Axial Skeleton Development Flashcards
somitomeres arise from where
paraxial mesoderm
what day do the somitomeres arise ?
day 18 approx
What day to the somites begin to form ?
day 20
somites differentiate into what ?
sclerotome and dermomyotome
how many occpipital, cervical, thoracic, lumbar, sacral and coccygeal somtes are there respectivelty
4,8,12,5,5,8-10
the ____________occipital somite and the cranial portion of the ________ cervical sclerotome help form the base of the occpital bone
fourth, first
how is the atlas formed ?
caudal half of the first cervical scleroome and the cranial half of the second cervical sclerotome
how is the first thoracic vertebrae formed ?
caudal half of the 8th cervical and the cranial half of the first thoracic sclerotome
the ribs form from
paraxial mesoderm
sterum forms from
somatic mesoderm
where do the intervertebral disks arise from ?>
a thin layer of mesenchymal cells between the cranial and caudal portions of the original sclerotome
notochord gives rise to what part of the interertebral disks
nucleus pulposis
annulus fibrosis develops from what /
sclerotome
scoliosis
abnormal curvature because of improper fusion or formation of the vertebral column
pescavatum
sucken in chest, deformity in sternal bone
hemivertebrae
abnormal fusion resulting from misformed vertebrae
spina bifida occulta
incomplete neural disk usually asymptomatic and accomapnied by a patch of hair over the lesion
Klippel Feil syndrome
short neck from reduced number of cervical vetebrae
chordoma
remnants of notochord may give rise to malignant tumors that invade bone they develop at the base of the skull in the lumbar region
vast majority of skeletal muscles are derived from what
paraxial mesoderm
muscles of the head arise from
somitomeres
muscles of the tonque, torso and limbs arise from
somites
extrinsic muscles of eye develop from
pre-optic somites
dorsal part of the myotome is formed by _____________ which migrate farther to form _____________ muscles
primaxial muscle cells, epaxial (instrinisc)
lateral part of myotome is formed by _____________ muscle cell precursors and gives rise to ____ muscles
abaxial, hypaxial
muscle dystrophies
conditions that result in weakness and muscle atrophy
accessory muscles
rectus sternalis
polan anomaly
congentical absence of pectoralis major
congenital torticollis
contracture or shortening of the sternocleidomastoid
slcerotome
gives rise to mesenchymal clles
mesemchyme develops into what three types of cells
fibroblasts, chondroblasts and osteoblasts
what gives rise to the sternum, shoulder and pelvic girdles
somatic layer of lateral place
what helps form many bones of the skull
neural crest cells
head somitomeres will form what parts othe the skull
cranial vault and the base of the skull
intramembranous ossification
occurs in mesencyme
forms a membranous sheat
mesenchyme condenses and becomes highly vascular
osteoblasts lay donw matrix
calcium is deposited
FLAT BONES of skull and most of the clavicle
endochondral osssification
from hyaline cartilage
occurs in preexisting cartilagenous model (starts by week 5)
occurs in the diaphysis (shaft)
cartilage cells hypertrophy, matrix becomes calcified and cells die
thin laye of bone is deposited under the perichondrium and becomes periosteum
invading cells differentiate into hemopoietic cells
LIMB bones
pathfinding
active movement of an axon toward a target
tropic substance
laminin related proteins
chemoaffinity hypothesis
axons can have differing affinities for molecules
pioneer axons
first axons to develop seem to play a role; there is a single axon that grows using the above methods to find a target and other axons follow
What are the ways an axon can find its target
tropic substnace
contact guidance theory
chemoaffinity hypothesis
growth cones
these are specializtion at the ends of an axon that are used to survey the environment
ventricular zone
layer of cells directly surrounding the ventricle
What are the three layers of the neural tube
ependymal layer-surrounds the central canal
mantle layer-middle layer contains cell bodies and astrocytes
marginal layer- contains nerve fibers and oligodendrocytes
sulcus limitans
separates the neural tube into dorsal and ventral areas
the mantle layer of the neural tube develops into two regions what are they
basal plate-motor cell bodies
alar plate- sensory relay cells
neural crest cells that remain close to the neural tube give rise to
ganglia (dorsal root and sensory ganglia for cranial nerves)
What three ways do the neural crest cells leave the neural tube ?
head and pharyngeal arches
autonomic ganglia in the torso
malanocytes
the last cells to leave the neural tube give rise too what cell type
melanocytes
What is the sequence of formation for spinal nerve
GSE
GVE
and then finally sensory GSA, and GVA
when does the process of myelination occur
late fetal period approx 20 weeks (motor before sensory)
when do the frontal lob tracts myelinate
2nd decade of life
myelination is largely complete by when
8 years of age
dermatome
area of the skin that is innervatedby a spinal cord segment, segmental and overlapping
myostome
innervation of skeletal muscle based on the relationship of the spinal nerve and somite
sympathetic innervation to head
t1-t4
sympathetic innervation to heart
t1-t4/5
sympathetic innervation to organs in the abdomen and pelvis
t5-t12
parasympathetics
vagus and S2,3 and 4
pia and arachnoid mater arise from
neural crest
dura mater arises from
ectoderm
spina bifida occulta
involves vertebral arch, patch of hair
spina bifida cystica
involves a cyst like sac containing CSF
spina bifida with meningocele
onyl meninges
spina bifida with meningomyelocele
involves some neural tissue (roootlets) meninges and CSF
spina bifida with myeloschisis
neural folds fail to fuse posteriorly
spinal cord is open to exterior
SERIOUS
spinal dural sinus
indicated by a dimple through the lumbar region, indicates the region of closure of the caudal nueropore; can be connected through a fibrous cord to dura mater
tethered cord syndrome
defect in secondary neurulation; conus medullaris and filum terminale are abnormally fixed to the vertebral column; associated with lower limb and bladder control problems
hirschprungs disease
1-5,000
delay in passage of meconium
results in constipation, vomiting, abdominal distension and rupture of cecum
characteristic feature revealed by barium enema
results from mutation in RET protooncogene
neural crest fail to reach the hind gut
neurofibromatosis (type 1)
1 in 4000
congenital disorder that affects ALL derivatives of neural crest cells and results in nerve sheath tumors and cafe aulait spots (pigmented spots in the skin)
