Human Reproduction

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Human Reproduction
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Human Reproduction
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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

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Human Reproduction
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Reproduction

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

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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

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Reproduction

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

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Male Reproductive System

• The male reproductive structures are responsible
  for
• producing sperm
• storing sperm
• delivering sperm
• to the female

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Male Reproductive System
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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.

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Male Reproductive System

• Testis
• descend about 2 months before birth
• spermatogenesis
• seminiferous tubule that produce sperm

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Male Reproductive System

• Epididymis holds sperm for about 2-4 days while
  they mature

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Male Reproductive System

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

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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.

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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.

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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

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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

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Spermatogenesis

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

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Spermatogenesis

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

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

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• Sertoli Cells- nourish sperm cells

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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.

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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.

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Regulation of the Male Reproductive Hormones
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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

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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

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Male Reproductive Hormones

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

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Female Reproductive Structures

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

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Female Reproductive Structures
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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

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Female Internal Structures

• Vagina
• intercourse accepts the penis
• birth canal during labor
• pH is generally acidic

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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

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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

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Female Internal Structures

• Ovaries
• produce the ovum from follicles found in the
  outer cortex

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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

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Female Internal Structures

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

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Female Internal Structures
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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.

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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.

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Oogenesis
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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

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Regulation of the Female Reproductive Hormones

• LH causes ovulation, development of the corpus
  luteum which secretes progesterone

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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

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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

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P 525 Fig 6
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The Uterine and Ovarian Cycles
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• 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.

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• 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.

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

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

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The Uterine Cycle

• Menstrualcycle

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Fertilization

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

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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)

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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

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Early Embryonic Development
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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)

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

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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

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Gastrulation
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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)

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Germ Layers
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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)

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• Gastrulation
• Embryonic development

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Embryo at 4 weeks
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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

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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

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Extra Embryonic Membranes

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

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Extra Embryonic Membranes

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

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How Old Are You?

• Gestational age
• -calculated from the first day of the mothers
  last menstrual period.
• length of pregnancy is 40 weeks

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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

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• Weeks 1 -9

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Trimesters

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

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Developmental Milestones

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

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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

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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

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

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Developmental Milestones

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

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Developmental Milestones

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

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Developmental Milestones

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

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Developmental Milestones
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Virtual Development

• Conception to Birth
• Visible Embryo

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Teratogens

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

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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.
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Parturition Birth

• Hormones
• -relaxin made by placenta, loosens pelvis
  ligaments
• -prostaglandins contractions
• -oxytocin from Post. Pit - contractions

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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

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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.

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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.

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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

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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

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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

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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

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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.

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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

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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

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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

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Fertility Technologies
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Human Reproduction