arteries of the penis, allowing blood to flow
    rapidly into the highly vascular penile tissue
  • veins are compressed preventing blood from
    leaving the penis.

24
Terminology
  • Ejaculation occurs when sexual stimulation
    forces semen to the urethra, where rhythmical
    muscle contractions cause the semen to be
    expelled from the penis.
  • Infertility the inability to produce viable
    sperm.
  • Impotency the inability to achieve a sustained
    erection.

25
Regulation of the Male Reproductive Hormones
26
Male Reproductive Hormones
  • GnRH gonadotropic releasing hormone
  • released from hypothalamus
  • stimulates the anterior pituitary to release LH
    and FSH
  • LH luteinizing hormone
  • stimulates the interstitial cells (cells in
    between seminiferous tubules) of the testes to
    produce testosterone

27
Male Reproductive Hormones
  • Testosterone responsible for male secondary sex
    characteristics, required for sperm production
  • FSH follicle stimulating hormone
  • stimulates production of sperm in the
    seminiferous tubules

28
Male Reproductive Hormones
  • Inhibin
  • produced by Sertoli cells when sperm count is
    high
  • Sends feedback to inhibit FSH and GnRH

29
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30
Female Reproductive Structures
  • The female reproductive structures are
    responsible for
  • reception of sperm
  • producing an egg
  • nourishing and protecting the fetus
  • delivering the baby

31
Female Reproductive Structures
32
Female External Structures (Vulva)
  • Labia majora large, fatty, hair covered folds
    that protect the genitals
  • Labia minora smaller folds of skin inside the
    labia that are kept moist by secretions
  • Clitoris small shaft of erectile tissue

33
Female Internal Structures
  • Vagina
  • intercourse accepts the penis
  • birth canal during labor
  • pH is generally acidic

34
Female Internal Structures
  • Cervix
  • Thick muscular tissue
  • plugs closed with mucous during pregnancy
  • prevents material from getting into the uterus,
    and holds the baby in

35
Female Internal Structures
  • Uterus (womb)
  • pear shaped muscular organ (5 cm wide)
  • houses the developing fetus during pregnancy (30
    cm wide)
  • strong contractions help push the baby out during
    birth

36
Female Internal Structures
  • Ovaries
  • produce the ovum from follicles found in the
    outer cortex

37
Female Internal Structures
  • Oviducts /Fallopian tubes
  • conduction of the ovum (egg) from the ovaries to
    the uterus
  • where fertilization usually takes place
  • If egg implants here ectopic pregnancy
  • frequency

38
Female Internal Structures
  • Fimbriae
  • small fingerlike projections at the ends of the
    oviducts that sweep to draw the egg into the
    fallopian tube

39
Female Internal Structures
40
Ovarian Structures
  • Follicle
  • cells that support and protect the ovum
  • secrete estrogen to mature the ovum
  • become a corpus luteum following ovulation.
  • Ovum egg cell, viable for about 24 hours after
    release.

41
Ovarian Structures
  • Corpus Luteum
  • cells remaining after a follicle has ruptured
    during ovulation
  • secretes progesterone and some estrogen for about
    3 months if fertilization and pregnancy occurs
  • deteriorates after about 14 days if fertilization
    does not occur.

42
Oogenesis
43
Regulation of the Female Reproductive Hormones
  • GnRH stimulates the anterior pituitary to
    produce FSH and LH
  • FSH stimulates development of the follicle and
    the production of estrogen within the ovary

44
Regulation of the Female Reproductive Hormones
  • LH causes ovulation, development of the corpus
    luteum which secretes progesterone

45
Reproductive Hormones
  • Estrogen
  • secreted by the follicles in the ovaries
  • causes maturation of the egg
  • stimulates growth of the endometrium (uterus
    lining)
  • Female secondary sex characteristics
  • Inhibits FSH

46
Reproductive Hormones
  • Progesterone
  • secreted by the corpus luteum
  • continues preparation of endometrium
  • inhibits both FSH and LH to prevent ovulation
  • prevents uterine contractions
  • firms the cervix

47
P 525 Fig 6
48
The Uterine and Ovarian Cycles
49
  • Day 1-5 Menstruation/Flow Phase
  • Estrogen and progesterone levels are low
  • endometrium is sloughed off and shed
  • Day 1-13 Follicular Phase
  • FSH secreted from ant. pit. promotes development
    of the follicle
  • follicle releases estrogen, which promotes growth
    of the endometrium.

