peds: embryology Flashcards
gastrulation
when it occurs
3 layers
why its important
at week 3 cell divisions occur
3 primary germ layers
- ectoderm
- mesoderm
- endoderm
if a baby has a congenital defect with 1 thing, all things developed in that layer may have a problem
embryologic stages (3) time and what happens
pre-embryonic - first 3 weeks
fertilization -> implantation
placenta formation
embyronic wk 3-8- new structures developing => very vulnerable fetus
organogenesis
fetal period 8-40 wks
maturation and growth of all structures
things developed in ectoderm cell layer (4)
- skin
- CNS
- cranial & sensory nerves
- teeth
things developed in mesoderm cell layer (6)
- blood vessels
- muscles
- connective tissue
- bone
- urogenital system
- CV system
things developed in endoderm cell layer (2)
- digestive
2. respiratory
neurulation
when its complete by
whats developed & by what
completed by week 4
our nervous system is formed (both CNS & PNS)
(1) ectodermal cells thicken => NEURAL PLATE, which folds (2)=> NEURAL TUBE.
(3) cells separate from folds and => NEURAL CREST
neural tube becomes our CNS
neural crest becomes our PNS
neural tube defects
failure to close cranially
failure to close caudally
3 possible causes
failure to close cranially = anencephaly => baby dies
failure to close caudally => spina bifida
3 possible causes
- genetics (spina bifida runs in families)
- nutritional (pre-natal folic acid helps)
- environmental (eg- certain anti SZ drugs the mom takes)
appendicular skeletal formation
type of ossification
physiomechanics (4- start then what happens at primary and secondary ossification centers)
endochondral ossfication
- mesenchymal cells differentiate into chondrocytes
- chondrocytes secrete collagen forming hyaline cartilage => embryonic skeleton
- at primary ossification centers (diaphysis): chondrocytest proliferate, hypertrophy then undergo apoptosis, leaving cavities for BV & osteoblasts, which cause osteogenesis
- at secondary ossification centers (epiphyseal plates = “growth plates”) cartilage plates separate epiphysis from diasphysis. endochondral ossification occurs => longitudinal bone growth
limb buds
at 4th week (2)
at 6th week
4th week of development:
- 1st upper limbs, 2 days later, lower limbs
- at apex of each bud is apical ectodermal ridge (AER) which secretes fibroblast growth factor which causes limb to grow (prox -> distal)
6th week of development
1. distal end forms a paddle, apoptosis occurs forming spaces btwn digits to form fingers and toes
most common limb anomaly
scientific word
why it happens
syndactyly
webbing or fusion of fingers or toes if apoptosis doesn’t occur
how disturbances affect limb buds at
4 weeks
5 weeks
8 weeks
4 weeks - absent limb formation
5 weeks - partial limb formed
8 weeks - teratogens can no longer cause major deformities
achondroplasia genetics causes... clinical manifestations what happens in infants
autosomal dominant mutation on short (p) arm of chrom 4 which limits endochondral ossification
causes 70% of dwarfism
clinical manifestations
- cuboid shaped vertebra => cord compression (20-47% frequency)
- spinal stenosis
- lordosis/ kyphosis
- tibia vara
infants have hypotonia and transient kyphosis => use propped sitting to stop kyphosis
some have hydrocephalus
vertebral column development (6)
(pretty sure we dont need to know this much detail!)
- mesoderm cells unite to form 42-44 pairs of somites
- at 4 weeks somites => sclerotomes => vertebral bodies
- annulus fibrosis forms from sclerotome cells
- notocord (that was from mesoderm) degenerates forming nucleus pulposus
- sclerotomes migrate around neural tube forming vertebral arch
- endochondral ossification occurs
vertebral anomalies (3 types)
- formation failure
- segmentation failure
- mixed
Vertebral formation defects def cause 2 types of defects congenital defect associated with this
absence of a structural vertebral element resulting in a mis-shaped vertebrae
caused by inadequate blood supply to vertebral bodies
2 types of defects
- wedged vertebrae (unilateral partial failure)
- hemi vertebrae (half missing)
can cause scolosis
Vertebral segmental defects def caused by... 2 congenital defects associated with this
- vertebrae don’t separate properly => no growth plate or disc
- caused by failure of sclerotome segmentation
can cause scolosis or tortis collis
congenial spinal deformities
when it happens
3 causes
failure of normal vertebral development during 4th -> 6th wk of gestation
3 causes
- neural tube defect
- vertebral formation failure
- segmentation failure
location of segmentation failure => \_\_\_\_\_ lateral anterior posterior in cervical or cervical thoracis
lateral - scolosis
anterior - kyphosis
posterior - lordosis (least common)
cervical - torticollis
signs of congenital scolosis (5)
- patch of hair at base of spine
- midline skin hemangioma
- congenital heart defects
- kidney defects
- LLD (leg length discrepancy)
3 & 4 because all form in mesoderm cell layer
Klippel-Feil syndrome
dx
type of failure
classic clinical traid
- congenital fusion of 2 or more c-vertebra
- segmentation failure
classic clinical triad
- low posterior hairline
- short neck
- cervical ROM limited in 40-50% of pts (usually in lateral bending and rotation)
congenial spinal deformities nemonic
V = vertebral abnormalities A= anal atresia (anus doesnt open to outside body) C= cardiac defects T= tracheal abnormalities (fistula) E = esophageal atresia (esophagous doesn't connect to stomach) R = renal L= limb abnormalities (absent or displaced thumbs, extra fingers, fused fingers, missing bone in arms or legs)
CV issues associated with congenital spinal deformities
stats
4 examples
congenital heart defects occur in 30% of pts
atrial or ventral septal defects
patent ductus arteriousus
tetrology of fallot
chest wall deformites
skull development type of ossification what happens (2)
- interossous ossification* differs from bones because mesenchymal cells => osteophytes directly (w/o forming hyaline cartilage like all other bones)
mesenchymal cells derived from neural crest
mesoderm cells encircle brain and form flat bones of cranium
Teratogens
def
when a fetus is most at risk
vulnerability depends on (4)
def- any agent affect fetal development
fetus most at risk from 4-8 weeks because this is organogenetic period
vulnerability depends on
- timing of fetal development
- magnitude
- duration of exposure
- ability to cross placenta barrier
maternal infections that can be passed to a fetus (nemonic)
S= syphillis T = toxoplasmosis O = other eg HIV R = rubella C= cytomegalovirus H = herpes
fetal alcohol syndrome
superlative
clinical signs (9)
most common cause of all non-genetic MR (10-20% of all cases)
clinical signs
- GDD
- small size and wt before and after birth
- poor coordination
- ADHD/ADD
- poor reasoning and judgement skills
- sleep and sucking problems => failure to thrive
- vision or hearing problems
- problems with heart, kidney, bones
- speech and language delays
