Fetal Development Flashcards
Pre-Embyronic
the first 2 weeks of life
from fertilization to 2 weeks
Embryo
2-8 weeks gestational age
heart development occurs now
Fetus
8 weeks to birth
now begins to look like a person
Neonate
from birth to 2 months of age
newborn
Infant
3 weeks to 12 months
Menstrual age
age of fetus counted from date of mother’s last period
full term is 40 weeks
gestational age
age counted from time of fertilization (mid-cycle) full term is 38 weeks 2 weeks later than menstrual age more commonly used age for child/fetus starts at mom's mid-cycle
Full term
range from 38-42 weeks
Chronological age
begins at time of birth
different expectations for motor development if born early
subtract number of weeks born early
vs adjusted age
if a baby is premature, they were born ___ weeks early or sooner?
36
What occurs during the first month of fertilization?
moves down fallopian tubes: mitosis, trophoblast, blastocyst
day 4: arrives in uterus
day 14: implants. Embryo stage weeks 2-8
What occurs during week 2.5 of development? (2 things)
Neural plate begins to form (beginning of the CNS)
- anterior neuropore = brain
- posterior = end of SC
Primitive placenta has now formed
What occurs during week 2.5 during days 20-24?
the heart begins to form.
- blood vessels come together to form the heart tube. Folding forms the chambers of the heart
Week 3
cell layer stuff
ectoderm, mesoderm etc
Week 3.5 (neural groove)
closes except for the neuropores
Week 4 (length, head, brain, sc)
length = 1/5th of an inch
head region is differentiated and is 1/3rd of length
brain and SC are developing
early stage (rudimentary) eyes, ears, and nose
week 4 (body, arms, etc)
body with head, trunk, tail heart branchial (gill) arches -- will form neck and facial anatomy arm buds initial brain development
Week 5 (length, cord, etc)
1/2 inch long head is more erect fingers are visible placenta is developming umbilical cord heart differentiating with atria and ventricles
Week 5-6 what occurs with brain?
cerebral hemispheres develop
week 6 hands, heart, liver
hands develop fingers
heart and liver separated by diaphragm
liver now produces blood cells
week 6: how many arteries?
two vertebral arteries
week 6: vertebrae present?
no
week 6:
deciduous teeth form
What are somites and when do they form?
week 6
develop on either sides of vertebral column
somite = nerve root
nerve, artery, vein and muscle tissue form from the somite
length of fetus at week 8
1-1.6 inches
weight of fetus at week 8
2/3 of an ounce
when are all adult body parts and organs functional and present?
week 8
week 8
startle reflex now noted! fetus now responds to stimuli, meaning the CNS is working
eyelids form, ears take shape, pigment in eyes, cartilage for skeleton
when does the first response via kicking in the legs occur?
week 9
what is special about week 9
more movement starts to occur
muscle movement in mouth and jaw
muscles in UE and LE respond to tactile stimulation
when is heart growth complete?
week 11-12
when do early stages of ossification occur?
week 11-12
week 11-12
heart is now functioning
primitive reflexes occur - grasp
shaft of limb bones are ossified
what is the VIP thing that occurs at week 12-13?
isolated movement of the hand to mouth and above the head – turning of head
week 12-13 (end of 1st trimester)
all major systems are developed umbilical cord and amniotic sac are established for nourishment determine sex btwn 12-20 weeks isolated mvmt production of urine
week 13-14 (month 4)
mother begins to feel movement (for sure by 16 weeks)
isolated elbow flex/ext, finger flex/ext, LE reciprocal movement
bone development continues
mass pattern movement
entire extremity moves within all of a certain movement
all flexion
isolated movement
requires coordination and motor control
- maintain shoulder flexion, isolate wrist extension
- isolate movement to one joint while stabilizing other joints – motor control!!!
at 6 weeks, which is more developed, the hand or the foot?
hand
at 11 weeks, describe hand development
nail beds are developed and hand has AROM
when is hand/foot development complete?