50
  • Day 14 Ovulation
  • An increase in LH causes the ovum to be released
  • FSH is lowered
  • Day 15 28 Luteal Phase
  • LH promotes formation of the corpus luteum
  • corpus luteum produces progesterone, inhibits
    GnRH, LH and FSH, preventing subsequent
    ovulation.

51
  • Many birth control pills are high in progesterone
    which prevents ovulation
  • cancer

52
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53
  • No Fertilization ? corpus luteum degenerates,
    estrogen and progesterone levels drop, and
    menstruation occurs.

54
The Uterine Cycle
  • Menstrualcycle

55
Fertilization
  • Fertilization
  • -union of sperm and secondary oocyte in the
    fallopian tube
  • Only one spermatozoa will fertilize an egg
  • Now called a zygote
  • fertilization

56
Early Embryonic Development
  • Zygote fertilized egg, divides by cleavage,
    mitosis with no increase in size
  • 36 hours 1st division (2 cells)
  • 60hours 4 cells
  • 72h 8 cells
  • Morula solid ball of cells the same size as the
    fertilized egg (day4-5)

57
Early Embryonic Development
  • Blastocyst
  • hollow ball of cells filled with fluid,
  • outer layer forms the chorion, inner layer forms
    the embryo
  • Implants day 7-10

58
Early Embryonic Development
59
Implantation
  • embryo embeds itself in the endometrium.
  • produces HCG (human chorionic gonadotropic
    hormone) maintains the corpus luteum for about
    2-3 months.
  • Reminder corpus luteum produces progesterone and
    estrogen to maintain the endometrium and prevent
    ovulation)

60
  • HCG detected in blood or urine with a pregnancy
    test
  • hCG Pregnancy Test ELISA

61
Early Embryonic Development
  • Gastrula
  • the blastocyst pushes in (invaginates) and forms
    the 3 primary germ layers
  • the hollow space forms a primitive gut
  • 2nd week

62
Gastrulation
63
Germ Layers
  • Ectoderm nervous system and epidermis of the
    skin
  • (hair, nails,retina, lens, inner ear, lining of
    the nose, mouth, anus and tooth enamel)
  • Neurula- notochord/neural tube forms from the
    ectoderm layer (forms in 3rd to 4th week)

64
Germ Layers
65
Germ Layers
  • Mesoderm skeleton, muscles, reproductive organs
  • (connective tissue,cartilage, blood, blood
    vessels, kidneys)
  • Endoderm lining of the digestive and respiratory
    system, endocrine glands
  • (trachea, bronchi, lungs, gallbladder, urethra,
    liver, pancreas, thyroid,bladder)

66
  • Gastrulation
  • Embryonic development

67
Embryo at 4 weeks
68
Extra Embryonic Membranes
  • Amnion inner membrane filled with fluid to
    provide protection, maintain temperature,
    swallowing
  • Chorion-outer membrane, contributes to placenta
  • Extraembryonic coelom fluid filled space
    between amnion and chorion

69
Extra Embryonic Membranes
  • Allantois collects nitrogenous wastes and forms
    the umbilical blood vessels
  • Yolk Sac surrounds embryo, first site of blood
    cell formation, becomes part of the primitive gut

70
Extra Embryonic Membranes
  • Placenta
  • forms around the fetus
  • exchange of gases, delivery of nutrients and
    removal of wastes for the fetus

71
Extra Embryonic Membranes
  • no blood shared between the mother and the fetus
  • Produces progesterone and estrogen at about 4
    months

72
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73
How Old Are You?
  • Gestational age
  • -calculated from the first day of the mothers
    last menstrual period.
  • length of pregnancy is 40 weeks

74
How Old Are You?
  • Fertilization age actual age of the fetus
  • - estimated to be about two weeks after the date
    of the last menstrual period.
  • To calculate due date LMP 3 months 7 days
  • calculator

75
  • Weeks 1 -9

76
Trimesters
  • 1rst until end of third month
  • 2nd 4-6months
  • 3rd 7-9 months

77
Developmental Milestones
  • 1 week fertilization, cleavage, blastocyst
  • 2 weeks implantation, chorion secretes HCG, 3
    germ layers form

78
Developmental Milestones
  • 3 weeks nervous system is evident, heart begins
    to form (2 tubes), heart beats around day 22
  • 4-5 weeks limb buds appear, eyes, ears and nose
    develop, umbilical cord is attached to placenta

