Development of skeletal system Flashcards by Tyler Turner

Vertebrae form as _______ derived from adjacent sclerotomes

Intersegmental structures

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Spinal nerves emerge between the vertebrae and grow out to contact _______

myotomes

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Cervical spinal nerves exit _______ vertebra of same number

above

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Their are originally how many cervical somites

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Fusion of somites results in how many cervical vertebra

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______ form neural arches surrounding the developing spinal cord

Sclerotomes

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what is centrum

Vertebral body

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The notochord regresses except where

it is incorporated into the intervertebral discs (nucleus pulposus)

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Congenital scoliosis can be be due to what 3 causes

Failure of formation, failure of segmentation, or a combination of both.

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What is scoliosis

Abnormal lateral curvature of the spine, resulting from disruption of normal vertebral development

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What leads to hemivertebrae and congenital scoliosis

semisegmented, fully segmented, wedge vertebrae

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What leads to block vertebrae and congential scoliosis

unsegmented bars

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Ribs arise form

zones of condensed mesenchyme lateral to the body of the vertebra

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Ribs develop from

Costal processes, in the thoracic region only

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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

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The sternum fuses with one another in what direction

cranial-caudal direction

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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

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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

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Anomalies in appendicular may be due to

disturbances in specific cellular or molecular interactions

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Initiation of limb development begins in what week

lat in the 4th week

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Positioning of the limbs along the craniocaudal axis is regulated by the ____ expresed along this axis

HOX genes

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HOX genes are expressed in _______ patterns from head to tail

overlapping patterns

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Once positioning along the craniocaudal axis is determined, gowth must be regulated along the _____, ______, and ______ axes

Proximodistal, anteroposterior, dorsoventral

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Limb outgrowth is initiated by _____ and ____ in the forelimb secreted by lateral plate mesoderm cells

TBX5, FGF10

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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

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