Development of skeletal system Flashcards
Vertebrae form as _______ derived from adjacent sclerotomes
Intersegmental structures
Spinal nerves emerge between the vertebrae and grow out to contact _______
myotomes
Cervical spinal nerves exit _______ vertebra of same number
above
Their are originally how many cervical somites
8
Fusion of somites results in how many cervical vertebra
7
______ form neural arches surrounding the developing spinal cord
Sclerotomes
what is centrum
Vertebral body
The notochord regresses except where
it is incorporated into the intervertebral discs (nucleus pulposus)
Congenital scoliosis can be be due to what 3 causes
Failure of formation, failure of segmentation, or a combination of both.
What is scoliosis
Abnormal lateral curvature of the spine, resulting from disruption of normal vertebral development
What leads to hemivertebrae and congenital scoliosis
semisegmented, fully segmented, wedge vertebrae
What leads to block vertebrae and congential scoliosis
unsegmented bars
Ribs arise form
zones of condensed mesenchyme lateral to the body of the vertebra
Ribs develop from
Costal processes, in the thoracic region only
The sternum develops from
From cartilaginous sternal bars in ventral body wall
fuse with on another in crainal-caudal direction
Forms manubrium, body and xiphoid process
The sternum fuses with one another in what direction
cranial-caudal direction
What is Pectus Carinatum
an overgrowth of cartilage causing the sternum to protrude
costal cartilage overgrowth restricts the expansion of the ribs and pushes the sternum inward
can be evident at birth; most common during growth spurt.
1 in 500-1000 children; 3x males
What is a Sternal Foramen
Ossification anomaly found in 4-10% of population
can be mistaken for bullet wound or sternal disease by CT scan (note bullet would show other fractures)
Common acupuncture point (so can lead to death if not known)
Directly over the heart
Anomalies in appendicular may be due to
disturbances in specific cellular or molecular interactions
Initiation of limb development begins in what week
lat in the 4th week
Positioning of the limbs along the craniocaudal axis is regulated by the ____ expresed along this axis
HOX genes
HOX genes are expressed in _______ patterns from head to tail
overlapping patterns
Once positioning along the craniocaudal axis is determined, gowth must be regulated along the _____, ______, and ______ axes
Proximodistal, anteroposterior, dorsoventral
Limb outgrowth is initiated by _____ and ____ in the forelimb secreted by lateral plate mesoderm cells
TBX5, FGF10
Limb outgrowth is initiated by ___ and ___ in the hindlimb secreted by lateral plate mesoderm cells
TBX4, FGF10
What is Meromelia
Part of the limb is missing
What is amelia
all of the limb is missing
What is phocomelia
Feet and hands arise close to the trunk
what is Mesomelia
shortened forearm or leg elements
typically diagnosed with fetal sonography at 20 weeks
What is radial club hand
congenital absence or hypoplasia of the radial structures of the forearm and hand
hypoplastic or absent muscular structures and radial nerve
treatment is best if early passive stretching exercises and corrective casing is started
How is the Apical Ectodermal Ridge (AER) formed
once limb outgrowth is initiated, BMPs, expressed in ventral ectoderm, induce formation of the apical ectodermal ridge (AER)
Limb bud has a strict pattern and _____
polarity
Development of limb is organized around ___ axes
3
The limb tissue differentiation is controlled by 2 regions called
apical ectodermal ridge (AER)
Zone of polarizing activity (ZPA)
The progress zone is the site where
mitosis and limb lengthening occurs
After the Apical ectodermal ridge (AER) is established, t expresses ___ and ___, which maintain the progress zone
FGF4, FGF8
What is the name of the rapidly proliferating population of mesenchyme cells adjacent to the ridge
Progress zone
Distal growth of the limb is affected by the rapidly proliferating cells (progress zone) which are under the influence of
FGFs
The zone of polarizing activity (ZPA) is made up of what
mesodermal cells located at base of limb bud
The Zone of polarizing activity (ZPA) produces ____ which initiates expression of SHH
Retionic acid
Retionic acid initiates expression of ____ in the ZPA
SHH
What is the function of the ZPA
Directs organization of limb bud and patterning of digits Determines anterior (preaxial/thumb), posterior (postaxial)
Misexpression of retinoic acid or SHH results in a ____
mirror image duplication of the limb structures
What is polydactyly
Extra digits
What are some things that lead to duplication defects
misexpression of RA and or SHH
duplication of AER (apical ectodermal ridge)
polydactyly is most common in which digit (s)
medial or lateral
in foot the extra digit is usually lateral
Is polydactyly dominant or recessive
dominant trait
Limb grows and develops in what direction
proximal to distally
what regulates type/shape of bones
HOX genes
The apical ectodermal ridge (AER) secretes FGFs that influence the closest cells (progress zone) to development into ___ structures
distal
What is syndactyly
Webbed fingers or toes
failure of programmed apoptosis in digital ray
most common limb abnormality
In what digits is syndactyly most common
between the 3rd and 4th fingers and 2nd and 3rd toes
IS syndactyly dominant or recessive
simple dominant or simple recessive
What is Brachydactyly
Reduction in length of phalanges
Inherited as dominant trait
short stature
uncommon
What is cleft hand or foot
Uncommon
Lobster-claw
absence of one or more central digits or between digits 2 and 4
Lobster claw deformity- hand or foot is divided into 2 parts that oppose each other
-Remaining digits are partly or completely fused
The upper limbs rotate 90 degrees _____
Laterally
The lower limbs rotate 90 degrees ___
medially
What is sirenomelia
Mermaid syndrome
What is achondroplasia
Most prevalent form of dwarfism
Mutation on FGF-R3
Pathological changes at epiphyseal plate; zones of proliferation and hypertrophy are narrow and disorganized
Achondroplasia is what form of reccessivity
Autosomal dominant
Osteogenesis Imperfecta
also known as brittle bone disease
bone fragility that predisposes to fractures and deformities related to CT abnormalities
Blue sclera
not always evident at birth
ED must rule out first in causes of possible child abuse
What is Talipes Equinovarus
Club foot
most common type of malformation
1/1000 births, two times more frequent in males
the sole of the foot is turned medially and the foot is inverted
What is flexible club foot
Results from abnormal positioning or restricted movement of the lower limbs in utero
Feet are structurally normal
These abnormalities usually correct themselves spontaneously
What is rigid club foot
abnormal development of the ankle and foot joints during the 6th and 7th week of development
Bony deformities particularly in the talus
How do you treat Talipes Equinovarus
over 2-3 months, on a daily basis, devices systematically revolve the feet into their proper positions
Zones of condensed mesenchyme lateral to the body of the vertebra form
The ribs
Once limb outgrowth is initiated, BMPs, expressed in ventral ectoderm, induce formation of the
Apical ectodermal ridge (AER)
What is the progress zone’s function in limb development
it is where mitosis and limb lengthening occurs
The development of the lower limbs is how far behind that of the upper limbs
1 to 2 days
On the 7th week of gestation the upper limbs rotate
90 degrees laterally
On the 7th week of gestation the lower limbs rotate
90 degrees medially
Misimpression of SHH in the anterior margin of a limb containing a normally expressing ZPA in the posterior border results in
A mirro image duplication of limb structures
What weeks are the most sensitive period for induction of limb defects
The 4th and 5th weeks
The AER directs limb bud organization along ______ while maintaining _______ axes
proximo-distal, dorsal/ventral axes
No AER means
no limb development
If AER is working normally but the Progress zone is not developing then if it starts developing after some time what happens
Distal structures form ex. like a hand
