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