The process of conception
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The process of conception

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The process of conception The process of conception Presentation Transcript

  • THE PROCESS OF CONCEPTION
  • OVA
    Released from the Graafian Follicle
    Will be surrounded by a ring of mucopolysaccharide fluid (Zonapellucida) and a circle of cells (Corona radiata)
    Zonapellucida and Corona Radiata protects the ova by serving as a buffer against injury
    Moves from the ovary to the fallopian tube through the cilia and peristaltic movement of fallopian tube
  • SPERM
    Per ejaculation, 2.5ml semen containing 50-200M spermatozoa is released (ave 400M sperm/ejaculation)
    Moves through the cervix, uterus, fallopian tube because of their flagella and uterine contractions
    Undergoes CAPACITATION (changes in the plasma membrane of the sperm head to reveal sperm binding receptor sites) before penetrating into the corona radiata
  • Sperm clusters around coronal cells
    Will release HYALURONIDASE (proteolytic enzyme) to dissolve the corona radiata
    Sperm penetrates the cell; cell membrane of ova changes composition to become impenetrable to other sperm
  • Sperm and ova fuse carrying 23 pairs of chromosomes each
    If sperm carries X sex chromosome paired with the ovum X chromosome = female zygote
    If sperm carries Y sex chromosome paired with the ovum X chromosome = male zygote
  • IMPLANTATION
    Zygote move from fallopian tube to uterus
    It will undergo series of mitotic divisions resulting to a cleavage formation, 1 in every 22 hour, with the cleavage division happening 24 hours after fertilization
    Once it reaches the uterus, zygote is now composed of 32 -50 ball of cell termed as a MORULA
  • Another 3-4 days, morula becomes a BLASTOCYST consisting of:
    An inner cell mass which will become the future embryo
    Trophoblast which will become the placenta and membranes
  • At approx 8-10 days after fertilization, blastocyst attaches to the endometrium
    Sheds off last residues of corona radiata and zonapellucida
    Brushes against endometrium (apposition) and settles down
    A slight vaginal bleeding is experienced during implantation stage because capillaries are ruptured by the implanting trophoblast cells
  • EMBRYONIC & FETAL STRUCTURES
    DECIDUA – uterus that has grown thick and vascular
    3 areas
    • Deciduabasalis – lies directly under the embryo (portion where the trophoblast establish communication with maternal blood vessel)
    • Deciduacapsularis – portion that stretches or encapsulates the surface of the trophoblast
    • Deciduavera – the remaining portion of the uterine lining
  • CHORIONIC VILLI
    • Miniature villi similar to probing fingers that appear on the 11th or 12th day
    • They begin the formation of the placenta
    • Consists of a central core of connective tissue and fetal capillaries
  • Consists of 2 layers of trophoblast cells:
    Syncytiotrophoblast(syncitial layer) – produces HCG, somatomammotropin (human placental lactogen), estrogen and progesterone
    Cytotrophoblast (middle or Langhan’s layer) – functions in early pregnancy to protect the growing embryo and fetus from infection (eg syphilis)
  • PLACENTA
    • 15-20CM IN DIAMETER, 2-3 CM DEEP, 400-600g at full term
    • Has 25-30 cotyledons (placental compartments that lie on the maternal side)
    • Has 2 sides
    • Maternal – dirty rough
    • Fetal – shiny smooth
  • FUNCTIONS:
    • Serves to conduct oxygen and nutrients for the fetus
    • Secretes endocrine hormones (syncytial cells)
    • hCG – 1st placental hormone
    - enusures corpus luteum to continuously produce progesterone and estrogen
    - supresses maternal immunologic reaction so that placental tissue is not detected and rejected as a foreign substance
  • - if fetus is male, stimulates the testes to begin producing testoterone
    - at 8 week, begins progesterone production, as a result, CL disintegrates and hCG production decreases
    • ESTROGEN (estriol) – “hormone of women”
    - contributes to mammary gland development of mother in preparation for lactation
    - stimulates uterine growth to accommodate growing fetus
    • PROGESTERONE - “Hormone for Mothers”
    - necessary to maintain endometrial lining of the uterus during pregnancy
    - reduces contractility of uterus during pregnancy preventing preterm labor
    • HUMAN PLACENTAL LACTOGEN (human chorionic somatomammotropin)
    - with both growth promoting and lactogenic (milk producing) properties
    - promotes mammary gland (breast) growth in preparation for lactation
  • - regulates maternal glucose, protein and fat levels so that adequate amounts of these are always available to the fetus
    AMNIOTIC FLUID
    • 800-1200ml
    • Slightly alkaline pH 7.2
    • Fetal urine adds to its volume
  • Functions:
    • Shields fetus against pressure or blow to the mother’s abdomen
    • Protects fetus from temperature change
    • Aids in muscular development because it allows fetus’ freedom to move
    • Protects the umbilical cord from pressure protecting fetal oxygen supply
  • Hydramnios – excessive amniotic fluid
    - more than 2000ml or pockets of fluid larger than 8cm on UTZ
    Oligohydramnios – reduction in the amount of amniotic fluid
    - less than 300ml or no pockets of fluid larger than 1 cm on UTZ
  • AMNIOTIC MEMBRANES
    • Chorionic membrane – the outermost fetal membrane; purpose is to form a sac that contains the amniotic fluid
    • Amniotic membrane – 2nd membrane lining the chorionic membrane; forms beneath the chorion
    - produces amniotic fluid
    - produces phospholipid that initiates the formation of prostaglandins which can cause uterine contractions and may be the trigger that initiates labor
  • UMBILICAL CORD
    • Formed from the amnion and chorion
    • 53cm (21 in) length; 2 cm thick
    • Wharton’s jelly – a gelatinous mucopolysaccharide that forms the bulk of the umbilical cord giving it its body; prevents pressure on the veins and arteries
    • Outer surface is covered with amniotic membrane
    • Composed of 1 vein (carrying blood from placental villi to the fetus) and 2 arteries (blood from fetus back to palcentalvilli)
    • Blood flow is 350ml/min at term
    • Walls are with smooth muscles, no nerve supply
    • Function:
    • Transports oxygen and nutrients to the fetus from placenta and return waste products from fetus to placenta