Top

Day 4 Notes: Prenatal

June 20, 2013 by  

prenatal exam

Prenatal

Prenatal development includes understanding the components (egg & sperm) and the processes (fertilization & implantation). It also raises the issue of when life begins.

Let’s try to make an outline:

  • Female sex cells
    • Eggs & Ovaries
    • Left & right
    • Attached to uterus by ligaments
      • Not attached to fallopian tubes
    • 250k cells in each at birth
      • Limited supply
      • Ovarian stem cells add more
  • Classic Example
    • Hormones stimulate monthly
      • FSH (folicle stimulating)
      • LH (luteinizing hormone)
    • One ovary ovulates
      • Randomly left or right
    • Release one egg
    • Follicle swells with fluid
    • Follicle erupts
    • Mature egg pushed thru wall
      • Fluid & cell
    • Fallopian tube fimbria (fringe)
      • Fill with blood
      • Brushes egg into tube
    • Fallopian tube contractions move egg along toward uterus
    • If unfertilized, egg moves to uterus, expelled
    • If fertilized, egg moves to uterus
      • Subdividing as it goes
      • Implanted
  • In real life
    • Can release more than one egg
      • Fraternal twins
      • Each can have its own Dad
    • Ovulate with no menstrual period
      • Can ovulate but no egg
    • Irregular ovulation
    • Normal cycle varies between folk
      • 21-35 days typical
    • Normal cycle can vary in you
    • Pain when ovulation begins
    • Pain when egg pushed out
    • Pain from fallopian contractions
    • Pain from uterine contractions
  • Ovum (ova is plural)
    • Grain of sand
    • 23 chromosomes
    • 22 match 22 of men
    • 23rd is X chromosome
  • Male sex cells
    • Testicles
    • Outside ovaries
    • Sperm factories
  • Sperm
    • Produced daily
    • Kept alive by nurse cells
    • Takes 2-3 months to mature
    • Stored for release
    • Die daily
    • 23 chromosomes
      • 22 match the 22 of women
      • 23rd determines sex
        • X or Y
        • Girl (XX) or boy (XY)
    • 3 parts
      • Head; covered with enzymes
      • Middle (connector)
      • Tail
  • Process
    • Sperm ejaculate 300 million
    • Enter vagina
    • 20% die immediately
    • Can live 4-5 days
    • 10% make it through cervix; 3 million
    • Must swim upstream
    • Go to correct fallopian tube
  • Fallopian tubes
    • About width of pencil
    • Collect & transport zygote
    • Go from ovary to uterus
    • Long, thin tubes
    • 2 (left & right)
  • Fimbria = fringe
    • collection end of tube
    • finger-like projections
    • actively go and get egg
  • Cilia = tiny hair-like fibers
    • “feed” it into fallopian tube
  • Problems:
    • tubal ectopic pregnancies
    • inflammation (infection)
    • cancer (extremely rare)
    • scar tissue (adhesions)
    • cysts
    • fertilization occurs in fallopian tube
  • Classic Example
    • Good swimmers
    • 1000 reach ovum
    • 1 binds with egg
    • Penetrates egg
    • Swells in size
    • Releases DNA
    • Chromosomes line up
    • Pairs connect
    • Dominant-recessive
    • Unique combinations
    • Takes 24 hours
  • Germinal Stage Week 1 & 2
    • Week 1
    • Fertilization to implantation
    • Zygote = 1 fertilized egg
      • Surrounded by plasma membrane
      • Mother’s body changes
      • Uterine lining is developing
    • Cleavage
      • partitions zygote into 2 cells
      • 30 hours after fertilization
    • Zygote remains the same size
      • Component cells are smaller
    • Morula
      • Solid ball of 32 cells
      • Day 4-5 but still same size
    • Blastula
      • Same size as original cell
      • Hollow ball of 250+ cells
      • Filled with fluid
      • 2 layers
        • Inner layer = blastocyst
          • becomes embryo
        • Outer layer = trophoblast
          • attaches itself to uterine wall = implantation
    • Implantation
      • Blastula arrives at uterus
  • Day 7-8
    • Stays in uterus a couple of days
    • Imbeds itself in uterine wall
  • Day 11-14
    • Blastula secretes hormones
    • hCG (human chorionic gonadotrophin)
    • Maintains corpus luteum
    • Corpus luteum secretes progesterone for 1st trimester
      • human placental lactogen (HPL)
    • Anti-insulin properties
    • Facilitates fetus’ energy supply
    • Mother may notice missed period
    • Conception = fertilization or implantation?
  • Embryo Stage Week 3-8
  • Fetal Stage Week 9-39
    • Week 24 (6 months)
      • 50% viability
      • Lungs produce surfactant
      • Surfactant
        • keeps lungs air sacs from collapsing when we exhale
    • Week 26-27 (3rd trimester)
      • 85% viability
      • 1.5-2 pounds, 10 inches
    • Week 28 (7 months)
      • Brain surface is wrinkled
      • Breathing & body temp controlled by brain
    • Week 32 (8 months
      • Eyes open when alert
      • Closed when sleeping
      • Eye color is blue
        • regardless of permanent color
        • requires exposure to light
    • Week 39-40
      • 98% viability
      • Expected date of delivery
      • 280 days from last menses period (LMP)
      • 8 pounds, 20 inches
    • Week 40-42
      • full term
      • 70+ reflexes
      • has 300 bones
      • adults have 206 (some fuse together)

 

 

Comments

2 Responses to “Day 4 Notes: Prenatal”

  1. Shawn Gibbons on May 16th, 2014 7:47 pm

    Does fertilization occur in the Fallopian tube or in the uterus?

  2. Developmental on May 16th, 2014 8:14 pm

    Usually fertilization occurs in the Fallopian tube, at the bend where it goes from the wide fimbria region to the narrower tube. It takes about a week for the fertilized egg to reach the uterus where it becomes implanted. Conception can be defined either as fertilization or implantation; both are necessary but not sufficient for survival.

Feel free to leave a comment...
and oh, if you want a pic to show with your comment, go get a gravatar!





Bottom