Fetal Development Flashcards
Pre-embryonic
Fertilization - 2 weeks
Embryo
2-8 weeks gestational age
Fetus
8 weeks to birth
8 weeks - extremities
Neonate
Birth to 2 months of age
Infant
3 weeks to 12 months of age
Menstrual age
Age counted from date of mothers last period - full term is 40 weeks
Gestational age
Age counted from the time of fertilization (mid cycle of mother)
Full term is 38 weeks
Full term
range of 38-42 weeks
premature is 36 weeks
Chronological age
Begins at time of birth
vs. adjusted age
First month of fertilization
Moves down fallopian tubes
Mitosis
Trophoblast
Blastocyst
First month of fertilization - day 4
Arrives in uterus
First month of fertilization - day 14
implants onto wall of uterus- embryo stage week 2-8
First month of fertilization - week 2.5
Neural plate - beginning of CNS
Primitive placenta has formed
Heart - paired heart tubes bulge into midline, become a single tube in coelom
First system to develop in the embryo
heart
Critical period of heart development is day 20-50 after fertilization
First month of fertilization - week 3.5
Neural groove - closes except for neuropores
First month of fertilization - week 4
Length
Head region
Brain and spinal cord
Length = 1/5 in Head differentiated and 1/3 of length Brain and spinal cord are developing Rudimentary eyes, ears, and nose Body with head, trunk, tail Heart Branchial (gill) arches - give rise to mandible, hyoid, larynx Arm buds Initial brain development
Week 5
1/2 in long Head is more erect Fingers visible Placenta developing Umbilical cord Hear differentiating with atria and ventricles
Week 6
Cerebrum makes curve in the forehead, development of hemispheres Hands develop fingers Heart and liver separated by diaphragm Liver is now producing blood cells Two vertebral arteries No vertebrae Deciduous teeth developing
Somite
will end up being a nerve root
Week 8
Length 1-1.6 in
Weight 2/3 ounce
All adult parts and organs become function
Eyelids forming, ears take shape, pigment in eyes, cartilage for skeleton
Startle reflex
Week 9
Amniotic sac
Muscle movement in mouth and jaw
Muscles in UE and LE respond to tactile stimulation
Week 11-12 = third month
length - 2.4 to 3 in
Weight 3/4 ounce
Inc activity, primitive reflexes noted (grasp)
Heart is complete
Lips open and close, head turns, forehead wrinkles
yolk sac will soon loosen all blood produced by liver and spleen
Bones - shaft of limb bones are ossified
Week 12 - 13 - end of first trimester
All major systems are developed
Umbilical cord and amniotic sac established for nourishment
Determine sex between 12-20 weeks
Isolated movement of hand to mouth and above head
Production of urine
Week 13-14 month 4
Mother begins to feel movement
Isolated elbow flex/ext, finger flex/ext, LE reciprocal movement
Bone development continues
Foot/hand development
6 week - hand further developed than foot
11 week - nail beds and AROM
5 month - complete
Week 16
Length 6 in Weight 4 ounces Finger prints appear Weak thumb suck Ears stand out from head
Month 5
First sigh Touches foot, isolated finger movement Turns and moves Swallows, hiccups Sleep/wake cycle Stronger suck Heart beat regular Lanugo, groove in fat layer protecting skin Vestibulocochlear system myelinated
Week 22
initial myelination of CNS and PNS
Month 6
Length 10-12 in Weight 2 pounds hair grows thicker Hears in utero Sx fetal distress if HR doesn't inc to noise End of 2nd trimester
25 weeks of gestation
the child is viable to live outside of the womb
Prematurity - appearance
Global hypotonia
Extremities in ext, abd, versus midline flexion (lack of muscle tone)
Minimal random movements
Prematurity - medically unstable
Temp regulation and resp problems
Complications - BPD, hyaline membrane disease, IVH
Feeding problems
Week 26-30
Dislike bright lights
Length 16 in
Weight 2.5 lbs
Week 26-30 premature
Primitive reflexes seen: rooting, suck/swllow, moro, crossed extension, flexor withdrawal, plantar grasp
Suck/swallow present but safe nippling wont occur until weeks 33-35 when coordinated gag reflex stronger
Week 32-36 in utero
Strong growth phase
Getal movement begins to slow
Turns head to diffuse light
Reflexes = galant, neonatal NOB, BOB, positive support, stepping
Week 32 premature
More pronouced state differentiation Mvt dominated by trunk will creep in isolette Dec in clonic mvt Attempt hand to mouth and erect head Dec in hip hypotonia
Week 36 premature
Vigorous sustained cry
Inc in co-contraction of muscles
UE and trunk more hypotonic than LE
Week 38-40 full term
State cycles
Brain
Reflexes
Organized state cycles of active, quiet, transitional
Brain is 25% of adult wt and size
Brain cells and synapses will be selectively eliminated with age
No myelinated fibers extend to cerebral cortex
PNS not myelinated
Reflexes DTR, superficial skin reflexes
Week 38-40 premature
Improved state differentiation
More organized spontaneous movement
Tone is normalizing but still less than full term, more ROM, poorer flex/ext balance of head and neck
More reactive startle, tremore, brisk reflexes
Factors that effect development
Teratogen - causes or mechanisms and patterns of abnormal development
20% of deaths in N America caused by birth defects
Genetic
Environmental
Genetic causes
Huntington - breakdown of brain cells
Sickle cell anemia
Muscular dystrophy
Chromososomal disorders
Environmental causes
Drugs
Chemicals
Organic mercury
Lead
Polychlorinated biphenyls
Infections
Rubella Cytomegalovirus Herpes simplex virus Varicella HIV Toxoplasmosis Listeria Congenital syphillis
Maternal factors
Maternal health Maternal age SES Rh blood compatibility Uncontrolled diabetes PKU
Non-teratogenic agents
Non-ionizing radiation - microwave ovens, UV light
Prenatal vitamins
Critical times - CNS
Week 3-5
Critical times - Heart
Week 3-6
Critical times - UE and LE
Weeks 4-8
Critical times - Eyes
Week 4-8
Critical times - Ears
Week 4 -12
Critical times - teeth and palate
Weeks 6-12