5 months
Week 16
length = 16" weight = 4 ounces finger prints appear weak thumb suck (prepares muscles for breastfeeding) ears stand out from head
Month 5
first sigh touches feet, isolated finger movement turns and moves swallows amniotic fluid, hiccups sleep/wake cycle stronger suck heart beat regular eyebrows vestibulocochlear system is myelinated human-like behaviors
what is the importance of the sleep/wake cycle?
gives brain time to interpret information and to rest
VIP to have this
month 5
What is the importance of the vestibulocochlear system?
balance without visual input
VIP as an infant to learn to move against gravity
if you don’t know how to hold your body upright against gravity, you won’t be able to crawl, walk, sit, etc
blind babies rely completely on this system
When is the end of the second trimester?
week 25
when does the initial myelination of the CNS and PNS occur?
week 22
week 22-25 (month 6)
length 10-12”
weight = 2 lbs
hair grows thicker
hears in utero and can diagnose fetal distress if HR does not increase in response to noises
What is important about the end of the second trimester? (week 25)
baby is now viable to live outside the room with medical science due to artificial respiration and surfactants
Appearance of premature infants
global hypotonia (weakness) extremitiies in extension, abduction vs midline flexion minimal random movements
describe physioloigical flexion and global hypotonia
physiological flexion: babies born in flexion b/c of growing in womb. this creates passive tone in muscles. Babies born prematurely have hypotonia b/c they didn’t grow big/long enough to get “squeezed” in womb and develop muscle tone
describe why premature infants are medically unstable
issues with temp regulation b/c they relied on mom for this
issues with respiration because lungs are not compliant
complications = BPD, hyaline membrane disease, IVH (intra-ventricular hemorrhage)
lungs not produces surfactants
germinal matrix - describe
walls of circulatory system are weak - germinal matrix in brain - can’t maintain homeostasis
difficulty regulating BP can rupture germinal matrix and cause IVH
weeks 24-28 in premature infant
week 24 = lungs matured so viability is possible
fed via NG tube
low muscle tone!! tremuolous, random mvmts, excessive ROM
difficulty regulating BP
requires a lot of sleep, but has some alert time
in utero weeks 25-28
lungs devleoping
gaining fat for temp control
muscle tone and sensory systems continue to develop
vital pathways for survival are myelinated, sleep a lot
when are the lungs matured so that viability is possible?
week 24
Weeks 26-30
dislikes bright lights
length = 16”
wt = 2.5 lbs
weeks 26-30 in premature infant
primitive reflexes seen: rooting, suck, swallow, crossed extension, flexor withdrawal, plantar grasp
suck/swallow present but safe nippling won’t occur until weeks 33-35 when coordinated and gag reflex are stronger
week 32 in premature infant
more pronouced state differentiation mvmt dominated by trunk decrease in clonic mvmt attempt hand to mouth and erect head decrase in hip hypotonia
weeks 32-36 in utero
strong growth phase
fetal mvmts begin to slow
turns head to diffuse light
reflexes: galant, neonatal NOB, BOB, positive support, stepping
week 36 in premature infant
vigorous sustained cry
increase in co-contraction of muscles
UE and trunk more hypotonic than LE (frog position)
big thing in 32 weeks in premature infant
muscle tone is less hypotonic
week 38-40 in premature infant
dependent upon others to achieve state cycles
improved state differentiation
more organized spontaneous mvmt than when born
tone is normalizing!!! but still less than normal infant
startle tremors, brisk reflexes
2 big things in week 38-40 in premature infant
reflexes now present
tone is normalizing
week 38-40 full term infant
organize sleep/awake state cycles
brain = 25% of adult wt and size
PNS not myelinated
Reflexes: DTR, superficial skin reflexes
Factors that effect prenatal development
teratogens: causes for/of different aspects of abnormal development – chemical, environmental
20% of deaths in N. America caused by birth defects
genetic
environmental
Genetic causes
huntington sickle cell anemia muscular dystrophy spina bifida chromosomal disorders others
Environmental causes
drugs
- alcohol, hormone imbalances, cocaine, methotrexate dilantin, tetracycline, thalidomide, warfarin, nicotine
chemicals
organic mercury
lead
PCBs (in plastics)
Infections
rubella, herpes, varicella, HIV, toxoplasmosis, listeria, congenital syphilis
cytomegalovirus: don’t treat Pt’s who have this if you are pregnant or want to get pregnant – causes severe cognitive/motor impairments in infants
Maternal Factors
maternal health, age, socioeconomic status, Rh blood compatibility, uncontrolled diabetes, PKU
Non-teratogenic agents (these are ok!)
non-ionizing radiation (microwave oven and UV light)
prenatal vitamins
critical times!!
CNS = 3-5 heart = 3-6 UE and LE = 4-8 eyes = 4-8 ears = 4-12 teeth and palate = 6-12
CNS development
weeks 3-5
heart development
3-6
UE and LE
4-8
eyes
4-8
ears
4-12
teeth and palate
6-12
