embryology Flashcards
vertebral anomalies
formation failure, segmentation failure, mixture of both
what forms vertebral bodies
sclerotomes, that migrate ventromedial on each side of the notochord. vertebral bodies are formed from cranial and caudal sclerotomes
somites
42-44 pairs formed by the union of mesoderm cells
somites give rise to ____, ____, and ____, at what week?
sclerotomes, myotomes, dermatomes, 4th week
notochord is formed by what cells
mesoderm cells
nucleus pulposus is formed by…
remnants of the degenerated notochord
annulus fibrosis orginates from what cells?
sclerotome cells
vertebral formation defects
absence of a structural vertebral element resulting in a misshaped vertebra. caused by inadequate blood supply to vertebral bodies
typed of vertebral formation defects
wedged vertebra, hemi-vertebra
wedged vertebra
unilateral partial failure of vertebral formation
hem-vertebra
half of the vertebra is absent
results of vertebral formation defects (dx)
genetic scoliosis, torticollis
vertebral segmentation defects
failure of sclerotome segmentation. vertebra don’t separate properly and produce a bar w/ no growth plate or disk btwn vertebra. can result in scoliosis
congenital spinal deformities
failure of normal vertebral formation in 4th-6th week of gestation. location of anomaly determines the deformity. in cervical region=torticollis, lateral=scoliosis, anterior=kyphosis.
congenital scoliosis
can dx w/ fetal US. may be diagnosed simultaneously with plagiocephally or torticollis. signs are patch of hair, midline skin hemangioma, congenital heart defects, kidney defects, LLD.
causes of spinal malformation
neural tube defects, vertebral formation failure, segmentation failure.
klippel-Feil syndrome
congenital fusion of 2 or more cervical vertebra/segmentation failure.
classic clinical triad of Klippel-Feil syndrome
low posterior hairline, short neck, cervical ROM limitation in 40-50% of pts. ROM usually limited in lateral bending and rotation.
VACTERL
acronym for syndromes that may co-exist with congenital spinal deformities. =vertebral anomalies, anal atresia, cardiac defects, tracheal anomalies, esophageal atresia, renal syndromes/problems, limb abnormalities.
% frequency of the presence of congenital heart defects with congenital spine defects
30%
congenital heart defects seen with congenital spinal deformities and why
b/c of the common origin of mesoderm. atrial or ventral septal defects. patent ductus arteriosus., tetralogy of Fallot, chest wall deformities (may present with rib fusion)
skull development is different in what was from other boney formations?
it does not develop out of endochondral ossification like long bones
skull development is derived from what cells?
mesenchymal cells derived from the neural crest and mesoderm cells
skull development is by what process
interosseous ossification-intramembranous ossification: mesenchyme cells differentiate directly into the osteocytes without forming the hyaline cartilage model
what is established during weeks 4-8 weeks of embryonic period?
all major external and internal structures are established. this organogenetic period starts development of all the major organ systems. teratogen from 4-8 weeks may cause major congenital anomalies.
teratogen
any agent affecting fetal development (birth defects).
vulnerability of fetus to teratogens is dependent upon
timing when cellular differentiation and morphogenesis is at its peak. magnitude, duration of exposure, ability to cross the placenta barrier.
teratogen examples-STORCH
alcohol and drugs and STORCH-acronym for infections that can be passed to the fetus: syphillis, toxoplasmosis, other (HIV), rubella, cytomegalovirus, herpes.
FAS
fetal alcohol syndrom. #1 cause of cognitive impairments. frontal lob disorder. comprises 10-20% of all cases of mental retardation. small size in weight and height, poor coordination, ADD/ADHD, poor memory, poor reasoning and judgement, sleep and sucking problems as a baby-failure to thrive, vision and hearing problems, heart, kidney, bone problems, hypotonia, learning disability, speech and language delay.
pre-embryonic stage
1st 3 weeks. fertilization and implantation and formation of the placenta.
embryonic stage
weeks 3-8. organogenesis period. very vulnerable to teratogens.
ogranogensis
formation of the organ systems
fetal period
weeks 8-40
gastrulation
division to three primary germ layers: mesoderm, ectoderm, endoderm
structures that originate from mesoderm
blood vessels, muscles, connective tissue, bone, urogenital system, cardiovascular system (reason that congenital spine disorders show up with cardiac and kidney and congenital bone defects
structures that originate from ectoderm
skin, CNS, cranial and sensory nerves, teeth
structures that originate from endoderm
digestive tract, respiratory system
neurulation is complete in ___ weeks
4
what forms the neural plate?
ectodermal cells thickening
how is the neural tube formed?
by the folding of the neural plate
how is the neural crest formed?
by the separation of cells from the neural folds
the neural tube…(does what?)
forms the CNS, extends from the hindbrain to S2, closes in a cranial to caudal direction by day 28 (end of week 4)
the neural crest forms the_____
PNS
causes of neural tube defects
genetic, nutritional (folic acid), environment (drugs like valproic acid)
types of neural tube defects
anencephaly-failure of neural tube to close cranially, spina bifida: failure of the neural tube to close caudally.
endochondral ossification* (add more detail)
long bone development from hyaline cartilage
primary ossification center*
diaphysis
Osteogenesis*
*
secondary ossification center*
growth plate
limb development early stage
limb bud development UE before LE
apical ectodermal ridge
@ the apex of each limb bud. secretes fibroblast growth factor that induces the limb to grow.
