anatomy physiology mrs halkuff n.
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Anatomy & Physiology Mrs. Halkuff. Menstrual Cycle, Pregnancy, & Birth. Menstrual Cycle. A series of hormonal changes that help to prepare a woman’s body for pregnancy. Menarche : First female period that usually occurs around age 12.

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menstrual cycle
Menstrual Cycle
  • A series of hormonal changes that help to prepare a woman’s body for pregnancy.
  • Menarche: First female period that usually occurs around age 12.
  • A cycle can range from 21-45 days, with 28-32 days being the average.
  • Consists of 2 cycles:
    • Ovarian Cycle
    • Uterine Cycle
ovarian cycle
Ovarian Cycle
  • Involves changes in the ovaries
  • Can be divided into 2 phases:
    • Follicular Phase (Days 1-13)
      • First day of menstruation until ovulation.
      • Egg growth/maturation is occurring in the ovaries.
    • Luteal Phase (Days 14-28)
      • From ovulation until menstruation begins.
uterine cycle
Uterine Cycle
  • Involves changes in the uterus.
  • Occurs together with the Ovarian Cycle.
  • Can be divided into 2 phases:
    • Proliferative Phase (Days 5-14)
      • Occurs after menstruation but before ovulation
      • Endometrium rapidly grows in thickness
    • Secretory Phase (Days 14-28)
      • Occurs at ovulation if fertilization does not occur.
      • Egg & endometrium begin to break down.
  • During the first half of the menstrual cycle, as many as 20 egg follicles begin to grow in the ovaries due to Follicle Stimulating Hormone (FSH).
  • Half way through the cycle, there is a spike in the Luteinizing Hormone (LH) which signals the release of the most mature egg from the ovary. This is referred to as ovulation.
  • The remaining egg follicles undergo atresia, or cell degeneration.
  • If more than one egg follicle grows to maturity, they can also be released from ovary increasing the chance of fraternal twins or triplets.
how conception occurs
How Conception Occurs
  • Fertilization occurs when a sperm and egg unite in the fallopian tube, creating new life.
  • The female egg can only be fertilized for 12-24 hours after being released.
  • An average 300 million sperm are released in one ejaculation, however only 10,000 will reach the uterus due to the harsh acidic environment of the vagina.
  • Most sperm only survive for 12-24 in the vagina with a maximum of about 72 hours.
  • This environment is necessary to deplete a fatty covering on the sperm that will then allow the sperm to fuse with the egg.
sperm physiology
Sperm Physiology
  • To fertilize an egg, sperm must undergo a 3-step modification process.
  • Capacitation: Secretions in the female reproductive tract modify the sperm’s membrane to allow it to fertilize the egg.
  • Hyperactivation: They become better, more efficient swimmers.
  • Acrosome Reaction: The acrosome creates an enzyme reaction with the egg’s zonapellucida, weakening it and allowing entry.
  • Once a sperm(X or Y) has penetrated the egg (X), a chemical reaction takes place within the egg making it impossible for another sperm to enter.
  • Almost immediately the nuclei of the sperm and egg fuse to produce a diploid zygote containing genetic material from both mother and father.
  • The sex of the fetus is determined at this point.
    • If an X sperm meets the X egg = girl (XX)
    • If a Y sperm meets the X egg = boy (XY)
  • The fertilized egg will make its way to the uterus where it will implant.
  • It takes roughly 7 days for the fertilized egg (blastocyst) to travel and implant.
  • Occasionally a fertilized, dividing egg will attach to the lining of the fallopian tube. This is called an ectopic pregnancy.
  • This type of pregnancy must be terminated for the safety of the mother. The fallopian tube is not elastic and the growing blastocyst will rupture the tube.
  • A typical pregnancy lasts approximately 40 weeks (280 days)
  • These 40 weeks are broken up into trimesters:
    • 1st Trimester: Weeks 1-14
    • 2nd Trimester: Weeks 14-27
    • 3rd Trimester: Weeks 27-40
embryonic development
Embryonic Development
  • Fertilized egg is called an embryo until 8 weeks after fertilization.
fetal development
Fetal Development
  • From weeks 10-40, the baby is termed a fetus.
birth parturition
Birth (Parturition)
  • 3 Stages

1. Shortening/dilation of cervix

2. Descent/birth of infant

3. Delivery of placenta

labor stage 1 effacement dilation
Labor Stage 1: Effacement & Dilation
  • As baby moves down, cervix thins (effaces).
    • Given as a percentage (75% effaced).
  • Cervix begins to open (dilates).
    • Assigned a number 1-10
labor stage 2 fetal expulsion
Labor Stage 2: Fetal Expulsion
  • Cervix must be fully dilated to 10 cm.
  • Mother is pushing
  • Baby’s head is crowning
  • Baby has large head and shoulders and must maneuver out in a specific pattern of rotation:
labor stage 3 umbilical cord clamped placenta expulsion
Labor Stage 3: Umbilical Cord Clamped & Placenta Expulsion
  • Typically the umbilical cord is clamped & cut in the first 3 minutes of birth.
  • The placenta is delivered 15-30 minutes after birth.