Intrauterine Stages Flashcards
What happens in the first week of development?
Week One - fertilization, zygote formation + cleavage, blastocyst formation
What happens in the 2nd week of development?
Week Two
- Implantation completes
- Bilaminar disc forms
- Chorionic sac develops
What happens in the 3rd week of development?
Week Three
- Gastrulation (germ layers)
- Cardiovascular Development
What happens in the 4th week of development?
- Somites (form + are visible)
- Neurulation
- Branchial Arches
- Folding
- Tail Forms
- Limb Buds Develop
- Ear/Eye Primordia
S N B F T L EE
What happens in the 5th week of development?
- Head/CNS growth
- Face in front of heart
- Cervical Sinus (mandib. and hyoid arch grow rapidly and latter telescopes into former)
- Forearm Epiphyses develop
- Spontaneous Movement begins
What happens in week 6 of development?
- Upper Limb Bud differentiation
- Ear Lobe + Ext. Acoustic Meatus form
- Finger Seperation starts
- Eye is now visible (w/ pigment)
- Thoraco-Lumbar Region straightens
- Head grows over heart
What happens in week 7 of development?
- Omphalomesenteric Duct disappears
- Fingers Fully Separated
- Physiological Umbilical Hernia???
What happens in week 8 of development?
- scalp vessels form
- tail withdraws
- toes develop
- limbs become proportional
- eyelids develop + fuse
What happens in weeks 9-12 of fetal period?
- craniocaudal length 50 > 87 mm
- weight increases 8-45 g
- head growth slows
- relative size of upper limb defined
- ext. genitals form
- ossification centers
- liver + spleen = important hematopoietic organs
- urine production
What happens in week 13-17?
- head is relatively smaller
- lower limbs elongate
- primordial follicles develop (in females)
- ossification
- coordinated movement
- eyes now frontal
- ears in position
- eye movement
length 87-140 mm, weight 45-200 g
What happens in weeks 17-20 of fetal period?
- growth slows
- lower limb at final relative length
- Vernix Caseosa - waxy substance, maybe for moisturization and lubrication, maybe antibacterial
- Lanugo - fine hair
- perception of first movements
- eyebrows + hair
- brown fat
- uterus + vagina separate
- testicles descend
What happens in weeks 21-25 of the fetal period?
- transparent skin
- REM
- vibroacoustic stimulation + blink reflex
- surfactant production
weight up to 1 kg
What happens in weeks 26-29 of fetal period?
- lung differentiates (surfactant + vascularization)
- eyelids de-fuse + open
- skin flattens via adipose
- spleen + marrow form blood
What happens in weeks 30-34 of the fetal period?
- can survive without external help
- pupil reflex can be seen
- rosy, smooth baby skin
length to 320 mm
weight to 2.5 kg
What happens in week 35-38 of the fetal period?
- forceful grip
- turns toward light
- head/belly circ. equal
- length + adipose increase
- blue/rosy skin
- thorax protrudes
- testes in scrotum
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