MSK embryology Flashcards
hemivertebra is one cause of ____
scoliosis
lack of development of the dorsal vertebral arch from the sclerotome can form
neural tube defects
like spina bifida
rib congenital anomalies
supernumeray or accessory ribs
lumbar rib congenital anomaly
an extra rib or pair of ribs may develop in the lumbar area from the L1 vertebra
no symptoms
more common than cervical rib anomalies
cervical rib congenital anomaly -
how many people does it affect?
- an extra rib or pair of ribs may develop in the cervical area from the C7 vertebra.
- 0.5 to 1% of the population
- may compress brachial plexus and subclavian artery! SYMPTOMATIC
boy has achondroplasia - lack of endochondrial ossification in distal areas of bone, so bone doesn’t grow -> short ribs
week that all cartilage models are formed in utero
week 8
week that all 4 limb buds have begun to form
week 4
syndactyly
polydactyly
notochord becomes the
nucleus pulposus of intervertebral discs
paraxial mesoderm becomes
somites - that then form vertebrae/ribs, muscles of the limbs and trunk, skin of the limbs and trunk
lateral plate mesoderm
limb skeleton
paraxial mesoderm forms ____ and they give rise to the body’s ____
somites
segments
each body segment includes
dermatome - skin
muscle, skeleton, and blood vessels
the limbs ____ during development, changing the orientation of the _______ from thne original orientation of the embryo
rotate
dermatomes
sclerotome
cartilage and bone
the lateral plate mesoderm is divided by the coelom into
an inner splanchnic visceral layer
an outer somatic layer (forms limb skeleton and anterolateral body wall)
intramembranous ossification
forms the skill
mesenchymal cells differentiate directly into bone forming osteoblasts, then the cells make a bone matrix (osteoid)
NO CARTILAGE MODEL
endochondral ossification
starts with hyaline cartilage and then kills the cartilage when a bone collar forms around the diaphysis (long shaft of bone).
then from the periostem, blood vessels, osteoblasts an clasts invade and form the primary ossification center, where bone formation spreads from here
then secondary ossification center forms epiphyses
all other bones of the body besides the skull
bone replaces hyaline carticlage throughout the cartilage model except the _____ and ____
articular cartilages (around joints of bone)
epiphyseal plates (growth plates needed for bone growth in puberty)
accessory ribs are most likely to develop from which vertebra?
L1
neural tube defects
also called spina bifida
mild and moderate forms arise from lack of development of dorsal vertebral arch from sclerotome (no arch so cord protrudes through where the spinous process would be
hemivertebra
lack of formation of part of a vertebra
- failure of ossiciation center to form properly
- improper subdivision of sclerotomes
the presence of ___ could be a cause for scoliosis
hemivertebra
cranial and caudal parts of adjacent sclerotomes that join together to create
vertebra
most common muscles for agenesis of upper limb
palmaris longus
part of pectoralis major
serratus anterior
etiology of achondroplasia
autosomal dominant
80% are spontaneous patermal mutations of FGFR 3 gene
clinical signs of achondroplasia
short limbs with large torso and head relative to limbs, prominant forehead and flattened nasal bridge
development of digits
forms wide paddle, then digital rays develop where each digit will form, then apoptosis occurs and separates individual digits
limbs grow distally by mitosis of cells beneath the
apical ectodermal ride (AER)
type of cartilage in limb skeleton during endochondral ossification
hyaline cartilage model
endochondral ossification follows this direction
proximal to distal, so distal elements are added progressively
most common cause of dwarfism
achondroplasia
