Prenatal

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Story

The human nest.

Prenatal development is both complicated and fast paced. In only 40 weeks, a single fertilized egg matures into a baby. We explore the question: when does life begin?

Here’s what is included in this lesson:

• Ovulation
• Fertilization
• Implantation
• Germinal stage
• Embryonic stage
• Fetal stage

Mind Map

Notes

• 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)

Terms

• 300 bones
• 70+ reflexes
• age of viability = somewhere about 6 months pregnant, fetus can survive if born
• alcohol-related neurodevelopmental disorder (ARND) = alcohol-related developmental disabilities
• amnion = fluid-filled sac that holds developing fetus
• anoxia = low oxygen; potential cause of brain damage during delivery
• Apgar Scale = evaluation of newborns on complexion, pulse, reflexes, activity & respiration
• blastocyst
• blastula
• breech position = non-head-first birth (buttocks or feet)
• cancer
• cervix
• cesarean delivery = surgical delivery of babies through abdominal wall, typically in distress
• chorion = outermost layer of an embryo, developed by follicle cells of ovary
• chromosomes
• cilia
• cleavage
• corpus luteum
• DNA
• egg
• ejaculatation
• embryo = first 8 weeks of prenatal development
• embryo stage
• enzymes
• expected date of delivery
• expel
• fallopian tube
• fallopian tube contractions
• female sex cells
• fertilization
• fertilized egg
• fetal alcohol spectrum disorder (FASD) = continuum of disorders cause by prenatal alcohol exposure
• fetal alcohol syndrome (FAS) = prenatal exposure to alcohol, leading cause of mental retardation
• fetal monitors = monitors fetal heart rate & mother’s uterine contractions
• fetal stage
• fetus = from week 8-40 of prenatal development
• fimbria
• follicle
• fraternal twins
• FSH (folicle stimulating)
• full term
• germinal stage
• hCG (human chorionic gonadotrophin)
• hormones
• human placental lactogen (HPL)
• implantation
• infant mortality = death of infant under 1 year old
• inflammation
• irregular ovulation
• lanugo = soft fine hair on fetus, normally disappears before birth
• last menses period (LMP)
• LH (luteinizing hormone)
• ligaments
• menstrual period
• morula
• natural childbirth (prepared) = 1930’s movement, noninvasive methods to reduce delivery pain
• Neonatal Behavioral Assessment Scale (NBAS) = test for infant 3 days to 4 weeks, checklist
• neural tube = develops into spinal cord and brain
• non-rapid-eye-movement (NREM) sleep = 3 sleep stages that precede REM
• ova (plural)
• ovarian stem cells
• ovaries
• ovulation
• ovum
• partial fetal alcohol syndrome (p-FAS) = prenatal alcohol exposure: CNS damage & growth deficiency
• placenta = organ that filters mother’s blood supply for developing fetus
• preterm infants
• progesterone
• rapid-eye-movement (REM) sleep = stage of sleep that includes vivid dreams & sleep paralysis
• reflex = smallest amount of behavior, sensory neuron goes to spinal cord & triggers motor neuron
• Rh factor incompatibility = can be a problem in delivery with fetus & mother’s blood come in contact
• scar tissue & cysts
• small-for-date infants = below 10th percentile in weight
• sperm
• sperm head
• sperm middle
• sperm tail
• states of arousal = levels of consciousness, including sleep
• sudden infant death syndrome (SIDS) = unexpected death of infant under age 1
• surfactant
• teratogen = any substance that interferes with embryo development
• testicles
• trimesters = 40 weeks of pregnancy divided into 3 sections
• trophoblast
• tubal ectopic pregnancy
• umbilical cord = connects fetus and placenta
• unfertilized egg
• uterine contractions
• uterus
• vagina
• vernix = vernix caseosa, white coating on newborn’s skin, waxy texture
• viability
• visual acuity = clearness, focus; newborn have limited vision
• XX
• XY
• zygote

Quiz

• 1. Which weeks are the fetal stage of development:
  • a.           1-4
  • b.           3-11
  • c.           9-40
  • d.           10-49
• 2. A solid ball of 32 cells is called a:
  • a.           ovumento
  • b.           morula
  • c.           zygote
  • d.           cilia
• 3. When is a fetus 50% viable?
  • a.           week 18
  • b.           week 24
  • c.           week 28
  • d.           week 32
• 4. If 300 million sperm enter the vagina, how many reach the ovum?
  • a.           1
  • b.           ~1000
    c.           ~10,000
  • d.           ~100,000
• 5. Typically, fertilization occurs in the:
  • a.           fallopian tube
  • b.           vagina
  • c.           uterus
  • d.           cervix

Answers

• 1. Which weeks are the fetal stage of development:
  • a.           1-4
  • b.           3-11
  • c.           9-40
  • d.           10-49
• 2. A solid ball of 32 cells is called a:
  • a.           ovumento
  • b.           morula
  • c.           zygote
  • d.           cilia
• 3. When is a fetus 50% viable?
  • a.           week 18
  • b.           week 24
  • c.           week 28
  • d.           week 32
• 4. If 300 million sperm enter the vagina, how many reach the ovum?
  • a.           1
  • b.           ~1000
    c.           ~10,000
  • d.           ~100,000
• 5. Typically, fertilization occurs in the:
  • a.           fallopian tube
  • b.           vagina
  • c.           uterus
  • d.           cervix

Summary

Bonus

Photo credit

Saga of Dave

Dave, our fictional character, does not exist…yet. When he does, there are a lot of things we are going to want to know about him. All of the following characteristics will be a part of understanding Dave.

Before we get to Dave, let’s discuss development itself. There are five things you should know.

Five Things To Remember

There are five major things we are going to look at:

• Mendel
• Dominant & Recessive Genes
• Autosomal Traits

 

Foto von Dylan Gillis auf Unsplash