79
Developmental Milestones
  • 6-8 weeks fetus is recognizable as a human, all
    organ system are developed, reflexes begin (size
    1.5, 0.5 g)
  • 8th week fetus

80
  • 9-16 weeks heartbeat is audible with a
    stethoscope, bone replaces cartilage, eyelashes
    formed, fetus can suck and swallow (size 6,
    0.5 lb)

81
Developmental Milestones
  • 17-28 weeks movement is felt by mother, eyelids
    open (size 12, 3lb)
  • Week 25 premature baby has 50 chance of survival

82
Developmental Milestones
  • 32 weeks fetus moves to head down position and
    lungs mature
  • (good survival rate if born)

83
Developmental Milestones
  • after about 32 weeks significant weight gain
  • 40 weeks full term (size 21, 7.5 lbs)
  • See summary chart on page 534

84
Developmental Milestones
85
Virtual Development
  • Conception to Birth
  • Visible Embryo

86
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87
Teratogens
  • Teratogens - chemical substances or infections
    that cause specific birth defects

88
Teratogens
-Thalidomide-prescribed for morning sickness in
the late 50s and early 60s -rubella during the
first 12 weeks of pregnancy eye problems,
hearing problems and heart damage.
89
Parturition Birth
  • Hormones
  • -relaxin made by placenta, loosens pelvis
    ligaments
  • -prostaglandins contractions
  • -oxytocin from Post. Pit - contractions

90
Parturition
  • Stage 1 dilation and effacement(thinning) of
    the cervix, mucous plug dislodges, uterine
    contractions open the cervix
  • Stage 2 delivery of the baby, cervix is dilated
    to about 10 cm, intense contractions every 1-2
    min push the baby down the birth canal
  • Stage 3 delivery of the placenta

91
Parturition
  • The average labor lasts about 12 hours, but can
    range from 1 hour to 36 hours.
  • caesarean section may be required.
  • involves removing the baby from an incision in
    the front of the abdomen.

92
Lactation
  • prolactin stimulates the glandular tissue in the
    breasts to produce fluids, colostrum, and milk.
  • Colostrum is a rich fluid containing mostly sugar
    and proteins. This first milk is believed to
    play a role in early immunity.

93
Lactation
  • Regular suckling stimulates the pituitary gland
    to release oxytocin
  • causes weak uterine contractions to return it to
    its pre pregnancy shape
  • causes let down of milk
  • 1.5 L of milk each day

94
Reproductive Technologies and Health
  • Pap Smear a sample of cervical cells are taken
    and examined for abnormal growth (cancer)
  • Ultrasound uses sound waves to view the baby in
    the womb
  • Ultrasound Scan Fetal Video Clips

95
Reproductive Technologies and Health
  • Amniocentesis sampling of the cells from the
    amniotic fluid at about 16 weeks to check for
    genetic abnormalities
  • Amniocentesis Flash Animation

96
Reproductive Technologies and Health
  • Chorionic Villus Sampling sampling of cells
    from the chorion at about 5 weeks to check for
    genetic abnormalities
  • http//www.pbs.org/wgbh/nova/miracle/windows.html

97
Fertility Technologies
  • IVF in vitro (in glass) fertilization
    fertilizing the egg in a petri dish, and
    implanting the embryo 2-4 days later
  • Life Changine Science - Program 3 IVF
  • AID artificial insemination by donor, sperm is
    artificially placed in the vagina.

98
Fertility Technologies
  • Egg Screening testing and selecting eggs to be
    fertilized, fertility drugs produce eggs that are
    collected using a needle biopsy
  • TSE testicular sperm extraction
  • removal of sperm via biopsy (not ejaculation)
  • ICSI intracytoplasmic sperm injection
  • sperm head is injected directly into the egg

99
Fertility Technologies
  • GIFT gamete intra-fallopian transfer
  • sperm and egg are transferred to the fallopian
    tube for fertilization
  • AH assisted hatching
  • a chemical solution is dripped over the egg to
    allow the sperm to penetrate more easily

100
Fertility Technologies
  • Embryo Transfer implantation of an embryo (at
    blastocyst stage) into the womb or fallopian
    tube, may be frozen or unfrozen
  • Fertility Drugs induce ovulation, usually many
    ova are produced at one time, often results in
    multiples

101
Fertility Technologies
102
Human Reproduction
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